This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
[win32] don't share TARG unless -DUSE_BROKEN_PAD_RESET
[perl5.git] / pod / perlguts.pod
CommitLineData
a0d0e21e
LW
1=head1 NAME
2
3perlguts - Perl's Internal Functions
4
5=head1 DESCRIPTION
6
7This document attempts to describe some of the internal functions of the
8Perl executable. It is far from complete and probably contains many errors.
9Please refer any questions or comments to the author below.
10
0a753a76
PP
11=head1 Variables
12
5f05dabc 13=head2 Datatypes
a0d0e21e
LW
14
15Perl has three typedefs that handle Perl's three main data types:
16
17 SV Scalar Value
18 AV Array Value
19 HV Hash Value
20
d1b91892 21Each typedef has specific routines that manipulate the various data types.
a0d0e21e
LW
22
23=head2 What is an "IV"?
24
5f05dabc
PP
25Perl uses a special typedef IV which is a simple integer type that is
26guaranteed to be large enough to hold a pointer (as well as an integer).
a0d0e21e 27
d1b91892
AD
28Perl also uses two special typedefs, I32 and I16, which will always be at
29least 32-bits and 16-bits long, respectively.
a0d0e21e 30
54310121 31=head2 Working with SVs
a0d0e21e
LW
32
33An SV can be created and loaded with one command. There are four types of
34values that can be loaded: an integer value (IV), a double (NV), a string,
35(PV), and another scalar (SV).
36
9da1e3b5 37The six routines are:
a0d0e21e
LW
38
39 SV* newSViv(IV);
40 SV* newSVnv(double);
41 SV* newSVpv(char*, int);
9da1e3b5 42 SV* newSVpvn(char*, int);
46fc3d4c 43 SV* newSVpvf(const char*, ...);
a0d0e21e
LW
44 SV* newSVsv(SV*);
45
deb3007b 46To change the value of an *already-existing* SV, there are seven routines:
a0d0e21e
LW
47
48 void sv_setiv(SV*, IV);
deb3007b 49 void sv_setuv(SV*, UV);
a0d0e21e 50 void sv_setnv(SV*, double);
a0d0e21e 51 void sv_setpv(SV*, char*);
46fc3d4c
PP
52 void sv_setpvn(SV*, char*, int)
53 void sv_setpvf(SV*, const char*, ...);
a0d0e21e
LW
54 void sv_setsv(SV*, SV*);
55
56Notice that you can choose to specify the length of the string to be
9da1e3b5
MUN
57assigned by using C<sv_setpvn>, C<newSVpvn>, or C<newSVpv>, or you may
58allow Perl to calculate the length by using C<sv_setpv> or by specifying
590 as the second argument to C<newSVpv>. Be warned, though, that Perl will
60determine the string's length by using C<strlen>, which depends on the
61string terminating with a NUL character. The arguments of C<sv_setpvf>
62are processed like C<sprintf>, and the formatted output becomes the value.
63The C<sv_set*()> functions are not generic enough to operate on values
64that have "magic". See L<Magic Virtual Tables> later in this document.
a0d0e21e 65
54310121 66All SVs that will contain strings should, but need not, be terminated
5f05dabc
PP
67with a NUL character. If it is not NUL-terminated there is a risk of
68core dumps and corruptions from code which passes the string to C
69functions or system calls which expect a NUL-terminated string.
70Perl's own functions typically add a trailing NUL for this reason.
71Nevertheless, you should be very careful when you pass a string stored
72in an SV to a C function or system call.
73
a0d0e21e
LW
74To access the actual value that an SV points to, you can use the macros:
75
76 SvIV(SV*)
77 SvNV(SV*)
78 SvPV(SV*, STRLEN len)
79
80which will automatically coerce the actual scalar type into an IV, double,
81or string.
82
83In the C<SvPV> macro, the length of the string returned is placed into the
84variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
85care what the length of the data is, use the global variable C<na>. Remember,
86however, that Perl allows arbitrary strings of data that may both contain
54310121 87NULs and might not be terminated by a NUL.
a0d0e21e 88
07fa94a1 89If you want to know if the scalar value is TRUE, you can use:
a0d0e21e
LW
90
91 SvTRUE(SV*)
92
93Although Perl will automatically grow strings for you, if you need to force
94Perl to allocate more memory for your SV, you can use the macro
95
96 SvGROW(SV*, STRLEN newlen)
97
98which will determine if more memory needs to be allocated. If so, it will
99call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
5f05dabc
PP
100decrease, the allocated memory of an SV and that it does not automatically
101add a byte for the a trailing NUL (perl's own string functions typically do
8ebc5c01 102C<SvGROW(sv, len + 1)>).
a0d0e21e
LW
103
104If you have an SV and want to know what kind of data Perl thinks is stored
105in it, you can use the following macros to check the type of SV you have.
106
107 SvIOK(SV*)
108 SvNOK(SV*)
109 SvPOK(SV*)
110
111You can get and set the current length of the string stored in an SV with
112the following macros:
113
114 SvCUR(SV*)
115 SvCUR_set(SV*, I32 val)
116
cb1a09d0
AD
117You can also get a pointer to the end of the string stored in the SV
118with the macro:
119
120 SvEND(SV*)
121
122But note that these last three macros are valid only if C<SvPOK()> is true.
a0d0e21e 123
d1b91892
AD
124If you want to append something to the end of string stored in an C<SV*>,
125you can use the following functions:
126
127 void sv_catpv(SV*, char*);
128 void sv_catpvn(SV*, char*, int);
46fc3d4c 129 void sv_catpvf(SV*, const char*, ...);
d1b91892
AD
130 void sv_catsv(SV*, SV*);
131
132The first function calculates the length of the string to be appended by
133using C<strlen>. In the second, you specify the length of the string
46fc3d4c
PP
134yourself. The third function processes its arguments like C<sprintf> and
135appends the formatted output. The fourth function extends the string
136stored in the first SV with the string stored in the second SV. It also
189b2af5
GS
137forces the second SV to be interpreted as a string. The C<sv_cat*()>
138functions are not generic enough to operate on values that have "magic".
139See L<Magic Virtual Tables> later in this document.
d1b91892 140
a0d0e21e
LW
141If you know the name of a scalar variable, you can get a pointer to its SV
142by using the following:
143
5f05dabc 144 SV* perl_get_sv("package::varname", FALSE);
a0d0e21e
LW
145
146This returns NULL if the variable does not exist.
147
d1b91892 148If you want to know if this variable (or any other SV) is actually C<defined>,
a0d0e21e
LW
149you can call:
150
151 SvOK(SV*)
152
153The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
154address can be used whenever an C<SV*> is needed.
155
156There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
157TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
158be used whenever an C<SV*> is needed.
159
160Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
161Take this code:
162
163 SV* sv = (SV*) 0;
164 if (I-am-to-return-a-real-value) {
165 sv = sv_2mortal(newSViv(42));
166 }
167 sv_setsv(ST(0), sv);
168
169This code tries to return a new SV (which contains the value 42) if it should
04343c6d 170return a real value, or undef otherwise. Instead it has returned a NULL
a0d0e21e 171pointer which, somewhere down the line, will cause a segmentation violation,
5f05dabc
PP
172bus error, or just weird results. Change the zero to C<&sv_undef> in the first
173line and all will be well.
a0d0e21e
LW
174
175To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
3fe9a6f1 176call is not necessary (see L<Reference Counts and Mortality>).
a0d0e21e 177
d1b91892 178=head2 What's Really Stored in an SV?
a0d0e21e
LW
179
180Recall that the usual method of determining the type of scalar you have is
5f05dabc 181to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
d1b91892 182usually these macros will always return TRUE and calling the C<Sv*V>
a0d0e21e
LW
183macros will do the appropriate conversion of string to integer/double or
184integer/double to string.
185
186If you I<really> need to know if you have an integer, double, or string
187pointer in an SV, you can use the following three macros instead:
188
189 SvIOKp(SV*)
190 SvNOKp(SV*)
191 SvPOKp(SV*)
192
193These will tell you if you truly have an integer, double, or string pointer
d1b91892 194stored in your SV. The "p" stands for private.
a0d0e21e 195
07fa94a1 196In general, though, it's best to use the C<Sv*V> macros.
a0d0e21e 197
54310121 198=head2 Working with AVs
a0d0e21e 199
07fa94a1
JO
200There are two ways to create and load an AV. The first method creates an
201empty AV:
a0d0e21e
LW
202
203 AV* newAV();
204
54310121 205The second method both creates the AV and initially populates it with SVs:
a0d0e21e
LW
206
207 AV* av_make(I32 num, SV **ptr);
208
5f05dabc 209The second argument points to an array containing C<num> C<SV*>'s. Once the
54310121 210AV has been created, the SVs can be destroyed, if so desired.
a0d0e21e 211
54310121 212Once the AV has been created, the following operations are possible on AVs:
a0d0e21e
LW
213
214 void av_push(AV*, SV*);
215 SV* av_pop(AV*);
216 SV* av_shift(AV*);
217 void av_unshift(AV*, I32 num);
218
219These should be familiar operations, with the exception of C<av_unshift>.
220This routine adds C<num> elements at the front of the array with the C<undef>
221value. You must then use C<av_store> (described below) to assign values
222to these new elements.
223
224Here are some other functions:
225
5f05dabc 226 I32 av_len(AV*);
a0d0e21e 227 SV** av_fetch(AV*, I32 key, I32 lval);
a0d0e21e 228 SV** av_store(AV*, I32 key, SV* val);
a0d0e21e 229
5f05dabc
PP
230The C<av_len> function returns the highest index value in array (just
231like $#array in Perl). If the array is empty, -1 is returned. The
232C<av_fetch> function returns the value at index C<key>, but if C<lval>
233is non-zero, then C<av_fetch> will store an undef value at that index.
04343c6d
GS
234The C<av_store> function stores the value C<val> at index C<key>, and does
235not increment the reference count of C<val>. Thus the caller is responsible
236for taking care of that, and if C<av_store> returns NULL, the caller will
237have to decrement the reference count to avoid a memory leak. Note that
238C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s as their
239return value.
d1b91892 240
a0d0e21e 241 void av_clear(AV*);
a0d0e21e 242 void av_undef(AV*);
cb1a09d0 243 void av_extend(AV*, I32 key);
5f05dabc
PP
244
245The C<av_clear> function deletes all the elements in the AV* array, but
246does not actually delete the array itself. The C<av_undef> function will
247delete all the elements in the array plus the array itself. The
248C<av_extend> function extends the array so that it contains C<key>
249elements. If C<key> is less than the current length of the array, then
250nothing is done.
a0d0e21e
LW
251
252If you know the name of an array variable, you can get a pointer to its AV
253by using the following:
254
5f05dabc 255 AV* perl_get_av("package::varname", FALSE);
a0d0e21e
LW
256
257This returns NULL if the variable does not exist.
258
04343c6d
GS
259See L<Understanding the Magic of Tied Hashes and Arrays> for more
260information on how to use the array access functions on tied arrays.
261
54310121 262=head2 Working with HVs
a0d0e21e
LW
263
264To create an HV, you use the following routine:
265
266 HV* newHV();
267
54310121 268Once the HV has been created, the following operations are possible on HVs:
a0d0e21e
LW
269
270 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
271 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
272
5f05dabc
PP
273The C<klen> parameter is the length of the key being passed in (Note that
274you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
275length of the key). The C<val> argument contains the SV pointer to the
54310121 276scalar being stored, and C<hash> is the precomputed hash value (zero if
5f05dabc
PP
277you want C<hv_store> to calculate it for you). The C<lval> parameter
278indicates whether this fetch is actually a part of a store operation, in
279which case a new undefined value will be added to the HV with the supplied
280key and C<hv_fetch> will return as if the value had already existed.
a0d0e21e 281
5f05dabc
PP
282Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
283C<SV*>. To access the scalar value, you must first dereference the return
284value. However, you should check to make sure that the return value is
285not NULL before dereferencing it.
a0d0e21e
LW
286
287These two functions check if a hash table entry exists, and deletes it.
288
289 bool hv_exists(HV*, char* key, U32 klen);
d1b91892 290 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
a0d0e21e 291
5f05dabc
PP
292If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
293create and return a mortal copy of the deleted value.
294
a0d0e21e
LW
295And more miscellaneous functions:
296
297 void hv_clear(HV*);
a0d0e21e 298 void hv_undef(HV*);
5f05dabc
PP
299
300Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
301table but does not actually delete the hash table. The C<hv_undef> deletes
302both the entries and the hash table itself.
a0d0e21e 303
d1b91892
AD
304Perl keeps the actual data in linked list of structures with a typedef of HE.
305These contain the actual key and value pointers (plus extra administrative
306overhead). The key is a string pointer; the value is an C<SV*>. However,
307once you have an C<HE*>, to get the actual key and value, use the routines
308specified below.
309
a0d0e21e
LW
310 I32 hv_iterinit(HV*);
311 /* Prepares starting point to traverse hash table */
312 HE* hv_iternext(HV*);
313 /* Get the next entry, and return a pointer to a
314 structure that has both the key and value */
315 char* hv_iterkey(HE* entry, I32* retlen);
316 /* Get the key from an HE structure and also return
317 the length of the key string */
cb1a09d0 318 SV* hv_iterval(HV*, HE* entry);
a0d0e21e
LW
319 /* Return a SV pointer to the value of the HE
320 structure */
cb1a09d0 321 SV* hv_iternextsv(HV*, char** key, I32* retlen);
d1b91892
AD
322 /* This convenience routine combines hv_iternext,
323 hv_iterkey, and hv_iterval. The key and retlen
324 arguments are return values for the key and its
325 length. The value is returned in the SV* argument */
a0d0e21e
LW
326
327If you know the name of a hash variable, you can get a pointer to its HV
328by using the following:
329
5f05dabc 330 HV* perl_get_hv("package::varname", FALSE);
a0d0e21e
LW
331
332This returns NULL if the variable does not exist.
333
8ebc5c01 334The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
a0d0e21e
LW
335
336 i = klen;
337 hash = 0;
338 s = key;
339 while (i--)
340 hash = hash * 33 + *s++;
341
04343c6d
GS
342See L<Understanding the Magic of Tied Hashes and Arrays> for more
343information on how to use the hash access functions on tied hashes.
344
1e422769
PP
345=head2 Hash API Extensions
346
347Beginning with version 5.004, the following functions are also supported:
348
349 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
350 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
351
352 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
353 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
354
355 SV* hv_iterkeysv (HE* entry);
356
357Note that these functions take C<SV*> keys, which simplifies writing
358of extension code that deals with hash structures. These functions
359also allow passing of C<SV*> keys to C<tie> functions without forcing
360you to stringify the keys (unlike the previous set of functions).
361
362They also return and accept whole hash entries (C<HE*>), making their
363use more efficient (since the hash number for a particular string
364doesn't have to be recomputed every time). See L<API LISTING> later in
365this document for detailed descriptions.
366
367The following macros must always be used to access the contents of hash
368entries. Note that the arguments to these macros must be simple
369variables, since they may get evaluated more than once. See
370L<API LISTING> later in this document for detailed descriptions of these
371macros.
372
373 HePV(HE* he, STRLEN len)
374 HeVAL(HE* he)
375 HeHASH(HE* he)
376 HeSVKEY(HE* he)
377 HeSVKEY_force(HE* he)
378 HeSVKEY_set(HE* he, SV* sv)
379
380These two lower level macros are defined, but must only be used when
381dealing with keys that are not C<SV*>s:
382
383 HeKEY(HE* he)
384 HeKLEN(HE* he)
385
04343c6d
GS
386Note that both C<hv_store> and C<hv_store_ent> do not increment the
387reference count of the stored C<val>, which is the caller's responsibility.
388If these functions return a NULL value, the caller will usually have to
389decrement the reference count of C<val> to avoid a memory leak.
1e422769 390
a0d0e21e
LW
391=head2 References
392
d1b91892
AD
393References are a special type of scalar that point to other data types
394(including references).
a0d0e21e 395
07fa94a1 396To create a reference, use either of the following functions:
a0d0e21e 397
5f05dabc
PP
398 SV* newRV_inc((SV*) thing);
399 SV* newRV_noinc((SV*) thing);
a0d0e21e 400
5f05dabc 401The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
07fa94a1
JO
402functions are identical except that C<newRV_inc> increments the reference
403count of the C<thing>, while C<newRV_noinc> does not. For historical
404reasons, C<newRV> is a synonym for C<newRV_inc>.
405
406Once you have a reference, you can use the following macro to dereference
407the reference:
a0d0e21e
LW
408
409 SvRV(SV*)
410
411then call the appropriate routines, casting the returned C<SV*> to either an
d1b91892 412C<AV*> or C<HV*>, if required.
a0d0e21e 413
d1b91892 414To determine if an SV is a reference, you can use the following macro:
a0d0e21e
LW
415
416 SvROK(SV*)
417
07fa94a1
JO
418To discover what type of value the reference refers to, use the following
419macro and then check the return value.
d1b91892
AD
420
421 SvTYPE(SvRV(SV*))
422
423The most useful types that will be returned are:
424
425 SVt_IV Scalar
426 SVt_NV Scalar
427 SVt_PV Scalar
5f05dabc 428 SVt_RV Scalar
d1b91892
AD
429 SVt_PVAV Array
430 SVt_PVHV Hash
431 SVt_PVCV Code
5f05dabc
PP
432 SVt_PVGV Glob (possible a file handle)
433 SVt_PVMG Blessed or Magical Scalar
434
435 See the sv.h header file for more details.
d1b91892 436
cb1a09d0
AD
437=head2 Blessed References and Class Objects
438
439References are also used to support object-oriented programming. In the
440OO lexicon, an object is simply a reference that has been blessed into a
441package (or class). Once blessed, the programmer may now use the reference
442to access the various methods in the class.
443
444A reference can be blessed into a package with the following function:
445
446 SV* sv_bless(SV* sv, HV* stash);
447
448The C<sv> argument must be a reference. The C<stash> argument specifies
3fe9a6f1 449which class the reference will belong to. See
2ae324a7 450L<Stashes and Globs> for information on converting class names into stashes.
cb1a09d0
AD
451
452/* Still under construction */
453
454Upgrades rv to reference if not already one. Creates new SV for rv to
8ebc5c01
PP
455point to. If C<classname> is non-null, the SV is blessed into the specified
456class. SV is returned.
cb1a09d0
AD
457
458 SV* newSVrv(SV* rv, char* classname);
459
8ebc5c01
PP
460Copies integer or double into an SV whose reference is C<rv>. SV is blessed
461if C<classname> is non-null.
cb1a09d0
AD
462
463 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
464 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
465
5f05dabc 466Copies the pointer value (I<the address, not the string!>) into an SV whose
8ebc5c01 467reference is rv. SV is blessed if C<classname> is non-null.
cb1a09d0
AD
468
469 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
470
8ebc5c01
PP
471Copies string into an SV whose reference is C<rv>. Set length to 0 to let
472Perl calculate the string length. SV is blessed if C<classname> is non-null.
cb1a09d0
AD
473
474 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
475
476 int sv_isa(SV* sv, char* name);
477 int sv_isobject(SV* sv);
478
5f05dabc 479=head2 Creating New Variables
cb1a09d0 480
5f05dabc
PP
481To create a new Perl variable with an undef value which can be accessed from
482your Perl script, use the following routines, depending on the variable type.
cb1a09d0 483
5f05dabc
PP
484 SV* perl_get_sv("package::varname", TRUE);
485 AV* perl_get_av("package::varname", TRUE);
486 HV* perl_get_hv("package::varname", TRUE);
cb1a09d0
AD
487
488Notice the use of TRUE as the second parameter. The new variable can now
489be set, using the routines appropriate to the data type.
490
5f05dabc
PP
491There are additional macros whose values may be bitwise OR'ed with the
492C<TRUE> argument to enable certain extra features. Those bits are:
cb1a09d0 493
5f05dabc 494 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
54310121 495 "Name <varname> used only once: possible typo" warning.
07fa94a1
JO
496 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
497 the variable did not exist before the function was called.
cb1a09d0 498
07fa94a1
JO
499If you do not specify a package name, the variable is created in the current
500package.
cb1a09d0 501
5f05dabc 502=head2 Reference Counts and Mortality
a0d0e21e 503
54310121
PP
504Perl uses an reference count-driven garbage collection mechanism. SVs,
505AVs, or HVs (xV for short in the following) start their life with a
55497cff 506reference count of 1. If the reference count of an xV ever drops to 0,
07fa94a1 507then it will be destroyed and its memory made available for reuse.
55497cff
PP
508
509This normally doesn't happen at the Perl level unless a variable is
5f05dabc
PP
510undef'ed or the last variable holding a reference to it is changed or
511overwritten. At the internal level, however, reference counts can be
55497cff
PP
512manipulated with the following macros:
513
514 int SvREFCNT(SV* sv);
5f05dabc 515 SV* SvREFCNT_inc(SV* sv);
55497cff
PP
516 void SvREFCNT_dec(SV* sv);
517
518However, there is one other function which manipulates the reference
07fa94a1
JO
519count of its argument. The C<newRV_inc> function, you will recall,
520creates a reference to the specified argument. As a side effect,
521it increments the argument's reference count. If this is not what
522you want, use C<newRV_noinc> instead.
523
524For example, imagine you want to return a reference from an XSUB function.
525Inside the XSUB routine, you create an SV which initially has a reference
526count of one. Then you call C<newRV_inc>, passing it the just-created SV.
5f05dabc
PP
527This returns the reference as a new SV, but the reference count of the
528SV you passed to C<newRV_inc> has been incremented to two. Now you
07fa94a1
JO
529return the reference from the XSUB routine and forget about the SV.
530But Perl hasn't! Whenever the returned reference is destroyed, the
531reference count of the original SV is decreased to one and nothing happens.
532The SV will hang around without any way to access it until Perl itself
533terminates. This is a memory leak.
5f05dabc
PP
534
535The correct procedure, then, is to use C<newRV_noinc> instead of
faed5253
JO
536C<newRV_inc>. Then, if and when the last reference is destroyed,
537the reference count of the SV will go to zero and it will be destroyed,
07fa94a1 538stopping any memory leak.
55497cff 539
5f05dabc 540There are some convenience functions available that can help with the
54310121 541destruction of xVs. These functions introduce the concept of "mortality".
07fa94a1
JO
542An xV that is mortal has had its reference count marked to be decremented,
543but not actually decremented, until "a short time later". Generally the
544term "short time later" means a single Perl statement, such as a call to
54310121 545an XSUB function. The actual determinant for when mortal xVs have their
07fa94a1
JO
546reference count decremented depends on two macros, SAVETMPS and FREETMPS.
547See L<perlcall> and L<perlxs> for more details on these macros.
55497cff
PP
548
549"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
550However, if you mortalize a variable twice, the reference count will
551later be decremented twice.
552
553You should be careful about creating mortal variables. Strange things
554can happen if you make the same value mortal within multiple contexts,
5f05dabc 555or if you make a variable mortal multiple times.
a0d0e21e
LW
556
557To create a mortal variable, use the functions:
558
559 SV* sv_newmortal()
560 SV* sv_2mortal(SV*)
561 SV* sv_mortalcopy(SV*)
562
5f05dabc
PP
563The first call creates a mortal SV, the second converts an existing
564SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
565third creates a mortal copy of an existing SV.
a0d0e21e 566
54310121 567The mortal routines are not just for SVs -- AVs and HVs can be
faed5253 568made mortal by passing their address (type-casted to C<SV*>) to the
07fa94a1 569C<sv_2mortal> or C<sv_mortalcopy> routines.
a0d0e21e 570
5f05dabc 571=head2 Stashes and Globs
a0d0e21e 572
aa689395
PP
573A "stash" is a hash that contains all of the different objects that
574are contained within a package. Each key of the stash is a symbol
575name (shared by all the different types of objects that have the same
576name), and each value in the hash table is a GV (Glob Value). This GV
577in turn contains references to the various objects of that name,
578including (but not limited to) the following:
cb1a09d0 579
a0d0e21e
LW
580 Scalar Value
581 Array Value
582 Hash Value
583 File Handle
584 Directory Handle
585 Format
586 Subroutine
587
5f05dabc
PP
588There is a single stash called "defstash" that holds the items that exist
589in the "main" package. To get at the items in other packages, append the
590string "::" to the package name. The items in the "Foo" package are in
591the stash "Foo::" in defstash. The items in the "Bar::Baz" package are
592in the stash "Baz::" in "Bar::"'s stash.
a0d0e21e 593
d1b91892 594To get the stash pointer for a particular package, use the function:
a0d0e21e
LW
595
596 HV* gv_stashpv(char* name, I32 create)
597 HV* gv_stashsv(SV*, I32 create)
598
599The first function takes a literal string, the second uses the string stored
d1b91892 600in the SV. Remember that a stash is just a hash table, so you get back an
cb1a09d0 601C<HV*>. The C<create> flag will create a new package if it is set.
a0d0e21e
LW
602
603The name that C<gv_stash*v> wants is the name of the package whose symbol table
604you want. The default package is called C<main>. If you have multiply nested
d1b91892
AD
605packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
606language itself.
a0d0e21e
LW
607
608Alternately, if you have an SV that is a blessed reference, you can find
609out the stash pointer by using:
610
611 HV* SvSTASH(SvRV(SV*));
612
613then use the following to get the package name itself:
614
615 char* HvNAME(HV* stash);
616
5f05dabc
PP
617If you need to bless or re-bless an object you can use the following
618function:
a0d0e21e
LW
619
620 SV* sv_bless(SV*, HV* stash)
621
622where the first argument, an C<SV*>, must be a reference, and the second
623argument is a stash. The returned C<SV*> can now be used in the same way
624as any other SV.
625
d1b91892
AD
626For more information on references and blessings, consult L<perlref>.
627
54310121 628=head2 Double-Typed SVs
0a753a76
PP
629
630Scalar variables normally contain only one type of value, an integer,
631double, pointer, or reference. Perl will automatically convert the
632actual scalar data from the stored type into the requested type.
633
634Some scalar variables contain more than one type of scalar data. For
635example, the variable C<$!> contains either the numeric value of C<errno>
636or its string equivalent from either C<strerror> or C<sys_errlist[]>.
637
638To force multiple data values into an SV, you must do two things: use the
639C<sv_set*v> routines to add the additional scalar type, then set a flag
640so that Perl will believe it contains more than one type of data. The
641four macros to set the flags are:
642
643 SvIOK_on
644 SvNOK_on
645 SvPOK_on
646 SvROK_on
647
648The particular macro you must use depends on which C<sv_set*v> routine
649you called first. This is because every C<sv_set*v> routine turns on
650only the bit for the particular type of data being set, and turns off
651all the rest.
652
653For example, to create a new Perl variable called "dberror" that contains
654both the numeric and descriptive string error values, you could use the
655following code:
656
657 extern int dberror;
658 extern char *dberror_list;
659
660 SV* sv = perl_get_sv("dberror", TRUE);
661 sv_setiv(sv, (IV) dberror);
662 sv_setpv(sv, dberror_list[dberror]);
663 SvIOK_on(sv);
664
665If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
666macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
667
668=head2 Magic Variables
a0d0e21e 669
d1b91892
AD
670[This section still under construction. Ignore everything here. Post no
671bills. Everything not permitted is forbidden.]
672
d1b91892
AD
673Any SV may be magical, that is, it has special features that a normal
674SV does not have. These features are stored in the SV structure in a
5f05dabc 675linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
d1b91892
AD
676
677 struct magic {
678 MAGIC* mg_moremagic;
679 MGVTBL* mg_virtual;
680 U16 mg_private;
681 char mg_type;
682 U8 mg_flags;
683 SV* mg_obj;
684 char* mg_ptr;
685 I32 mg_len;
686 };
687
688Note this is current as of patchlevel 0, and could change at any time.
689
690=head2 Assigning Magic
691
692Perl adds magic to an SV using the sv_magic function:
693
694 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
695
696The C<sv> argument is a pointer to the SV that is to acquire a new magical
697feature.
698
699If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
700set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
701it to the beginning of the linked list of magical features. Any prior
702entry of the same type of magic is deleted. Note that this can be
5fb8527f 703overridden, and multiple instances of the same type of magic can be
d1b91892
AD
704associated with an SV.
705
54310121
PP
706The C<name> and C<namlen> arguments are used to associate a string with
707the magic, typically the name of a variable. C<namlen> is stored in the
708C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
d1b91892
AD
709copy of the name is stored in C<mg_ptr> field.
710
711The sv_magic function uses C<how> to determine which, if any, predefined
712"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
cb1a09d0
AD
713See the "Magic Virtual Table" section below. The C<how> argument is also
714stored in the C<mg_type> field.
d1b91892
AD
715
716The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
717structure. If it is not the same as the C<sv> argument, the reference
718count of the C<obj> object is incremented. If it is the same, or if
04343c6d 719the C<how> argument is "#", or if it is a NULL pointer, then C<obj> is
d1b91892
AD
720merely stored, without the reference count being incremented.
721
cb1a09d0
AD
722There is also a function to add magic to an C<HV>:
723
724 void hv_magic(HV *hv, GV *gv, int how);
725
726This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
727
728To remove the magic from an SV, call the function sv_unmagic:
729
730 void sv_unmagic(SV *sv, int type);
731
732The C<type> argument should be equal to the C<how> value when the C<SV>
733was initially made magical.
734
d1b91892
AD
735=head2 Magic Virtual Tables
736
737The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
738C<MGVTBL>, which is a structure of function pointers and stands for
739"Magic Virtual Table" to handle the various operations that might be
740applied to that variable.
741
742The C<MGVTBL> has five pointers to the following routine types:
743
744 int (*svt_get)(SV* sv, MAGIC* mg);
745 int (*svt_set)(SV* sv, MAGIC* mg);
746 U32 (*svt_len)(SV* sv, MAGIC* mg);
747 int (*svt_clear)(SV* sv, MAGIC* mg);
748 int (*svt_free)(SV* sv, MAGIC* mg);
749
750This MGVTBL structure is set at compile-time in C<perl.h> and there are
751currently 19 types (or 21 with overloading turned on). These different
752structures contain pointers to various routines that perform additional
753actions depending on which function is being called.
754
755 Function pointer Action taken
756 ---------------- ------------
757 svt_get Do something after the value of the SV is retrieved.
758 svt_set Do something after the SV is assigned a value.
759 svt_len Report on the SV's length.
760 svt_clear Clear something the SV represents.
761 svt_free Free any extra storage associated with the SV.
762
763For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
764to an C<mg_type> of '\0') contains:
765
766 { magic_get, magic_set, magic_len, 0, 0 }
767
768Thus, when an SV is determined to be magical and of type '\0', if a get
769operation is being performed, the routine C<magic_get> is called. All
770the various routines for the various magical types begin with C<magic_>.
771
772The current kinds of Magic Virtual Tables are:
773
bdbeb323 774 mg_type MGVTBL Type of magic
5f05dabc 775 ------- ------ ----------------------------
bdbeb323
SM
776 \0 vtbl_sv Special scalar variable
777 A vtbl_amagic %OVERLOAD hash
778 a vtbl_amagicelem %OVERLOAD hash element
779 c (none) Holds overload table (AMT) on stash
780 B vtbl_bm Boyer-Moore (fast string search)
d1b91892
AD
781 E vtbl_env %ENV hash
782 e vtbl_envelem %ENV hash element
bdbeb323
SM
783 f vtbl_fm Formline ('compiled' format)
784 g vtbl_mglob m//g target / study()ed string
d1b91892
AD
785 I vtbl_isa @ISA array
786 i vtbl_isaelem @ISA array element
bdbeb323
SM
787 k vtbl_nkeys scalar(keys()) lvalue
788 L (none) Debugger %_<filename
789 l vtbl_dbline Debugger %_<filename element
44a8e56a 790 o vtbl_collxfrm Locale transformation
bdbeb323
SM
791 P vtbl_pack Tied array or hash
792 p vtbl_packelem Tied array or hash element
793 q vtbl_packelem Tied scalar or handle
794 S vtbl_sig %SIG hash
795 s vtbl_sigelem %SIG hash element
d1b91892 796 t vtbl_taint Taintedness
bdbeb323
SM
797 U vtbl_uvar Available for use by extensions
798 v vtbl_vec vec() lvalue
799 x vtbl_substr substr() lvalue
800 y vtbl_defelem Shadow "foreach" iterator variable /
801 smart parameter vivification
802 * vtbl_glob GV (typeglob)
803 # vtbl_arylen Array length ($#ary)
804 . vtbl_pos pos() lvalue
805 ~ (none) Available for use by extensions
d1b91892 806
68dc0745
PP
807When an uppercase and lowercase letter both exist in the table, then the
808uppercase letter is used to represent some kind of composite type (a list
809or a hash), and the lowercase letter is used to represent an element of
d1b91892
AD
810that composite type.
811
bdbeb323
SM
812The '~' and 'U' magic types are defined specifically for use by
813extensions and will not be used by perl itself. Extensions can use
814'~' magic to 'attach' private information to variables (typically
815objects). This is especially useful because there is no way for
816normal perl code to corrupt this private information (unlike using
817extra elements of a hash object).
818
819Similarly, 'U' magic can be used much like tie() to call a C function
820any time a scalar's value is used or changed. The C<MAGIC>'s
821C<mg_ptr> field points to a C<ufuncs> structure:
822
823 struct ufuncs {
824 I32 (*uf_val)(IV, SV*);
825 I32 (*uf_set)(IV, SV*);
826 IV uf_index;
827 };
828
829When the SV is read from or written to, the C<uf_val> or C<uf_set>
830function will be called with C<uf_index> as the first arg and a
831pointer to the SV as the second.
5f05dabc 832
bdbeb323
SM
833Note that because multiple extensions may be using '~' or 'U' magic,
834it is important for extensions to take extra care to avoid conflict.
835Typically only using the magic on objects blessed into the same class
836as the extension is sufficient. For '~' magic, it may also be
837appropriate to add an I32 'signature' at the top of the private data
838area and check that.
5f05dabc 839
189b2af5
GS
840Also note that most of the C<sv_set*()> functions that modify scalars do
841B<not> invoke 'set' magic on their targets. This must be done by the user
842either by calling the C<SvSETMAGIC()> macro after calling these functions,
843or by using one of the C<SvSetMagic*()> macros. Similarly, generic C code
844must call the C<SvGETMAGIC()> macro to invoke any 'get' magic if they use
845an SV obtained from external sources in functions that don't handle magic.
846L<API LISTING> later in this document identifies such macros and functions.
847For example, calls to the C<sv_cat*()> functions typically need to be
848followed by C<SvSETMAGIC()>, but they don't need a prior C<SvGETMAGIC()>
849since their implementation handles 'get' magic.
850
d1b91892
AD
851=head2 Finding Magic
852
853 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
854
855This routine returns a pointer to the C<MAGIC> structure stored in the SV.
856If the SV does not have that magical feature, C<NULL> is returned. Also,
54310121 857if the SV is not of type SVt_PVMG, Perl may core dump.
d1b91892
AD
858
859 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
860
861This routine checks to see what types of magic C<sv> has. If the mg_type
68dc0745
PP
862field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
863the mg_type field is changed to be the lowercase letter.
a0d0e21e 864
04343c6d
GS
865=head2 Understanding the Magic of Tied Hashes and Arrays
866
867Tied hashes and arrays are magical beasts of the 'P' magic type.
9edb2b46
GS
868
869WARNING: As of the 5.004 release, proper usage of the array and hash
870access functions requires understanding a few caveats. Some
871of these caveats are actually considered bugs in the API, to be fixed
872in later releases, and are bracketed with [MAYCHANGE] below. If
873you find yourself actually applying such information in this section, be
874aware that the behavior may change in the future, umm, without warning.
04343c6d
GS
875
876The C<av_store> function, when given a tied array argument, merely
877copies the magic of the array onto the value to be "stored", using
878C<mg_copy>. It may also return NULL, indicating that the value did not
9edb2b46
GS
879actually need to be stored in the array. [MAYCHANGE] After a call to
880C<av_store> on a tied array, the caller will usually need to call
881C<mg_set(val)> to actually invoke the perl level "STORE" method on the
882TIEARRAY object. If C<av_store> did return NULL, a call to
883C<SvREFCNT_dec(val)> will also be usually necessary to avoid a memory
884leak. [/MAYCHANGE]
04343c6d
GS
885
886The previous paragraph is applicable verbatim to tied hash access using the
887C<hv_store> and C<hv_store_ent> functions as well.
888
889C<av_fetch> and the corresponding hash functions C<hv_fetch> and
890C<hv_fetch_ent> actually return an undefined mortal value whose magic
891has been initialized using C<mg_copy>. Note the value so returned does not
9edb2b46
GS
892need to be deallocated, as it is already mortal. [MAYCHANGE] But you will
893need to call C<mg_get()> on the returned value in order to actually invoke
894the perl level "FETCH" method on the underlying TIE object. Similarly,
04343c6d
GS
895you may also call C<mg_set()> on the return value after possibly assigning
896a suitable value to it using C<sv_setsv>, which will invoke the "STORE"
9edb2b46 897method on the TIE object. [/MAYCHANGE]
04343c6d 898
9edb2b46 899[MAYCHANGE]
04343c6d
GS
900In other words, the array or hash fetch/store functions don't really
901fetch and store actual values in the case of tied arrays and hashes. They
902merely call C<mg_copy> to attach magic to the values that were meant to be
903"stored" or "fetched". Later calls to C<mg_get> and C<mg_set> actually
904do the job of invoking the TIE methods on the underlying objects. Thus
9edb2b46 905the magic mechanism currently implements a kind of lazy access to arrays
04343c6d
GS
906and hashes.
907
908Currently (as of perl version 5.004), use of the hash and array access
909functions requires the user to be aware of whether they are operating on
9edb2b46
GS
910"normal" hashes and arrays, or on their tied variants. The API may be
911changed to provide more transparent access to both tied and normal data
912types in future versions.
913[/MAYCHANGE]
04343c6d
GS
914
915You would do well to understand that the TIEARRAY and TIEHASH interfaces
916are mere sugar to invoke some perl method calls while using the uniform hash
917and array syntax. The use of this sugar imposes some overhead (typically
918about two to four extra opcodes per FETCH/STORE operation, in addition to
919the creation of all the mortal variables required to invoke the methods).
920This overhead will be comparatively small if the TIE methods are themselves
921substantial, but if they are only a few statements long, the overhead
922will not be insignificant.
923
d1c897a1
IZ
924=head2 Localizing changes
925
926Perl has a very handy construction
927
928 {
929 local $var = 2;
930 ...
931 }
932
933This construction is I<approximately> equivalent to
934
935 {
936 my $oldvar = $var;
937 $var = 2;
938 ...
939 $var = $oldvar;
940 }
941
942The biggest difference is that the first construction would
943reinstate the initial value of $var, irrespective of how control exits
944the block: C<goto>, C<return>, C<die>/C<eval> etc. It is a little bit
945more efficient as well.
946
947There is a way to achieve a similar task from C via Perl API: create a
948I<pseudo-block>, and arrange for some changes to be automatically
949undone at the end of it, either explicit, or via a non-local exit (via
950die()). A I<block>-like construct is created by a pair of
951C<ENTER>/C<LEAVE> macros (see L<perlcall/EXAMPLE/"Returning a
952Scalar">). Such a construct may be created specially for some
953important localized task, or an existing one (like boundaries of
954enclosing Perl subroutine/block, or an existing pair for freeing TMPs)
955may be used. (In the second case the overhead of additional
956localization must be almost negligible.) Note that any XSUB is
957automatically enclosed in an C<ENTER>/C<LEAVE> pair.
958
959Inside such a I<pseudo-block> the following service is available:
960
961=over
962
963=item C<SAVEINT(int i)>
964
965=item C<SAVEIV(IV i)>
966
967=item C<SAVEI32(I32 i)>
968
969=item C<SAVELONG(long i)>
970
971These macros arrange things to restore the value of integer variable
972C<i> at the end of enclosing I<pseudo-block>.
973
974=item C<SAVESPTR(s)>
975
976=item C<SAVEPPTR(p)>
977
978These macros arrange things to restore the value of pointers C<s> and
979C<p>. C<s> must be a pointer of a type which survives conversion to
980C<SV*> and back, C<p> should be able to survive conversion to C<char*>
981and back.
982
983=item C<SAVEFREESV(SV *sv)>
984
985The refcount of C<sv> would be decremented at the end of
986I<pseudo-block>. This is similar to C<sv_2mortal>, which should (?) be
987used instead.
988
989=item C<SAVEFREEOP(OP *op)>
990
991The C<OP *> is op_free()ed at the end of I<pseudo-block>.
992
993=item C<SAVEFREEPV(p)>
994
995The chunk of memory which is pointed to by C<p> is Safefree()ed at the
996end of I<pseudo-block>.
997
998=item C<SAVECLEARSV(SV *sv)>
999
1000Clears a slot in the current scratchpad which corresponds to C<sv> at
1001the end of I<pseudo-block>.
1002
1003=item C<SAVEDELETE(HV *hv, char *key, I32 length)>
1004
1005The key C<key> of C<hv> is deleted at the end of I<pseudo-block>. The
1006string pointed to by C<key> is Safefree()ed. If one has a I<key> in
1007short-lived storage, the corresponding string may be reallocated like
1008this:
1009
1010 SAVEDELETE(defstash, savepv(tmpbuf), strlen(tmpbuf));
1011
1012=item C<SAVEDESTRUCTOR(f,p)>
1013
1014At the end of I<pseudo-block> the function C<f> is called with the
1015only argument (of type C<void*>) C<p>.
1016
1017=item C<SAVESTACK_POS()>
1018
1019The current offset on the Perl internal stack (cf. C<SP>) is restored
1020at the end of I<pseudo-block>.
1021
1022=back
1023
1024The following API list contains functions, thus one needs to
1025provide pointers to the modifiable data explicitly (either C pointers,
1026or Perlish C<GV *>s). Where the above macros take C<int>, a similar
1027function takes C<int *>.
1028
1029=over
1030
1031=item C<SV* save_scalar(GV *gv)>
1032
1033Equivalent to Perl code C<local $gv>.
1034
1035=item C<AV* save_ary(GV *gv)>
1036
1037=item C<HV* save_hash(GV *gv)>
1038
1039Similar to C<save_scalar>, but localize C<@gv> and C<%gv>.
1040
1041=item C<void save_item(SV *item)>
1042
1043Duplicates the current value of C<SV>, on the exit from the current
1044C<ENTER>/C<LEAVE> I<pseudo-block> will restore the value of C<SV>
1045using the stored value.
1046
1047=item C<void save_list(SV **sarg, I32 maxsarg)>
1048
1049A variant of C<save_item> which takes multiple arguments via an array
1050C<sarg> of C<SV*> of length C<maxsarg>.
1051
1052=item C<SV* save_svref(SV **sptr)>
1053
1054Similar to C<save_scalar>, but will reinstate a C<SV *>.
1055
1056=item C<void save_aptr(AV **aptr)>
1057
1058=item C<void save_hptr(HV **hptr)>
1059
1060Similar to C<save_svref>, but localize C<AV *> and C<HV *>.
1061
1062=back
1063
1064The C<Alias> module implements localization of the basic types within the
1065I<caller's scope>. People who are interested in how to localize things in
1066the containing scope should take a look there too.
1067
0a753a76 1068=head1 Subroutines
a0d0e21e 1069
68dc0745 1070=head2 XSUBs and the Argument Stack
5f05dabc
PP
1071
1072The XSUB mechanism is a simple way for Perl programs to access C subroutines.
1073An XSUB routine will have a stack that contains the arguments from the Perl
1074program, and a way to map from the Perl data structures to a C equivalent.
1075
1076The stack arguments are accessible through the C<ST(n)> macro, which returns
1077the C<n>'th stack argument. Argument 0 is the first argument passed in the
1078Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
1079an C<SV*> is used.
1080
1081Most of the time, output from the C routine can be handled through use of
1082the RETVAL and OUTPUT directives. However, there are some cases where the
1083argument stack is not already long enough to handle all the return values.
1084An example is the POSIX tzname() call, which takes no arguments, but returns
1085two, the local time zone's standard and summer time abbreviations.
1086
1087To handle this situation, the PPCODE directive is used and the stack is
1088extended using the macro:
1089
1090 EXTEND(sp, num);
1091
1092where C<sp> is the stack pointer, and C<num> is the number of elements the
1093stack should be extended by.
1094
1095Now that there is room on the stack, values can be pushed on it using the
54310121 1096macros to push IVs, doubles, strings, and SV pointers respectively:
5f05dabc
PP
1097
1098 PUSHi(IV)
1099 PUSHn(double)
1100 PUSHp(char*, I32)
1101 PUSHs(SV*)
1102
1103And now the Perl program calling C<tzname>, the two values will be assigned
1104as in:
1105
1106 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
1107
1108An alternate (and possibly simpler) method to pushing values on the stack is
1109to use the macros:
1110
1111 XPUSHi(IV)
1112 XPUSHn(double)
1113 XPUSHp(char*, I32)
1114 XPUSHs(SV*)
1115
1116These macros automatically adjust the stack for you, if needed. Thus, you
1117do not need to call C<EXTEND> to extend the stack.
1118
1119For more information, consult L<perlxs> and L<perlxstut>.
1120
1121=head2 Calling Perl Routines from within C Programs
a0d0e21e
LW
1122
1123There are four routines that can be used to call a Perl subroutine from
1124within a C program. These four are:
1125
1126 I32 perl_call_sv(SV*, I32);
1127 I32 perl_call_pv(char*, I32);
1128 I32 perl_call_method(char*, I32);
1129 I32 perl_call_argv(char*, I32, register char**);
1130
d1b91892
AD
1131The routine most often used is C<perl_call_sv>. The C<SV*> argument
1132contains either the name of the Perl subroutine to be called, or a
1133reference to the subroutine. The second argument consists of flags
1134that control the context in which the subroutine is called, whether
1135or not the subroutine is being passed arguments, how errors should be
1136trapped, and how to treat return values.
a0d0e21e
LW
1137
1138All four routines return the number of arguments that the subroutine returned
1139on the Perl stack.
1140
d1b91892
AD
1141When using any of these routines (except C<perl_call_argv>), the programmer
1142must manipulate the Perl stack. These include the following macros and
1143functions:
a0d0e21e
LW
1144
1145 dSP
1146 PUSHMARK()
1147 PUTBACK
1148 SPAGAIN
1149 ENTER
1150 SAVETMPS
1151 FREETMPS
1152 LEAVE
1153 XPUSH*()
cb1a09d0 1154 POP*()
a0d0e21e 1155
5f05dabc
PP
1156For a detailed description of calling conventions from C to Perl,
1157consult L<perlcall>.
a0d0e21e 1158
5f05dabc 1159=head2 Memory Allocation
a0d0e21e 1160
5f05dabc
PP
1161It is suggested that you use the version of malloc that is distributed
1162with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
1163order to satisfy allocation requests more quickly. However, on some
1164platforms, it may cause spurious malloc or free errors.
d1b91892
AD
1165
1166 New(x, pointer, number, type);
1167 Newc(x, pointer, number, type, cast);
1168 Newz(x, pointer, number, type);
1169
07fa94a1 1170These three macros are used to initially allocate memory.
5f05dabc
PP
1171
1172The first argument C<x> was a "magic cookie" that was used to keep track
1173of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
1174the current code makes no use of this feature (most Perl developers now
1175use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
1176
1177The second argument C<pointer> should be the name of a variable that will
1178point to the newly allocated memory.
d1b91892 1179
d1b91892
AD
1180The third and fourth arguments C<number> and C<type> specify how many of
1181the specified type of data structure should be allocated. The argument
1182C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
1183should be used if the C<pointer> argument is different from the C<type>
1184argument.
1185
1186Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
1187to zero out all the newly allocated memory.
1188
1189 Renew(pointer, number, type);
1190 Renewc(pointer, number, type, cast);
1191 Safefree(pointer)
1192
1193These three macros are used to change a memory buffer size or to free a
1194piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
1195match those of C<New> and C<Newc> with the exception of not needing the
1196"magic cookie" argument.
1197
1198 Move(source, dest, number, type);
1199 Copy(source, dest, number, type);
1200 Zero(dest, number, type);
1201
1202These three macros are used to move, copy, or zero out previously allocated
1203memory. The C<source> and C<dest> arguments point to the source and
1204destination starting points. Perl will move, copy, or zero out C<number>
1205instances of the size of the C<type> data structure (using the C<sizeof>
1206function).
a0d0e21e 1207
5f05dabc 1208=head2 PerlIO
ce3d39e2 1209
5f05dabc
PP
1210The most recent development releases of Perl has been experimenting with
1211removing Perl's dependency on the "normal" standard I/O suite and allowing
1212other stdio implementations to be used. This involves creating a new
1213abstraction layer that then calls whichever implementation of stdio Perl
68dc0745 1214was compiled with. All XSUBs should now use the functions in the PerlIO
5f05dabc
PP
1215abstraction layer and not make any assumptions about what kind of stdio
1216is being used.
1217
1218For a complete description of the PerlIO abstraction, consult L<perlapio>.
1219
8ebc5c01 1220=head2 Putting a C value on Perl stack
ce3d39e2
IZ
1221
1222A lot of opcodes (this is an elementary operation in the internal perl
1223stack machine) put an SV* on the stack. However, as an optimization
1224the corresponding SV is (usually) not recreated each time. The opcodes
1225reuse specially assigned SVs (I<target>s) which are (as a corollary)
1226not constantly freed/created.
1227
0a753a76 1228Each of the targets is created only once (but see
ce3d39e2
IZ
1229L<Scratchpads and recursion> below), and when an opcode needs to put
1230an integer, a double, or a string on stack, it just sets the
1231corresponding parts of its I<target> and puts the I<target> on stack.
1232
1233The macro to put this target on stack is C<PUSHTARG>, and it is
1234directly used in some opcodes, as well as indirectly in zillions of
1235others, which use it via C<(X)PUSH[pni]>.
1236
8ebc5c01 1237=head2 Scratchpads
ce3d39e2 1238
54310121 1239The question remains on when the SVs which are I<target>s for opcodes
5f05dabc
PP
1240are created. The answer is that they are created when the current unit --
1241a subroutine or a file (for opcodes for statements outside of
1242subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
1243array is created, which is called a scratchpad for the current
1244unit.
1245
54310121 1246A scratchpad keeps SVs which are lexicals for the current unit and are
ce3d39e2
IZ
1247targets for opcodes. One can deduce that an SV lives on a scratchpad
1248by looking on its flags: lexicals have C<SVs_PADMY> set, and
1249I<target>s have C<SVs_PADTMP> set.
1250
54310121
PP
1251The correspondence between OPs and I<target>s is not 1-to-1. Different
1252OPs in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
1253would not conflict with the expected life of the temporary.
1254
2ae324a7 1255=head2 Scratchpads and recursion
ce3d39e2
IZ
1256
1257In fact it is not 100% true that a compiled unit contains a pointer to
1258the scratchpad AV. In fact it contains a pointer to an AV of
1259(initially) one element, and this element is the scratchpad AV. Why do
1260we need an extra level of indirection?
1261
1262The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1263these can create several execution pointers going into the same
1264subroutine. For the subroutine-child not write over the temporaries
1265for the subroutine-parent (lifespan of which covers the call to the
1266child), the parent and the child should have different
1267scratchpads. (I<And> the lexicals should be separate anyway!)
1268
5f05dabc
PP
1269So each subroutine is born with an array of scratchpads (of length 1).
1270On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
1271depth of the recursion is not more than the length of this array, and
1272if it is, new scratchpad is created and pushed into the array.
1273
1274The I<target>s on this scratchpad are C<undef>s, but they are already
1275marked with correct flags.
1276
0a753a76
PP
1277=head1 Compiled code
1278
1279=head2 Code tree
1280
1281Here we describe the internal form your code is converted to by
1282Perl. Start with a simple example:
1283
1284 $a = $b + $c;
1285
1286This is converted to a tree similar to this one:
1287
1288 assign-to
1289 / \
1290 + $a
1291 / \
1292 $b $c
1293
1294(but slightly more complicated). This tree reflect the way Perl
1295parsed your code, but has nothing to do with the execution order.
1296There is an additional "thread" going through the nodes of the tree
1297which shows the order of execution of the nodes. In our simplified
1298example above it looks like:
1299
1300 $b ---> $c ---> + ---> $a ---> assign-to
1301
1302But with the actual compile tree for C<$a = $b + $c> it is different:
1303some nodes I<optimized away>. As a corollary, though the actual tree
1304contains more nodes than our simplified example, the execution order
1305is the same as in our example.
1306
1307=head2 Examining the tree
1308
1309If you have your perl compiled for debugging (usually done with C<-D
1310optimize=-g> on C<Configure> command line), you may examine the
1311compiled tree by specifying C<-Dx> on the Perl command line. The
1312output takes several lines per node, and for C<$b+$c> it looks like
1313this:
1314
1315 5 TYPE = add ===> 6
1316 TARG = 1
1317 FLAGS = (SCALAR,KIDS)
1318 {
1319 TYPE = null ===> (4)
1320 (was rv2sv)
1321 FLAGS = (SCALAR,KIDS)
1322 {
1323 3 TYPE = gvsv ===> 4
1324 FLAGS = (SCALAR)
1325 GV = main::b
1326 }
1327 }
1328 {
1329 TYPE = null ===> (5)
1330 (was rv2sv)
1331 FLAGS = (SCALAR,KIDS)
1332 {
1333 4 TYPE = gvsv ===> 5
1334 FLAGS = (SCALAR)
1335 GV = main::c
1336 }
1337 }
1338
1339This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1340not optimized away (one per number in the left column). The immediate
1341children of the given node correspond to C<{}> pairs on the same level
1342of indentation, thus this listing corresponds to the tree:
1343
1344 add
1345 / \
1346 null null
1347 | |
1348 gvsv gvsv
1349
1350The execution order is indicated by C<===E<gt>> marks, thus it is C<3
13514 5 6> (node C<6> is not included into above listing), i.e.,
1352C<gvsv gvsv add whatever>.
1353
1354=head2 Compile pass 1: check routines
1355
1356The tree is created by the I<pseudo-compiler> while yacc code feeds it
1357the constructions it recognizes. Since yacc works bottom-up, so does
1358the first pass of perl compilation.
1359
1360What makes this pass interesting for perl developers is that some
1361optimization may be performed on this pass. This is optimization by
1362so-called I<check routines>. The correspondence between node names
1363and corresponding check routines is described in F<opcode.pl> (do not
1364forget to run C<make regen_headers> if you modify this file).
1365
1366A check routine is called when the node is fully constructed except
1367for the execution-order thread. Since at this time there is no
1368back-links to the currently constructed node, one can do most any
1369operation to the top-level node, including freeing it and/or creating
1370new nodes above/below it.
1371
1372The check routine returns the node which should be inserted into the
1373tree (if the top-level node was not modified, check routine returns
1374its argument).
1375
1376By convention, check routines have names C<ck_*>. They are usually
1377called from C<new*OP> subroutines (or C<convert>) (which in turn are
1378called from F<perly.y>).
1379
1380=head2 Compile pass 1a: constant folding
1381
1382Immediately after the check routine is called the returned node is
1383checked for being compile-time executable. If it is (the value is
1384judged to be constant) it is immediately executed, and a I<constant>
1385node with the "return value" of the corresponding subtree is
1386substituted instead. The subtree is deleted.
1387
1388If constant folding was not performed, the execution-order thread is
1389created.
1390
1391=head2 Compile pass 2: context propagation
1392
1393When a context for a part of compile tree is known, it is propagated
1394down through the tree. Aat this time the context can have 5 values
1395(instead of 2 for runtime context): void, boolean, scalar, list, and
1396lvalue. In contrast with the pass 1 this pass is processed from top
1397to bottom: a node's context determines the context for its children.
1398
1399Additional context-dependent optimizations are performed at this time.
1400Since at this moment the compile tree contains back-references (via
1401"thread" pointers), nodes cannot be free()d now. To allow
1402optimized-away nodes at this stage, such nodes are null()ified instead
1403of free()ing (i.e. their type is changed to OP_NULL).
1404
1405=head2 Compile pass 3: peephole optimization
1406
1407After the compile tree for a subroutine (or for an C<eval> or a file)
1408is created, an additional pass over the code is performed. This pass
1409is neither top-down or bottom-up, but in the execution order (with
1410additional compilications for conditionals). These optimizations are
1411done in the subroutine peep(). Optimizations performed at this stage
1412are subject to the same restrictions as in the pass 2.
1413
1414=head1 API LISTING
a0d0e21e 1415
cb1a09d0
AD
1416This is a listing of functions, macros, flags, and variables that may be
1417useful to extension writers or that may be found while reading other
1418extensions.
a0d0e21e 1419
cb1a09d0 1420=over 8
a0d0e21e 1421
cb1a09d0
AD
1422=item AvFILL
1423
fb73857a 1424Same as C<av_len>.
cb1a09d0
AD
1425
1426=item av_clear
1427
0146554f
GA
1428Clears an array, making it empty. Does not free the memory used by the
1429array itself.
cb1a09d0
AD
1430
1431 void av_clear _((AV* ar));
1432
1433=item av_extend
1434
1435Pre-extend an array. The C<key> is the index to which the array should be
1436extended.
1437
1438 void av_extend _((AV* ar, I32 key));
1439
1440=item av_fetch
1441
1442Returns the SV at the specified index in the array. The C<key> is the
1443index. If C<lval> is set then the fetch will be part of a store. Check
1444that the return value is non-null before dereferencing it to a C<SV*>.
1445
04343c6d
GS
1446See L<Understanding the Magic of Tied Hashes and Arrays> for more
1447information on how to use this function on tied arrays.
1448
cb1a09d0
AD
1449 SV** av_fetch _((AV* ar, I32 key, I32 lval));
1450
1451=item av_len
1452
1453Returns the highest index in the array. Returns -1 if the array is empty.
1454
1455 I32 av_len _((AV* ar));
1456
1457=item av_make
1458
5fb8527f
PP
1459Creates a new AV and populates it with a list of SVs. The SVs are copied
1460into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1461will have a reference count of 1.
cb1a09d0
AD
1462
1463 AV* av_make _((I32 size, SV** svp));
1464
1465=item av_pop
1466
1467Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
1468empty.
1469
1470 SV* av_pop _((AV* ar));
1471
1472=item av_push
1473
5fb8527f
PP
1474Pushes an SV onto the end of the array. The array will grow automatically
1475to accommodate the addition.
cb1a09d0
AD
1476
1477 void av_push _((AV* ar, SV* val));
1478
1479=item av_shift
1480
1481Shifts an SV off the beginning of the array.
1482
1483 SV* av_shift _((AV* ar));
1484
1485=item av_store
1486
1487Stores an SV in an array. The array index is specified as C<key>. The
04343c6d
GS
1488return value will be NULL if the operation failed or if the value did not
1489need to be actually stored within the array (as in the case of tied arrays).
1490Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1491caller is responsible for suitably incrementing the reference count of C<val>
1492before the call, and decrementing it if the function returned NULL.
1493
1494See L<Understanding the Magic of Tied Hashes and Arrays> for more
1495information on how to use this function on tied arrays.
cb1a09d0
AD
1496
1497 SV** av_store _((AV* ar, I32 key, SV* val));
1498
1499=item av_undef
1500
0146554f 1501Undefines the array. Frees the memory used by the array itself.
cb1a09d0
AD
1502
1503 void av_undef _((AV* ar));
1504
1505=item av_unshift
1506
0146554f
GA
1507Unshift the given number of C<undef> values onto the beginning of the
1508array. The array will grow automatically to accommodate the addition.
1509You must then use C<av_store> to assign values to these new elements.
cb1a09d0
AD
1510
1511 void av_unshift _((AV* ar, I32 num));
1512
1513=item CLASS
1514
1515Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1516constructor. This is always a C<char*>. See C<THIS> and
1517L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1518
1519=item Copy
1520
1521The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1522source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1523the type. May fail on overlapping copies. See also C<Move>.
cb1a09d0
AD
1524
1525 (void) Copy( s, d, n, t );
1526
1527=item croak
1528
1529This is the XSUB-writer's interface to Perl's C<die> function. Use this
1530function the same way you use the C C<printf> function. See C<warn>.
1531
1532=item CvSTASH
1533
1534Returns the stash of the CV.
1535
1536 HV * CvSTASH( SV* sv )
1537
1538=item DBsingle
1539
1540When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1541boolean which indicates whether subs are being single-stepped.
5fb8527f
PP
1542Single-stepping is automatically turned on after every step. This is the C
1543variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
cb1a09d0
AD
1544
1545=item DBsub
1546
1547When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f
PP
1548the SV which holds the name of the sub being debugged. This is the C
1549variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
cb1a09d0
AD
1550The sub name can be found by
1551
1552 SvPV( GvSV( DBsub ), na )
1553
5fb8527f
PP
1554=item DBtrace
1555
1556Trace variable used when Perl is run in debugging mode, with the B<-d>
1557switch. This is the C variable which corresponds to Perl's $DB::trace
1558variable. See C<DBsingle>.
1559
cb1a09d0
AD
1560=item dMARK
1561
5fb8527f
PP
1562Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1563C<dORIGMARK>.
cb1a09d0
AD
1564
1565=item dORIGMARK
1566
1567Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1568
5fb8527f
PP
1569=item dowarn
1570
1571The C variable which corresponds to Perl's $^W warning variable.
1572
cb1a09d0
AD
1573=item dSP
1574
5fb8527f 1575Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
cb1a09d0
AD
1576
1577=item dXSARGS
1578
1579Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1580usually handled automatically by C<xsubpp>. Declares the C<items> variable
1581to indicate the number of items on the stack.
1582
5fb8527f
PP
1583=item dXSI32
1584
1585Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1586handled automatically by C<xsubpp>.
1587
cb1a09d0
AD
1588=item ENTER
1589
1590Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1591
1592 ENTER;
1593
1594=item EXTEND
1595
1596Used to extend the argument stack for an XSUB's return values.
1597
1598 EXTEND( sp, int x );
1599
1600=item FREETMPS
1601
1602Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1603L<perlcall>.
1604
1605 FREETMPS;
1606
1607=item G_ARRAY
1608
54310121 1609Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
cb1a09d0
AD
1610
1611=item G_DISCARD
1612
1613Indicates that arguments returned from a callback should be discarded. See
1614L<perlcall>.
1615
1616=item G_EVAL
1617
1618Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1619
1620=item GIMME
1621
54310121
PP
1622A backward-compatible version of C<GIMME_V> which can only return
1623C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1624
1625=item GIMME_V
1626
1627The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1628C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1629context, respectively.
cb1a09d0
AD
1630
1631=item G_NOARGS
1632
1633Indicates that no arguments are being sent to a callback. See L<perlcall>.
1634
1635=item G_SCALAR
1636
54310121
PP
1637Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1638
1639=item G_VOID
1640
1641Used to indicate void context. See C<GIMME_V> and L<perlcall>.
cb1a09d0 1642
faed5253
JO
1643=item gv_fetchmeth
1644
1645Returns the glob with the given C<name> and a defined subroutine or
9607fc9c
PP
1646C<NULL>. The glob lives in the given C<stash>, or in the stashes
1647accessable via @ISA and @<UNIVERSAL>.
faed5253 1648
9607fc9c 1649The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
1650side-effect creates a glob with the given C<name> in the given
1651C<stash> which in the case of success contains an alias for the
1652subroutine, and sets up caching info for this glob. Similarly for all
1653the searched stashes.
1654
9607fc9c
PP
1655This function grants C<"SUPER"> token as a postfix of the stash name.
1656
0a753a76
PP
1657The GV returned from C<gv_fetchmeth> may be a method cache entry,
1658which is not visible to Perl code. So when calling C<perl_call_sv>,
1659you should not use the GV directly; instead, you should use the
1660method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253
JO
1661
1662 GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
1663
1664=item gv_fetchmethod
1665
dc848c6f
PP
1666=item gv_fetchmethod_autoload
1667
faed5253 1668Returns the glob which contains the subroutine to call to invoke the
dc848c6f
PP
1669method on the C<stash>. In fact in the presense of autoloading this may
1670be the glob for "AUTOLOAD". In this case the corresponding variable
faed5253
JO
1671$AUTOLOAD is already setup.
1672
dc848c6f
PP
1673The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1674lookup is performed if the given method is not present: non-zero means
1675yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1676C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1677non-zero C<autoload> parameter.
1678
1679These functions grant C<"SUPER"> token as a prefix of the method name.
1680
1681Note that if you want to keep the returned glob for a long time, you
1682need to check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
1683may load a different subroutine due to $AUTOLOAD changing its value.
1684Use the glob created via a side effect to do this.
1685
dc848c6f
PP
1686These functions have the same side-effects and as C<gv_fetchmeth> with
1687C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
0a753a76 1688The warning against passing the GV returned by C<gv_fetchmeth> to
dc848c6f 1689C<perl_call_sv> apply equally to these functions.
faed5253
JO
1690
1691 GV* gv_fetchmethod _((HV* stash, char* name));
dc848c6f
PP
1692 GV* gv_fetchmethod_autoload _((HV* stash, char* name,
1693 I32 autoload));
faed5253 1694
cb1a09d0
AD
1695=item gv_stashpv
1696
1697Returns a pointer to the stash for a specified package. If C<create> is set
1698then the package will be created if it does not already exist. If C<create>
1699is not set and the package does not exist then NULL is returned.
1700
1701 HV* gv_stashpv _((char* name, I32 create));
1702
1703=item gv_stashsv
1704
1705Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1706
1707 HV* gv_stashsv _((SV* sv, I32 create));
1708
e5581bf4 1709=item GvSV
cb1a09d0 1710
e5581bf4 1711Return the SV from the GV.
44a8e56a 1712
1e422769
PP
1713=item HEf_SVKEY
1714
1715This flag, used in the length slot of hash entries and magic
1716structures, specifies the structure contains a C<SV*> pointer where a
1717C<char*> pointer is to be expected. (For information only--not to be used).
1718
1e422769
PP
1719=item HeHASH
1720
1721Returns the computed hash (type C<U32>) stored in the hash entry.
1722
1723 HeHASH(HE* he)
1724
1725=item HeKEY
1726
1727Returns the actual pointer stored in the key slot of the hash entry.
1728The pointer may be either C<char*> or C<SV*>, depending on the value of
1729C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1730are usually preferable for finding the value of a key.
1731
1732 HeKEY(HE* he)
1733
1734=item HeKLEN
1735
1736If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1737holds an C<SV*> key. Otherwise, holds the actual length of the key.
1738Can be assigned to. The C<HePV()> macro is usually preferable for finding
1739key lengths.
1740
1741 HeKLEN(HE* he)
1742
1743=item HePV
1744
1745Returns the key slot of the hash entry as a C<char*> value, doing any
1746necessary dereferencing of possibly C<SV*> keys. The length of
1747the string is placed in C<len> (this is a macro, so do I<not> use
1748C<&len>). If you do not care about what the length of the key is,
1749you may use the global variable C<na>. Remember though, that hash
1750keys in perl are free to contain embedded nulls, so using C<strlen()>
1751or similar is not a good way to find the length of hash keys.
1752This is very similar to the C<SvPV()> macro described elsewhere in
1753this document.
1754
1755 HePV(HE* he, STRLEN len)
1756
1757=item HeSVKEY
1758
1759Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1760does not contain an C<SV*> key.
1761
1762 HeSVKEY(HE* he)
1763
1764=item HeSVKEY_force
1765
1766Returns the key as an C<SV*>. Will create and return a temporary
1767mortal C<SV*> if the hash entry contains only a C<char*> key.
1768
1769 HeSVKEY_force(HE* he)
1770
1771=item HeSVKEY_set
1772
1773Sets the key to a given C<SV*>, taking care to set the appropriate flags
1774to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1775
1776 HeSVKEY_set(HE* he, SV* sv)
1777
1778=item HeVAL
1779
1780Returns the value slot (type C<SV*>) stored in the hash entry.
1781
1782 HeVAL(HE* he)
1783
cb1a09d0
AD
1784=item hv_clear
1785
1786Clears a hash, making it empty.
1787
1788 void hv_clear _((HV* tb));
1789
68dc0745
PP
1790=item hv_delayfree_ent
1791
1792Releases a hash entry, such as while iterating though the hash, but
1793delays actual freeing of key and value until the end of the current
1794statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
1795and C<hv_free_ent>.
1796
1797 void hv_delayfree_ent _((HV* hv, HE* entry));
1798
cb1a09d0
AD
1799=item hv_delete
1800
1801Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1802and returned to the caller. The C<klen> is the length of the key. The
04343c6d 1803C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
cb1a09d0
AD
1804returned.
1805
1806 SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
1807
1e422769
PP
1808=item hv_delete_ent
1809
1810Deletes a key/value pair in the hash. The value SV is removed from the hash
1811and returned to the caller. The C<flags> value will normally be zero; if set
04343c6d 1812to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1e422769
PP
1813hash value, or 0 to ask for it to be computed.
1814
1815 SV* hv_delete_ent _((HV* tb, SV* key, I32 flags, U32 hash));
1816
cb1a09d0
AD
1817=item hv_exists
1818
1819Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1820C<klen> is the length of the key.
cb1a09d0
AD
1821
1822 bool hv_exists _((HV* tb, char* key, U32 klen));
1823
1e422769
PP
1824=item hv_exists_ent
1825
1826Returns a boolean indicating whether the specified hash key exists. C<hash>
54310121 1827can be a valid precomputed hash value, or 0 to ask for it to be computed.
1e422769
PP
1828
1829 bool hv_exists_ent _((HV* tb, SV* key, U32 hash));
1830
cb1a09d0
AD
1831=item hv_fetch
1832
1833Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1834C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1835part of a store. Check that the return value is non-null before
1836dereferencing it to a C<SV*>.
1837
04343c6d
GS
1838See L<Understanding the Magic of Tied Hashes and Arrays> for more
1839information on how to use this function on tied hashes.
1840
cb1a09d0
AD
1841 SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
1842
1e422769
PP
1843=item hv_fetch_ent
1844
1845Returns the hash entry which corresponds to the specified key in the hash.
54310121 1846C<hash> must be a valid precomputed hash number for the given C<key>, or
1e422769
PP
18470 if you want the function to compute it. IF C<lval> is set then the
1848fetch will be part of a store. Make sure the return value is non-null
1849before accessing it. The return value when C<tb> is a tied hash
1850is a pointer to a static location, so be sure to make a copy of the
1851structure if you need to store it somewhere.
1852
04343c6d
GS
1853See L<Understanding the Magic of Tied Hashes and Arrays> for more
1854information on how to use this function on tied hashes.
1855
1e422769
PP
1856 HE* hv_fetch_ent _((HV* tb, SV* key, I32 lval, U32 hash));
1857
68dc0745
PP
1858=item hv_free_ent
1859
1860Releases a hash entry, such as while iterating though the hash. See
1861C<hv_iternext> and C<hv_delayfree_ent>.
1862
1863 void hv_free_ent _((HV* hv, HE* entry));
1864
cb1a09d0
AD
1865=item hv_iterinit
1866
1867Prepares a starting point to traverse a hash table.
1868
1869 I32 hv_iterinit _((HV* tb));
1870
fb73857a
PP
1871Note that hv_iterinit I<currently> returns the number of I<buckets> in
1872the hash and I<not> the number of keys (as indicated in the Advanced
1873Perl Programming book). This may change in future. Use the HvKEYS(hv)
1874macro to find the number of keys in a hash.
1875
cb1a09d0
AD
1876=item hv_iterkey
1877
1878Returns the key from the current position of the hash iterator. See
1879C<hv_iterinit>.
1880
1881 char* hv_iterkey _((HE* entry, I32* retlen));
1882
1e422769 1883=item hv_iterkeysv
3fe9a6f1 1884
1e422769
PP
1885Returns the key as an C<SV*> from the current position of the hash
1886iterator. The return value will always be a mortal copy of the
1887key. Also see C<hv_iterinit>.
1888
1889 SV* hv_iterkeysv _((HE* entry));
1890
cb1a09d0
AD
1891=item hv_iternext
1892
1893Returns entries from a hash iterator. See C<hv_iterinit>.
1894
1895 HE* hv_iternext _((HV* tb));
1896
1897=item hv_iternextsv
1898
1899Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1900operation.
1901
1902 SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
1903
1904=item hv_iterval
1905
1906Returns the value from the current position of the hash iterator. See
1907C<hv_iterkey>.
1908
1909 SV* hv_iterval _((HV* tb, HE* entry));
1910
1911=item hv_magic
1912
1913Adds magic to a hash. See C<sv_magic>.
1914
1915 void hv_magic _((HV* hv, GV* gv, int how));
1916
1917=item HvNAME
1918
1919Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1920
1921 char *HvNAME (HV* stash)
1922
1923=item hv_store
1924
1925Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
54310121 1926the length of the key. The C<hash> parameter is the precomputed hash
cb1a09d0 1927value; if it is zero then Perl will compute it. The return value will be
04343c6d
GS
1928NULL if the operation failed or if the value did not need to be actually
1929stored within the hash (as in the case of tied hashes). Otherwise it can
1930be dereferenced to get the original C<SV*>. Note that the caller is
1931responsible for suitably incrementing the reference count of C<val>
1932before the call, and decrementing it if the function returned NULL.
1933
1934See L<Understanding the Magic of Tied Hashes and Arrays> for more
1935information on how to use this function on tied hashes.
cb1a09d0
AD
1936
1937 SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
1938
1e422769
PP
1939=item hv_store_ent
1940
1941Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
54310121 1942parameter is the precomputed hash value; if it is zero then Perl will
1e422769 1943compute it. The return value is the new hash entry so created. It will be
04343c6d
GS
1944NULL if the operation failed or if the value did not need to be actually
1945stored within the hash (as in the case of tied hashes). Otherwise the
1946contents of the return value can be accessed using the C<He???> macros
1947described here. Note that the caller is responsible for suitably
1948incrementing the reference count of C<val> before the call, and decrementing
1949it if the function returned NULL.
1950
1951See L<Understanding the Magic of Tied Hashes and Arrays> for more
1952information on how to use this function on tied hashes.
1e422769
PP
1953
1954 HE* hv_store_ent _((HV* tb, SV* key, SV* val, U32 hash));
1955
cb1a09d0
AD
1956=item hv_undef
1957
1958Undefines the hash.
1959
1960 void hv_undef _((HV* tb));
1961
1962=item isALNUM
1963
1964Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 1965character or digit.
cb1a09d0
AD
1966
1967 int isALNUM (char c)
1968
1969=item isALPHA
1970
5fb8527f 1971Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
1972character.
1973
1974 int isALPHA (char c)
1975
1976=item isDIGIT
1977
1978Returns a boolean indicating whether the C C<char> is an ascii digit.
1979
1980 int isDIGIT (char c)
1981
1982=item isLOWER
1983
1984Returns a boolean indicating whether the C C<char> is a lowercase character.
1985
1986 int isLOWER (char c)
1987
1988=item isSPACE
1989
1990Returns a boolean indicating whether the C C<char> is whitespace.
1991
1992 int isSPACE (char c)
1993
1994=item isUPPER
1995
1996Returns a boolean indicating whether the C C<char> is an uppercase character.
1997
1998 int isUPPER (char c)
1999
2000=item items
2001
2002Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
2003stack. See L<perlxs/"Variable-length Parameter Lists">.
2004
2005=item ix
2006
2007Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
2008was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
2009
2010=item LEAVE
2011
2012Closing bracket on a callback. See C<ENTER> and L<perlcall>.
2013
2014 LEAVE;
2015
2016=item MARK
2017
5fb8527f 2018Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
2019
2020=item mg_clear
2021
2022Clear something magical that the SV represents. See C<sv_magic>.
2023
2024 int mg_clear _((SV* sv));
2025
2026=item mg_copy
2027
2028Copies the magic from one SV to another. See C<sv_magic>.
2029
2030 int mg_copy _((SV *, SV *, char *, STRLEN));
2031
2032=item mg_find
2033
2034Finds the magic pointer for type matching the SV. See C<sv_magic>.
2035
2036 MAGIC* mg_find _((SV* sv, int type));
2037
2038=item mg_free
2039
2040Free any magic storage used by the SV. See C<sv_magic>.
2041
2042 int mg_free _((SV* sv));
2043
2044=item mg_get
2045
2046Do magic after a value is retrieved from the SV. See C<sv_magic>.
2047
2048 int mg_get _((SV* sv));
2049
2050=item mg_len
2051
2052Report on the SV's length. See C<sv_magic>.
2053
2054 U32 mg_len _((SV* sv));
2055
2056=item mg_magical
2057
2058Turns on the magical status of an SV. See C<sv_magic>.
2059
2060 void mg_magical _((SV* sv));
2061
2062=item mg_set
2063
2064Do magic after a value is assigned to the SV. See C<sv_magic>.
2065
2066 int mg_set _((SV* sv));
2067
2068=item Move
2069
2070The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
2071source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 2072the type. Can do overlapping moves. See also C<Copy>.
cb1a09d0
AD
2073
2074 (void) Move( s, d, n, t );
2075
2076=item na
2077
2078A variable which may be used with C<SvPV> to tell Perl to calculate the
2079string length.
2080
2081=item New
2082
2083The XSUB-writer's interface to the C C<malloc> function.
2084
2085 void * New( x, void *ptr, int size, type )
2086
2087=item Newc
2088
2089The XSUB-writer's interface to the C C<malloc> function, with cast.
2090
2091 void * Newc( x, void *ptr, int size, type, cast )
2092
2093=item Newz
2094
2095The XSUB-writer's interface to the C C<malloc> function. The allocated
2096memory is zeroed with C<memzero>.
2097
2098 void * Newz( x, void *ptr, int size, type )
2099
2100=item newAV
2101
5f05dabc 2102Creates a new AV. The reference count is set to 1.
cb1a09d0
AD
2103
2104 AV* newAV _((void));
2105
2106=item newHV
2107
5f05dabc 2108Creates a new HV. The reference count is set to 1.
cb1a09d0
AD
2109
2110 HV* newHV _((void));
2111
5f05dabc 2112=item newRV_inc
cb1a09d0 2113
5f05dabc 2114Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
2115incremented.
2116
5f05dabc
PP
2117 SV* newRV_inc _((SV* ref));
2118
2119For historical reasons, "newRV" is a synonym for "newRV_inc".
2120
2121=item newRV_noinc
2122
2123Creates an RV wrapper for an SV. The reference count for the original
2124SV is B<not> incremented.
2125
07fa94a1 2126 SV* newRV_noinc _((SV* ref));
cb1a09d0 2127
8c52afec 2128=item NEWSV
cb1a09d0
AD
2129
2130Creates a new SV. The C<len> parameter indicates the number of bytes of
68dc0745 2131preallocated string space the SV should have. The reference count for the
8c52afec
IZ
2132new SV is set to 1. C<id> is an integer id between 0 and 1299 (used to
2133identify leaks).
cb1a09d0 2134
8c52afec 2135 SV* NEWSV _((int id, STRLEN len));
cb1a09d0
AD
2136
2137=item newSViv
2138
07fa94a1
JO
2139Creates a new SV and copies an integer into it. The reference count for the
2140SV is set to 1.
cb1a09d0
AD
2141
2142 SV* newSViv _((IV i));
2143
2144=item newSVnv
2145
07fa94a1
JO
2146Creates a new SV and copies a double into it. The reference count for the
2147SV is set to 1.
cb1a09d0
AD
2148
2149 SV* newSVnv _((NV i));
2150
2151=item newSVpv
2152
07fa94a1
JO
2153Creates a new SV and copies a string into it. The reference count for the
2154SV is set to 1. If C<len> is zero then Perl will compute the length.
cb1a09d0
AD
2155
2156 SV* newSVpv _((char* s, STRLEN len));
2157
9da1e3b5
MUN
2158=item newSVpvn
2159
2160Creates a new SV and copies a string into it. The reference count for the
2161SV is set to 1. If C<len> is zero then Perl will create a zero length
2162string.
2163
2164 SV* newSVpvn _((char* s, STRLEN len));
2165
cb1a09d0
AD
2166=item newSVrv
2167
2168Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 2169it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 2170be blessed in the specified package. The new SV is returned and its
5f05dabc 2171reference count is 1.
8ebc5c01 2172
cb1a09d0
AD
2173 SV* newSVrv _((SV* rv, char* classname));
2174
2175=item newSVsv
2176
5fb8527f 2177Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0
AD
2178
2179 SV* newSVsv _((SV* old));
2180
2181=item newXS
2182
2183Used by C<xsubpp> to hook up XSUBs as Perl subs.
2184
2185=item newXSproto
2186
2187Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
2188the subs.
2189
2190=item Nullav
2191
2192Null AV pointer.
2193
2194=item Nullch
2195
2196Null character pointer.
2197
2198=item Nullcv
2199
2200Null CV pointer.
2201
2202=item Nullhv
2203
2204Null HV pointer.
2205
2206=item Nullsv
2207
2208Null SV pointer.
2209
2210=item ORIGMARK
2211
2212The original stack mark for the XSUB. See C<dORIGMARK>.
2213
2214=item perl_alloc
2215
2216Allocates a new Perl interpreter. See L<perlembed>.
2217
2218=item perl_call_argv
2219
2220Performs a callback to the specified Perl sub. See L<perlcall>.
2221
2222 I32 perl_call_argv _((char* subname, I32 flags, char** argv));
2223
2224=item perl_call_method
2225
2226Performs a callback to the specified Perl method. The blessed object must
2227be on the stack. See L<perlcall>.
2228
2229 I32 perl_call_method _((char* methname, I32 flags));
2230
2231=item perl_call_pv
2232
2233Performs a callback to the specified Perl sub. See L<perlcall>.
2234
2235 I32 perl_call_pv _((char* subname, I32 flags));
2236
2237=item perl_call_sv
2238
2239Performs a callback to the Perl sub whose name is in the SV. See
2240L<perlcall>.
2241
2242 I32 perl_call_sv _((SV* sv, I32 flags));
2243
2244=item perl_construct
2245
2246Initializes a new Perl interpreter. See L<perlembed>.
2247
2248=item perl_destruct
2249
2250Shuts down a Perl interpreter. See L<perlembed>.
2251
2252=item perl_eval_sv
2253
2254Tells Perl to C<eval> the string in the SV.
2255
2256 I32 perl_eval_sv _((SV* sv, I32 flags));
2257
137443ea
PP
2258=item perl_eval_pv
2259
2260Tells Perl to C<eval> the given string and return an SV* result.
2261
2262 SV* perl_eval_pv _((char* p, I32 croak_on_error));
2263
cb1a09d0
AD
2264=item perl_free
2265
2266Releases a Perl interpreter. See L<perlembed>.
2267
2268=item perl_get_av
2269
2270Returns the AV of the specified Perl array. If C<create> is set and the
2271Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2272set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2273
2274 AV* perl_get_av _((char* name, I32 create));
2275
2276=item perl_get_cv
2277
2278Returns the CV of the specified Perl sub. If C<create> is set and the Perl
2279variable does not exist then it will be created. If C<create> is not
04343c6d 2280set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2281
2282 CV* perl_get_cv _((char* name, I32 create));
2283
2284=item perl_get_hv
2285
2286Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2287variable does not exist then it will be created. If C<create> is not
04343c6d 2288set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2289
2290 HV* perl_get_hv _((char* name, I32 create));
2291
2292=item perl_get_sv
2293
2294Returns the SV of the specified Perl scalar. If C<create> is set and the
2295Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2296set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2297
2298 SV* perl_get_sv _((char* name, I32 create));
2299
2300=item perl_parse
2301
2302Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2303
2304=item perl_require_pv
2305
2306Tells Perl to C<require> a module.
2307
2308 void perl_require_pv _((char* pv));
2309
2310=item perl_run
2311
2312Tells a Perl interpreter to run. See L<perlembed>.
2313
2314=item POPi
2315
2316Pops an integer off the stack.
2317
2318 int POPi();
2319
2320=item POPl
2321
2322Pops a long off the stack.
2323
2324 long POPl();
2325
2326=item POPp
2327
2328Pops a string off the stack.
2329
2330 char * POPp();
2331
2332=item POPn
2333
2334Pops a double off the stack.
2335
2336 double POPn();
2337
2338=item POPs
2339
2340Pops an SV off the stack.
2341
2342 SV* POPs();
2343
2344=item PUSHMARK
2345
2346Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2347
2348 PUSHMARK(p)
2349
2350=item PUSHi
2351
2352Push an integer onto the stack. The stack must have room for this element.
189b2af5 2353Handles 'set' magic. See C<XPUSHi>.
cb1a09d0
AD
2354
2355 PUSHi(int d)
2356
2357=item PUSHn
2358
2359Push a double onto the stack. The stack must have room for this element.
189b2af5 2360Handles 'set' magic. See C<XPUSHn>.
cb1a09d0
AD
2361
2362 PUSHn(double d)
2363
2364=item PUSHp
2365
2366Push a string onto the stack. The stack must have room for this element.
189b2af5
GS
2367The C<len> indicates the length of the string. Handles 'set' magic. See
2368C<XPUSHp>.
cb1a09d0
AD
2369
2370 PUSHp(char *c, int len )
2371
2372=item PUSHs
2373
189b2af5
GS
2374Push an SV onto the stack. The stack must have room for this element. Does
2375not handle 'set' magic. See C<XPUSHs>.
cb1a09d0
AD
2376
2377 PUSHs(sv)
2378
2379=item PUTBACK
2380
2381Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2382See C<PUSHMARK> and L<perlcall> for other uses.
2383
2384 PUTBACK;
2385
2386=item Renew
2387
2388The XSUB-writer's interface to the C C<realloc> function.
2389
2390 void * Renew( void *ptr, int size, type )
2391
2392=item Renewc
2393
2394The XSUB-writer's interface to the C C<realloc> function, with cast.
2395
2396 void * Renewc( void *ptr, int size, type, cast )
2397
2398=item RETVAL
2399
2400Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2401This is always the proper type for the XSUB.
2402See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2403
2404=item safefree
2405
2406The XSUB-writer's interface to the C C<free> function.
2407
2408=item safemalloc
2409
2410The XSUB-writer's interface to the C C<malloc> function.
2411
2412=item saferealloc
2413
2414The XSUB-writer's interface to the C C<realloc> function.
2415
2416=item savepv
2417
2418Copy a string to a safe spot. This does not use an SV.
2419
2420 char* savepv _((char* sv));
2421
2422=item savepvn
2423
2424Copy a string to a safe spot. The C<len> indicates number of bytes to
2425copy. This does not use an SV.
2426
2427 char* savepvn _((char* sv, I32 len));
2428
2429=item SAVETMPS
2430
2431Opening bracket for temporaries on a callback. See C<FREETMPS> and
2432L<perlcall>.
2433
2434 SAVETMPS;
2435
2436=item SP
2437
2438Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2439C<SPAGAIN>.
2440
2441=item SPAGAIN
2442
54310121 2443Refetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2444
2445 SPAGAIN;
2446
2447=item ST
2448
2449Used to access elements on the XSUB's stack.
2450
2451 SV* ST(int x)
2452
2453=item strEQ
2454
2455Test two strings to see if they are equal. Returns true or false.
2456
2457 int strEQ( char *s1, char *s2 )
2458
2459=item strGE
2460
2461Test two strings to see if the first, C<s1>, is greater than or equal to the
2462second, C<s2>. Returns true or false.
2463
2464 int strGE( char *s1, char *s2 )
2465
2466=item strGT
2467
2468Test two strings to see if the first, C<s1>, is greater than the second,
2469C<s2>. Returns true or false.
2470
2471 int strGT( char *s1, char *s2 )
2472
2473=item strLE
2474
2475Test two strings to see if the first, C<s1>, is less than or equal to the
2476second, C<s2>. Returns true or false.
2477
2478 int strLE( char *s1, char *s2 )
2479
2480=item strLT
2481
2482Test two strings to see if the first, C<s1>, is less than the second,
2483C<s2>. Returns true or false.
2484
2485 int strLT( char *s1, char *s2 )
2486
2487=item strNE
2488
2489Test two strings to see if they are different. Returns true or false.
2490
2491 int strNE( char *s1, char *s2 )
2492
2493=item strnEQ
2494
2495Test two strings to see if they are equal. The C<len> parameter indicates
2496the number of bytes to compare. Returns true or false.
2497
2498 int strnEQ( char *s1, char *s2 )
2499
2500=item strnNE
2501
2502Test two strings to see if they are different. The C<len> parameter
2503indicates the number of bytes to compare. Returns true or false.
2504
2505 int strnNE( char *s1, char *s2, int len )
2506
2507=item sv_2mortal
2508
2509Marks an SV as mortal. The SV will be destroyed when the current context
2510ends.
2511
2512 SV* sv_2mortal _((SV* sv));
2513
2514=item sv_bless
2515
2516Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2517must be designated by its stash (see C<gv_stashpv()>). The reference count
2518of the SV is unaffected.
cb1a09d0
AD
2519
2520 SV* sv_bless _((SV* sv, HV* stash));
2521
189b2af5
GS
2522=item SvCatMagicPV
2523
2524=item SvCatMagicPVN
2525
2526=item SvCatMagicSV
2527
cb1a09d0
AD
2528=item sv_catpv
2529
2530Concatenates the string onto the end of the string which is in the SV.
189b2af5 2531Handles 'get' magic, but not 'set' magic. See C<SvCatMagicPV>.
cb1a09d0
AD
2532
2533 void sv_catpv _((SV* sv, char* ptr));
2534
2535=item sv_catpvn
2536
2537Concatenates the string onto the end of the string which is in the SV. The
189b2af5
GS
2538C<len> indicates number of bytes to copy. Handles 'get' magic, but not
2539'set' magic. See C<SvCatMagicPVN).
cb1a09d0
AD
2540
2541 void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
2542
46fc3d4c
PP
2543=item sv_catpvf
2544
2545Processes its arguments like C<sprintf> and appends the formatted output
189b2af5
GS
2546to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
2547typically be called after calling this function to handle 'set' magic.
46fc3d4c
PP
2548
2549 void sv_catpvf _((SV* sv, const char* pat, ...));
2550
cb1a09d0
AD
2551=item sv_catsv
2552
5fb8527f 2553Concatenates the string from SV C<ssv> onto the end of the string in SV
189b2af5 2554C<dsv>. Handles 'get' magic, but not 'set' magic. See C<SvCatMagicSV).
cb1a09d0
AD
2555
2556 void sv_catsv _((SV* dsv, SV* ssv));
2557
5fb8527f
PP
2558=item sv_cmp
2559
2560Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2561string in C<sv1> is less than, equal to, or greater than the string in
2562C<sv2>.
2563
2564 I32 sv_cmp _((SV* sv1, SV* sv2));
2565
cb1a09d0
AD
2566=item SvCUR
2567
2568Returns the length of the string which is in the SV. See C<SvLEN>.
2569
2570 int SvCUR (SV* sv)
2571
2572=item SvCUR_set
2573
2574Set the length of the string which is in the SV. See C<SvCUR>.
2575
2576 SvCUR_set (SV* sv, int val )
2577
5fb8527f
PP
2578=item sv_dec
2579
5f05dabc 2580Auto-decrement of the value in the SV.
5fb8527f
PP
2581
2582 void sv_dec _((SV* sv));
2583
cb1a09d0
AD
2584=item SvEND
2585
2586Returns a pointer to the last character in the string which is in the SV.
2587See C<SvCUR>. Access the character as
2588
2589 *SvEND(sv)
2590
5fb8527f
PP
2591=item sv_eq
2592
2593Returns a boolean indicating whether the strings in the two SVs are
2594identical.
2595
2596 I32 sv_eq _((SV* sv1, SV* sv2));
2597
189b2af5
GS
2598=item SvGETMAGIC
2599
2600Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
2601its argument more than once.
2602
2603 void SvGETMAGIC( SV *sv )
2604
cb1a09d0
AD
2605=item SvGROW
2606
5fb8527f
PP
2607Expands the character buffer in the SV. Calls C<sv_grow> to perform the
2608expansion if necessary. Returns a pointer to the character buffer.
cb1a09d0
AD
2609
2610 char * SvGROW( SV* sv, int len )
2611
5fb8527f
PP
2612=item sv_grow
2613
2614Expands the character buffer in the SV. This will use C<sv_unref> and will
2615upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2616Use C<SvGROW>.
2617
2618=item sv_inc
2619
07fa94a1 2620Auto-increment of the value in the SV.
5fb8527f
PP
2621
2622 void sv_inc _((SV* sv));
2623
cb1a09d0
AD
2624=item SvIOK
2625
2626Returns a boolean indicating whether the SV contains an integer.
2627
2628 int SvIOK (SV* SV)
2629
2630=item SvIOK_off
2631
2632Unsets the IV status of an SV.
2633
2634 SvIOK_off (SV* sv)
2635
2636=item SvIOK_on
2637
2638Tells an SV that it is an integer.
2639
2640 SvIOK_on (SV* sv)
2641
5fb8527f
PP
2642=item SvIOK_only
2643
2644Tells an SV that it is an integer and disables all other OK bits.
2645
2646 SvIOK_on (SV* sv)
2647
cb1a09d0
AD
2648=item SvIOKp
2649
2650Returns a boolean indicating whether the SV contains an integer. Checks the
2651B<private> setting. Use C<SvIOK>.
2652
2653 int SvIOKp (SV* SV)
2654
2655=item sv_isa
2656
2657Returns a boolean indicating whether the SV is blessed into the specified
2658class. This does not know how to check for subtype, so it doesn't work in
2659an inheritance relationship.
2660
2661 int sv_isa _((SV* sv, char* name));
2662
2663=item SvIV
2664
2665Returns the integer which is in the SV.
2666
2667 int SvIV (SV* sv)
2668
2669=item sv_isobject
2670
2671Returns a boolean indicating whether the SV is an RV pointing to a blessed
2672object. If the SV is not an RV, or if the object is not blessed, then this
2673will return false.
2674
2675 int sv_isobject _((SV* sv));
2676
2677=item SvIVX
2678
2679Returns the integer which is stored in the SV.
2680
2681 int SvIVX (SV* sv);
2682
2683=item SvLEN
2684
2685Returns the size of the string buffer in the SV. See C<SvCUR>.
2686
2687 int SvLEN (SV* sv)
2688
5fb8527f
PP
2689=item sv_len
2690
2691Returns the length of the string in the SV. Use C<SvCUR>.
2692
2693 STRLEN sv_len _((SV* sv));
2694
cb1a09d0
AD
2695=item sv_magic
2696
2697Adds magic to an SV.
2698
2699 void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
2700
2701=item sv_mortalcopy
2702
2703Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2704as mortal.
cb1a09d0
AD
2705
2706 SV* sv_mortalcopy _((SV* oldsv));
2707
2708=item SvOK
2709
2710Returns a boolean indicating whether the value is an SV.
2711
2712 int SvOK (SV* sv)
2713
2714=item sv_newmortal
2715
5f05dabc 2716Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0
AD
2717
2718 SV* sv_newmortal _((void));
2719
2720=item sv_no
2721
2722This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
2723
2724=item SvNIOK
2725
2726Returns a boolean indicating whether the SV contains a number, integer or
2727double.
2728
2729 int SvNIOK (SV* SV)
2730
2731=item SvNIOK_off
2732
2733Unsets the NV/IV status of an SV.
2734
2735 SvNIOK_off (SV* sv)
2736
2737=item SvNIOKp
2738
2739Returns a boolean indicating whether the SV contains a number, integer or
2740double. Checks the B<private> setting. Use C<SvNIOK>.
2741
2742 int SvNIOKp (SV* SV)
2743
2744=item SvNOK
2745
2746Returns a boolean indicating whether the SV contains a double.
2747
2748 int SvNOK (SV* SV)
2749
2750=item SvNOK_off
2751
2752Unsets the NV status of an SV.
2753
2754 SvNOK_off (SV* sv)
2755
2756=item SvNOK_on
2757
2758Tells an SV that it is a double.
2759
2760 SvNOK_on (SV* sv)
2761
5fb8527f
PP
2762=item SvNOK_only
2763
2764Tells an SV that it is a double and disables all other OK bits.
2765
2766 SvNOK_on (SV* sv)
2767
cb1a09d0
AD
2768=item SvNOKp
2769
2770Returns a boolean indicating whether the SV contains a double. Checks the
2771B<private> setting. Use C<SvNOK>.
2772
2773 int SvNOKp (SV* SV)
2774
2775=item SvNV
2776
2777Returns the double which is stored in the SV.
2778
2779 double SvNV (SV* sv);
2780
2781=item SvNVX
2782
2783Returns the double which is stored in the SV.
2784
2785 double SvNVX (SV* sv);
2786
2787=item SvPOK
2788
2789Returns a boolean indicating whether the SV contains a character string.
2790
2791 int SvPOK (SV* SV)
2792
2793=item SvPOK_off
2794
2795Unsets the PV status of an SV.
2796
2797 SvPOK_off (SV* sv)
2798
2799=item SvPOK_on
2800
2801Tells an SV that it is a string.
2802
2803 SvPOK_on (SV* sv)
2804
5fb8527f
PP
2805=item SvPOK_only
2806
2807Tells an SV that it is a string and disables all other OK bits.
2808
2809 SvPOK_on (SV* sv)
2810
cb1a09d0
AD
2811=item SvPOKp
2812
2813Returns a boolean indicating whether the SV contains a character string.
2814Checks the B<private> setting. Use C<SvPOK>.
2815
2816 int SvPOKp (SV* SV)
2817
2818=item SvPV
2819
2820Returns a pointer to the string in the SV, or a stringified form of the SV
2821if the SV does not contain a string. If C<len> is C<na> then Perl will
189b2af5 2822handle the length on its own. Handles 'get' magic.
cb1a09d0
AD
2823
2824 char * SvPV (SV* sv, int len )
2825
2826=item SvPVX
2827
2828Returns a pointer to the string in the SV. The SV must contain a string.
2829
2830 char * SvPVX (SV* sv)
2831
2832=item SvREFCNT
2833
5f05dabc 2834Returns the value of the object's reference count.
cb1a09d0
AD
2835
2836 int SvREFCNT (SV* sv);
2837
2838=item SvREFCNT_dec
2839
5f05dabc 2840Decrements the reference count of the given SV.
cb1a09d0
AD
2841
2842 void SvREFCNT_dec (SV* sv)
2843
2844=item SvREFCNT_inc
2845
5f05dabc 2846Increments the reference count of the given SV.
cb1a09d0
AD
2847
2848 void SvREFCNT_inc (SV* sv)
2849
2850=item SvROK
2851
2852Tests if the SV is an RV.
2853
2854 int SvROK (SV* sv)
2855
2856=item SvROK_off
2857
2858Unsets the RV status of an SV.
2859
2860 SvROK_off (SV* sv)
2861
2862=item SvROK_on
2863
2864Tells an SV that it is an RV.
2865
2866 SvROK_on (SV* sv)
2867
2868=item SvRV
2869
2870Dereferences an RV to return the SV.
2871
2872 SV* SvRV (SV* sv);
2873
189b2af5
GS
2874=item SvSETMAGIC
2875
2876Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
2877its argument more than once.
2878
2879 void SvSETMAGIC( SV *sv )
2880
fb73857a
PP
2881=item SvTAINT
2882
2883Taints an SV if tainting is enabled
2884
2885 SvTAINT (SV* sv);
2886
2887=item SvTAINTED
2888
2889Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
2890
2891 SvTAINTED (SV* sv);
2892
2893=item SvTAINTED_off
2894
2895Untaints an SV. Be I<very> careful with this routine, as it short-circuits
2896some of Perl's fundamental security features. XS module authors should
2897not use this function unless they fully understand all the implications
2898of unconditionally untainting the value. Untainting should be done in
2899the standard perl fashion, via a carefully crafted regexp, rather than
2900directly untainting variables.
2901
2902 SvTAINTED_off (SV* sv);
2903
2904=item SvTAINTED_on
2905
2906Marks an SV as tainted.
2907
2908 SvTAINTED_on (SV* sv);
2909
189b2af5
GS
2910=item SvSetMagicIV
2911
2912A macro that calls C<sv_setiv>, and invokes 'set' magic on the SV.
2913May evaluate arguments more than once.
2914
2915 void SvSetMagicIV (SV* sv, IV num)
2916
2917=item SvSetMagicNV
2918
2919A macro that calls C<sv_setnv>, and invokes 'set' magic on the SV.
2920May evaluate arguments more than once.
2921
2922 void SvSetMagicNV (SV* sv, double num)
2923
2924=item SvSetMagicPV
2925
2926A macro that calls C<sv_setpv>, and invokes 'set' magic on the SV.
2927May evaluate arguments more than once.
2928
2929 void SvSetMagicPV (SV* sv, char *ptr)
2930
2931=item SvSetMagicPVIV
2932
2933A macro that calls C<sv_setpviv>, and invokes 'set' magic on the SV.
2934May evaluate arguments more than once.
2935
2936 void SvSetMagicPVIV (SV* sv, IV num)
2937
2938=item SvSetMagicPVN
2939
2940A macro that calls C<sv_setpvn>, and invokes 'set' magic on the SV.
2941May evaluate arguments more than once.
2942
2943 void SvSetMagicPVN (SV* sv, char* ptr, STRLEN len)
2944
2945=item SvSetMagicSV
2946
2947Same as C<SvSetSV>, but also invokes 'set' magic on the SV.
2948May evaluate arguments more than once.
2949
2950 void SvSetMagicSV (SV* dsv, SV* ssv)
2951
2952=item SvSetMagicSV_nosteal
2953
2954Same as C<SvSetSV_nosteal>, but also invokes 'set' magic on the SV.
2955May evaluate arguments more than once.
2956
2957 void SvSetMagicSV_nosteal (SV* dsv, SV* ssv)
2958
2959=item SvSetMagicUV
2960
2961A macro that calls C<sv_setuv>, and invokes 'set' magic on the SV.
2962May evaluate arguments more than once.
2963
2964 void SvSetMagicUV (SV* sv, UV num)
2965
cb1a09d0
AD
2966=item sv_setiv
2967
189b2af5
GS
2968Copies an integer into the given SV. Does not handle 'set' magic.
2969See C<SvSetMagicIV>.
cb1a09d0
AD
2970
2971 void sv_setiv _((SV* sv, IV num));
2972
2973=item sv_setnv
2974
189b2af5
GS
2975Copies a double into the given SV. Does not handle 'set' magic.
2976See C<SvSetMagicNV>.
cb1a09d0
AD
2977
2978 void sv_setnv _((SV* sv, double num));
2979
2980=item sv_setpv
2981
2982Copies a string into an SV. The string must be null-terminated.
189b2af5 2983Does not handle 'set' magic. See C<SvSetMagicPV>.
cb1a09d0
AD
2984
2985 void sv_setpv _((SV* sv, char* ptr));
2986
189b2af5
GS
2987=item sv_setpviv
2988
2989Copies an integer into the given SV, also updating its string value.
2990Does not handle 'set' magic. See C<SvSetMagicPVIV>.
2991
2992 void sv_setpviv _((SV* sv, IV num));
2993
cb1a09d0
AD
2994=item sv_setpvn
2995
2996Copies a string into an SV. The C<len> parameter indicates the number of
189b2af5 2997bytes to be copied. Does not handle 'set' magic. See C<SvSetMagicPVN>.
cb1a09d0
AD
2998
2999 void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
3000
46fc3d4c
PP
3001=item sv_setpvf
3002
3003Processes its arguments like C<sprintf> and sets an SV to the formatted
189b2af5
GS
3004output. Does not handle 'set' magic. C<SvSETMAGIC()> must typically
3005be called after calling this function to handle 'set' magic.
46fc3d4c
PP
3006
3007 void sv_setpvf _((SV* sv, const char* pat, ...));
3008
cb1a09d0
AD
3009=item sv_setref_iv
3010
5fb8527f
PP
3011Copies an integer into a new SV, optionally blessing the SV. The C<rv>
3012argument will be upgraded to an RV. That RV will be modified to point to
3013the new SV. The C<classname> argument indicates the package for the
3014blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3015will be returned and will have a reference count of 1.
cb1a09d0
AD
3016
3017 SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
3018
3019=item sv_setref_nv
3020
5fb8527f
PP
3021Copies a double into a new SV, optionally blessing the SV. The C<rv>
3022argument will be upgraded to an RV. That RV will be modified to point to
3023the new SV. The C<classname> argument indicates the package for the
3024blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3025will be returned and will have a reference count of 1.
cb1a09d0
AD
3026
3027 SV* sv_setref_nv _((SV *rv, char *classname, double nv));
3028
3029=item sv_setref_pv
3030
5fb8527f
PP
3031Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
3032argument will be upgraded to an RV. That RV will be modified to point to
3033the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
3034into the SV. The C<classname> argument indicates the package for the
3035blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3036will be returned and will have a reference count of 1.
cb1a09d0
AD
3037
3038 SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
3039
3040Do not use with integral Perl types such as HV, AV, SV, CV, because those
3041objects will become corrupted by the pointer copy process.
3042
3043Note that C<sv_setref_pvn> copies the string while this copies the pointer.
3044
3045=item sv_setref_pvn
3046
5fb8527f
PP
3047Copies a string into a new SV, optionally blessing the SV. The length of the
3048string must be specified with C<n>. The C<rv> argument will be upgraded to
3049an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
3050argument indicates the package for the blessing. Set C<classname> to
3051C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 3052a reference count of 1.
cb1a09d0
AD
3053
3054 SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
3055
3056Note that C<sv_setref_pv> copies the pointer while this copies the string.
3057
189b2af5
GS
3058=item SvSetSV
3059
3060Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
3061more than once.
3062
3063 void SvSetSV (SV* dsv, SV* ssv)
3064
3065=item SvSetSV_nosteal
3066
3067Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
3068May evaluate arguments more than once.
3069
3070 void SvSetSV_nosteal (SV* dsv, SV* ssv)
3071
cb1a09d0
AD
3072=item sv_setsv
3073
3074Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
189b2af5
GS
3075The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
3076See the macro forms C<SvSetSV>, C<SvSetSV_nosteal>, C<SvSetMagicSV> and
3077C<SvSetMagicSV_nosteal>.
cb1a09d0
AD
3078
3079 void sv_setsv _((SV* dsv, SV* ssv));
3080
189b2af5
GS
3081=item sv_setuv
3082
3083Copies an unsigned integer into the given SV. Does not handle 'set' magic.
3084See C<SvSetMagicUV>.
3085
3086 void sv_setuv _((SV* sv, UV num));
3087
cb1a09d0
AD
3088=item SvSTASH
3089
3090Returns the stash of the SV.
3091
3092 HV * SvSTASH (SV* sv)
3093
3094=item SVt_IV
3095
3096Integer type flag for scalars. See C<svtype>.
3097
3098=item SVt_PV
3099
3100Pointer type flag for scalars. See C<svtype>.
3101
3102=item SVt_PVAV
3103
3104Type flag for arrays. See C<svtype>.
3105
3106=item SVt_PVCV
3107
3108Type flag for code refs. See C<svtype>.
3109
3110=item SVt_PVHV
3111
3112Type flag for hashes. See C<svtype>.
3113
3114=item SVt_PVMG
3115
3116Type flag for blessed scalars. See C<svtype>.
3117
3118=item SVt_NV
3119
3120Double type flag for scalars. See C<svtype>.
3121
3122=item SvTRUE
3123
3124Returns a boolean indicating whether Perl would evaluate the SV as true or
189b2af5 3125false, defined or undefined. Does not handle 'get' magic.
cb1a09d0
AD
3126
3127 int SvTRUE (SV* sv)
3128
3129=item SvTYPE
3130
3131Returns the type of the SV. See C<svtype>.
3132
3133 svtype SvTYPE (SV* sv)
3134
3135=item svtype
3136
3137An enum of flags for Perl types. These are found in the file B<sv.h> in the
3138C<svtype> enum. Test these flags with the C<SvTYPE> macro.
3139
3140=item SvUPGRADE
3141
5fb8527f
PP
3142Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
3143the upgrade if necessary. See C<svtype>.
3144
3145 bool SvUPGRADE _((SV* sv, svtype mt));
3146
3147=item sv_upgrade
3148
3149Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
cb1a09d0
AD
3150
3151=item sv_undef
3152
3153This is the C<undef> SV. Always refer to this as C<&sv_undef>.
3154
5fb8527f
PP
3155=item sv_unref
3156
07fa94a1
JO
3157Unsets the RV status of the SV, and decrements the reference count of
3158whatever was being referenced by the RV. This can almost be thought of
3159as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f
PP
3160
3161 void sv_unref _((SV* sv));
3162
189b2af5
GS
3163=item SvUseMagicPVN
3164
cb1a09d0
AD
3165=item sv_usepvn
3166
3167Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
3168stored inside the SV but sv_usepvn allows the SV to use an outside string.
3169The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
3170string length, C<len>, must be supplied. This function will realloc the
3171memory pointed to by C<ptr>, so that pointer should not be freed or used by
189b2af5
GS
3172the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
3173See C<SvUseMagicPVN>.
cb1a09d0
AD
3174
3175 void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
3176
3177=item sv_yes
3178
3179This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
3180
3181=item THIS
3182
3183Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
3184This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 3185L<perlxs/"Using XS With C++">.
cb1a09d0
AD
3186
3187=item toLOWER
3188
3189Converts the specified character to lowercase.
3190
3191 int toLOWER (char c)
3192
3193=item toUPPER
3194
3195Converts the specified character to uppercase.
3196
3197 int toUPPER (char c)
3198
3199=item warn
3200
3201This is the XSUB-writer's interface to Perl's C<warn> function. Use this
3202function the same way you use the C C<printf> function. See C<croak()>.
3203
3204=item XPUSHi
3205
189b2af5
GS
3206Push an integer onto the stack, extending the stack if necessary. Handles
3207'set' magic. See C<PUSHi>.
cb1a09d0
AD
3208
3209 XPUSHi(int d)
3210
3211=item XPUSHn
3212
189b2af5
GS
3213Push a double onto the stack, extending the stack if necessary. Handles 'set'
3214magic. See C<PUSHn>.
cb1a09d0
AD
3215
3216 XPUSHn(double d)
3217
3218=item XPUSHp
3219
3220Push a string onto the stack, extending the stack if necessary. The C<len>
189b2af5 3221indicates the length of the string. Handles 'set' magic. See C<PUSHp>.
cb1a09d0
AD
3222
3223 XPUSHp(char *c, int len)
3224
3225=item XPUSHs
3226
189b2af5
GS
3227Push an SV onto the stack, extending the stack if necessary. Does not
3228handle 'set' magic. See C<PUSHs>.
cb1a09d0
AD
3229
3230 XPUSHs(sv)
3231
5fb8527f
PP
3232=item XS
3233
3234Macro to declare an XSUB and its C parameter list. This is handled by
3235C<xsubpp>.
3236
cb1a09d0
AD
3237=item XSRETURN
3238
3239Return from XSUB, indicating number of items on the stack. This is usually
3240handled by C<xsubpp>.
3241
5fb8527f 3242 XSRETURN(int x);
cb1a09d0
AD
3243
3244=item XSRETURN_EMPTY
3245
5fb8527f 3246Return an empty list from an XSUB immediately.
cb1a09d0
AD
3247
3248 XSRETURN_EMPTY;
3249
5fb8527f
PP
3250=item XSRETURN_IV
3251
3252Return an integer from an XSUB immediately. Uses C<XST_mIV>.
3253
3254 XSRETURN_IV(IV v);
3255
cb1a09d0
AD
3256=item XSRETURN_NO
3257
5fb8527f 3258Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
3259
3260 XSRETURN_NO;
3261
5fb8527f
PP
3262=item XSRETURN_NV
3263
3264Return an double from an XSUB immediately. Uses C<XST_mNV>.
3265
3266 XSRETURN_NV(NV v);
3267
3268=item XSRETURN_PV
3269
3270Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
3271
3272 XSRETURN_PV(char *v);
3273
cb1a09d0
AD
3274=item XSRETURN_UNDEF
3275
5fb8527f 3276Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
3277
3278 XSRETURN_UNDEF;
3279
3280=item XSRETURN_YES
3281
5fb8527f 3282Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
3283
3284 XSRETURN_YES;
3285
5fb8527f
PP
3286=item XST_mIV
3287
3288Place an integer into the specified position C<i> on the stack. The value is
3289stored in a new mortal SV.
3290
3291 XST_mIV( int i, IV v );
3292
3293=item XST_mNV
3294
3295Place a double into the specified position C<i> on the stack. The value is
3296stored in a new mortal SV.
3297
3298 XST_mNV( int i, NV v );
3299
3300=item XST_mNO
3301
3302Place C<&sv_no> into the specified position C<i> on the stack.
3303
3304 XST_mNO( int i );
3305
3306=item XST_mPV
3307
3308Place a copy of a string into the specified position C<i> on the stack. The
3309value is stored in a new mortal SV.
3310
3311 XST_mPV( int i, char *v );
3312
3313=item XST_mUNDEF
3314
3315Place C<&sv_undef> into the specified position C<i> on the stack.
3316
3317 XST_mUNDEF( int i );
3318
3319=item XST_mYES
3320
3321Place C<&sv_yes> into the specified position C<i> on the stack.
3322
3323 XST_mYES( int i );
3324
3325=item XS_VERSION
3326
3327The version identifier for an XS module. This is usually handled
3328automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
3329
3330=item XS_VERSION_BOOTCHECK
3331
3332Macro to verify that a PM module's $VERSION variable matches the XS module's
3333C<XS_VERSION> variable. This is usually handled automatically by
3334C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
3335
cb1a09d0
AD
3336=item Zero
3337
3338The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
3339destination, C<n> is the number of items, and C<t> is the type.
3340
3341 (void) Zero( d, n, t );
3342
3343=back
3344
5f05dabc 3345=head1 EDITOR
cb1a09d0 3346
9607fc9c 3347Jeff Okamoto <F<okamoto@corp.hp.com>>
cb1a09d0
AD
3348
3349With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
3350Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
189b2af5
GS
3351Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
3352Stephen McCamant, and Gurusamy Sarathy.
cb1a09d0 3353
9607fc9c 3354API Listing by Dean Roehrich <F<roehrich@cray.com>>.
cb1a09d0
AD
3355
3356=head1 DATE
3357
04343c6d 3358Version 31.8: 1997/5/17