[perl5.git] / util.c

/*    util.c
 *
 *    Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
 *    2002, 2003, 2004, 2005, 2006, 2007, 2008 by Larry Wall and others
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/*
 * 'Very useful, no doubt, that was to Saruman; yet it seems that he was
 *  not content.'                                    --Gandalf to Pippin
 *
 *     [p.598 of _The Lord of the Rings_, III/xi: "The Palantír"]
 */

/* This file contains assorted utility routines.
 * Which is a polite way of saying any stuff that people couldn't think of
 * a better place for. Amongst other things, it includes the warning and
 * dieing stuff, plus wrappers for malloc code.
 */

#include "EXTERN.h"
#define PERL_IN_UTIL_C
#include "perl.h"
#include "reentr.h"

#ifdef USE_PERLIO
#include "perliol.h" /* For PerlIOUnix_refcnt */
#endif

#ifndef PERL_MICRO
#include <signal.h>
#ifndef SIG_ERR
# define SIG_ERR ((Sighandler_t) -1)
#endif
#endif

#ifdef __Lynx__
/* Missing protos on LynxOS */
int putenv(char *);
#endif

#ifdef HAS_SELECT
# ifdef I_SYS_SELECT
#  include <sys/select.h>
# endif
#endif

#define FLUSH

#if defined(HAS_FCNTL) && defined(F_SETFD) && !defined(FD_CLOEXEC)
#  define FD_CLOEXEC 1                  /* NeXT needs this */
#endif

/* NOTE:  Do not call the next three routines directly.  Use the macros
 * in handy.h, so that we can easily redefine everything to do tracking of
 * allocated hunks back to the original New to track down any memory leaks.
 * XXX This advice seems to be widely ignored :-(   --AD  August 1996.
 */

#if defined (DEBUGGING) || defined(PERL_IMPLICIT_SYS) || defined (PERL_TRACK_MEMPOOL)
#  define ALWAYS_NEED_THX
#endif

/* paranoid version of system's malloc() */

Malloc_t
Perl_safesysmalloc(MEM_SIZE size)
{
#ifdef ALWAYS_NEED_THX
    dTHX;
#endif
    Malloc_t ptr;
#ifdef HAS_64K_LIMIT
        if (size > 0xffff) {
            PerlIO_printf(Perl_error_log,
                          "Allocation too large: %lx\n", size) FLUSH;
            my_exit(1);
        }
#endif /* HAS_64K_LIMIT */
#ifdef PERL_TRACK_MEMPOOL
    size += sTHX;
#endif
#ifdef DEBUGGING
    if ((SSize_t)size < 0)
        Perl_croak_nocontext("panic: malloc, size=%"UVuf, (UV) size);
#endif
    ptr = (Malloc_t)PerlMem_malloc(size?size:1);        /* malloc(0) is NASTY on our system */
    PERL_ALLOC_CHECK(ptr);
    if (ptr != NULL) {
#ifdef PERL_TRACK_MEMPOOL
        struct perl_memory_debug_header *const header
            = (struct perl_memory_debug_header *)ptr;
#endif

#ifdef PERL_POISON
        PoisonNew(((char *)ptr), size, char);
#endif

#ifdef PERL_TRACK_MEMPOOL
        header->interpreter = aTHX;
        /* Link us into the list.  */
        header->prev = &PL_memory_debug_header;
        header->next = PL_memory_debug_header.next;
        PL_memory_debug_header.next = header;
        header->next->prev = header;
#  ifdef PERL_POISON
        header->size = size;
#  endif
        ptr = (Malloc_t)((char*)ptr+sTHX);
#endif
        DEBUG_m(PerlIO_printf(Perl_debug_log, "0x%"UVxf": (%05ld) malloc %ld bytes\n",PTR2UV(ptr),(long)PL_an++,(long)size));
        return ptr;
}
    else {
#ifndef ALWAYS_NEED_THX
        dTHX;
#endif
        if (PL_nomemok)
            return NULL;
        else {
            croak_no_mem();
        }
    }
    /*NOTREACHED*/
}

/* paranoid version of system's realloc() */

Malloc_t
Perl_safesysrealloc(Malloc_t where,MEM_SIZE size)
{
#ifdef ALWAYS_NEED_THX
    dTHX;
#endif
    Malloc_t ptr;
#if !defined(STANDARD_C) && !defined(HAS_REALLOC_PROTOTYPE) && !defined(PERL_MICRO)
    Malloc_t PerlMem_realloc();
#endif /* !defined(STANDARD_C) && !defined(HAS_REALLOC_PROTOTYPE) */

#ifdef HAS_64K_LIMIT
    if (size > 0xffff) {
        PerlIO_printf(Perl_error_log,
                      "Reallocation too large: %lx\n", size) FLUSH;
        my_exit(1);
    }
#endif /* HAS_64K_LIMIT */
    if (!size) {
        safesysfree(where);
        return NULL;
    }

    if (!where)
        return safesysmalloc(size);
#ifdef PERL_TRACK_MEMPOOL
    where = (Malloc_t)((char*)where-sTHX);
    size += sTHX;
    {
        struct perl_memory_debug_header *const header
            = (struct perl_memory_debug_header *)where;

        if (header->interpreter != aTHX) {
            Perl_croak_nocontext("panic: realloc from wrong pool, %p!=%p",
                                 header->interpreter, aTHX);
        }
        assert(header->next->prev == header);
        assert(header->prev->next == header);
#  ifdef PERL_POISON
        if (header->size > size) {
            const MEM_SIZE freed_up = header->size - size;
            char *start_of_freed = ((char *)where) + size;
            PoisonFree(start_of_freed, freed_up, char);
        }
        header->size = size;
#  endif
    }
#endif
#ifdef DEBUGGING
    if ((SSize_t)size < 0)
        Perl_croak_nocontext("panic: realloc, size=%"UVuf, (UV)size);
#endif
    ptr = (Malloc_t)PerlMem_realloc(where,size);
    PERL_ALLOC_CHECK(ptr);

    /* MUST do this fixup first, before doing ANYTHING else, as anything else
       might allocate memory/free/move memory, and until we do the fixup, it
       may well be chasing (and writing to) free memory.  */
#ifdef PERL_TRACK_MEMPOOL
    if (ptr != NULL) {
        struct perl_memory_debug_header *const header
            = (struct perl_memory_debug_header *)ptr;

#  ifdef PERL_POISON
        if (header->size < size) {
            const MEM_SIZE fresh = size - header->size;
            char *start_of_fresh = ((char *)ptr) + size;
            PoisonNew(start_of_fresh, fresh, char);
        }
#  endif

        header->next->prev = header;
        header->prev->next = header;

        ptr = (Malloc_t)((char*)ptr+sTHX);
    }
#endif

    /* In particular, must do that fixup above before logging anything via
     *printf(), as it can reallocate memory, which can cause SEGVs.  */

    DEBUG_m(PerlIO_printf(Perl_debug_log, "0x%"UVxf": (%05ld) rfree\n",PTR2UV(where),(long)PL_an++));
    DEBUG_m(PerlIO_printf(Perl_debug_log, "0x%"UVxf": (%05ld) realloc %ld bytes\n",PTR2UV(ptr),(long)PL_an++,(long)size));


    if (ptr != NULL) {
        return ptr;
    }
    else {
#ifndef ALWAYS_NEED_THX
        dTHX;
#endif
        if (PL_nomemok)
            return NULL;
        else {
            croak_no_mem();
        }
    }
    /*NOTREACHED*/
}

/* safe version of system's free() */

Free_t
Perl_safesysfree(Malloc_t where)
{
#ifdef ALWAYS_NEED_THX
    dTHX;
#else
    dVAR;
#endif
    DEBUG_m( PerlIO_printf(Perl_debug_log, "0x%"UVxf": (%05ld) free\n",PTR2UV(where),(long)PL_an++));
    if (where) {
#ifdef PERL_TRACK_MEMPOOL
        where = (Malloc_t)((char*)where-sTHX);
        {
            struct perl_memory_debug_header *const header
                = (struct perl_memory_debug_header *)where;

            if (header->interpreter != aTHX) {
                Perl_croak_nocontext("panic: free from wrong pool, %p!=%p",
                                     header->interpreter, aTHX);
            }
            if (!header->prev) {
                Perl_croak_nocontext("panic: duplicate free");
            }
            if (!(header->next))
                Perl_croak_nocontext("panic: bad free, header->next==NULL");
            if (header->next->prev != header || header->prev->next != header) {
                Perl_croak_nocontext("panic: bad free, ->next->prev=%p, "
                                     "header=%p, ->prev->next=%p",
                                     header->next->prev, header,
                                     header->prev->next);
            }
            /* Unlink us from the chain.  */
            header->next->prev = header->prev;
            header->prev->next = header->next;
#  ifdef PERL_POISON
            PoisonNew(where, header->size, char);
#  endif
            /* Trigger the duplicate free warning.  */
            header->next = NULL;
        }
#endif
        PerlMem_free(where);
    }
}

/* safe version of system's calloc() */

Malloc_t
Perl_safesyscalloc(MEM_SIZE count, MEM_SIZE size)
{
#ifdef ALWAYS_NEED_THX
    dTHX;
#endif
    Malloc_t ptr;
#if defined(PERL_TRACK_MEMPOOL) || defined(HAS_64K_LIMIT) || defined(DEBUGGING)
    MEM_SIZE total_size = 0;
#endif

    /* Even though calloc() for zero bytes is strange, be robust. */
    if (size && (count <= MEM_SIZE_MAX / size)) {
#if defined(PERL_TRACK_MEMPOOL) || defined(HAS_64K_LIMIT) || defined(DEBUGGING)
        total_size = size * count;
#endif
    }
    else
        croak_memory_wrap();
#ifdef PERL_TRACK_MEMPOOL
    if (sTHX <= MEM_SIZE_MAX - (MEM_SIZE)total_size)
        total_size += sTHX;
    else
        croak_memory_wrap();
#endif
#ifdef HAS_64K_LIMIT
    if (total_size > 0xffff) {
        PerlIO_printf(Perl_error_log,
                      "Allocation too large: %lx\n", total_size) FLUSH;
        my_exit(1);
    }
#endif /* HAS_64K_LIMIT */
#ifdef DEBUGGING
    if ((SSize_t)size < 0 || (SSize_t)count < 0)
        Perl_croak_nocontext("panic: calloc, size=%"UVuf", count=%"UVuf,
                             (UV)size, (UV)count);
#endif
#ifdef PERL_TRACK_MEMPOOL
    /* Have to use malloc() because we've added some space for our tracking
       header.  */
    /* malloc(0) is non-portable. */
    ptr = (Malloc_t)PerlMem_malloc(total_size ? total_size : 1);
#else
    /* Use calloc() because it might save a memset() if the memory is fresh
       and clean from the OS.  */
    if (count && size)
        ptr = (Malloc_t)PerlMem_calloc(count, size);
    else /* calloc(0) is non-portable. */
        ptr = (Malloc_t)PerlMem_calloc(count ? count : 1, size ? size : 1);
#endif
    PERL_ALLOC_CHECK(ptr);
    DEBUG_m(PerlIO_printf(Perl_debug_log, "0x%"UVxf": (%05ld) calloc %ld x %ld bytes\n",PTR2UV(ptr),(long)PL_an++,(long)count,(long)total_size));
    if (ptr != NULL) {
#ifdef PERL_TRACK_MEMPOOL
        {
            struct perl_memory_debug_header *const header
                = (struct perl_memory_debug_header *)ptr;

            memset((void*)ptr, 0, total_size);
            header->interpreter = aTHX;
            /* Link us into the list.  */
            header->prev = &PL_memory_debug_header;
            header->next = PL_memory_debug_header.next;
            PL_memory_debug_header.next = header;
            header->next->prev = header;
#  ifdef PERL_POISON
            header->size = total_size;
#  endif
            ptr = (Malloc_t)((char*)ptr+sTHX);
        }
#endif
        return ptr;
    }
    else {
#ifndef ALWAYS_NEED_THX
        dTHX;
#endif
        if (PL_nomemok)
            return NULL;
        croak_no_mem();
    }
}

/* These must be defined when not using Perl's malloc for binary
 * compatibility */

#ifndef MYMALLOC

Malloc_t Perl_malloc (MEM_SIZE nbytes)
{
    dTHXs;
    return (Malloc_t)PerlMem_malloc(nbytes);
}

Malloc_t Perl_calloc (MEM_SIZE elements, MEM_SIZE size)
{
    dTHXs;
    return (Malloc_t)PerlMem_calloc(elements, size);
}

Malloc_t Perl_realloc (Malloc_t where, MEM_SIZE nbytes)
{
    dTHXs;
    return (Malloc_t)PerlMem_realloc(where, nbytes);
}

Free_t   Perl_mfree (Malloc_t where)
{
    dTHXs;
    PerlMem_free(where);
}

#endif

/* copy a string up to some (non-backslashed) delimiter, if any */

char *
Perl_delimcpy(char *to, const char *toend, const char *from, const char *fromend, int delim, I32 *retlen)
{
    I32 tolen;

    PERL_ARGS_ASSERT_DELIMCPY;

    for (tolen = 0; from < fromend; from++, tolen++) {
        if (*from == '\\') {
            if (from[1] != delim) {
                if (to < toend)
                    *to++ = *from;
                tolen++;
            }
            from++;
        }
        else if (*from == delim)
            break;
        if (to < toend)
            *to++ = *from;
    }
    if (to < toend)
        *to = '\0';
    *retlen = tolen;
    return (char *)from;
}

/* return ptr to little string in big string, NULL if not found */
/* This routine was donated by Corey Satten. */

char *
Perl_instr(const char *big, const char *little)
{

    PERL_ARGS_ASSERT_INSTR;

    /* libc prior to 4.6.27 did not work properly on a NULL 'little' */
    if (!little)
        return (char*)big;
    return strstr((char*)big, (char*)little);
}

/* same as instr but allow embedded nulls.  The end pointers point to 1 beyond
 * the final character desired to be checked */

char *
Perl_ninstr(const char *big, const char *bigend, const char *little, const char *lend)
{
    PERL_ARGS_ASSERT_NINSTR;
    if (little >= lend)
        return (char*)big;
    {
        const char first = *little;
        const char *s, *x;
        bigend -= lend - little++;
    OUTER:
        while (big <= bigend) {
            if (*big++ == first) {
                for (x=big,s=little; s < lend; x++,s++) {
                    if (*s != *x)
                        goto OUTER;
                }
                return (char*)(big-1);
            }
        }
    }
    return NULL;
}

/* reverse of the above--find last substring */

char *
Perl_rninstr(const char *big, const char *bigend, const char *little, const char *lend)
{
    const char *bigbeg;
    const I32 first = *little;
    const char * const littleend = lend;

    PERL_ARGS_ASSERT_RNINSTR;

    if (little >= littleend)
        return (char*)bigend;
    bigbeg = big;
    big = bigend - (littleend - little++);
    while (big >= bigbeg) {
        const char *s, *x;
        if (*big-- != first)
            continue;
        for (x=big+2,s=little; s < littleend; /**/ ) {
            if (*s != *x)
                break;
            else {
                x++;
                s++;
            }
        }
        if (s >= littleend)
            return (char*)(big+1);
    }
    return NULL;
}

/* As a space optimization, we do not compile tables for strings of length
   0 and 1, and for strings of length 2 unless FBMcf_TAIL.  These are
   special-cased in fbm_instr().

   If FBMcf_TAIL, the table is created as if the string has a trailing \n. */

/*
=head1 Miscellaneous Functions

=for apidoc fbm_compile

Analyses the string in order to make fast searches on it using fbm_instr()
-- the Boyer-Moore algorithm.

=cut
*/

void
Perl_fbm_compile(pTHX_ SV *sv, U32 flags)
{
    dVAR;
    const U8 *s;
    STRLEN i;
    STRLEN len;
    U32 frequency = 256;
    MAGIC *mg;
    PERL_DEB( STRLEN rarest = 0 );

    PERL_ARGS_ASSERT_FBM_COMPILE;

    if (isGV_with_GP(sv) || SvROK(sv))
        return;

    if (SvVALID(sv))
        return;

    if (flags & FBMcf_TAIL) {
        MAGIC * const mg = SvUTF8(sv) && SvMAGICAL(sv) ? mg_find(sv, PERL_MAGIC_utf8) : NULL;
        sv_catpvs(sv, "\n");            /* Taken into account in fbm_instr() */
        if (mg && mg->mg_len >= 0)
            mg->mg_len++;
    }
    if (!SvPOK(sv) || SvNIOKp(sv))
        s = (U8*)SvPV_force_mutable(sv, len);
    else s = (U8 *)SvPV_mutable(sv, len);
    if (len == 0)               /* TAIL might be on a zero-length string. */
        return;
    SvUPGRADE(sv, SVt_PVMG);
    SvIOK_off(sv);
    SvNOK_off(sv);
    SvVALID_on(sv);

    /* "deep magic", the comment used to add. The use of MAGIC itself isn't
       really. MAGIC was originally added in 79072805bf63abe5 (perl 5.0 alpha 2)
       to call SvVALID_off() if the scalar was assigned to.

       The comment itself (and "deeper magic" below) date back to
       378cc40b38293ffc (perl 2.0). "deep magic" was an annotation on
       str->str_pok |= 2;
       where the magic (presumably) was that the scalar had a BM table hidden
       inside itself.

       As MAGIC is always present on BMs [in Perl 5 :-)], we can use it to store
       the table instead of the previous (somewhat hacky) approach of co-opting
       the string buffer and storing it after the string.  */

    assert(!mg_find(sv, PERL_MAGIC_bm));
    mg = sv_magicext(sv, NULL, PERL_MAGIC_bm, &PL_vtbl_bm, NULL, 0);
    assert(mg);

    if (len > 2) {
        /* Shorter strings are special-cased in Perl_fbm_instr(), and don't use
           the BM table.  */
        const U8 mlen = (len>255) ? 255 : (U8)len;
        const unsigned char *const sb = s + len - mlen; /* first char (maybe) */
        U8 *table;

        Newx(table, 256, U8);
        memset((void*)table, mlen, 256);
        mg->mg_ptr = (char *)table;
        mg->mg_len = 256;

        s += len - 1; /* last char */
        i = 0;
        while (s >= sb) {
            if (table[*s] == mlen)
                table[*s] = (U8)i;
            s--, i++;
        }
    }

    s = (const unsigned char*)(SvPVX_const(sv));        /* deeper magic */
    for (i = 0; i < len; i++) {
        if (PL_freq[s[i]] < frequency) {
            PERL_DEB( rarest = i );
            frequency = PL_freq[s[i]];
        }
    }
    BmUSEFUL(sv) = 100;                 /* Initial value */
    if (flags & FBMcf_TAIL)
        SvTAIL_on(sv);
    DEBUG_r(PerlIO_printf(Perl_debug_log, "rarest char %c at %"UVuf"\n",
                          s[rarest], (UV)rarest));
}

/* If SvTAIL(littlestr), it has a fake '\n' at end. */
/* If SvTAIL is actually due to \Z or \z, this gives false positives
   if multiline */

/*
=for apidoc fbm_instr

Returns the location of the SV in the string delimited by C<big> and
C<bigend>.  It returns C<NULL> if the string can't be found.  The C<sv>
does not have to be fbm_compiled, but the search will not be as fast
then.

=cut
*/

char *
Perl_fbm_instr(pTHX_ unsigned char *big, unsigned char *bigend, SV *littlestr, U32 flags)
{
    unsigned char *s;
    STRLEN l;
    const unsigned char *little = (const unsigned char *)SvPV_const(littlestr,l);
    STRLEN littlelen = l;
    const I32 multiline = flags & FBMrf_MULTILINE;

    PERL_ARGS_ASSERT_FBM_INSTR;

    if ((STRLEN)(bigend - big) < littlelen) {
        if ( SvTAIL(littlestr)
             && ((STRLEN)(bigend - big) == littlelen - 1)
             && (littlelen == 1
                 || (*big == *little &&
                     memEQ((char *)big, (char *)little, littlelen - 1))))
            return (char*)big;
        return NULL;
    }

    switch (littlelen) { /* Special cases for 0, 1 and 2  */
    case 0:
        return (char*)big;              /* Cannot be SvTAIL! */
    case 1:
            if (SvTAIL(littlestr) && !multiline) { /* Anchor only! */
                /* Know that bigend != big.  */
                if (bigend[-1] == '\n')
                    return (char *)(bigend - 1);
                return (char *) bigend;
            }
            s = big;
            while (s < bigend) {
                if (*s == *little)
                    return (char *)s;
                s++;
            }
            if (SvTAIL(littlestr))
                return (char *) bigend;
            return NULL;
    case 2:
        if (SvTAIL(littlestr) && !multiline) {
            if (bigend[-1] == '\n' && bigend[-2] == *little)
                return (char*)bigend - 2;
            if (bigend[-1] == *little)
                return (char*)bigend - 1;
            return NULL;
        }
        {
            /* This should be better than FBM if c1 == c2, and almost
               as good otherwise: maybe better since we do less indirection.
               And we save a lot of memory by caching no table. */
            const unsigned char c1 = little[0];
            const unsigned char c2 = little[1];

            s = big + 1;
            bigend--;
            if (c1 != c2) {
                while (s <= bigend) {
                    if (s[0] == c2) {
                        if (s[-1] == c1)
                            return (char*)s - 1;
                        s += 2;
                        continue;
                    }
                  next_chars:
                    if (s[0] == c1) {
                        if (s == bigend)
                            goto check_1char_anchor;
                        if (s[1] == c2)
                            return (char*)s;
                        else {
                            s++;
                            goto next_chars;
                        }
                    }
                    else
                        s += 2;
                }
                goto check_1char_anchor;
            }
            /* Now c1 == c2 */
            while (s <= bigend) {
                if (s[0] == c1) {
                    if (s[-1] == c1)
                        return (char*)s - 1;
                    if (s == bigend)
                        goto check_1char_anchor;
                    if (s[1] == c1)
                        return (char*)s;
                    s += 3;
                }
                else
                    s += 2;
            }
        }
      check_1char_anchor:               /* One char and anchor! */
        if (SvTAIL(littlestr) && (*bigend == *little))
            return (char *)bigend;      /* bigend is already decremented. */
        return NULL;
    default:
        break; /* Only lengths 0 1 and 2 have special-case code.  */
    }

    if (SvTAIL(littlestr) && !multiline) {      /* tail anchored? */
        s = bigend - littlelen;
        if (s >= big && bigend[-1] == '\n' && *s == *little
            /* Automatically of length > 2 */
            && memEQ((char*)s + 1, (char*)little + 1, littlelen - 2))
        {
            return (char*)s;            /* how sweet it is */
        }
        if (s[1] == *little
            && memEQ((char*)s + 2, (char*)little + 1, littlelen - 2))
        {
            return (char*)s + 1;        /* how sweet it is */
        }
        return NULL;
    }
    if (!SvVALID(littlestr)) {
        char * const b = ninstr((char*)big,(char*)bigend,
                         (char*)little, (char*)little + littlelen);

        if (!b && SvTAIL(littlestr)) {  /* Automatically multiline!  */
            /* Chop \n from littlestr: */
            s = bigend - littlelen + 1;
            if (*s == *little
                && memEQ((char*)s + 1, (char*)little + 1, littlelen - 2))
            {
                return (char*)s;
            }
            return NULL;
        }
        return b;
    }

    /* Do actual FBM.  */
    if (littlelen > (STRLEN)(bigend - big))
        return NULL;

    {
        const MAGIC *const mg = mg_find(littlestr, PERL_MAGIC_bm);
        const unsigned char * const table = (const unsigned char *) mg->mg_ptr;
        const unsigned char *oldlittle;

        --littlelen;                    /* Last char found by table lookup */

        s = big + littlelen;
        little += littlelen;            /* last char */
        oldlittle = little;
        if (s < bigend) {
            I32 tmp;

          top2:
            if ((tmp = table[*s])) {
                if ((s += tmp) < bigend)
                    goto top2;
                goto check_end;
            }
            else {              /* less expensive than calling strncmp() */
                unsigned char * const olds = s;

                tmp = littlelen;

                while (tmp--) {
                    if (*--s == *--little)
                        continue;
                    s = olds + 1;       /* here we pay the price for failure */
                    little = oldlittle;
                    if (s < bigend)     /* fake up continue to outer loop */
                        goto top2;
                    goto check_end;
                }
                return (char *)s;
            }
        }
      check_end:
        if ( s == bigend
             && SvTAIL(littlestr)
             && memEQ((char *)(bigend - littlelen),
                      (char *)(oldlittle - littlelen), littlelen) )
            return (char*)bigend - littlelen;
        return NULL;
    }
}

char *
Perl_screaminstr(pTHX_ SV *bigstr, SV *littlestr, I32 start_shift, I32 end_shift, I32 *old_posp, I32 last)
{
    dVAR;
    PERL_ARGS_ASSERT_SCREAMINSTR;
    PERL_UNUSED_ARG(bigstr);
    PERL_UNUSED_ARG(littlestr);
    PERL_UNUSED_ARG(start_shift);
    PERL_UNUSED_ARG(end_shift);
    PERL_UNUSED_ARG(old_posp);
    PERL_UNUSED_ARG(last);

    /* This function must only ever be called on a scalar with study magic,
       but those do not happen any more. */
    Perl_croak(aTHX_ "panic: screaminstr");
    return NULL;
}

/*
=for apidoc foldEQ

Returns true if the leading len bytes of the strings s1 and s2 are the same
case-insensitively; false otherwise.  Uppercase and lowercase ASCII range bytes
match themselves and their opposite case counterparts.  Non-cased and non-ASCII
range bytes match only themselves.

=cut
*/


I32
Perl_foldEQ(const char *s1, const char *s2, I32 len)
{
    const U8 *a = (const U8 *)s1;
    const U8 *b = (const U8 *)s2;

    PERL_ARGS_ASSERT_FOLDEQ;

    assert(len >= 0);

    while (len--) {
        if (*a != *b && *a != PL_fold[*b])
            return 0;
        a++,b++;
    }
    return 1;
}
I32
Perl_foldEQ_latin1(const char *s1, const char *s2, I32 len)
{
    /* Compare non-utf8 using Unicode (Latin1) semantics.  Does not work on
     * MICRO_SIGN, LATIN_SMALL_LETTER_SHARP_S, nor
     * LATIN_SMALL_LETTER_Y_WITH_DIAERESIS, and does not check for these.  Nor
     * does it check that the strings each have at least 'len' characters */

    const U8 *a = (const U8 *)s1;
    const U8 *b = (const U8 *)s2;

    PERL_ARGS_ASSERT_FOLDEQ_LATIN1;

    assert(len >= 0);

    while (len--) {
        if (*a != *b && *a != PL_fold_latin1[*b]) {
            return 0;
        }
        a++, b++;
    }
    return 1;
}

/*
=for apidoc foldEQ_locale

Returns true if the leading len bytes of the strings s1 and s2 are the same
case-insensitively in the current locale; false otherwise.

=cut
*/

I32
Perl_foldEQ_locale(const char *s1, const char *s2, I32 len)
{
    dVAR;
    const U8 *a = (const U8 *)s1;
    const U8 *b = (const U8 *)s2;

    PERL_ARGS_ASSERT_FOLDEQ_LOCALE;

    assert(len >= 0);

    while (len--) {
        if (*a != *b && *a != PL_fold_locale[*b])
            return 0;
        a++,b++;
    }
    return 1;
}

/* copy a string to a safe spot */

/*
=head1 Memory Management

=for apidoc savepv

Perl's version of C<strdup()>. Returns a pointer to a newly allocated
string which is a duplicate of C<pv>. The size of the string is
determined by C<strlen()>. The memory allocated for the new string can
be freed with the C<Safefree()> function.

=cut
*/

char *
Perl_savepv(pTHX_ const char *pv)
{
    PERL_UNUSED_CONTEXT;
    if (!pv)
        return NULL;
    else {
        char *newaddr;
        const STRLEN pvlen = strlen(pv)+1;
        Newx(newaddr, pvlen, char);
        return (char*)memcpy(newaddr, pv, pvlen);
    }
}

/* same thing but with a known length */

/*
=for apidoc savepvn

Perl's version of what C<strndup()> would be if it existed. Returns a
pointer to a newly allocated string which is a duplicate of the first
C<len> bytes from C<pv>, plus a trailing NUL byte. The memory allocated for
the new string can be freed with the C<Safefree()> function.

=cut
*/

char *
Perl_savepvn(pTHX_ const char *pv, I32 len)
{
    char *newaddr;
    PERL_UNUSED_CONTEXT;

    assert(len >= 0);

    Newx(newaddr,len+1,char);
    /* Give a meaning to NULL pointer mainly for the use in sv_magic() */
    if (pv) {
        /* might not be null terminated */
        newaddr[len] = '\0';
        return (char *) CopyD(pv,newaddr,len,char);
    }
    else {
        return (char *) ZeroD(newaddr,len+1,char);
    }
}

/*
=for apidoc savesharedpv

A version of C<savepv()> which allocates the duplicate string in memory
which is shared between threads.

=cut
*/
char *
Perl_savesharedpv(pTHX_ const char *pv)
{
    char *newaddr;
    STRLEN pvlen;
    if (!pv)
        return NULL;

    pvlen = strlen(pv)+1;
    newaddr = (char*)PerlMemShared_malloc(pvlen);
    if (!newaddr) {
        croak_no_mem();
    }
    return (char*)memcpy(newaddr, pv, pvlen);
}

/*
=for apidoc savesharedpvn

A version of C<savepvn()> which allocates the duplicate string in memory
which is shared between threads. (With the specific difference that a NULL
pointer is not acceptable)

=cut
*/
char *
Perl_savesharedpvn(pTHX_ const char *const pv, const STRLEN len)
{
    char *const newaddr = (char*)PerlMemShared_malloc(len + 1);

    /* PERL_ARGS_ASSERT_SAVESHAREDPVN; */

    if (!newaddr) {
        croak_no_mem();
    }
    newaddr[len] = '\0';
    return (char*)memcpy(newaddr, pv, len);
}

/*
=for apidoc savesvpv

A version of C<savepv()>/C<savepvn()> which gets the string to duplicate from
the passed in SV using C<SvPV()>

=cut
*/

char *
Perl_savesvpv(pTHX_ SV *sv)
{
    STRLEN len;
    const char * const pv = SvPV_const(sv, len);
    char *newaddr;

    PERL_ARGS_ASSERT_SAVESVPV;

    ++len;
    Newx(newaddr,len,char);
    return (char *) CopyD(pv,newaddr,len,char);
}

/*
=for apidoc savesharedsvpv

A version of C<savesharedpv()> which allocates the duplicate string in
memory which is shared between threads.

=cut
*/

char *
Perl_savesharedsvpv(pTHX_ SV *sv)
{
    STRLEN len;
    const char * const pv = SvPV_const(sv, len);

    PERL_ARGS_ASSERT_SAVESHAREDSVPV;

    return savesharedpvn(pv, len);
}

/* the SV for Perl_form() and mess() is not kept in an arena */

STATIC SV *
S_mess_alloc(pTHX)
{
    dVAR;
    SV *sv;
    XPVMG *any;

    if (PL_phase != PERL_PHASE_DESTRUCT)
        return newSVpvs_flags("", SVs_TEMP);

    if (PL_mess_sv)
        return PL_mess_sv;

    /* Create as PVMG now, to avoid any upgrading later */
    Newx(sv, 1, SV);
    Newxz(any, 1, XPVMG);
    SvFLAGS(sv) = SVt_PVMG;
    SvANY(sv) = (void*)any;
    SvPV_set(sv, NULL);
    SvREFCNT(sv) = 1 << 30; /* practically infinite */
    PL_mess_sv = sv;
    return sv;
}

#if defined(PERL_IMPLICIT_CONTEXT)
char *
Perl_form_nocontext(const char* pat, ...)
{
    dTHX;
    char *retval;
    va_list args;
    PERL_ARGS_ASSERT_FORM_NOCONTEXT;
    va_start(args, pat);
    retval = vform(pat, &args);
    va_end(args);
    return retval;
}
#endif /* PERL_IMPLICIT_CONTEXT */

/*
=head1 Miscellaneous Functions
=for apidoc form

Takes a sprintf-style format pattern and conventional
(non-SV) arguments and returns the formatted string.

    (char *) Perl_form(pTHX_ const char* pat, ...)

can be used any place a string (char *) is required:

    char * s = Perl_form("%d.%d",major,minor);

Uses a single private buffer so if you want to format several strings you
must explicitly copy the earlier strings away (and free the copies when you
are done).

=cut
*/

char *
Perl_form(pTHX_ const char* pat, ...)
{
    char *retval;
    va_list args;
    PERL_ARGS_ASSERT_FORM;
    va_start(args, pat);
    retval = vform(pat, &args);
    va_end(args);
    return retval;
}

char *
Perl_vform(pTHX_ const char *pat, va_list *args)
{
    SV * const sv = mess_alloc();
    PERL_ARGS_ASSERT_VFORM;
    sv_vsetpvfn(sv, pat, strlen(pat), args, NULL, 0, NULL);
    return SvPVX(sv);
}

/*
=for apidoc Am|SV *|mess|const char *pat|...

Take a sprintf-style format pattern and argument list.  These are used to
generate a string message.  If the message does not end with a newline,
then it will be extended with some indication of the current location
in the code, as described for L</mess_sv>.

Normally, the resulting message is returned in a new mortal SV.
During global destruction a single SV may be shared between uses of
this function.

=cut
*/

#if defined(PERL_IMPLICIT_CONTEXT)
SV *
Perl_mess_nocontext(const char *pat, ...)
{
    dTHX;
    SV *retval;
    va_list args;
    PERL_ARGS_ASSERT_MESS_NOCONTEXT;
    va_start(args, pat);
    retval = vmess(pat, &args);
    va_end(args);
    return retval;
}
#endif /* PERL_IMPLICIT_CONTEXT */

SV *
Perl_mess(pTHX_ const char *pat, ...)
{
    SV *retval;
    va_list args;
    PERL_ARGS_ASSERT_MESS;
    va_start(args, pat);
    retval = vmess(pat, &args);
    va_end(args);
    return retval;
}

const COP*
Perl_closest_cop(pTHX_ const COP *cop, const OP *o, const OP *curop,
                       bool opnext)
{
    dVAR;
    /* Look for curop starting from o.  cop is the last COP we've seen. */
    /* opnext means that curop is actually the ->op_next of the op we are
       seeking. */

    PERL_ARGS_ASSERT_CLOSEST_COP;

    if (!o || !curop || (
        opnext ? o->op_next == curop && o->op_type != OP_SCOPE : o == curop
    ))
        return cop;

    if (o->op_flags & OPf_KIDS) {
        const OP *kid;
        for (kid = cUNOPo->op_first; kid; kid = kid->op_sibling) {
            const COP *new_cop;

            /* If the OP_NEXTSTATE has been optimised away we can still use it
             * the get the file and line number. */

            if (kid->op_type == OP_NULL && kid->op_targ == OP_NEXTSTATE)
                cop = (const COP *)kid;

            /* Keep searching, and return when we've found something. */

            new_cop = closest_cop(cop, kid, curop, opnext);
            if (new_cop)
                return new_cop;
        }
    }

    /* Nothing found. */

    return NULL;
}

/*
=for apidoc Am|SV *|mess_sv|SV *basemsg|bool consume

Expands a message, intended for the user, to include an indication of
the current location in the code, if the message does not already appear
to be complete.

C<basemsg> is the initial message or object.  If it is a reference, it
will be used as-is and will be the result of this function.  Otherwise it
is used as a string, and if it already ends with a newline, it is taken
to be complete, and the result of this function will be the same string.
If the message does not end with a newline, then a segment such as C<at
foo.pl line 37> will be appended, and possibly other clauses indicating
the current state of execution.  The resulting message will end with a
dot and a newline.

Normally, the resulting message is returned in a new mortal SV.
During global destruction a single SV may be shared between uses of this
function.  If C<consume> is true, then the function is permitted (but not
required) to modify and return C<basemsg> instead of allocating a new SV.

=cut
*/

SV *
Perl_mess_sv(pTHX_ SV *basemsg, bool consume)
{
    dVAR;
    SV *sv;

    PERL_ARGS_ASSERT_MESS_SV;

    if (SvROK(basemsg)) {
        if (consume) {
            sv = basemsg;
        }
        else {
            sv = mess_alloc();
            sv_setsv(sv, basemsg);
        }
        return sv;
    }

    if (SvPOK(basemsg) && consume) {
        sv = basemsg;
    }
    else {
        sv = mess_alloc();
        sv_copypv(sv, basemsg);
    }

    if (!SvCUR(sv) || *(SvEND(sv) - 1) != '\n') {
        /*
         * Try and find the file and line for PL_op.  This will usually be
         * PL_curcop, but it might be a cop that has been optimised away.  We
         * can try to find such a cop by searching through the optree starting
         * from the sibling of PL_curcop.
         */

        const COP *cop =
            closest_cop(PL_curcop, PL_curcop->op_sibling, PL_op, FALSE);
        if (!cop)
            cop = PL_curcop;

        if (CopLINE(cop))
            Perl_sv_catpvf(aTHX_ sv, " at %s line %"IVdf,
            OutCopFILE(cop), (IV)CopLINE(cop));
        /* Seems that GvIO() can be untrustworthy during global destruction. */
        if (GvIO(PL_last_in_gv) && (SvTYPE(GvIOp(PL_last_in_gv)) == SVt_PVIO)
                && IoLINES(GvIOp(PL_last_in_gv)))
        {
            STRLEN l;
            const bool line_mode = (RsSIMPLE(PL_rs) &&
                                   *SvPV_const(PL_rs,l) == '\n' && l == 1);
            Perl_sv_catpvf(aTHX_ sv, ", <%"SVf"> %s %"IVdf,
                           SVfARG(PL_last_in_gv == PL_argvgv
                                 ? &PL_sv_no
                                 : sv_2mortal(newSVhek(GvNAME_HEK(PL_last_in_gv)))),
                           line_mode ? "line" : "chunk",
                           (IV)IoLINES(GvIOp(PL_last_in_gv)));
        }
        if (PL_phase == PERL_PHASE_DESTRUCT)
            sv_catpvs(sv, " during global destruction");
        sv_catpvs(sv, ".\n");
    }
    return sv;
}

/*
=for apidoc Am|SV *|vmess|const char *pat|va_list *args

C<pat> and C<args> are a sprintf-style format pattern and encapsulated
argument list.  These are used to generate a string message.  If the
message does not end with a newline, then it will be extended with
some indication of the current location in the code, as described for
L</mess_sv>.

Normally, the resulting message is returned in a new mortal SV.
During global destruction a single SV may be shared between uses of
this function.

=cut
*/

SV *
Perl_vmess(pTHX_ const char *pat, va_list *args)
{
    dVAR;
    SV * const sv = mess_alloc();

    PERL_ARGS_ASSERT_VMESS;

    sv_vsetpvfn(sv, pat, strlen(pat), args, NULL, 0, NULL);
    return mess_sv(sv, 1);
}

void
Perl_write_to_stderr(pTHX_ SV* msv)
{
    dVAR;
    IO *io;
    MAGIC *mg;

    PERL_ARGS_ASSERT_WRITE_TO_STDERR;

    if (PL_stderrgv && SvREFCNT(PL_stderrgv) 
        && (io = GvIO(PL_stderrgv))
        && (mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar))) 
        Perl_magic_methcall(aTHX_ MUTABLE_SV(io), mg, SV_CONST(PRINT),
                            G_SCALAR | G_DISCARD | G_WRITING_TO_STDERR, 1, msv);
    else {
#ifdef USE_SFIO
        /* SFIO can really mess with your errno */
        dSAVED_ERRNO;
#endif
        PerlIO * const serr = Perl_error_log;

        do_print(msv, serr);
        (void)PerlIO_flush(serr);
#ifdef USE_SFIO
        RESTORE_ERRNO;
#endif
    }
}

/*
=head1 Warning and Dieing
*/

/* Common code used in dieing and warning */

STATIC SV *
S_with_queued_errors(pTHX_ SV *ex)
{
    PERL_ARGS_ASSERT_WITH_QUEUED_ERRORS;
    if (PL_errors && SvCUR(PL_errors) && !SvROK(ex)) {
        sv_catsv(PL_errors, ex);
        ex = sv_mortalcopy(PL_errors);
        SvCUR_set(PL_errors, 0);
    }
    return ex;
}

STATIC bool
S_invoke_exception_hook(pTHX_ SV *ex, bool warn)
{
    dVAR;
    HV *stash;
    GV *gv;
    CV *cv;
    SV **const hook = warn ? &PL_warnhook : &PL_diehook;
    /* sv_2cv might call Perl_croak() or Perl_warner() */
    SV * const oldhook = *hook;

    if (!oldhook)
        return FALSE;

    ENTER;
    SAVESPTR(*hook);
    *hook = NULL;
    cv = sv_2cv(oldhook, &stash, &gv, 0);
    LEAVE;
    if (cv && !CvDEPTH(cv) && (CvROOT(cv) || CvXSUB(cv))) {
        dSP;
        SV *exarg;

        ENTER;
        save_re_context();
        if (warn) {
            SAVESPTR(*hook);
            *hook = NULL;
        }
        exarg = newSVsv(ex);
        SvREADONLY_on(exarg);
        SAVEFREESV(exarg);

        PUSHSTACKi(warn ? PERLSI_WARNHOOK : PERLSI_DIEHOOK);
        PUSHMARK(SP);
        XPUSHs(exarg);
        PUTBACK;
        call_sv(MUTABLE_SV(cv), G_DISCARD);
        POPSTACK;
        LEAVE;
        return TRUE;
    }
    return FALSE;
}

/*
=for apidoc Am|OP *|die_sv|SV *baseex

Behaves the same as L</croak_sv>, except for the return type.
It should be used only where the C<OP *> return type is required.
The function never actually returns.

=cut
*/

OP *
Perl_die_sv(pTHX_ SV *baseex)
{
    PERL_ARGS_ASSERT_DIE_SV;
    croak_sv(baseex);
    assert(0); /* NOTREACHED */
    return NULL;
}

/*
=for apidoc Am|OP *|die|const char *pat|...

Behaves the same as L</croak>, except for the return type.
It should be used only where the C<OP *> return type is required.
The function never actually returns.

=cut
*/

#if defined(PERL_IMPLICIT_CONTEXT)
OP *
Perl_die_nocontext(const char* pat, ...)
{
    dTHX;
    va_list args;
    va_start(args, pat);
    vcroak(pat, &args);
    assert(0); /* NOTREACHED */
    va_end(args);
    return NULL;
}
#endif /* PERL_IMPLICIT_CONTEXT */

OP *
Perl_die(pTHX_ const char* pat, ...)
{
    va_list args;
    va_start(args, pat);
    vcroak(pat, &args);
    assert(0); /* NOTREACHED */
    va_end(args);
    return NULL;
}

/*
=for apidoc Am|void|croak_sv|SV *baseex

This is an XS interface to Perl's C<die> function.

C<baseex> is the error message or object.  If it is a reference, it
will be used as-is.  Otherwise it is used as a string, and if it does
not end with a newline then it will be extended with some indication of
the current location in the code, as described for L</mess_sv>.

The error message or object will be used as an exception, by default
returning control to the nearest enclosing C<eval>, but subject to
modification by a C<$SIG{__DIE__}> handler.  In any case, the C<croak_sv>
function never returns normally.

To die with a simple string message, the L</croak> function may be
more convenient.

=cut
*/

void
Perl_croak_sv(pTHX_ SV *baseex)
{
    SV *ex = with_queued_errors(mess_sv(baseex, 0));
    PERL_ARGS_ASSERT_CROAK_SV;
    invoke_exception_hook(ex, FALSE);
    die_unwind(ex);
}

/*
=for apidoc Am|void|vcroak|const char *pat|va_list *args

This is an XS interface to Perl's C<die> function.

C<pat> and C<args> are a sprintf-style format pattern and encapsulated
argument list.  These are used to generate a string message.  If the
message does not end with a newline, then it will be extended with
some indication of the current location in the code, as described for
L</mess_sv>.

The error message will be used as an exception, by default
returning control to the nearest enclosing C<eval>, but subject to
modification by a C<$SIG{__DIE__}> handler.  In any case, the C<croak>
function never returns normally.

For historical reasons, if C<pat> is null then the contents of C<ERRSV>
(C<$@>) will be used as an error message or object instead of building an
error message from arguments.  If you want to throw a non-string object,
or build an error message in an SV yourself, it is preferable to use
the L</croak_sv> function, which does not involve clobbering C<ERRSV>.

=cut
*/

void
Perl_vcroak(pTHX_ const char* pat, va_list *args)
{
    SV *ex = with_queued_errors(pat ? vmess(pat, args) : mess_sv(ERRSV, 0));
    invoke_exception_hook(ex, FALSE);
    die_unwind(ex);
}

/*
=for apidoc Am|void|croak|const char *pat|...

This is an XS interface to Perl's C<die> function.

Take a sprintf-style format pattern and argument list.  These are used to
generate a string message.  If the message does not end with a newline,
then it will be extended with some indication of the current location
in the code, as described for L</mess_sv>.

The error message will be used as an exception, by default
returning control to the nearest enclosing C<eval>, but subject to
modification by a C<$SIG{__DIE__}> handler.  In any case, the C<croak>
function never returns normally.

For historical reasons, if C<pat> is null then the contents of C<ERRSV>
(C<$@>) will be used as an error message or object instead of building an
error message from arguments.  If you want to throw a non-string object,
or build an error message in an SV yourself, it is preferable to use
the L</croak_sv> function, which does not involve clobbering C<ERRSV>.

=cut
*/

#if defined(PERL_IMPLICIT_CONTEXT)
void
Perl_croak_nocontext(const char *pat, ...)
{
    dTHX;
    va_list args;
    va_start(args, pat);
    vcroak(pat, &args);
    assert(0); /* NOTREACHED */
    va_end(args);
}
#endif /* PERL_IMPLICIT_CONTEXT */

void
Perl_croak(pTHX_ const char *pat, ...)
{
    va_list args;
    va_start(args, pat);
    vcroak(pat, &args);
    assert(0); /* NOTREACHED */
    va_end(args);
}

/*
=for apidoc Am|void|croak_no_modify

Exactly equivalent to C<Perl_croak(aTHX_ "%s", PL_no_modify)>, but generates
terser object code than using C<Perl_croak>. Less code used on exception code
paths reduces CPU cache pressure.

=cut
*/

void
Perl_croak_no_modify()
{
    Perl_croak_nocontext( "%s", PL_no_modify);
}

/* does not return, used in util.c perlio.c and win32.c
   This is typically called when malloc returns NULL.
*/
void
Perl_croak_no_mem()
{
    dTHX;

    /* Can't use PerlIO to write as it allocates memory */
    PerlLIO_write(PerlIO_fileno(Perl_error_log),
                  PL_no_mem, sizeof(PL_no_mem)-1);
    my_exit(1);
}

/* does not return, used only in POPSTACK */
void
Perl_croak_popstack(void)
{
    dTHX;
    PerlIO_printf(Perl_error_log, "panic: POPSTACK\n");
    my_exit(1);
}

/*
=for apidoc Am|void|warn_sv|SV *baseex

This is an XS interface to Perl's C<warn> function.

C<baseex> is the error message or object.  If it is a reference, it
will be used as-is.  Otherwise it is used as a string, and if it does
not end with a newline then it will be extended with some indication of
the current location in the code, as described for L</mess_sv>.

The error message or object will by default be written to standard error,
but this is subject to modification by a C<$SIG{__WARN__}> handler.

To warn with a simple string message, the L</warn> function may be
more convenient.

=cut
*/

void
Perl_warn_sv(pTHX_ SV *baseex)
{
    SV *ex = mess_sv(baseex, 0);
    PERL_ARGS_ASSERT_WARN_SV;
    if (!invoke_exception_hook(ex, TRUE))
        write_to_stderr(ex);
}

/*
=for apidoc Am|void|vwarn|const char *pat|va_list *args

This is an XS interface to Perl's C<warn> function.

C<pat> and C<args> are a sprintf-style format pattern and encapsulated
argument list.  These are used to generate a string message.  If the
message does not end with a newline, then it will be extended with
some indication of the current location in the code, as described for
L</mess_sv>.

The error message or object will by default be written to standard error,
but this is subject to modification by a C<$SIG{__WARN__}> handler.

Unlike with L</vcroak>, C<pat> is not permitted to be null.

=cut
*/

void
Perl_vwarn(pTHX_ const char* pat, va_list *args)
{
    SV *ex = vmess(pat, args);
    PERL_ARGS_ASSERT_VWARN;
    if (!invoke_exception_hook(ex, TRUE))
        write_to_stderr(ex);
}

/*
=for apidoc Am|void|warn|const char *pat|...

This is an XS interface to Perl's C<warn> function.

Take a sprintf-style format pattern and argument list.  These are used to
generate a string message.  If the message does not end with a newline,
then it will be extended with some indication of the current location
in the code, as described for L</mess_sv>.

The error message or object will by default be written to standard error,
but this is subject to modification by a C<$SIG{__WARN__}> handler.

Unlike with L</croak>, C<pat> is not permitted to be null.

=cut
*/

#if defined(PERL_IMPLICIT_CONTEXT)
void
Perl_warn_nocontext(const char *pat, ...)
{
    dTHX;
    va_list args;
    PERL_ARGS_ASSERT_WARN_NOCONTEXT;
    va_start(args, pat);
    vwarn(pat, &args);
    va_end(args);
}
#endif /* PERL_IMPLICIT_CONTEXT */

void
Perl_warn(pTHX_ const char *pat, ...)
{
    va_list args;
    PERL_ARGS_ASSERT_WARN;
    va_start(args, pat);
    vwarn(pat, &args);
    va_end(args);
}

#if defined(PERL_IMPLICIT_CONTEXT)
void
Perl_warner_nocontext(U32 err, const char *pat, ...)
{
    dTHX; 
    va_list args;
    PERL_ARGS_ASSERT_WARNER_NOCONTEXT;
    va_start(args, pat);
    vwarner(err, pat, &args);
    va_end(args);
}
#endif /* PERL_IMPLICIT_CONTEXT */

void
Perl_ck_warner_d(pTHX_ U32 err, const char* pat, ...)
{
    PERL_ARGS_ASSERT_CK_WARNER_D;

    if (Perl_ckwarn_d(aTHX_ err)) {
        va_list args;
        va_start(args, pat);
        vwarner(err, pat, &args);
        va_end(args);
    }
}

void
Perl_ck_warner(pTHX_ U32 err, const char* pat, ...)
{
    PERL_ARGS_ASSERT_CK_WARNER;

    if (Perl_ckwarn(aTHX_ err)) {
        va_list args;
        va_start(args, pat);
        vwarner(err, pat, &args);
        va_end(args);
    }
}

void
Perl_warner(pTHX_ U32  err, const char* pat,...)
{
    va_list args;
    PERL_ARGS_ASSERT_WARNER;
    va_start(args, pat);
    vwarner(err, pat, &args);
    va_end(args);
}

void
Perl_vwarner(pTHX_ U32  err, const char* pat, va_list* args)
{
    dVAR;
    PERL_ARGS_ASSERT_VWARNER;
    if (PL_warnhook == PERL_WARNHOOK_FATAL || ckDEAD(err)) {
        SV * const msv = vmess(pat, args);

        invoke_exception_hook(msv, FALSE);
        die_unwind(msv);
    }
    else {
        Perl_vwarn(aTHX_ pat, args);
    }
}

/* implements the ckWARN? macros */

bool
Perl_ckwarn(pTHX_ U32 w)
{
    dVAR;
    /* If lexical warnings have not been set, use $^W.  */
    if (isLEXWARN_off)
        return PL_dowarn & G_WARN_ON;

    return ckwarn_common(w);
}

/* implements the ckWARN?_d macro */

bool
Perl_ckwarn_d(pTHX_ U32 w)
{
    dVAR;
    /* If lexical warnings have not been set then default classes warn.  */
    if (isLEXWARN_off)
        return TRUE;

    return ckwarn_common(w);
}

static bool
S_ckwarn_common(pTHX_ U32 w)
{
    if (PL_curcop->cop_warnings == pWARN_ALL)
        return TRUE;

    if (PL_curcop->cop_warnings == pWARN_NONE)
        return FALSE;

    /* Check the assumption that at least the first slot is non-zero.  */
    assert(unpackWARN1(w));

    /* Check the assumption that it is valid to stop as soon as a zero slot is
       seen.  */
    if (!unpackWARN2(w)) {
        assert(!unpackWARN3(w));
        assert(!unpackWARN4(w));
    } else if (!unpackWARN3(w)) {
        assert(!unpackWARN4(w));
    }
        
    /* Right, dealt with all the special cases, which are implemented as non-
       pointers, so there is a pointer to a real warnings mask.  */
    do {
        if (isWARN_on(PL_curcop->cop_warnings, unpackWARN1(w)))
            return TRUE;
    } while (w >>= WARNshift);

    return FALSE;
}

/* Set buffer=NULL to get a new one.  */
STRLEN *
Perl_new_warnings_bitfield(pTHX_ STRLEN *buffer, const char *const bits,
                           STRLEN size) {
    const MEM_SIZE len_wanted =
        sizeof(STRLEN) + (size > WARNsize ? size : WARNsize);
    PERL_UNUSED_CONTEXT;
    PERL_ARGS_ASSERT_NEW_WARNINGS_BITFIELD;

    buffer = (STRLEN*)
        (specialWARN(buffer) ?
         PerlMemShared_malloc(len_wanted) :
         PerlMemShared_realloc(buffer, len_wanted));
    buffer[0] = size;
    Copy(bits, (buffer + 1), size, char);
    if (size < WARNsize)
        Zero((char *)(buffer + 1) + size, WARNsize - size, char);
    return buffer;
}

/* since we've already done strlen() for both nam and val
 * we can use that info to make things faster than
 * sprintf(s, "%s=%s", nam, val)
 */
#define my_setenv_format(s, nam, nlen, val, vlen) \
   Copy(nam, s, nlen, char); \
   *(s+nlen) = '='; \
   Copy(val, s+(nlen+1), vlen, char); \
   *(s+(nlen+1+vlen)) = '\0'

#ifdef USE_ENVIRON_ARRAY
       /* VMS' my_setenv() is in vms.c */
#if !defined(WIN32) && !defined(NETWARE)
void
Perl_my_setenv(pTHX_ const char *nam, const char *val)
{
  dVAR;
#ifdef USE_ITHREADS
  /* only parent thread can modify process environment */
  if (PL_curinterp == aTHX)
#endif
  {
#ifndef PERL_USE_SAFE_PUTENV
    if (!PL_use_safe_putenv) {
    /* most putenv()s leak, so we manipulate environ directly */
    I32 i;
    const I32 len = strlen(nam);
    int nlen, vlen;

    /* where does it go? */
    for (i = 0; environ[i]; i++) {
        if (strnEQ(environ[i],nam,len) && environ[i][len] == '=')
            break;
    }

    if (environ == PL_origenviron) {   /* need we copy environment? */
       I32 j;
       I32 max;
       char **tmpenv;

       max = i;
       while (environ[max])
           max++;
       tmpenv = (char**)safesysmalloc((max+2) * sizeof(char*));
       for (j=0; j<max; j++) {         /* copy environment */
           const int len = strlen(environ[j]);
           tmpenv[j] = (char*)safesysmalloc((len+1)*sizeof(char));
           Copy(environ[j], tmpenv[j], len+1, char);
       }
       tmpenv[max] = NULL;
       environ = tmpenv;               /* tell exec where it is now */
    }
    if (!val) {
       safesysfree(environ[i]);
       while (environ[i]) {
           environ[i] = environ[i+1];
           i++;
        }
       return;
    }
    if (!environ[i]) {                 /* does not exist yet */
       environ = (char**)safesysrealloc(environ, (i+2) * sizeof(char*));
       environ[i+1] = NULL;    /* make sure it's null terminated */
    }
    else
       safesysfree(environ[i]);
       nlen = strlen(nam);
       vlen = strlen(val);

       environ[i] = (char*)safesysmalloc((nlen+vlen+2) * sizeof(char));
       /* all that work just for this */
       my_setenv_format(environ[i], nam, nlen, val, vlen);
    } else {
# endif
#   if defined(__CYGWIN__)|| defined(__SYMBIAN32__) || defined(__riscos__)
#       if defined(HAS_UNSETENV)
        if (val == NULL) {
            (void)unsetenv(nam);
        } else {
            (void)setenv(nam, val, 1);
        }
#       else /* ! HAS_UNSETENV */
        (void)setenv(nam, val, 1);
#       endif /* HAS_UNSETENV */
#   else
#       if defined(HAS_UNSETENV)
        if (val == NULL) {
            if (environ) /* old glibc can crash with null environ */
                (void)unsetenv(nam);
        } else {
            const int nlen = strlen(nam);
            const int vlen = strlen(val);
            char * const new_env =
                (char*)safesysmalloc((nlen + vlen + 2) * sizeof(char));
            my_setenv_format(new_env, nam, nlen, val, vlen);
            (void)putenv(new_env);
        }
#       else /* ! HAS_UNSETENV */
        char *new_env;
        const int nlen = strlen(nam);
        int vlen;
        if (!val) {
           val = "";
        }
        vlen = strlen(val);
        new_env = (char*)safesysmalloc((nlen + vlen + 2) * sizeof(char));
        /* all that work just for this */
        my_setenv_format(new_env, nam, nlen, val, vlen);
        (void)putenv(new_env);
#       endif /* HAS_UNSETENV */
#   endif /* __CYGWIN__ */
#ifndef PERL_USE_SAFE_PUTENV
    }
#endif
  }
}

#else /* WIN32 || NETWARE */

void
Perl_my_setenv(pTHX_ const char *nam, const char *val)
{
    dVAR;
    char *envstr;
    const int nlen = strlen(nam);
    int vlen;

    if (!val) {
       val = "";
    }
    vlen = strlen(val);
    Newx(envstr, nlen+vlen+2, char);
    my_setenv_format(envstr, nam, nlen, val, vlen);
    (void)PerlEnv_putenv(envstr);
    Safefree(envstr);
}

#endif /* WIN32 || NETWARE */

#endif /* !VMS */

#ifdef UNLINK_ALL_VERSIONS
I32
Perl_unlnk(pTHX_ const char *f) /* unlink all versions of a file */
{
    I32 retries = 0;

    PERL_ARGS_ASSERT_UNLNK;

    while (PerlLIO_unlink(f) >= 0)
        retries++;
    return retries ? 0 : -1;
}
#endif

/* this is a drop-in replacement for bcopy() */
#if (!defined(HAS_MEMCPY) && !defined(HAS_BCOPY)) || (!defined(HAS_MEMMOVE) && !defined(HAS_SAFE_MEMCPY) && !defined(HAS_SAFE_BCOPY))
char *
Perl_my_bcopy(const char *from, char *to, I32 len)
{
    char * const retval = to;

    PERL_ARGS_ASSERT_MY_BCOPY;

    assert(len >= 0);

    if (from - to >= 0) {
        while (len--)
            *to++ = *from++;
    }
    else {
        to += len;
        from += len;
        while (len--)
            *(--to) = *(--from);
    }
    return retval;
}
#endif

/* this is a drop-in replacement for memset() */
#ifndef HAS_MEMSET
void *
Perl_my_memset(char *loc, I32 ch, I32 len)
{
    char * const retval = loc;

    PERL_ARGS_ASSERT_MY_MEMSET;

    assert(len >= 0);

    while (len--)
        *loc++ = ch;
    return retval;
}
#endif

/* this is a drop-in replacement for bzero() */
#if !defined(HAS_BZERO) && !defined(HAS_MEMSET)
char *
Perl_my_bzero(char *loc, I32 len)
{
    char * const retval = loc;

    PERL_ARGS_ASSERT_MY_BZERO;

    assert(len >= 0);

    while (len--)
        *loc++ = 0;
    return retval;
}
#endif

/* this is a drop-in replacement for memcmp() */
#if !defined(HAS_MEMCMP) || !defined(HAS_SANE_MEMCMP)
I32
Perl_my_memcmp(const char *s1, const char *s2, I32 len)
{
    const U8 *a = (const U8 *)s1;
    const U8 *b = (const U8 *)s2;
    I32 tmp;

    PERL_ARGS_ASSERT_MY_MEMCMP;

    assert(len >= 0);

    while (len--) {
        if ((tmp = *a++ - *b++))
            return tmp;
    }
    return 0;
}
#endif /* !HAS_MEMCMP || !HAS_SANE_MEMCMP */

#ifndef HAS_VPRINTF
/* This vsprintf replacement should generally never get used, since
   vsprintf was available in both System V and BSD 2.11.  (There may
   be some cross-compilation or embedded set-ups where it is needed,
   however.)

   If you encounter a problem in this function, it's probably a symptom
   that Configure failed to detect your system's vprintf() function.
   See the section on "item vsprintf" in the INSTALL file.

   This version may compile on systems with BSD-ish <stdio.h>,
   but probably won't on others.
*/

#ifdef USE_CHAR_VSPRINTF
char *
#else
int
#endif
vsprintf(char *dest, const char *pat, void *args)
{
    FILE fakebuf;

#if defined(STDIO_PTR_LVALUE) && defined(STDIO_CNT_LVALUE)
    FILE_ptr(&fakebuf) = (STDCHAR *) dest;
    FILE_cnt(&fakebuf) = 32767;
#else
    /* These probably won't compile -- If you really need
       this, you'll have to figure out some other method. */
    fakebuf._ptr = dest;
    fakebuf._cnt = 32767;
#endif
#ifndef _IOSTRG
#define _IOSTRG 0
#endif
    fakebuf._flag = _IOWRT|_IOSTRG;
    _doprnt(pat, args, &fakebuf);       /* what a kludge */
#if defined(STDIO_PTR_LVALUE)
    *(FILE_ptr(&fakebuf)++) = '\0';
#else
    /* PerlIO has probably #defined away fputc, but we want it here. */
#  ifdef fputc
#    undef fputc  /* XXX Should really restore it later */
#  endif
    (void)fputc('\0', &fakebuf);
#endif
#ifdef USE_CHAR_VSPRINTF
    return(dest);
#else
    return 0;           /* perl doesn't use return value */
#endif
}

#endif /* HAS_VPRINTF */

PerlIO *
Perl_my_popen_list(pTHX_ const char *mode, int n, SV **args)
{
#if (!defined(DOSISH) || defined(HAS_FORK) || defined(AMIGAOS)) && !defined(OS2) && !defined(VMS) && !defined(NETWARE) && !defined(__LIBCATAMOUNT__)
    dVAR;
    int p[2];
    I32 This, that;
    Pid_t pid;
    SV *sv;
    I32 did_pipes = 0;
    int pp[2];

    PERL_ARGS_ASSERT_MY_POPEN_LIST;

    PERL_FLUSHALL_FOR_CHILD;
    This = (*mode == 'w');
    that = !This;
    if (TAINTING_get) {
        taint_env();
        taint_proper("Insecure %s%s", "EXEC");
    }
    if (PerlProc_pipe(p) < 0)
        return NULL;
    /* Try for another pipe pair for error return */
    if (PerlProc_pipe(pp) >= 0)
        did_pipes = 1;
    while ((pid = PerlProc_fork()) < 0) {
        if (errno != EAGAIN) {
            PerlLIO_close(p[This]);
            PerlLIO_close(p[that]);
            if (did_pipes) {
                PerlLIO_close(pp[0]);
                PerlLIO_close(pp[1]);
            }
            return NULL;
        }
        Perl_ck_warner(aTHX_ packWARN(WARN_PIPE), "Can't fork, trying again in 5 seconds");
        sleep(5);
    }
    if (pid == 0) {
        /* Child */
#undef THIS
#undef THAT
#define THIS that
#define THAT This
        /* Close parent's end of error status pipe (if any) */
        if (did_pipes) {
            PerlLIO_close(pp[0]);
#if defined(HAS_FCNTL) && defined(F_SETFD)
            /* Close error pipe automatically if exec works */
            fcntl(pp[1], F_SETFD, FD_CLOEXEC);
#endif
        }
        /* Now dup our end of _the_ pipe to right position */
        if (p[THIS] != (*mode == 'r')) {
            PerlLIO_dup2(p[THIS], *mode == 'r');
            PerlLIO_close(p[THIS]);
            if (p[THAT] != (*mode == 'r'))      /* if dup2() didn't close it */
                PerlLIO_close(p[THAT]); /* close parent's end of _the_ pipe */
        }
        else
            PerlLIO_close(p[THAT]);     /* close parent's end of _the_ pipe */
#if !defined(HAS_FCNTL) || !defined(F_SETFD)
        /* No automatic close - do it by hand */
#  ifndef NOFILE
#  define NOFILE 20
#  endif
        {
            int fd;

            for (fd = PL_maxsysfd + 1; fd < NOFILE; fd++) {
                if (fd != pp[1])
                    PerlLIO_close(fd);
            }
        }
#endif
        do_aexec5(NULL, args-1, args-1+n, pp[1], did_pipes);
        PerlProc__exit(1);
#undef THIS
#undef THAT
    }
    /* Parent */
    do_execfree();      /* free any memory malloced by child on fork */
    if (did_pipes)
        PerlLIO_close(pp[1]);
    /* Keep the lower of the two fd numbers */
    if (p[that] < p[This]) {
        PerlLIO_dup2(p[This], p[that]);
        PerlLIO_close(p[This]);
        p[This] = p[that];
    }
    else
        PerlLIO_close(p[that]);         /* close child's end of pipe */

    sv = *av_fetch(PL_fdpid,p[This],TRUE);
    SvUPGRADE(sv,SVt_IV);
    SvIV_set(sv, pid);
    PL_forkprocess = pid;
    /* If we managed to get status pipe check for exec fail */
    if (did_pipes && pid > 0) {
        int errkid;
        unsigned n = 0;
        SSize_t n1;

        while (n < sizeof(int)) {
            n1 = PerlLIO_read(pp[0],
                              (void*)(((char*)&errkid)+n),
                              (sizeof(int)) - n);
            if (n1 <= 0)
                break;
            n += n1;
        }
        PerlLIO_close(pp[0]);
        did_pipes = 0;
        if (n) {                        /* Error */
            int pid2, status;
            PerlLIO_close(p[This]);
            if (n != sizeof(int))
                Perl_croak(aTHX_ "panic: kid popen errno read, n=%u", n);
            do {
                pid2 = wait4pid(pid, &status, 0);
            } while (pid2 == -1 && errno == EINTR);
            errno = errkid;             /* Propagate errno from kid */
            return NULL;
        }
    }
    if (did_pipes)
         PerlLIO_close(pp[0]);
    return PerlIO_fdopen(p[This], mode);
#else
#  ifdef OS2    /* Same, without fork()ing and all extra overhead... */
    return my_syspopen4(aTHX_ NULL, mode, n, args);
#  else
    Perl_croak(aTHX_ "List form of piped open not implemented");
    return (PerlIO *) NULL;
#  endif
#endif
}

    /* VMS' my_popen() is in VMS.c, same with OS/2. */
#if (!defined(DOSISH) || defined(HAS_FORK) || defined(AMIGAOS)) && !defined(VMS) && !defined(__LIBCATAMOUNT__)
PerlIO *
Perl_my_popen(pTHX_ const char *cmd, const char *mode)
{
    dVAR;
    int p[2];
    I32 This, that;
    Pid_t pid;
    SV *sv;
    const I32 doexec = !(*cmd == '-' && cmd[1] == '\0');
    I32 did_pipes = 0;
    int pp[2];

    PERL_ARGS_ASSERT_MY_POPEN;

    PERL_FLUSHALL_FOR_CHILD;
#ifdef OS2
    if (doexec) {
        return my_syspopen(aTHX_ cmd,mode);
    }
#endif
    This = (*mode == 'w');
    that = !This;
    if (doexec && TAINTING_get) {
        taint_env();
        taint_proper("Insecure %s%s", "EXEC");
    }
    if (PerlProc_pipe(p) < 0)
        return NULL;
    if (doexec && PerlProc_pipe(pp) >= 0)
        did_pipes = 1;
    while ((pid = PerlProc_fork()) < 0) {
        if (errno != EAGAIN) {
            PerlLIO_close(p[This]);
            PerlLIO_close(p[that]);
            if (did_pipes) {
                PerlLIO_close(pp[0]);
                PerlLIO_close(pp[1]);
            }
            if (!doexec)
                Perl_croak(aTHX_ "Can't fork: %s", Strerror(errno));
            return NULL;
        }
        Perl_ck_warner(aTHX_ packWARN(WARN_PIPE), "Can't fork, trying again in 5 seconds");
        sleep(5);
    }
    if (pid == 0) {

#undef THIS
#undef THAT
#define THIS that
#define THAT This
        if (did_pipes) {
            PerlLIO_close(pp[0]);
#if defined(HAS_FCNTL) && defined(F_SETFD)
            fcntl(pp[1], F_SETFD, FD_CLOEXEC);
#endif
        }
        if (p[THIS] != (*mode == 'r')) {
            PerlLIO_dup2(p[THIS], *mode == 'r');
            PerlLIO_close(p[THIS]);
            if (p[THAT] != (*mode == 'r'))      /* if dup2() didn't close it */
                PerlLIO_close(p[THAT]);
        }
        else
            PerlLIO_close(p[THAT]);
#ifndef OS2
        if (doexec) {
#if !defined(HAS_FCNTL) || !defined(F_SETFD)
#ifndef NOFILE
#define NOFILE 20
#endif
            {
                int fd;

                for (fd = PL_maxsysfd + 1; fd < NOFILE; fd++)
                    if (fd != pp[1])
                        PerlLIO_close(fd);
            }
#endif
            /* may or may not use the shell */
            do_exec3(cmd, pp[1], did_pipes);
            PerlProc__exit(1);
        }
#endif  /* defined OS2 */

#ifdef PERLIO_USING_CRLF
   /* Since we circumvent IO layers when we manipulate low-level
      filedescriptors directly, need to manually switch to the
      default, binary, low-level mode; see PerlIOBuf_open(). */
   PerlLIO_setmode((*mode == 'r'), O_BINARY);
#endif 
        PL_forkprocess = 0;
#ifdef PERL_USES_PL_PIDSTATUS
        hv_clear(PL_pidstatus); /* we have no children */
#endif
        return NULL;
#undef THIS
#undef THAT
    }
    do_execfree();      /* free any memory malloced by child on vfork */
    if (did_pipes)
        PerlLIO_close(pp[1]);
    if (p[that] < p[This]) {
        PerlLIO_dup2(p[This], p[that]);
        PerlLIO_close(p[This]);
        p[This] = p[that];
    }
    else
        PerlLIO_close(p[that]);

    sv = *av_fetch(PL_fdpid,p[This],TRUE);
    SvUPGRADE(sv,SVt_IV);
    SvIV_set(sv, pid);
    PL_forkprocess = pid;
    if (did_pipes && pid > 0) {
        int errkid;
        unsigned n = 0;
        SSize_t n1;

        while (n < sizeof(int)) {
            n1 = PerlLIO_read(pp[0],
                              (void*)(((char*)&errkid)+n),
                              (sizeof(int)) - n);
            if (n1 <= 0)
                break;
            n += n1;
        }
        PerlLIO_close(pp[0]);
        did_pipes = 0;
        if (n) {                        /* Error */
            int pid2, status;
            PerlLIO_close(p[This]);
            if (n != sizeof(int))
                Perl_croak(aTHX_ "panic: kid popen errno read, n=%u", n);
            do {
                pid2 = wait4pid(pid, &status, 0);
            } while (pid2 == -1 && errno == EINTR);
            errno = errkid;             /* Propagate errno from kid */
            return NULL;
        }
    }
    if (did_pipes)
         PerlLIO_close(pp[0]);
    return PerlIO_fdopen(p[This], mode);
}
#else
#if defined(DJGPP)
FILE *djgpp_popen();
PerlIO *
Perl_my_popen(pTHX_ const char *cmd, const char *mode)
{
    PERL_FLUSHALL_FOR_CHILD;
    /* Call system's popen() to get a FILE *, then import it.
       used 0 for 2nd parameter to PerlIO_importFILE;
       apparently not used
    */
    return PerlIO_importFILE(djgpp_popen(cmd, mode), 0);
}
#else
#if defined(__LIBCATAMOUNT__)
PerlIO *
Perl_my_popen(pTHX_ const char *cmd, const char *mode)
{
    return NULL;
}
#endif
#endif

#endif /* !DOSISH */

/* this is called in parent before the fork() */
void
Perl_atfork_lock(void)
{
   dVAR;
#if defined(USE_ITHREADS)
    /* locks must be held in locking order (if any) */
#  ifdef USE_PERLIO
    MUTEX_LOCK(&PL_perlio_mutex);
#  endif
#  ifdef MYMALLOC
    MUTEX_LOCK(&PL_malloc_mutex);
#  endif
    OP_REFCNT_LOCK;
#endif
}

/* this is called in both parent and child after the fork() */
void
Perl_atfork_unlock(void)
{
    dVAR;
#if defined(USE_ITHREADS)
    /* locks must be released in same order as in atfork_lock() */
#  ifdef USE_PERLIO
    MUTEX_UNLOCK(&PL_perlio_mutex);
#  endif
#  ifdef MYMALLOC
    MUTEX_UNLOCK(&PL_malloc_mutex);
#  endif
    OP_REFCNT_UNLOCK;
#endif
}

Pid_t
Perl_my_fork(void)
{
#if defined(HAS_FORK)
    Pid_t pid;
#if defined(USE_ITHREADS) && !defined(HAS_PTHREAD_ATFORK)
    atfork_lock();
    pid = fork();
    atfork_unlock();
#else
    /* atfork_lock() and atfork_unlock() are installed as pthread_atfork()
     * handlers elsewhere in the code */
    pid = fork();
#endif
    return pid;
#else
    /* this "canna happen" since nothing should be calling here if !HAS_FORK */
    Perl_croak_nocontext("fork() not available");
    return 0;
#endif /* HAS_FORK */
}

#ifdef DUMP_FDS
void
Perl_dump_fds(pTHX_ const char *const s)
{
    int fd;
    Stat_t tmpstatbuf;

    PERL_ARGS_ASSERT_DUMP_FDS;

    PerlIO_printf(Perl_debug_log,"%s", s);
    for (fd = 0; fd < 32; fd++) {
        if (PerlLIO_fstat(fd,&tmpstatbuf) >= 0)
            PerlIO_printf(Perl_debug_log," %d",fd);
    }
    PerlIO_printf(Perl_debug_log,"\n");
    return;
}
#endif  /* DUMP_FDS */

#ifndef HAS_DUP2
int
dup2(int oldfd, int newfd)
{
#if defined(HAS_FCNTL) && defined(F_DUPFD)
    if (oldfd == newfd)
        return oldfd;
    PerlLIO_close(newfd);
    return fcntl(oldfd, F_DUPFD, newfd);
#else
#define DUP2_MAX_FDS 256
    int fdtmp[DUP2_MAX_FDS];
    I32 fdx = 0;
    int fd;

    if (oldfd == newfd)
        return oldfd;
    PerlLIO_close(newfd);
    /* good enough for low fd's... */
    while ((fd = PerlLIO_dup(oldfd)) != newfd && fd >= 0) {
        if (fdx >= DUP2_MAX_FDS) {
            PerlLIO_close(fd);
            fd = -1;
            break;
        }
        fdtmp[fdx++] = fd;
    }
    while (fdx > 0)
        PerlLIO_close(fdtmp[--fdx]);
    return fd;
#endif
}
#endif

#ifndef PERL_MICRO
#ifdef HAS_SIGACTION

Sighandler_t
Perl_rsignal(pTHX_ int signo, Sighandler_t handler)
{
    dVAR;
    struct sigaction act, oact;

#ifdef USE_ITHREADS
    /* only "parent" interpreter can diddle signals */
    if (PL_curinterp != aTHX)
        return (Sighandler_t) SIG_ERR;
#endif

    act.sa_handler = (void(*)(int))handler;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
#ifdef SA_RESTART
    if (PL_signals & PERL_SIGNALS_UNSAFE_FLAG)
        act.sa_flags |= SA_RESTART;     /* SVR4, 4.3+BSD */
#endif
#if defined(SA_NOCLDWAIT) && !defined(BSDish) /* See [perl #18849] */
    if (signo == SIGCHLD && handler == (Sighandler_t) SIG_IGN)
        act.sa_flags |= SA_NOCLDWAIT;
#endif
    if (sigaction(signo, &act, &oact) == -1)
        return (Sighandler_t) SIG_ERR;
    else
        return (Sighandler_t) oact.sa_handler;
}

Sighandler_t
Perl_rsignal_state(pTHX_ int signo)
{
    struct sigaction oact;
    PERL_UNUSED_CONTEXT;

    if (sigaction(signo, (struct sigaction *)NULL, &oact) == -1)
        return (Sighandler_t) SIG_ERR;
    else
        return (Sighandler_t) oact.sa_handler;
}

int
Perl_rsignal_save(pTHX_ int signo, Sighandler_t handler, Sigsave_t *save)
{
    dVAR;
    struct sigaction act;

    PERL_ARGS_ASSERT_RSIGNAL_SAVE;

#ifdef USE_ITHREADS
    /* only "parent" interpreter can diddle signals */
    if (PL_curinterp != aTHX)
        return -1;
#endif

    act.sa_handler = (void(*)(int))handler;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
#ifdef SA_RESTART
    if (PL_signals & PERL_SIGNALS_UNSAFE_FLAG)
        act.sa_flags |= SA_RESTART;     /* SVR4, 4.3+BSD */
#endif
#if defined(SA_NOCLDWAIT) && !defined(BSDish) /* See [perl #18849] */
    if (signo == SIGCHLD && handler == (Sighandler_t) SIG_IGN)
        act.sa_flags |= SA_NOCLDWAIT;
#endif
    return sigaction(signo, &act, save);
}

int
Perl_rsignal_restore(pTHX_ int signo, Sigsave_t *save)
{
    dVAR;
#ifdef USE_ITHREADS
    /* only "parent" interpreter can diddle signals */
    if (PL_curinterp != aTHX)
        return -1;
#endif

    return sigaction(signo, save, (struct sigaction *)NULL);
}

#else /* !HAS_SIGACTION */

Sighandler_t
Perl_rsignal(pTHX_ int signo, Sighandler_t handler)
{
#if defined(USE_ITHREADS) && !defined(WIN32)
    /* only "parent" interpreter can diddle signals */
    if (PL_curinterp != aTHX)
        return (Sighandler_t) SIG_ERR;
#endif

    return PerlProc_signal(signo, handler);
}

static Signal_t
sig_trap(int signo)
{
    dVAR;
    PL_sig_trapped++;
}

Sighandler_t
Perl_rsignal_state(pTHX_ int signo)
{
    dVAR;
    Sighandler_t oldsig;

#if defined(USE_ITHREADS) && !defined(WIN32)
    /* only "parent" interpreter can diddle signals */
    if (PL_curinterp != aTHX)
        return (Sighandler_t) SIG_ERR;
#endif

    PL_sig_trapped = 0;
    oldsig = PerlProc_signal(signo, sig_trap);
    PerlProc_signal(signo, oldsig);
    if (PL_sig_trapped)
        PerlProc_kill(PerlProc_getpid(), signo);
    return oldsig;
}

int
Perl_rsignal_save(pTHX_ int signo, Sighandler_t handler, Sigsave_t *save)
{
#if defined(USE_ITHREADS) && !defined(WIN32)
    /* only "parent" interpreter can diddle signals */
    if (PL_curinterp != aTHX)
        return -1;
#endif
    *save = PerlProc_signal(signo, handler);
    return (*save == (Sighandler_t) SIG_ERR) ? -1 : 0;
}

int
Perl_rsignal_restore(pTHX_ int signo, Sigsave_t *save)
{
#if defined(USE_ITHREADS) && !defined(WIN32)
    /* only "parent" interpreter can diddle signals */
    if (PL_curinterp != aTHX)
        return -1;
#endif
    return (PerlProc_signal(signo, *save) == (Sighandler_t) SIG_ERR) ? -1 : 0;
}

#endif /* !HAS_SIGACTION */
#endif /* !PERL_MICRO */

    /* VMS' my_pclose() is in VMS.c; same with OS/2 */
#if (!defined(DOSISH) || defined(HAS_FORK) || defined(AMIGAOS)) && !defined(VMS) && !defined(__LIBCATAMOUNT__)
I32
Perl_my_pclose(pTHX_ PerlIO *ptr)
{
    dVAR;
    int status;
    SV **svp;
    Pid_t pid;
    Pid_t pid2 = 0;
    bool close_failed;
    dSAVEDERRNO;
    const int fd = PerlIO_fileno(ptr);

#ifdef USE_PERLIO
    /* Find out whether the refcount is low enough for us to wait for the
       child proc without blocking. */
    const bool should_wait = PerlIOUnix_refcnt(fd) == 1;
#else
    const bool should_wait = 1;
#endif

    svp = av_fetch(PL_fdpid,fd,TRUE);
    pid = (SvTYPE(*svp) == SVt_IV) ? SvIVX(*svp) : -1;
    SvREFCNT_dec(*svp);
    *svp = &PL_sv_undef;
#ifdef OS2
    if (pid == -1) {                    /* Opened by popen. */
        return my_syspclose(ptr);
    }
#endif
    close_failed = (PerlIO_close(ptr) == EOF);
    SAVE_ERRNO;
    if (should_wait) do {
        pid2 = wait4pid(pid, &status, 0);
    } while (pid2 == -1 && errno == EINTR);
    if (close_failed) {
        RESTORE_ERRNO;
        return -1;
    }
    return(
      should_wait
       ? pid2 < 0 ? pid2 : status == 0 ? 0 : (errno = 0, status)
       : 0
    );
}
#else
#if defined(__LIBCATAMOUNT__)
I32
Perl_my_pclose(pTHX_ PerlIO *ptr)
{
    return -1;
}
#endif
#endif /* !DOSISH */

#if  (!defined(DOSISH) || defined(OS2) || defined(WIN32) || defined(NETWARE)) && !defined(__LIBCATAMOUNT__)
I32
Perl_wait4pid(pTHX_ Pid_t pid, int *statusp, int flags)
{
    dVAR;
    I32 result = 0;
    PERL_ARGS_ASSERT_WAIT4PID;
    if (!pid)
        return -1;
#ifdef PERL_USES_PL_PIDSTATUS
    {
        if (pid > 0) {
            /* The keys in PL_pidstatus are now the raw 4 (or 8) bytes of the
               pid, rather than a string form.  */
            SV * const * const svp = hv_fetch(PL_pidstatus,(const char*) &pid,sizeof(Pid_t),FALSE);
            if (svp && *svp != &PL_sv_undef) {
                *statusp = SvIVX(*svp);
                (void)hv_delete(PL_pidstatus,(const char*) &pid,sizeof(Pid_t),
                                G_DISCARD);
                return pid;
            }
        }
        else {
            HE *entry;

            hv_iterinit(PL_pidstatus);
            if ((entry = hv_iternext(PL_pidstatus))) {
                SV * const sv = hv_iterval(PL_pidstatus,entry);
                I32 len;
                const char * const spid = hv_iterkey(entry,&len);

                assert (len == sizeof(Pid_t));
                memcpy((char *)&pid, spid, len);
                *statusp = SvIVX(sv);
                /* The hash iterator is currently on this entry, so simply
                   calling hv_delete would trigger the lazy delete, which on
                   aggregate does more work, beacuse next call to hv_iterinit()
                   would spot the flag, and have to call the delete routine,
                   while in the meantime any new entries can't re-use that
                   memory.  */
                hv_iterinit(PL_pidstatus);
                (void)hv_delete(PL_pidstatus,spid,len,G_DISCARD);
                return pid;
            }
        }
    }
#endif
#ifdef HAS_WAITPID
#  ifdef HAS_WAITPID_RUNTIME
    if (!HAS_WAITPID_RUNTIME)
        goto hard_way;
#  endif
    result = PerlProc_waitpid(pid,statusp,flags);
    goto finish;
#endif
#if !defined(HAS_WAITPID) && defined(HAS_WAIT4)
    result = wait4((pid==-1)?0:pid,statusp,flags,NULL);
    goto finish;
#endif
#ifdef PERL_USES_PL_PIDSTATUS
#if defined(HAS_WAITPID) && defined(HAS_WAITPID_RUNTIME)
  hard_way:
#endif
    {
        if (flags)
            Perl_croak(aTHX_ "Can't do waitpid with flags");
        else {
            while ((result = PerlProc_wait(statusp)) != pid && pid > 0 && result >= 0)
                pidgone(result,*statusp);
            if (result < 0)
                *statusp = -1;
        }
    }
#endif
#if defined(HAS_WAITPID) || defined(HAS_WAIT4)
  finish:
#endif
    if (result < 0 && errno == EINTR) {
        PERL_ASYNC_CHECK();
        errno = EINTR; /* reset in case a signal handler changed $! */
    }
    return result;
}
#endif /* !DOSISH || OS2 || WIN32 || NETWARE */

#ifdef PERL_USES_PL_PIDSTATUS
void
S_pidgone(pTHX_ Pid_t pid, int status)
{
    SV *sv;

    sv = *hv_fetch(PL_pidstatus,(const char*)&pid,sizeof(Pid_t),TRUE);
    SvUPGRADE(sv,SVt_IV);
    SvIV_set(sv, status);
    return;
}
#endif

#if defined(OS2)
int pclose();
#ifdef HAS_FORK
int                                     /* Cannot prototype with I32
                                           in os2ish.h. */
my_syspclose(PerlIO *ptr)
#else
I32
Perl_my_pclose(pTHX_ PerlIO *ptr)
#endif
{
    /* Needs work for PerlIO ! */
    FILE * const f = PerlIO_findFILE(ptr);
    const I32 result = pclose(f);
    PerlIO_releaseFILE(ptr,f);
    return result;
}
#endif

#if defined(DJGPP)
int djgpp_pclose();
I32
Perl_my_pclose(pTHX_ PerlIO *ptr)
{
    /* Needs work for PerlIO ! */
    FILE * const f = PerlIO_findFILE(ptr);
    I32 result = djgpp_pclose(f);
    result = (result << 8) & 0xff00;
    PerlIO_releaseFILE(ptr,f);
    return result;
}
#endif

#define PERL_REPEATCPY_LINEAR 4
void
Perl_repeatcpy(char *to, const char *from, I32 len, IV count)
{
    PERL_ARGS_ASSERT_REPEATCPY;

    assert(len >= 0);

    if (count < 0)
        croak_memory_wrap();

    if (len == 1)
        memset(to, *from, count);
    else if (count) {
        char *p = to;
        IV items, linear, half;

        linear = count < PERL_REPEATCPY_LINEAR ? count : PERL_REPEATCPY_LINEAR;
        for (items = 0; items < linear; ++items) {
            const char *q = from;
            IV todo;
            for (todo = len; todo > 0; todo--)
                *p++ = *q++;
        }

        half = count / 2;
        while (items <= half) {
            IV size = items * len;
            memcpy(p, to, size);
            p     += size;
            items *= 2;
        }

        if (count > items)
            memcpy(p, to, (count - items) * len);
    }
}

#ifndef HAS_RENAME
I32
Perl_same_dirent(pTHX_ const char *a, const char *b)
{
    char *fa = strrchr(a,'/');
    char *fb = strrchr(b,'/');
    Stat_t tmpstatbuf1;
    Stat_t tmpstatbuf2;
    SV * const tmpsv = sv_newmortal();

    PERL_ARGS_ASSERT_SAME_DIRENT;

    if (fa)
        fa++;
    else
        fa = a;
    if (fb)
        fb++;
    else
        fb = b;
    if (strNE(a,b))
        return FALSE;
    if (fa == a)
        sv_setpvs(tmpsv, ".");
    else
        sv_setpvn(tmpsv, a, fa - a);
    if (PerlLIO_stat(SvPVX_const(tmpsv), &tmpstatbuf1) < 0)
        return FALSE;
    if (fb == b)
        sv_setpvs(tmpsv, ".");
    else
        sv_setpvn(tmpsv, b, fb - b);
    if (PerlLIO_stat(SvPVX_const(tmpsv), &tmpstatbuf2) < 0)
        return FALSE;
    return tmpstatbuf1.st_dev == tmpstatbuf2.st_dev &&
           tmpstatbuf1.st_ino == tmpstatbuf2.st_ino;
}
#endif /* !HAS_RENAME */

char*
Perl_find_script(pTHX_ const char *scriptname, bool dosearch,
                 const char *const *const search_ext, I32 flags)
{
    dVAR;
    const char *xfound = NULL;
    char *xfailed = NULL;
    char tmpbuf[MAXPATHLEN];
    char *s;
    I32 len = 0;
    int retval;
    char *bufend;
#if defined(DOSISH) && !defined(OS2)
#  define SEARCH_EXTS ".bat", ".cmd", NULL
#  define MAX_EXT_LEN 4
#endif
#ifdef OS2
#  define SEARCH_EXTS ".cmd", ".btm", ".bat", ".pl", NULL
#  define MAX_EXT_LEN 4
#endif
#ifdef VMS
#  define SEARCH_EXTS ".pl", ".com", NULL
#  define MAX_EXT_LEN 4
#endif
    /* additional extensions to try in each dir if scriptname not found */
#ifdef SEARCH_EXTS
    static const char *const exts[] = { SEARCH_EXTS };
    const char *const *const ext = search_ext ? search_ext : exts;
    int extidx = 0, i = 0;
    const char *curext = NULL;
#else
    PERL_UNUSED_ARG(search_ext);
#  define MAX_EXT_LEN 0
#endif

    PERL_ARGS_ASSERT_FIND_SCRIPT;

    /*
     * If dosearch is true and if scriptname does not contain path
     * delimiters, search the PATH for scriptname.
     *
     * If SEARCH_EXTS is also defined, will look for each
     * scriptname{SEARCH_EXTS} whenever scriptname is not found
     * while searching the PATH.
     *
     * Assuming SEARCH_EXTS is C<".foo",".bar",NULL>, PATH search
     * proceeds as follows:
     *   If DOSISH or VMSISH:
     *     + look for ./scriptname{,.foo,.bar}
     *     + search the PATH for scriptname{,.foo,.bar}
     *
     *   If !DOSISH:
     *     + look *only* in the PATH for scriptname{,.foo,.bar} (note
     *       this will not look in '.' if it's not in the PATH)
     */
    tmpbuf[0] = '\0';

#ifdef VMS
#  ifdef ALWAYS_DEFTYPES
    len = strlen(scriptname);
    if (!(len == 1 && *scriptname == '-') && scriptname[len-1] != ':') {
        int idx = 0, deftypes = 1;
        bool seen_dot = 1;

        const int hasdir = !dosearch || (strpbrk(scriptname,":[</") != NULL);
#  else
    if (dosearch) {
        int idx = 0, deftypes = 1;
        bool seen_dot = 1;

        const int hasdir = (strpbrk(scriptname,":[</") != NULL);
#  endif
        /* The first time through, just add SEARCH_EXTS to whatever we
         * already have, so we can check for default file types. */
        while (deftypes ||
               (!hasdir && my_trnlnm("DCL$PATH",tmpbuf,idx++)) )
        {
            if (deftypes) {
                deftypes = 0;
                *tmpbuf = '\0';
            }
            if ((strlen(tmpbuf) + strlen(scriptname)
                 + MAX_EXT_LEN) >= sizeof tmpbuf)
                continue;       /* don't search dir with too-long name */
            my_strlcat(tmpbuf, scriptname, sizeof(tmpbuf));
#else  /* !VMS */

#ifdef DOSISH
    if (strEQ(scriptname, "-"))
        dosearch = 0;
    if (dosearch) {             /* Look in '.' first. */
        const char *cur = scriptname;
#ifdef SEARCH_EXTS
        if ((curext = strrchr(scriptname,'.'))) /* possible current ext */
            while (ext[i])
                if (strEQ(ext[i++],curext)) {
                    extidx = -1;                /* already has an ext */
                    break;
                }
        do {
#endif
            DEBUG_p(PerlIO_printf(Perl_debug_log,
                                  "Looking for %s\n",cur));
            if (PerlLIO_stat(cur,&PL_statbuf) >= 0
                && !S_ISDIR(PL_statbuf.st_mode)) {
                dosearch = 0;
                scriptname = cur;
#ifdef SEARCH_EXTS
                break;
#endif
            }
#ifdef SEARCH_EXTS
            if (cur == scriptname) {
                len = strlen(scriptname);
                if (len+MAX_EXT_LEN+1 >= sizeof(tmpbuf))
                    break;
                my_strlcpy(tmpbuf, scriptname, sizeof(tmpbuf));
                cur = tmpbuf;
            }
        } while (extidx >= 0 && ext[extidx]     /* try an extension? */
                 && my_strlcpy(tmpbuf+len, ext[extidx++], sizeof(tmpbuf) - len));
#endif
    }
#endif

    if (dosearch && !strchr(scriptname, '/')
#ifdef DOSISH
                 && !strchr(scriptname, '\\')
#endif
                 && (s = PerlEnv_getenv("PATH")))
    {
        bool seen_dot = 0;

        bufend = s + strlen(s);
        while (s < bufend) {
#  ifdef DOSISH
            for (len = 0; *s
                    && *s != ';'; len++, s++) {
                if (len < sizeof tmpbuf)
                    tmpbuf[len] = *s;
            }
            if (len < sizeof tmpbuf)
                tmpbuf[len] = '\0';
#  else
            s = delimcpy(tmpbuf, tmpbuf + sizeof tmpbuf, s, bufend,
                        ':',
                        &len);
#  endif
            if (s < bufend)
                s++;
            if (len + 1 + strlen(scriptname) + MAX_EXT_LEN >= sizeof tmpbuf)
                continue;       /* don't search dir with too-long name */
            if (len
#  ifdef DOSISH
                && tmpbuf[len - 1] != '/'
                && tmpbuf[len - 1] != '\\'
#  endif
               )
                tmpbuf[len++] = '/';
            if (len == 2 && tmpbuf[0] == '.')
                seen_dot = 1;
            (void)my_strlcpy(tmpbuf + len, scriptname, sizeof(tmpbuf) - len);
#endif  /* !VMS */

#ifdef SEARCH_EXTS
            len = strlen(tmpbuf);
            if (extidx > 0)     /* reset after previous loop */
                extidx = 0;
            do {
#endif
                DEBUG_p(PerlIO_printf(Perl_debug_log, "Looking for %s\n",tmpbuf));
                retval = PerlLIO_stat(tmpbuf,&PL_statbuf);
                if (S_ISDIR(PL_statbuf.st_mode)) {
                    retval = -1;
                }
#ifdef SEARCH_EXTS
            } while (  retval < 0               /* not there */
                    && extidx>=0 && ext[extidx] /* try an extension? */
                    && my_strlcpy(tmpbuf+len, ext[extidx++], sizeof(tmpbuf) - len)
                );
#endif
            if (retval < 0)
                continue;
            if (S_ISREG(PL_statbuf.st_mode)
                && cando(S_IRUSR,TRUE,&PL_statbuf)
#if !defined(DOSISH)
                && cando(S_IXUSR,TRUE,&PL_statbuf)
#endif
                )
            {
                xfound = tmpbuf;                /* bingo! */
                break;
            }
            if (!xfailed)
                xfailed = savepv(tmpbuf);
        }
#ifndef DOSISH
        if (!xfound && !seen_dot && !xfailed &&
            (PerlLIO_stat(scriptname,&PL_statbuf) < 0
             || S_ISDIR(PL_statbuf.st_mode)))
#endif
            seen_dot = 1;                       /* Disable message. */
        if (!xfound) {
            if (flags & 1) {                    /* do or die? */
                /* diag_listed_as: Can't execute %s */
                Perl_croak(aTHX_ "Can't %s %s%s%s",
                      (xfailed ? "execute" : "find"),
                      (xfailed ? xfailed : scriptname),
                      (xfailed ? "" : " on PATH"),
                      (xfailed || seen_dot) ? "" : ", '.' not in PATH");
            }
            scriptname = NULL;
        }
        Safefree(xfailed);
        scriptname = xfound;
    }
    return (scriptname ? savepv(scriptname) : NULL);
}

#ifndef PERL_GET_CONTEXT_DEFINED

void *
Perl_get_context(void)
{
    dVAR;
#if defined(USE_ITHREADS)
#  ifdef OLD_PTHREADS_API
    pthread_addr_t t;
    int error = pthread_getspecific(PL_thr_key, &t)
    if (error)
        Perl_croak_nocontext("panic: pthread_getspecific, error=%d", error);
    return (void*)t;
#  else
#    ifdef I_MACH_CTHREADS
    return (void*)cthread_data(cthread_self());
#    else
    return (void*)PTHREAD_GETSPECIFIC(PL_thr_key);
#    endif
#  endif
#else
    return (void*)NULL;
#endif
}

void
Perl_set_context(void *t)
{
    dVAR;
    PERL_ARGS_ASSERT_SET_CONTEXT;
#if defined(USE_ITHREADS)
#  ifdef I_MACH_CTHREADS
    cthread_set_data(cthread_self(), t);
#  else
    {
        const int error = pthread_setspecific(PL_thr_key, t);
        if (error)
            Perl_croak_nocontext("panic: pthread_setspecific, error=%d", error);
    }
#  endif
#else
    PERL_UNUSED_ARG(t);
#endif
}

#endif /* !PERL_GET_CONTEXT_DEFINED */

#if defined(PERL_GLOBAL_STRUCT) && !defined(PERL_GLOBAL_STRUCT_PRIVATE)
struct perl_vars *
Perl_GetVars(pTHX)
{
 return &PL_Vars;
}
#endif

char **
Perl_get_op_names(pTHX)
{
    PERL_UNUSED_CONTEXT;
    return (char **)PL_op_name;
}

char **
Perl_get_op_descs(pTHX)
{
    PERL_UNUSED_CONTEXT;
    return (char **)PL_op_desc;
}

const char *
Perl_get_no_modify(pTHX)
{
    PERL_UNUSED_CONTEXT;
    return PL_no_modify;
}

U32 *
Perl_get_opargs(pTHX)
{
    PERL_UNUSED_CONTEXT;
    return (U32 *)PL_opargs;
}

PPADDR_t*
Perl_get_ppaddr(pTHX)
{
    dVAR;
    PERL_UNUSED_CONTEXT;
    return (PPADDR_t*)PL_ppaddr;
}

#ifndef HAS_GETENV_LEN
char *
Perl_getenv_len(pTHX_ const char *env_elem, unsigned long *len)
{
    char * const env_trans = PerlEnv_getenv(env_elem);
    PERL_UNUSED_CONTEXT;
    PERL_ARGS_ASSERT_GETENV_LEN;
    if (env_trans)
        *len = strlen(env_trans);
    return env_trans;
}
#endif


MGVTBL*
Perl_get_vtbl(pTHX_ int vtbl_id)
{
    PERL_UNUSED_CONTEXT;

    return (vtbl_id < 0 || vtbl_id >= magic_vtable_max)
        ? NULL : PL_magic_vtables + vtbl_id;
}

I32
Perl_my_fflush_all(pTHX)
{
#if defined(USE_PERLIO) || defined(FFLUSH_NULL) || defined(USE_SFIO)
    return PerlIO_flush(NULL);
#else
# if defined(HAS__FWALK)
    extern int fflush(FILE *);
    /* undocumented, unprototyped, but very useful BSDism */
    extern void _fwalk(int (*)(FILE *));
    _fwalk(&fflush);
    return 0;
# else
#  if defined(FFLUSH_ALL) && defined(HAS_STDIO_STREAM_ARRAY)
    long open_max = -1;
#   ifdef PERL_FFLUSH_ALL_FOPEN_MAX
    open_max = PERL_FFLUSH_ALL_FOPEN_MAX;
#   else
#    if defined(HAS_SYSCONF) && defined(_SC_OPEN_MAX)
    open_max = sysconf(_SC_OPEN_MAX);
#     else
#      ifdef FOPEN_MAX
    open_max = FOPEN_MAX;
#      else
#       ifdef OPEN_MAX
    open_max = OPEN_MAX;
#       else
#        ifdef _NFILE
    open_max = _NFILE;
#        endif
#       endif
#      endif
#     endif
#    endif
    if (open_max > 0) {
      long i;
      for (i = 0; i < open_max; i++)
            if (STDIO_STREAM_ARRAY[i]._file >= 0 &&
                STDIO_STREAM_ARRAY[i]._file < open_max &&
                STDIO_STREAM_ARRAY[i]._flag)
                PerlIO_flush(&STDIO_STREAM_ARRAY[i]);
      return 0;
    }
#  endif
    SETERRNO(EBADF,RMS_IFI);
    return EOF;
# endif
#endif
}

void
Perl_report_wrongway_fh(pTHX_ const GV *gv, const char have)
{
    if (ckWARN(WARN_IO)) {
        HEK * const name
           = gv && (isGV_with_GP(gv))
                ? GvENAME_HEK((gv))
                : NULL;
        const char * const direction = have == '>' ? "out" : "in";

        if (name && HEK_LEN(name))
            Perl_warner(aTHX_ packWARN(WARN_IO),
                        "Filehandle %"HEKf" opened only for %sput",
                        name, direction);
        else
            Perl_warner(aTHX_ packWARN(WARN_IO),
                        "Filehandle opened only for %sput", direction);
    }
}

void
Perl_report_evil_fh(pTHX_ const GV *gv)
{
    const IO *io = gv ? GvIO(gv) : NULL;
    const PERL_BITFIELD16 op = PL_op->op_type;
    const char *vile;
    I32 warn_type;

    if (io && IoTYPE(io) == IoTYPE_CLOSED) {
        vile = "closed";
        warn_type = WARN_CLOSED;
    }
    else {
        vile = "unopened";
        warn_type = WARN_UNOPENED;
    }

    if (ckWARN(warn_type)) {
        SV * const name
            = gv && isGV_with_GP(gv) && GvENAMELEN(gv) ?
                                     sv_2mortal(newSVhek(GvENAME_HEK(gv))) : NULL;
        const char * const pars =
            (const char *)(OP_IS_FILETEST(op) ? "" : "()");
        const char * const func =
            (const char *)
            (op == OP_READLINE   ? "readline"  :        /* "<HANDLE>" not nice */
             op == OP_LEAVEWRITE ? "write" :            /* "write exit" not nice */
             PL_op_desc[op]);
        const char * const type =
            (const char *)
            (OP_IS_SOCKET(op) || (io && IoTYPE(io) == IoTYPE_SOCKET)
             ? "socket" : "filehandle");
        const bool have_name = name && SvCUR(name);
        Perl_warner(aTHX_ packWARN(warn_type),
                   "%s%s on %s %s%s%"SVf, func, pars, vile, type,
                    have_name ? " " : "",
                    SVfARG(have_name ? name : &PL_sv_no));
        if (io && IoDIRP(io) && !(IoFLAGS(io) & IOf_FAKE_DIRP))
                Perl_warner(
                            aTHX_ packWARN(warn_type),
                        "\t(Are you trying to call %s%s on dirhandle%s%"SVf"?)\n",
                        func, pars, have_name ? " " : "",
                        SVfARG(have_name ? name : &PL_sv_no)
                            );
    }
}

/* To workaround core dumps from the uninitialised tm_zone we get the
 * system to give us a reasonable struct to copy.  This fix means that
 * strftime uses the tm_zone and tm_gmtoff values returned by
 * localtime(time()). That should give the desired result most of the
 * time. But probably not always!
 *
 * This does not address tzname aspects of NETaa14816.
 *
 */

#ifdef HAS_GNULIBC
# ifndef STRUCT_TM_HASZONE
#    define STRUCT_TM_HASZONE
# endif
#endif

#ifdef STRUCT_TM_HASZONE /* Backward compat */
# ifndef HAS_TM_TM_ZONE
#    define HAS_TM_TM_ZONE
# endif
#endif

void
Perl_init_tm(pTHX_ struct tm *ptm)      /* see mktime, strftime and asctime */
{
#ifdef HAS_TM_TM_ZONE
    Time_t now;
    const struct tm* my_tm;
    PERL_ARGS_ASSERT_INIT_TM;
    (void)time(&now);
    my_tm = localtime(&now);
    if (my_tm)
        Copy(my_tm, ptm, 1, struct tm);
#else
    PERL_ARGS_ASSERT_INIT_TM;
    PERL_UNUSED_ARG(ptm);
#endif
}

/*
 * mini_mktime - normalise struct tm values without the localtime()
 * semantics (and overhead) of mktime().
 */
void
Perl_mini_mktime(pTHX_ struct tm *ptm)
{
    int yearday;
    int secs;
    int month, mday, year, jday;
    int odd_cent, odd_year;
    PERL_UNUSED_CONTEXT;

    PERL_ARGS_ASSERT_MINI_MKTIME;

#define DAYS_PER_YEAR   365
#define DAYS_PER_QYEAR  (4*DAYS_PER_YEAR+1)
#define DAYS_PER_CENT   (25*DAYS_PER_QYEAR-1)
#define DAYS_PER_QCENT  (4*DAYS_PER_CENT+1)
#define SECS_PER_HOUR   (60*60)
#define SECS_PER_DAY    (24*SECS_PER_HOUR)
/* parentheses deliberately absent on these two, otherwise they don't work */
#define MONTH_TO_DAYS   153/5
#define DAYS_TO_MONTH   5/153
/* offset to bias by March (month 4) 1st between month/mday & year finding */
#define YEAR_ADJUST     (4*MONTH_TO_DAYS+1)
/* as used here, the algorithm leaves Sunday as day 1 unless we adjust it */
#define WEEKDAY_BIAS    6       /* (1+6)%7 makes Sunday 0 again */

/*
 * Year/day algorithm notes:
 *
 * With a suitable offset for numeric value of the month, one can find
 * an offset into the year by considering months to have 30.6 (153/5) days,
 * using integer arithmetic (i.e., with truncation).  To avoid too much
 * messing about with leap days, we consider January and February to be
 * the 13th and 14th month of the previous year.  After that transformation,
 * we need the month index we use to be high by 1 from 'normal human' usage,
 * so the month index values we use run from 4 through 15.
 *
 * Given that, and the rules for the Gregorian calendar (leap years are those
 * divisible by 4 unless also divisible by 100, when they must be divisible
 * by 400 instead), we can simply calculate the number of days since some
 * arbitrary 'beginning of time' by futzing with the (adjusted) year number,
 * the days we derive from our month index, and adding in the day of the
 * month.  The value used here is not adjusted for the actual origin which
 * it normally would use (1 January A.D. 1), since we're not exposing it.
 * We're only building the value so we can turn around and get the
 * normalised values for the year, month, day-of-month, and day-of-year.
 *
 * For going backward, we need to bias the value we're using so that we find
 * the right year value.  (Basically, we don't want the contribution of
 * March 1st to the number to apply while deriving the year).  Having done
 * that, we 'count up' the contribution to the year number by accounting for
 * full quadracenturies (400-year periods) with their extra leap days, plus
 * the contribution from full centuries (to avoid counting in the lost leap
 * days), plus the contribution from full quad-years (to count in the normal
 * leap days), plus the leftover contribution from any non-leap years.
 * At this point, if we were working with an actual leap day, we'll have 0
 * days left over.  This is also true for March 1st, however.  So, we have
 * to special-case that result, and (earlier) keep track of the 'odd'
 * century and year contributions.  If we got 4 extra centuries in a qcent,
 * or 4 extra years in a qyear, then it's a leap day and we call it 29 Feb.
 * Otherwise, we add back in the earlier bias we removed (the 123 from
 * figuring in March 1st), find the month index (integer division by 30.6),
 * and the remainder is the day-of-month.  We then have to convert back to
 * 'real' months (including fixing January and February from being 14/15 in
 * the previous year to being in the proper year).  After that, to get
 * tm_yday, we work with the normalised year and get a new yearday value for
 * January 1st, which we subtract from the yearday value we had earlier,
 * representing the date we've re-built.  This is done from January 1
 * because tm_yday is 0-origin.
 *
 * Since POSIX time routines are only guaranteed to work for times since the
 * UNIX epoch (00:00:00 1 Jan 1970 UTC), the fact that this algorithm
 * applies Gregorian calendar rules even to dates before the 16th century
 * doesn't bother me.  Besides, you'd need cultural context for a given
 * date to know whether it was Julian or Gregorian calendar, and that's
 * outside the scope for this routine.  Since we convert back based on the
 * same rules we used to build the yearday, you'll only get strange results
 * for input which needed normalising, or for the 'odd' century years which
 * were leap years in the Julian calendar but not in the Gregorian one.
 * I can live with that.
 *
 * This algorithm also fails to handle years before A.D. 1 gracefully, but
 * that's still outside the scope for POSIX time manipulation, so I don't
 * care.
 */

    year = 1900 + ptm->tm_year;
    month = ptm->tm_mon;
    mday = ptm->tm_mday;
    jday = 0;
    if (month >= 2)
        month+=2;
    else
        month+=14, year--;
    yearday = DAYS_PER_YEAR * year + year/4 - year/100 + year/400;
    yearday += month*MONTH_TO_DAYS + mday + jday;
    /*
     * Note that we don't know when leap-seconds were or will be,
     * so we have to trust the user if we get something which looks
     * like a sensible leap-second.  Wild values for seconds will
     * be rationalised, however.
     */
    if ((unsigned) ptm->tm_sec <= 60) {
        secs = 0;
    }
    else {
        secs = ptm->tm_sec;
        ptm->tm_sec = 0;
    }
    secs += 60 * ptm->tm_min;
    secs += SECS_PER_HOUR * ptm->tm_hour;
    if (secs < 0) {
        if (secs-(secs/SECS_PER_DAY*SECS_PER_DAY) < 0) {
            /* got negative remainder, but need positive time */
            /* back off an extra day to compensate */
            yearday += (secs/SECS_PER_DAY)-1;
            secs -= SECS_PER_DAY * (secs/SECS_PER_DAY - 1);
        }
        else {
            yearday += (secs/SECS_PER_DAY);
            secs -= SECS_PER_DAY * (secs/SECS_PER_DAY);
        }
    }
    else if (secs >= SECS_PER_DAY) {
        yearday += (secs/SECS_PER_DAY);
        secs %= SECS_PER_DAY;
    }
    ptm->tm_hour = secs/SECS_PER_HOUR;
    secs %= SECS_PER_HOUR;
    ptm->tm_min = secs/60;
    secs %= 60;
    ptm->tm_sec += secs;
    /* done with time of day effects */
    /*
     * The algorithm for yearday has (so far) left it high by 428.
     * To avoid mistaking a legitimate Feb 29 as Mar 1, we need to
     * bias it by 123 while trying to figure out what year it
     * really represents.  Even with this tweak, the reverse
     * translation fails for years before A.D. 0001.
     * It would still fail for Feb 29, but we catch that one below.
     */
    jday = yearday;     /* save for later fixup vis-a-vis Jan 1 */
    yearday -= YEAR_ADJUST;
    year = (yearday / DAYS_PER_QCENT) * 400;
    yearday %= DAYS_PER_QCENT;
    odd_cent = yearday / DAYS_PER_CENT;
    year += odd_cent * 100;
    yearday %= DAYS_PER_CENT;
    year += (yearday / DAYS_PER_QYEAR) * 4;
    yearday %= DAYS_PER_QYEAR;
    odd_year = yearday / DAYS_PER_YEAR;
    year += odd_year;
    yearday %= DAYS_PER_YEAR;
    if (!yearday && (odd_cent==4 || odd_year==4)) { /* catch Feb 29 */
        month = 1;
        yearday = 29;
    }
    else {
        yearday += YEAR_ADJUST; /* recover March 1st crock */
        month = yearday*DAYS_TO_MONTH;
        yearday -= month*MONTH_TO_DAYS;
        /* recover other leap-year adjustment */
        if (month > 13) {
            month-=14;
            year++;
        }
        else {
            month-=2;
        }
    }
    ptm->tm_year = year - 1900;
    if (yearday) {
      ptm->tm_mday = yearday;
      ptm->tm_mon = month;
    }
    else {
      ptm->tm_mday = 31;
      ptm->tm_mon = month - 1;
    }
    /* re-build yearday based on Jan 1 to get tm_yday */
    year--;
    yearday = year*DAYS_PER_YEAR + year/4 - year/100 + year/400;
    yearday += 14*MONTH_TO_DAYS + 1;
    ptm->tm_yday = jday - yearday;
    ptm->tm_wday = (jday + WEEKDAY_BIAS) % 7;
}

char *
Perl_my_strftime(pTHX_ const char *fmt, int sec, int min, int hour, int mday, int mon, int year, int wday, int yday, int isdst)
{
#ifdef HAS_STRFTIME
  char *buf;
  int buflen;
  struct tm mytm;
  int len;

  PERL_ARGS_ASSERT_MY_STRFTIME;

  init_tm(&mytm);       /* XXX workaround - see init_tm() above */
  mytm.tm_sec = sec;
  mytm.tm_min = min;
  mytm.tm_hour = hour;
  mytm.tm_mday = mday;
  mytm.tm_mon = mon;
  mytm.tm_year = year;
  mytm.tm_wday = wday;
  mytm.tm_yday = yday;
  mytm.tm_isdst = isdst;
  mini_mktime(&mytm);
  /* use libc to get the values for tm_gmtoff and tm_zone [perl #18238] */
#if defined(HAS_MKTIME) && (defined(HAS_TM_TM_GMTOFF) || defined(HAS_TM_TM_ZONE))
  STMT_START {
    struct tm mytm2;
    mytm2 = mytm;
    mktime(&mytm2);
#ifdef HAS_TM_TM_GMTOFF
    mytm.tm_gmtoff = mytm2.tm_gmtoff;
#endif
#ifdef HAS_TM_TM_ZONE
    mytm.tm_zone = mytm2.tm_zone;
#endif
  } STMT_END;
#endif
  buflen = 64;
  Newx(buf, buflen, char);
  len = strftime(buf, buflen, fmt, &mytm);
  /*
  ** The following is needed to handle to the situation where
  ** tmpbuf overflows.  Basically we want to allocate a buffer
  ** and try repeatedly.  The reason why it is so complicated
  ** is that getting a return value of 0 from strftime can indicate
  ** one of the following:
  ** 1. buffer overflowed,
  ** 2. illegal conversion specifier, or
  ** 3. the format string specifies nothing to be returned(not
  **      an error).  This could be because format is an empty string
  **    or it specifies %p that yields an empty string in some locale.
  ** If there is a better way to make it portable, go ahead by
  ** all means.
  */
  if ((len > 0 && len < buflen) || (len == 0 && *fmt == '\0'))
    return buf;
  else {
    /* Possibly buf overflowed - try again with a bigger buf */
    const int fmtlen = strlen(fmt);
    int bufsize = fmtlen + buflen;

    Renew(buf, bufsize, char);
    while (buf) {
      buflen = strftime(buf, bufsize, fmt, &mytm);
      if (buflen > 0 && buflen < bufsize)
        break;
      /* heuristic to prevent out-of-memory errors */
      if (bufsize > 100*fmtlen) {
        Safefree(buf);
        buf = NULL;
        break;
      }
      bufsize *= 2;
      Renew(buf, bufsize, char);
    }
    return buf;
  }
#else
  Perl_croak(aTHX_ "panic: no strftime");
  return NULL;
#endif
}


#define SV_CWD_RETURN_UNDEF \
sv_setsv(sv, &PL_sv_undef); \
return FALSE

#define SV_CWD_ISDOT(dp) \
    (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
        (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))

/*
=head1 Miscellaneous Functions

=for apidoc getcwd_sv

Fill the sv with current working directory

=cut
*/

/* Originally written in Perl by John Bazik; rewritten in C by Ben Sugars.
 * rewritten again by dougm, optimized for use with xs TARG, and to prefer
 * getcwd(3) if available
 * Comments from the orignal:
 *     This is a faster version of getcwd.  It's also more dangerous
 *     because you might chdir out of a directory that you can't chdir
 *     back into. */

int
Perl_getcwd_sv(pTHX_ SV *sv)
{
#ifndef PERL_MICRO
    dVAR;
#ifndef INCOMPLETE_TAINTS
    SvTAINTED_on(sv);
#endif

    PERL_ARGS_ASSERT_GETCWD_SV;

#ifdef HAS_GETCWD
    {
        char buf[MAXPATHLEN];

        /* Some getcwd()s automatically allocate a buffer of the given
         * size from the heap if they are given a NULL buffer pointer.
         * The problem is that this behaviour is not portable. */
        if (getcwd(buf, sizeof(buf) - 1)) {
            sv_setpv(sv, buf);
            return TRUE;
        }
        else {
            sv_setsv(sv, &PL_sv_undef);
            return FALSE;
        }
    }

#else

    Stat_t statbuf;
    int orig_cdev, orig_cino, cdev, cino, odev, oino, tdev, tino;
    int pathlen=0;
    Direntry_t *dp;

    SvUPGRADE(sv, SVt_PV);

    if (PerlLIO_lstat(".", &statbuf) < 0) {
        SV_CWD_RETURN_UNDEF;
    }

    orig_cdev = statbuf.st_dev;
    orig_cino = statbuf.st_ino;
    cdev = orig_cdev;
    cino = orig_cino;

    for (;;) {
        DIR *dir;
        int namelen;
        odev = cdev;
        oino = cino;

        if (PerlDir_chdir("..") < 0) {
            SV_CWD_RETURN_UNDEF;
        }
        if (PerlLIO_stat(".", &statbuf) < 0) {
            SV_CWD_RETURN_UNDEF;
        }

        cdev = statbuf.st_dev;
        cino = statbuf.st_ino;

        if (odev == cdev && oino == cino) {
            break;
        }
        if (!(dir = PerlDir_open("."))) {
            SV_CWD_RETURN_UNDEF;
        }

        while ((dp = PerlDir_read(dir)) != NULL) {
#ifdef DIRNAMLEN
            namelen = dp->d_namlen;
#else
            namelen = strlen(dp->d_name);
#endif
            /* skip . and .. */
            if (SV_CWD_ISDOT(dp)) {
                continue;
            }

            if (PerlLIO_lstat(dp->d_name, &statbuf) < 0) {
                SV_CWD_RETURN_UNDEF;
            }

            tdev = statbuf.st_dev;
            tino = statbuf.st_ino;
            if (tino == oino && tdev == odev) {
                break;
            }
        }

        if (!dp) {
            SV_CWD_RETURN_UNDEF;
        }

        if (pathlen + namelen + 1 >= MAXPATHLEN) {
            SV_CWD_RETURN_UNDEF;
        }

        SvGROW(sv, pathlen + namelen + 1);

        if (pathlen) {
            /* shift down */
            Move(SvPVX_const(sv), SvPVX(sv) + namelen + 1, pathlen, char);
        }

        /* prepend current directory to the front */
        *SvPVX(sv) = '/';
        Move(dp->d_name, SvPVX(sv)+1, namelen, char);
        pathlen += (namelen + 1);

#ifdef VOID_CLOSEDIR
        PerlDir_close(dir);
#else
        if (PerlDir_close(dir) < 0) {
            SV_CWD_RETURN_UNDEF;
        }
#endif
    }

    if (pathlen) {
        SvCUR_set(sv, pathlen);
        *SvEND(sv) = '\0';
        SvPOK_only(sv);

        if (PerlDir_chdir(SvPVX_const(sv)) < 0) {
            SV_CWD_RETURN_UNDEF;
        }
    }
    if (PerlLIO_stat(".", &statbuf) < 0) {
        SV_CWD_RETURN_UNDEF;
    }

    cdev = statbuf.st_dev;
    cino = statbuf.st_ino;

    if (cdev != orig_cdev || cino != orig_cino) {
        Perl_croak(aTHX_ "Unstable directory path, "
                   "current directory changed unexpectedly");
    }

    return TRUE;
#endif

#else
    return FALSE;
#endif
}

#define VERSION_MAX 0x7FFFFFFF

/*
=for apidoc prescan_version

Validate that a given string can be parsed as a version object, but doesn't
actually perform the parsing.  Can use either strict or lax validation rules.
Can optionally set a number of hint variables to save the parsing code
some time when tokenizing.

=cut
*/
const char *
Perl_prescan_version(pTHX_ const char *s, bool strict,
                     const char **errstr,
                     bool *sqv, int *ssaw_decimal, int *swidth, bool *salpha) {
    bool qv = (sqv ? *sqv : FALSE);
    int width = 3;
    int saw_decimal = 0;
    bool alpha = FALSE;
    const char *d = s;

    PERL_ARGS_ASSERT_PRESCAN_VERSION;

    if (qv && isDIGIT(*d))
        goto dotted_decimal_version;

    if (*d == 'v') { /* explicit v-string */
        d++;
        if (isDIGIT(*d)) {
            qv = TRUE;
        }
        else { /* degenerate v-string */
            /* requires v1.2.3 */
            BADVERSION(s,errstr,"Invalid version format (dotted-decimal versions require at least three parts)");
        }

dotted_decimal_version:
        if (strict && d[0] == '0' && isDIGIT(d[1])) {
            /* no leading zeros allowed */
            BADVERSION(s,errstr,"Invalid version format (no leading zeros)");
        }

        while (isDIGIT(*d))     /* integer part */
            d++;

        if (*d == '.')
        {
            saw_decimal++;
            d++;                /* decimal point */
        }
        else
        {
            if (strict) {
                /* require v1.2.3 */
                BADVERSION(s,errstr,"Invalid version format (dotted-decimal versions require at least three parts)");
            }
            else {
                goto version_prescan_finish;
            }
        }

        {
            int i = 0;
            int j = 0;
            while (isDIGIT(*d)) {       /* just keep reading */
                i++;
                while (isDIGIT(*d)) {
                    d++; j++;
                    /* maximum 3 digits between decimal */
                    if (strict && j > 3) {
                        BADVERSION(s,errstr,"Invalid version format (maximum 3 digits between decimals)");
                    }
                }
                if (*d == '_') {
                    if (strict) {
                        BADVERSION(s,errstr,"Invalid version format (no underscores)");
                    }
                    if ( alpha ) {
                        BADVERSION(s,errstr,"Invalid version format (multiple underscores)");
                    }
                    d++;
                    alpha = TRUE;
                }
                else if (*d == '.') {
                    if (alpha) {
                        BADVERSION(s,errstr,"Invalid version format (underscores before decimal)");
                    }
                    saw_decimal++;
                    d++;
                }
                else if (!isDIGIT(*d)) {
                    break;
                }
                j = 0;
            }

            if (strict && i < 2) {
                /* requires v1.2.3 */
                BADVERSION(s,errstr,"Invalid version format (dotted-decimal versions require at least three parts)");
            }
        }
    }                                   /* end if dotted-decimal */
    else
    {                                   /* decimal versions */
        int j = 0;                      /* may need this later */
        /* special strict case for leading '.' or '0' */
        if (strict) {
            if (*d == '.') {
                BADVERSION(s,errstr,"Invalid version format (0 before decimal required)");
            }
            if (*d == '0' && isDIGIT(d[1])) {
                BADVERSION(s,errstr,"Invalid version format (no leading zeros)");
            }
        }

        /* and we never support negative versions */
        if ( *d == '-') {
            BADVERSION(s,errstr,"Invalid version format (negative version number)");
        }

        /* consume all of the integer part */
        while (isDIGIT(*d))
            d++;

        /* look for a fractional part */
        if (*d == '.') {
            /* we found it, so consume it */
            saw_decimal++;
            d++;
        }
        else if (!*d || *d == ';' || isSPACE(*d) || *d == '{' || *d == '}') {
            if ( d == s ) {
                /* found nothing */
                BADVERSION(s,errstr,"Invalid version format (version required)");
            }
            /* found just an integer */
            goto version_prescan_finish;
        }
        else if ( d == s ) {
            /* didn't find either integer or period */
            BADVERSION(s,errstr,"Invalid version format (non-numeric data)");
        }
        else if (*d == '_') {
            /* underscore can't come after integer part */
            if (strict) {
                BADVERSION(s,errstr,"Invalid version format (no underscores)");
            }
            else if (isDIGIT(d[1])) {
                BADVERSION(s,errstr,"Invalid version format (alpha without decimal)");
            }
            else {
                BADVERSION(s,errstr,"Invalid version format (misplaced underscore)");
            }
        }
        else {
            /* anything else after integer part is just invalid data */
            BADVERSION(s,errstr,"Invalid version format (non-numeric data)");
        }

        /* scan the fractional part after the decimal point*/

        if (!isDIGIT(*d) && (strict || ! (!*d || *d == ';' || isSPACE(*d) || *d == '{' || *d == '}') )) {
                /* strict or lax-but-not-the-end */
                BADVERSION(s,errstr,"Invalid version format (fractional part required)");
        }

        while (isDIGIT(*d)) {
            d++; j++;
            if (*d == '.' && isDIGIT(d[-1])) {
                if (alpha) {
                    BADVERSION(s,errstr,"Invalid version format (underscores before decimal)");
                }
                if (strict) {
                    BADVERSION(s,errstr,"Invalid version format (dotted-decimal versions must begin with 'v')");
                }
                d = (char *)s;          /* start all over again */
                qv = TRUE;
                goto dotted_decimal_version;
            }
            if (*d == '_') {
                if (strict) {
                    BADVERSION(s,errstr,"Invalid version format (no underscores)");
                }
                if ( alpha ) {
                    BADVERSION(s,errstr,"Invalid version format (multiple underscores)");
                }
                if ( ! isDIGIT(d[1]) ) {
                    BADVERSION(s,errstr,"Invalid version format (misplaced underscore)");
                }
                width = j;
                d++;
                alpha = TRUE;
            }
        }
    }

version_prescan_finish:
    while (isSPACE(*d))
        d++;

    if (!isDIGIT(*d) && (! (!*d || *d == ';' || *d == '{' || *d == '}') )) {
        /* trailing non-numeric data */
        BADVERSION(s,errstr,"Invalid version format (non-numeric data)");
    }

    if (sqv)
        *sqv = qv;
    if (swidth)
        *swidth = width;
    if (ssaw_decimal)
        *ssaw_decimal = saw_decimal;
    if (salpha)
        *salpha = alpha;
    return d;
}

/*
=for apidoc scan_version

Returns a pointer to the next character after the parsed
version string, as well as upgrading the passed in SV to
an RV.

Function must be called with an already existing SV like

    sv = newSV(0);
    s = scan_version(s, SV *sv, bool qv);

Performs some preprocessing to the string to ensure that
it has the correct characteristics of a version.  Flags the
object if it contains an underscore (which denotes this
is an alpha version).  The boolean qv denotes that the version
should be interpreted as if it had multiple decimals, even if
it doesn't.

=cut
*/

const char *
Perl_scan_version(pTHX_ const char *s, SV *rv, bool qv)
{
    const char *start = s;
    const char *pos;
    const char *last;
    const char *errstr = NULL;
    int saw_decimal = 0;
    int width = 3;
    bool alpha = FALSE;
    bool vinf = FALSE;
    AV * av;
    SV * hv;

    PERL_ARGS_ASSERT_SCAN_VERSION;

    while (isSPACE(*s)) /* leading whitespace is OK */
        s++;

    last = prescan_version(s, FALSE, &errstr, &qv, &saw_decimal, &width, &alpha);
    if (errstr) {
        /* "undef" is a special case and not an error */
        if ( ! ( *s == 'u' && strEQ(s,"undef")) ) {
            Safefree(start);
            Perl_croak(aTHX_ "%s", errstr);
        }
    }

    start = s;
    if (*s == 'v')
        s++;
    pos = s;

    /* Now that we are through the prescan, start creating the object */
    av = newAV();
    hv = newSVrv(rv, "version"); /* create an SV and upgrade the RV */
    (void)sv_upgrade(hv, SVt_PVHV); /* needs to be an HV type */

#ifndef NODEFAULT_SHAREKEYS
    HvSHAREKEYS_on(hv);         /* key-sharing on by default */
#endif

    if ( qv )
        (void)hv_stores(MUTABLE_HV(hv), "qv", newSViv(qv));
    if ( alpha )
        (void)hv_stores(MUTABLE_HV(hv), "alpha", newSViv(alpha));
    if ( !qv && width < 3 )
        (void)hv_stores(MUTABLE_HV(hv), "width", newSViv(width));

    while (isDIGIT(*pos))
        pos++;
    if (!isALPHA(*pos)) {
        I32 rev;

        for (;;) {
            rev = 0;
            {
                /* this is atoi() that delimits on underscores */
                const char *end = pos;
                I32 mult = 1;
                I32 orev;

                /* the following if() will only be true after the decimal
                 * point of a version originally created with a bare
                 * floating point number, i.e. not quoted in any way
                 */
                if ( !qv && s > start && saw_decimal == 1 ) {
                    mult *= 100;
                    while ( s < end ) {
                        orev = rev;
                        rev += (*s - '0') * mult;
                        mult /= 10;
                        if (   (PERL_ABS(orev) > PERL_ABS(rev)) 
                            || (PERL_ABS(rev) > VERSION_MAX )) {
                            Perl_ck_warner(aTHX_ packWARN(WARN_OVERFLOW), 
                                           "Integer overflow in version %d",VERSION_MAX);
                            s = end - 1;
                            rev = VERSION_MAX;
                            vinf = 1;
                        }
                        s++;
                        if ( *s == '_' )
                            s++;
                    }
                }
                else {
                    while (--end >= s) {
                        orev = rev;
                        rev += (*end - '0') * mult;
                        mult *= 10;
                        if (   (PERL_ABS(orev) > PERL_ABS(rev)) 
                            || (PERL_ABS(rev) > VERSION_MAX )) {
                            Perl_ck_warner(aTHX_ packWARN(WARN_OVERFLOW), 
                                           "Integer overflow in version");
                            end = s - 1;
                            rev = VERSION_MAX;
                            vinf = 1;
                        }
                    }
                } 
            }

            /* Append revision */
            av_push(av, newSViv(rev));
            if ( vinf ) {
                s = last;
                break;
            }
            else if ( *pos == '.' )
                s = ++pos;
            else if ( *pos == '_' && isDIGIT(pos[1]) )
                s = ++pos;
            else if ( *pos == ',' && isDIGIT(pos[1]) )
                s = ++pos;
            else if ( isDIGIT(*pos) )
                s = pos;
            else {
                s = pos;
                break;
            }
            if ( qv ) {
                while ( isDIGIT(*pos) )
                    pos++;
            }
            else {
                int digits = 0;
                while ( ( isDIGIT(*pos) || *pos == '_' ) && digits < 3 ) {
                    if ( *pos != '_' )
                        digits++;
                    pos++;
                }
            }
        }
    }
    if ( qv ) { /* quoted versions always get at least three terms*/
        SSize_t len = av_len(av);
        /* This for loop appears to trigger a compiler bug on OS X, as it
           loops infinitely. Yes, len is negative. No, it makes no sense.
           Compiler in question is:
           gcc version 3.3 20030304 (Apple Computer, Inc. build 1640)
           for ( len = 2 - len; len > 0; len-- )
           av_push(MUTABLE_AV(sv), newSViv(0));
        */
        len = 2 - len;
        while (len-- > 0)
            av_push(av, newSViv(0));
    }

    /* need to save off the current version string for later */
    if ( vinf ) {
        SV * orig = newSVpvn("v.Inf", sizeof("v.Inf")-1);
        (void)hv_stores(MUTABLE_HV(hv), "original", orig);
        (void)hv_stores(MUTABLE_HV(hv), "vinf", newSViv(1));
    }
    else if ( s > start ) {
        SV * orig = newSVpvn(start,s-start);
        if ( qv && saw_decimal == 1 && *start != 'v' ) {
            /* need to insert a v to be consistent */
            sv_insert(orig, 0, 0, "v", 1);
        }
        (void)hv_stores(MUTABLE_HV(hv), "original", orig);
    }
    else {
        (void)hv_stores(MUTABLE_HV(hv), "original", newSVpvs("0"));
        av_push(av, newSViv(0));
    }

    /* And finally, store the AV in the hash */
    (void)hv_stores(MUTABLE_HV(hv), "version", newRV_noinc(MUTABLE_SV(av)));

    /* fix RT#19517 - special case 'undef' as string */
    if ( *s == 'u' && strEQ(s,"undef") ) {
        s += 5;
    }

    return s;
}

/*
=for apidoc new_version

Returns a new version object based on the passed in SV:

    SV *sv = new_version(SV *ver);

Does not alter the passed in ver SV.  See "upg_version" if you
want to upgrade the SV.

=cut
*/

SV *
Perl_new_version(pTHX_ SV *ver)
{
    dVAR;
    SV * const rv = newSV(0);
    PERL_ARGS_ASSERT_NEW_VERSION;
    if ( sv_isobject(ver) && sv_derived_from(ver, "version") )
         /* can just copy directly */
    {
        SSize_t key;
        AV * const av = newAV();
        AV *sav;
        /* This will get reblessed later if a derived class*/
        SV * const hv = newSVrv(rv, "version"); 
        (void)sv_upgrade(hv, SVt_PVHV); /* needs to be an HV type */
#ifndef NODEFAULT_SHAREKEYS
        HvSHAREKEYS_on(hv);         /* key-sharing on by default */
#endif

        if ( SvROK(ver) )
            ver = SvRV(ver);

        /* Begin copying all of the elements */
        if ( hv_exists(MUTABLE_HV(ver), "qv", 2) )
            (void)hv_stores(MUTABLE_HV(hv), "qv", newSViv(1));

        if ( hv_exists(MUTABLE_HV(ver), "alpha", 5) )
            (void)hv_stores(MUTABLE_HV(hv), "alpha", newSViv(1));

        if ( hv_exists(MUTABLE_HV(ver), "width", 5 ) )
        {
            const I32 width = SvIV(*hv_fetchs(MUTABLE_HV(ver), "width", FALSE));
            (void)hv_stores(MUTABLE_HV(hv), "width", newSViv(width));
        }

        if ( hv_exists(MUTABLE_HV(ver), "original", 8 ) )
        {
            SV * pv = *hv_fetchs(MUTABLE_HV(ver), "original", FALSE);
            (void)hv_stores(MUTABLE_HV(hv), "original", newSVsv(pv));
        }

        sav = MUTABLE_AV(SvRV(*hv_fetchs(MUTABLE_HV(ver), "version", FALSE)));
        /* This will get reblessed later if a derived class*/
        for ( key = 0; key <= av_len(sav); key++ )
        {
            const I32 rev = SvIV(*av_fetch(sav, key, FALSE));
            av_push(av, newSViv(rev));
        }

        (void)hv_stores(MUTABLE_HV(hv), "version", newRV_noinc(MUTABLE_SV(av)));
        return rv;
    }
#ifdef SvVOK
    {
        const MAGIC* const mg = SvVSTRING_mg(ver);
        if ( mg ) { /* already a v-string */
            const STRLEN len = mg->mg_len;
            char * const version = savepvn( (const char*)mg->mg_ptr, len);
            sv_setpvn(rv,version,len);
            /* this is for consistency with the pure Perl class */
            if ( isDIGIT(*version) )
                sv_insert(rv, 0, 0, "v", 1);
            Safefree(version);
        }
        else {
#endif
        sv_setsv(rv,ver); /* make a duplicate */
#ifdef SvVOK
        }
    }
#endif
    return upg_version(rv, FALSE);
}

/*
=for apidoc upg_version

In-place upgrade of the supplied SV to a version object.

    SV *sv = upg_version(SV *sv, bool qv);

Returns a pointer to the upgraded SV.  Set the boolean qv if you want
to force this SV to be interpreted as an "extended" version.

=cut
*/

SV *
Perl_upg_version(pTHX_ SV *ver, bool qv)
{
    const char *version, *s;
#ifdef SvVOK
    const MAGIC *mg;
#endif

    PERL_ARGS_ASSERT_UPG_VERSION;

    if ( SvNOK(ver) && !( SvPOK(ver) && sv_len(ver) == 3 ) )
    {
        STRLEN len;

        /* may get too much accuracy */ 
        char tbuf[64];
        SV *sv = SvNVX(ver) > 10e50 ? newSV(64) : 0;
        char *buf;
#ifdef USE_LOCALE_NUMERIC
        char *loc = NULL;
        if (! PL_numeric_standard) {
            loc = savepv(setlocale(LC_NUMERIC, NULL));
            setlocale(LC_NUMERIC, "C");
        }
#endif
        if (sv) {
            Perl_sv_setpvf(aTHX_ sv, "%.9"NVff, SvNVX(ver));
            buf = SvPV(sv, len);
        }
        else {
            len = my_snprintf(tbuf, sizeof(tbuf), "%.9"NVff, SvNVX(ver));
            buf = tbuf;
        }
#ifdef USE_LOCALE_NUMERIC
        if (loc) {
            setlocale(LC_NUMERIC, loc);
            Safefree(loc);
        }
#endif
        while (buf[len-1] == '0' && len > 0) len--;
        if ( buf[len-1] == '.' ) len--; /* eat the trailing decimal */
        version = savepvn(buf, len);
        SvREFCNT_dec(sv);
    }
#ifdef SvVOK
    else if ( (mg = SvVSTRING_mg(ver)) ) { /* already a v-string */
        version = savepvn( (const char*)mg->mg_ptr,mg->mg_len );
        qv = TRUE;
    }
#endif
    else /* must be a string or something like a string */
    {
        STRLEN len;
        version = savepv(SvPV(ver,len));
#ifndef SvVOK
#  if PERL_VERSION > 5
        /* This will only be executed for 5.6.0 - 5.8.0 inclusive */
        if ( len >= 3 && !instr(version,".") && !instr(version,"_")) {
            /* may be a v-string */
            char *testv = (char *)version;
            STRLEN tlen = len;
            for (tlen=0; tlen < len; tlen++, testv++) {
                /* if one of the characters is non-text assume v-string */
                if (testv[0] < ' ') {
                    SV * const nsv = sv_newmortal();
                    const char *nver;
                    const char *pos;
                    int saw_decimal = 0;
                    sv_setpvf(nsv,"v%vd",ver);
                    pos = nver = savepv(SvPV_nolen(nsv));

                    /* scan the resulting formatted string */
                    pos++; /* skip the leading 'v' */
                    while ( *pos == '.' || isDIGIT(*pos) ) {
                        if ( *pos == '.' )
                            saw_decimal++ ;
                        pos++;
                    }

                    /* is definitely a v-string */
                    if ( saw_decimal >= 2 ) {
                        Safefree(version);
                        version = nver;
                    }
                    break;
                }
            }
        }
#  endif
#endif
    }

    s = scan_version(version, ver, qv);
    if ( *s != '\0' ) 
        Perl_ck_warner(aTHX_ packWARN(WARN_MISC), 
                       "Version string '%s' contains invalid data; "
                       "ignoring: '%s'", version, s);
    Safefree(version);
    return ver;
}

/*
=for apidoc vverify

Validates that the SV contains valid internal structure for a version object.
It may be passed either the version object (RV) or the hash itself (HV).  If
the structure is valid, it returns the HV.  If the structure is invalid,
it returns NULL.

    SV *hv = vverify(sv);

Note that it only confirms the bare minimum structure (so as not to get
confused by derived classes which may contain additional hash entries):

=over 4

=item * The SV is an HV or a reference to an HV

=item * The hash contains a "version" key

=item * The "version" key has a reference to an AV as its value

=back

=cut
*/

SV *
Perl_vverify(pTHX_ SV *vs)
{
    SV *sv;

    PERL_ARGS_ASSERT_VVERIFY;

    if ( SvROK(vs) )
        vs = SvRV(vs);

    /* see if the appropriate elements exist */
    if ( SvTYPE(vs) == SVt_PVHV
         && hv_exists(MUTABLE_HV(vs), "version", 7)
         && (sv = SvRV(*hv_fetchs(MUTABLE_HV(vs), "version", FALSE)))
         && SvTYPE(sv) == SVt_PVAV )
        return vs;
    else
        return NULL;
}

/*
=for apidoc vnumify

Accepts a version object and returns the normalized floating
point representation.  Call like:

    sv = vnumify(rv);

NOTE: you can pass either the object directly or the SV
contained within the RV.

The SV returned has a refcount of 1.

=cut
*/

SV *
Perl_vnumify(pTHX_ SV *vs)
{
    SSize_t i, len;
    I32 digit;
    int width;
    bool alpha = FALSE;
    SV *sv;
    AV *av;

    PERL_ARGS_ASSERT_VNUMIFY;

    /* extract the HV from the object */
    vs = vverify(vs);
    if ( ! vs )
        Perl_croak(aTHX_ "Invalid version object");

    /* see if various flags exist */
    if ( hv_exists(MUTABLE_HV(vs), "alpha", 5 ) )
        alpha = TRUE;
    if ( hv_exists(MUTABLE_HV(vs), "width", 5 ) )
        width = SvIV(*hv_fetchs(MUTABLE_HV(vs), "width", FALSE));
    else
        width = 3;


    /* attempt to retrieve the version array */
    if ( !(av = MUTABLE_AV(SvRV(*hv_fetchs(MUTABLE_HV(vs), "version", FALSE))) ) ) {
        return newSVpvs("0");
    }

    len = av_len(av);
    if ( len == -1 )
    {
        return newSVpvs("0");
    }

    digit = SvIV(*av_fetch(av, 0, 0));
    sv = Perl_newSVpvf(aTHX_ "%d.", (int)PERL_ABS(digit));
    for ( i = 1 ; i < len ; i++ )
    {
        digit = SvIV(*av_fetch(av, i, 0));
        if ( width < 3 ) {
            const int denom = (width == 2 ? 10 : 100);
            const div_t term = div((int)PERL_ABS(digit),denom);
            Perl_sv_catpvf(aTHX_ sv, "%0*d_%d", width, term.quot, term.rem);
        }
        else {
            Perl_sv_catpvf(aTHX_ sv, "%0*d", width, (int)digit);
        }
    }

    if ( len > 0 )
    {
        digit = SvIV(*av_fetch(av, len, 0));
        if ( alpha && width == 3 ) /* alpha version */
            sv_catpvs(sv,"_");
        Perl_sv_catpvf(aTHX_ sv, "%0*d", width, (int)digit);
    }
    else /* len == 0 */
    {
        sv_catpvs(sv, "000");
    }
    return sv;
}

/*
=for apidoc vnormal

Accepts a version object and returns the normalized string
representation.  Call like:

    sv = vnormal(rv);

NOTE: you can pass either the object directly or the SV
contained within the RV.

The SV returned has a refcount of 1.

=cut
*/

SV *
Perl_vnormal(pTHX_ SV *vs)
{
    I32 i, len, digit;
    bool alpha = FALSE;
    SV *sv;
    AV *av;

    PERL_ARGS_ASSERT_VNORMAL;

    /* extract the HV from the object */
    vs = vverify(vs);
    if ( ! vs )
        Perl_croak(aTHX_ "Invalid version object");

    if ( hv_exists(MUTABLE_HV(vs), "alpha", 5 ) )
        alpha = TRUE;
    av = MUTABLE_AV(SvRV(*hv_fetchs(MUTABLE_HV(vs), "version", FALSE)));

    len = av_len(av);
    if ( len == -1 )
    {
        return newSVpvs("");
    }
    digit = SvIV(*av_fetch(av, 0, 0));
    sv = Perl_newSVpvf(aTHX_ "v%"IVdf, (IV)digit);
    for ( i = 1 ; i < len ; i++ ) {
        digit = SvIV(*av_fetch(av, i, 0));
        Perl_sv_catpvf(aTHX_ sv, ".%"IVdf, (IV)digit);
    }

    if ( len > 0 )
    {
        /* handle last digit specially */
        digit = SvIV(*av_fetch(av, len, 0));
        if ( alpha )
            Perl_sv_catpvf(aTHX_ sv, "_%"IVdf, (IV)digit);
        else
            Perl_sv_catpvf(aTHX_ sv, ".%"IVdf, (IV)digit);
    }

    if ( len <= 2 ) { /* short version, must be at least three */
        for ( len = 2 - len; len != 0; len-- )
            sv_catpvs(sv,".0");
    }
    return sv;
}

/*
=for apidoc vstringify

In order to maintain maximum compatibility with earlier versions
of Perl, this function will return either the floating point
notation or the multiple dotted notation, depending on whether
the original version contained 1 or more dots, respectively.

The SV returned has a refcount of 1.

=cut
*/

SV *
Perl_vstringify(pTHX_ SV *vs)
{
    PERL_ARGS_ASSERT_VSTRINGIFY;

    /* extract the HV from the object */
    vs = vverify(vs);
    if ( ! vs )
        Perl_croak(aTHX_ "Invalid version object");

    if (hv_exists(MUTABLE_HV(vs), "original",  sizeof("original") - 1)) {
        SV *pv;
        pv = *hv_fetchs(MUTABLE_HV(vs), "original", FALSE);
        if ( SvPOK(pv) )
            return newSVsv(pv);
        else
            return &PL_sv_undef;
    }
    else {
        if ( hv_exists(MUTABLE_HV(vs), "qv", 2) )
            return vnormal(vs);
        else
            return vnumify(vs);
    }
}

/*
=for apidoc vcmp

Version object aware cmp.  Both operands must already have been 
converted into version objects.

=cut
*/

int
Perl_vcmp(pTHX_ SV *lhv, SV *rhv)
{
    SSize_t i,l,m,r;
    I32 retval;
    bool lalpha = FALSE;
    bool ralpha = FALSE;
    I32 left = 0;
    I32 right = 0;
    AV *lav, *rav;

    PERL_ARGS_ASSERT_VCMP;

    /* extract the HVs from the objects */
    lhv = vverify(lhv);
    rhv = vverify(rhv);
    if ( ! ( lhv && rhv ) )
        Perl_croak(aTHX_ "Invalid version object");

    /* get the left hand term */
    lav = MUTABLE_AV(SvRV(*hv_fetchs(MUTABLE_HV(lhv), "version", FALSE)));
    if ( hv_exists(MUTABLE_HV(lhv), "alpha", 5 ) )
        lalpha = TRUE;

    /* and the right hand term */
    rav = MUTABLE_AV(SvRV(*hv_fetchs(MUTABLE_HV(rhv), "version", FALSE)));
    if ( hv_exists(MUTABLE_HV(rhv), "alpha", 5 ) )
        ralpha = TRUE;

    l = av_len(lav);
    r = av_len(rav);
    m = l < r ? l : r;
    retval = 0;
    i = 0;
    while ( i <= m && retval == 0 )
    {
        left  = SvIV(*av_fetch(lav,i,0));
        right = SvIV(*av_fetch(rav,i,0));
        if ( left < right  )
            retval = -1;
        if ( left > right )
            retval = +1;
        i++;
    }

    /* tiebreaker for alpha with identical terms */
    if ( retval == 0 && l == r && left == right && ( lalpha || ralpha ) )
    {
        if ( lalpha && !ralpha )
        {
            retval = -1;
        }
        else if ( ralpha && !lalpha)
        {
            retval = +1;
        }
    }

    if ( l != r && retval == 0 ) /* possible match except for trailing 0's */
    {
        if ( l < r )
        {
            while ( i <= r && retval == 0 )
            {
                if ( SvIV(*av_fetch(rav,i,0)) != 0 )
                    retval = -1; /* not a match after all */
                i++;
            }
        }
        else
        {
            while ( i <= l && retval == 0 )
            {
                if ( SvIV(*av_fetch(lav,i,0)) != 0 )
                    retval = +1; /* not a match after all */
                i++;
            }
        }
    }
    return retval;
}

#if !defined(HAS_SOCKETPAIR) && defined(HAS_SOCKET) && defined(AF_INET) && defined(PF_INET) && defined(SOCK_DGRAM) && defined(HAS_SELECT)
#   define EMULATE_SOCKETPAIR_UDP
#endif

#ifdef EMULATE_SOCKETPAIR_UDP
static int
S_socketpair_udp (int fd[2]) {
    dTHX;
    /* Fake a datagram socketpair using UDP to localhost.  */
    int sockets[2] = {-1, -1};
    struct sockaddr_in addresses[2];
    int i;
    Sock_size_t size = sizeof(struct sockaddr_in);
    unsigned short port;
    int got;

    memset(&addresses, 0, sizeof(addresses));
    i = 1;
    do {
        sockets[i] = PerlSock_socket(AF_INET, SOCK_DGRAM, PF_INET);
        if (sockets[i] == -1)
            goto tidy_up_and_fail;

        addresses[i].sin_family = AF_INET;
        addresses[i].sin_addr.s_addr = htonl(INADDR_LOOPBACK);
        addresses[i].sin_port = 0;      /* kernel choses port.  */
        if (PerlSock_bind(sockets[i], (struct sockaddr *) &addresses[i],
                sizeof(struct sockaddr_in)) == -1)
            goto tidy_up_and_fail;
    } while (i--);

    /* Now have 2 UDP sockets. Find out which port each is connected to, and
       for each connect the other socket to it.  */
    i = 1;
    do {
        if (PerlSock_getsockname(sockets[i], (struct sockaddr *) &addresses[i],
                &size) == -1)
            goto tidy_up_and_fail;
        if (size != sizeof(struct sockaddr_in))
            goto abort_tidy_up_and_fail;
        /* !1 is 0, !0 is 1 */
        if (PerlSock_connect(sockets[!i], (struct sockaddr *) &addresses[i],
                sizeof(struct sockaddr_in)) == -1)
            goto tidy_up_and_fail;
    } while (i--);

    /* Now we have 2 sockets connected to each other. I don't trust some other
       process not to have already sent a packet to us (by random) so send
       a packet from each to the other.  */
    i = 1;
    do {
        /* I'm going to send my own port number.  As a short.
           (Who knows if someone somewhere has sin_port as a bitfield and needs
           this routine. (I'm assuming crays have socketpair)) */
        port = addresses[i].sin_port;
        got = PerlLIO_write(sockets[i], &port, sizeof(port));
        if (got != sizeof(port)) {
            if (got == -1)
                goto tidy_up_and_fail;
            goto abort_tidy_up_and_fail;
        }
    } while (i--);

    /* Packets sent. I don't trust them to have arrived though.
       (As I understand it Solaris TCP stack is multithreaded. Non-blocking
       connect to localhost will use a second kernel thread. In 2.6 the
       first thread running the connect() returns before the second completes,
       so EINPROGRESS> In 2.7 the improved stack is faster and connect()
       returns 0. Poor programs have tripped up. One poor program's authors'
       had a 50-1 reverse stock split. Not sure how connected these were.)
       So I don't trust someone not to have an unpredictable UDP stack.
    */

    {
        struct timeval waitfor = {0, 100000}; /* You have 0.1 seconds */
        int max = sockets[1] > sockets[0] ? sockets[1] : sockets[0];
        fd_set rset;

        FD_ZERO(&rset);
        FD_SET((unsigned int)sockets[0], &rset);
        FD_SET((unsigned int)sockets[1], &rset);

        got = PerlSock_select(max + 1, &rset, NULL, NULL, &waitfor);
        if (got != 2 || !FD_ISSET(sockets[0], &rset)
                || !FD_ISSET(sockets[1], &rset)) {
            /* I hope this is portable and appropriate.  */
            if (got == -1)
                goto tidy_up_and_fail;
            goto abort_tidy_up_and_fail;
        }
    }

    /* And the paranoia department even now doesn't trust it to have arrive
       (hence MSG_DONTWAIT). Or that what arrives was sent by us.  */
    {
        struct sockaddr_in readfrom;
        unsigned short buffer[2];

        i = 1;
        do {
#ifdef MSG_DONTWAIT
            got = PerlSock_recvfrom(sockets[i], (char *) &buffer,
                    sizeof(buffer), MSG_DONTWAIT,
                    (struct sockaddr *) &readfrom, &size);
#else
            got = PerlSock_recvfrom(sockets[i], (char *) &buffer,
                    sizeof(buffer), 0,
                    (struct sockaddr *) &readfrom, &size);
#endif

            if (got == -1)
                goto tidy_up_and_fail;
            if (got != sizeof(port)
                    || size != sizeof(struct sockaddr_in)
                    /* Check other socket sent us its port.  */
                    || buffer[0] != (unsigned short) addresses[!i].sin_port
                    /* Check kernel says we got the datagram from that socket */
                    || readfrom.sin_family != addresses[!i].sin_family
                    || readfrom.sin_addr.s_addr != addresses[!i].sin_addr.s_addr
                    || readfrom.sin_port != addresses[!i].sin_port)
                goto abort_tidy_up_and_fail;
        } while (i--);
    }
    /* My caller (my_socketpair) has validated that this is non-NULL  */
    fd[0] = sockets[0];
    fd[1] = sockets[1];
    /* I hereby declare this connection open.  May God bless all who cross
       her.  */
    return 0;

  abort_tidy_up_and_fail:
    errno = ECONNABORTED;
  tidy_up_and_fail:
    {
        dSAVE_ERRNO;
        if (sockets[0] != -1)
            PerlLIO_close(sockets[0]);
        if (sockets[1] != -1)
            PerlLIO_close(sockets[1]);
        RESTORE_ERRNO;
        return -1;
    }
}
#endif /*  EMULATE_SOCKETPAIR_UDP */

#if !defined(HAS_SOCKETPAIR) && defined(HAS_SOCKET) && defined(AF_INET) && defined(PF_INET)
int
Perl_my_socketpair (int family, int type, int protocol, int fd[2]) {
    /* Stevens says that family must be AF_LOCAL, protocol 0.
       I'm going to enforce that, then ignore it, and use TCP (or UDP).  */
    dTHXa(NULL);
    int listener = -1;
    int connector = -1;
    int acceptor = -1;
    struct sockaddr_in listen_addr;
    struct sockaddr_in connect_addr;
    Sock_size_t size;

    if (protocol
#ifdef AF_UNIX
        || family != AF_UNIX
#endif
    ) {
        errno = EAFNOSUPPORT;
        return -1;
    }
    if (!fd) {
        errno = EINVAL;
        return -1;
    }

#ifdef EMULATE_SOCKETPAIR_UDP
    if (type == SOCK_DGRAM)
        return S_socketpair_udp(fd);
#endif