[perl #78040] regcomp.c: malloc enough space

Commit 9de15fec376a8ff90a38fad0ff322c72c2995765 introduced /u, /d, and
/l regex modifiers.  Unfortunately, I forgot to adequately account for
them in the space required for the stringification of the regex.

This patch figures out separately if the caret is needed, and if one of
these charset modifiers is needed, and allocates space accordingly.

I could not figure out a simple test case for this fix.  valgrind
prior to this will show errors, and after this doesn't.

diff --git a/regcomp.c b/regcomp.c
index bcdc65f..44f75b7 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -4425,33 +4425,46 @@ Perl_re_compile(pTHX_ SV * const pattern, U32 pm_flags)
     r->extflags = pm_flags;
     {
         bool has_p     = ((r->extflags & RXf_PMf_KEEPCOPY) == RXf_PMf_KEEPCOPY);
-       bool has_minus = ((r->extflags & RXf_PMf_STD_PMMOD) != RXf_PMf_STD_PMMOD);
+        bool has_charset = (r->extflags & (RXf_PMf_LOCALE|RXf_PMf_UNICODE));
+
+        /* The caret is output if there are any defaults: if not all the STD
+         * flags are set, or if no character set specifier is needed */
+        bool has_default =
+                    (((r->extflags & RXf_PMf_STD_PMMOD) != RXf_PMf_STD_PMMOD)
+                    || ! has_charset);
        bool has_runon = ((RExC_seen & REG_SEEN_RUN_ON_COMMENT)==REG_SEEN_RUN_ON_COMMENT);
        U16 reganch = (U16)((r->extflags & RXf_PMf_STD_PMMOD)
                            >> RXf_PMf_STD_PMMOD_SHIFT);
        const char *fptr = STD_PAT_MODS;        /*"msix"*/
        char *p;
         /* Allocate for the worst case, which is all the std flags are turned
-         * on, but this means no caret.  We never output a minus, as all those
-         * are defaults, so are covered by the caret */
+         * on.  If more precision is desired, we could do a population count of
+         * the flags set.  This could be done with a small lookup table, or by
+         * shifting, masking and adding, or even, when available, assembly
+         * language for a machine-language population count.
+         * We never output a minus, as all those are defaults, so are
+         * covered by the caret */
        const STRLEN wraplen = plen + has_p + has_runon
+            + has_default       /* If needs a caret */
+            + has_charset       /* If needs a character set specifier */
             + (sizeof(STD_PAT_MODS) - 1)
             + (sizeof("(?:)") - 1);
 
-       p = sv_grow(MUTABLE_SV(rx), wraplen + 1);
+        p = sv_grow(MUTABLE_SV(rx), wraplen + 1); /* +1 for the ending NUL */
        SvPOK_on(rx);
        SvFLAGS(rx) |= SvUTF8(pattern);
         *p++='('; *p++='?';
 
         /* If a default, cover it using the caret */
-        if (has_minus || (r->extflags & ~(RXf_PMf_LOCALE|RXf_PMf_UNICODE))) {
+        if (has_default) {
             *p++= DEFAULT_PAT_MOD;
         }
-        if (r->extflags & RXf_PMf_LOCALE) {
-            *p++ = LOCALE_PAT_MOD;
-        }
-        else if (r->extflags & RXf_PMf_UNICODE) {
-            *p++ = UNICODE_PAT_MOD;
+        if (has_charset) {
+            if (r->extflags & RXf_PMf_LOCALE) {
+                *p++ = LOCALE_PAT_MOD;
+            } else {
+                *p++ = UNICODE_PAT_MOD;
+            }
         }
         if (has_p)
             *p++ = KEEPCOPY_PAT_MOD; /*'p'*/