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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
5f05dabc 11=head2 Datatypes
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12
13Perl has three typedefs that handle Perl's three main data types:
14
15 SV Scalar Value
16 AV Array Value
17 HV Hash Value
18
d1b91892 19Each typedef has specific routines that manipulate the various data types.
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20
21=head2 What is an "IV"?
22
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23Perl uses a special typedef IV which is a simple integer type that is
24guaranteed to be large enough to hold a pointer (as well as an integer).
a0d0e21e 25
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26Perl also uses two special typedefs, I32 and I16, which will always be at
27least 32-bits and 16-bits long, respectively.
a0d0e21e 28
5f05dabc 29=head2 Working with SV's
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30
31An SV can be created and loaded with one command. There are four types of
32values that can be loaded: an integer value (IV), a double (NV), a string,
33(PV), and another scalar (SV).
34
35The four routines are:
36
37 SV* newSViv(IV);
38 SV* newSVnv(double);
39 SV* newSVpv(char*, int);
40 SV* newSVsv(SV*);
41
5fb8527f 42To change the value of an *already-existing* SV, there are five routines:
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43
44 void sv_setiv(SV*, IV);
45 void sv_setnv(SV*, double);
46 void sv_setpvn(SV*, char*, int)
47 void sv_setpv(SV*, char*);
48 void sv_setsv(SV*, SV*);
49
50Notice that you can choose to specify the length of the string to be
d1b91892 51assigned by using C<sv_setpvn> or C<newSVpv>, or you may allow Perl to
cb1a09d0 52calculate the length by using C<sv_setpv> or by specifying 0 as the second
d1b91892 53argument to C<newSVpv>. Be warned, though, that Perl will determine the
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54string's length by using C<strlen>, which depends on the string terminating
55with a NUL character.
56
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57All SV's that will contain strings should, but need not, be terminated
58with a NUL character. If it is not NUL-terminated there is a risk of
59core dumps and corruptions from code which passes the string to C
60functions or system calls which expect a NUL-terminated string.
61Perl's own functions typically add a trailing NUL for this reason.
62Nevertheless, you should be very careful when you pass a string stored
63in an SV to a C function or system call.
64
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65To access the actual value that an SV points to, you can use the macros:
66
67 SvIV(SV*)
68 SvNV(SV*)
69 SvPV(SV*, STRLEN len)
70
71which will automatically coerce the actual scalar type into an IV, double,
72or string.
73
74In the C<SvPV> macro, the length of the string returned is placed into the
75variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
76care what the length of the data is, use the global variable C<na>. Remember,
77however, that Perl allows arbitrary strings of data that may both contain
5f05dabc 78NUL's and might not be terminated by a NUL.
a0d0e21e 79
07fa94a1 80If you want to know if the scalar value is TRUE, you can use:
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81
82 SvTRUE(SV*)
83
84Although Perl will automatically grow strings for you, if you need to force
85Perl to allocate more memory for your SV, you can use the macro
86
87 SvGROW(SV*, STRLEN newlen)
88
89which will determine if more memory needs to be allocated. If so, it will
90call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
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91decrease, the allocated memory of an SV and that it does not automatically
92add a byte for the a trailing NUL (perl's own string functions typically do
8ebc5c01 93C<SvGROW(sv, len + 1)>).
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94
95If you have an SV and want to know what kind of data Perl thinks is stored
96in it, you can use the following macros to check the type of SV you have.
97
98 SvIOK(SV*)
99 SvNOK(SV*)
100 SvPOK(SV*)
101
102You can get and set the current length of the string stored in an SV with
103the following macros:
104
105 SvCUR(SV*)
106 SvCUR_set(SV*, I32 val)
107
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108You can also get a pointer to the end of the string stored in the SV
109with the macro:
110
111 SvEND(SV*)
112
113But note that these last three macros are valid only if C<SvPOK()> is true.
a0d0e21e 114
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115If you want to append something to the end of string stored in an C<SV*>,
116you can use the following functions:
117
118 void sv_catpv(SV*, char*);
119 void sv_catpvn(SV*, char*, int);
120 void sv_catsv(SV*, SV*);
121
122The first function calculates the length of the string to be appended by
123using C<strlen>. In the second, you specify the length of the string
124yourself. The third function extends the string stored in the first SV
125with the string stored in the second SV. It also forces the second SV to
126be interpreted as a string.
127
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128If you know the name of a scalar variable, you can get a pointer to its SV
129by using the following:
130
5f05dabc 131 SV* perl_get_sv("package::varname", FALSE);
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132
133This returns NULL if the variable does not exist.
134
d1b91892 135If you want to know if this variable (or any other SV) is actually C<defined>,
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136you can call:
137
138 SvOK(SV*)
139
140The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
141address can be used whenever an C<SV*> is needed.
142
143There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
144TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
145be used whenever an C<SV*> is needed.
146
147Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
148Take this code:
149
150 SV* sv = (SV*) 0;
151 if (I-am-to-return-a-real-value) {
152 sv = sv_2mortal(newSViv(42));
153 }
154 sv_setsv(ST(0), sv);
155
156This code tries to return a new SV (which contains the value 42) if it should
157return a real value, or undef otherwise. Instead it has returned a null
158pointer which, somewhere down the line, will cause a segmentation violation,
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159bus error, or just weird results. Change the zero to C<&sv_undef> in the first
160line and all will be well.
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161
162To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
5f05dabc 163call is not necessary (see the section on L<Mortality>).
a0d0e21e 164
d1b91892 165=head2 What's Really Stored in an SV?
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166
167Recall that the usual method of determining the type of scalar you have is
5f05dabc 168to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
d1b91892 169usually these macros will always return TRUE and calling the C<Sv*V>
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170macros will do the appropriate conversion of string to integer/double or
171integer/double to string.
172
173If you I<really> need to know if you have an integer, double, or string
174pointer in an SV, you can use the following three macros instead:
175
176 SvIOKp(SV*)
177 SvNOKp(SV*)
178 SvPOKp(SV*)
179
180These will tell you if you truly have an integer, double, or string pointer
d1b91892 181stored in your SV. The "p" stands for private.
a0d0e21e 182
07fa94a1 183In general, though, it's best to use the C<Sv*V> macros.
a0d0e21e 184
5f05dabc 185=head2 Working with AV's
a0d0e21e 186
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187There are two ways to create and load an AV. The first method creates an
188empty AV:
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189
190 AV* newAV();
191
5f05dabc 192The second method both creates the AV and initially populates it with SV's:
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193
194 AV* av_make(I32 num, SV **ptr);
195
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196The second argument points to an array containing C<num> C<SV*>'s. Once the
197AV has been created, the SV's can be destroyed, if so desired.
a0d0e21e 198
5f05dabc 199Once the AV has been created, the following operations are possible on AV's:
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200
201 void av_push(AV*, SV*);
202 SV* av_pop(AV*);
203 SV* av_shift(AV*);
204 void av_unshift(AV*, I32 num);
205
206These should be familiar operations, with the exception of C<av_unshift>.
207This routine adds C<num> elements at the front of the array with the C<undef>
208value. You must then use C<av_store> (described below) to assign values
209to these new elements.
210
211Here are some other functions:
212
5f05dabc 213 I32 av_len(AV*);
a0d0e21e 214 SV** av_fetch(AV*, I32 key, I32 lval);
a0d0e21e 215 SV** av_store(AV*, I32 key, SV* val);
a0d0e21e 216
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217The C<av_len> function returns the highest index value in array (just
218like $#array in Perl). If the array is empty, -1 is returned. The
219C<av_fetch> function returns the value at index C<key>, but if C<lval>
220is non-zero, then C<av_fetch> will store an undef value at that index.
221The C<av_store> function stores the value C<val> at index C<key>.
222note that C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s
223as their return value.
d1b91892 224
a0d0e21e 225 void av_clear(AV*);
a0d0e21e 226 void av_undef(AV*);
cb1a09d0 227 void av_extend(AV*, I32 key);
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228
229The C<av_clear> function deletes all the elements in the AV* array, but
230does not actually delete the array itself. The C<av_undef> function will
231delete all the elements in the array plus the array itself. The
232C<av_extend> function extends the array so that it contains C<key>
233elements. If C<key> is less than the current length of the array, then
234nothing is done.
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235
236If you know the name of an array variable, you can get a pointer to its AV
237by using the following:
238
5f05dabc 239 AV* perl_get_av("package::varname", FALSE);
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240
241This returns NULL if the variable does not exist.
242
5f05dabc 243=head2 Working with HV's
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244
245To create an HV, you use the following routine:
246
247 HV* newHV();
248
5f05dabc 249Once the HV has been created, the following operations are possible on HV's:
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250
251 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
252 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
253
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254The C<klen> parameter is the length of the key being passed in (Note that
255you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
256length of the key). The C<val> argument contains the SV pointer to the
257scalar being stored, and C<hash> is the pre-computed hash value (zero if
258you want C<hv_store> to calculate it for you). The C<lval> parameter
259indicates whether this fetch is actually a part of a store operation, in
260which case a new undefined value will be added to the HV with the supplied
261key and C<hv_fetch> will return as if the value had already existed.
a0d0e21e 262
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263Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
264C<SV*>. To access the scalar value, you must first dereference the return
265value. However, you should check to make sure that the return value is
266not NULL before dereferencing it.
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267
268These two functions check if a hash table entry exists, and deletes it.
269
270 bool hv_exists(HV*, char* key, U32 klen);
d1b91892 271 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
a0d0e21e 272
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273If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
274create and return a mortal copy of the deleted value.
275
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276And more miscellaneous functions:
277
278 void hv_clear(HV*);
a0d0e21e 279 void hv_undef(HV*);
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280
281Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
282table but does not actually delete the hash table. The C<hv_undef> deletes
283both the entries and the hash table itself.
a0d0e21e 284
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285Perl keeps the actual data in linked list of structures with a typedef of HE.
286These contain the actual key and value pointers (plus extra administrative
287overhead). The key is a string pointer; the value is an C<SV*>. However,
288once you have an C<HE*>, to get the actual key and value, use the routines
289specified below.
290
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291 I32 hv_iterinit(HV*);
292 /* Prepares starting point to traverse hash table */
293 HE* hv_iternext(HV*);
294 /* Get the next entry, and return a pointer to a
295 structure that has both the key and value */
296 char* hv_iterkey(HE* entry, I32* retlen);
297 /* Get the key from an HE structure and also return
298 the length of the key string */
cb1a09d0 299 SV* hv_iterval(HV*, HE* entry);
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300 /* Return a SV pointer to the value of the HE
301 structure */
cb1a09d0 302 SV* hv_iternextsv(HV*, char** key, I32* retlen);
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303 /* This convenience routine combines hv_iternext,
304 hv_iterkey, and hv_iterval. The key and retlen
305 arguments are return values for the key and its
306 length. The value is returned in the SV* argument */
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307
308If you know the name of a hash variable, you can get a pointer to its HV
309by using the following:
310
5f05dabc 311 HV* perl_get_hv("package::varname", FALSE);
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312
313This returns NULL if the variable does not exist.
314
8ebc5c01 315The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
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316
317 i = klen;
318 hash = 0;
319 s = key;
320 while (i--)
321 hash = hash * 33 + *s++;
322
323=head2 References
324
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325References are a special type of scalar that point to other data types
326(including references).
a0d0e21e 327
07fa94a1 328To create a reference, use either of the following functions:
a0d0e21e 329
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330 SV* newRV_inc((SV*) thing);
331 SV* newRV_noinc((SV*) thing);
a0d0e21e 332
5f05dabc 333The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
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334functions are identical except that C<newRV_inc> increments the reference
335count of the C<thing>, while C<newRV_noinc> does not. For historical
336reasons, C<newRV> is a synonym for C<newRV_inc>.
337
338Once you have a reference, you can use the following macro to dereference
339the reference:
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340
341 SvRV(SV*)
342
343then call the appropriate routines, casting the returned C<SV*> to either an
d1b91892 344C<AV*> or C<HV*>, if required.
a0d0e21e 345
d1b91892 346To determine if an SV is a reference, you can use the following macro:
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347
348 SvROK(SV*)
349
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350To discover what type of value the reference refers to, use the following
351macro and then check the return value.
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352
353 SvTYPE(SvRV(SV*))
354
355The most useful types that will be returned are:
356
357 SVt_IV Scalar
358 SVt_NV Scalar
359 SVt_PV Scalar
5f05dabc 360 SVt_RV Scalar
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361 SVt_PVAV Array
362 SVt_PVHV Hash
363 SVt_PVCV Code
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364 SVt_PVGV Glob (possible a file handle)
365 SVt_PVMG Blessed or Magical Scalar
366
367 See the sv.h header file for more details.
d1b91892 368
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369=head2 Blessed References and Class Objects
370
371References are also used to support object-oriented programming. In the
372OO lexicon, an object is simply a reference that has been blessed into a
373package (or class). Once blessed, the programmer may now use the reference
374to access the various methods in the class.
375
376A reference can be blessed into a package with the following function:
377
378 SV* sv_bless(SV* sv, HV* stash);
379
380The C<sv> argument must be a reference. The C<stash> argument specifies
55497cff 381which class the reference will belong to. See the section on L<Stashes>
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382for information on converting class names into stashes.
383
384/* Still under construction */
385
386Upgrades rv to reference if not already one. Creates new SV for rv to
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387point to. If C<classname> is non-null, the SV is blessed into the specified
388class. SV is returned.
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389
390 SV* newSVrv(SV* rv, char* classname);
391
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392Copies integer or double into an SV whose reference is C<rv>. SV is blessed
393if C<classname> is non-null.
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394
395 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
396 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
397
5f05dabc 398Copies the pointer value (I<the address, not the string!>) into an SV whose
8ebc5c01 399reference is rv. SV is blessed if C<classname> is non-null.
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400
401 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
402
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403Copies string into an SV whose reference is C<rv>. Set length to 0 to let
404Perl calculate the string length. SV is blessed if C<classname> is non-null.
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405
406 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
407
408 int sv_isa(SV* sv, char* name);
409 int sv_isobject(SV* sv);
410
5f05dabc 411=head2 Creating New Variables
cb1a09d0 412
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413To create a new Perl variable with an undef value which can be accessed from
414your Perl script, use the following routines, depending on the variable type.
cb1a09d0 415
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416 SV* perl_get_sv("package::varname", TRUE);
417 AV* perl_get_av("package::varname", TRUE);
418 HV* perl_get_hv("package::varname", TRUE);
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419
420Notice the use of TRUE as the second parameter. The new variable can now
421be set, using the routines appropriate to the data type.
422
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423There are additional macros whose values may be bitwise OR'ed with the
424C<TRUE> argument to enable certain extra features. Those bits are:
cb1a09d0 425
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426 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
427 "Indentifier <varname> used only once: possible typo" warning.
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428 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
429 the variable did not exist before the function was called.
cb1a09d0 430
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431If you do not specify a package name, the variable is created in the current
432package.
cb1a09d0 433
5f05dabc 434=head2 Reference Counts and Mortality
a0d0e21e 435
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436Perl uses an reference count-driven garbage collection mechanism. SV's,
437AV's, or HV's (xV for short in the following) start their life with a
438reference count of 1. If the reference count of an xV ever drops to 0,
07fa94a1 439then it will be destroyed and its memory made available for reuse.
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440
441This normally doesn't happen at the Perl level unless a variable is
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442undef'ed or the last variable holding a reference to it is changed or
443overwritten. At the internal level, however, reference counts can be
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444manipulated with the following macros:
445
446 int SvREFCNT(SV* sv);
5f05dabc 447 SV* SvREFCNT_inc(SV* sv);
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448 void SvREFCNT_dec(SV* sv);
449
450However, there is one other function which manipulates the reference
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451count of its argument. The C<newRV_inc> function, you will recall,
452creates a reference to the specified argument. As a side effect,
453it increments the argument's reference count. If this is not what
454you want, use C<newRV_noinc> instead.
455
456For example, imagine you want to return a reference from an XSUB function.
457Inside the XSUB routine, you create an SV which initially has a reference
458count of one. Then you call C<newRV_inc>, passing it the just-created SV.
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459This returns the reference as a new SV, but the reference count of the
460SV you passed to C<newRV_inc> has been incremented to two. Now you
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461return the reference from the XSUB routine and forget about the SV.
462But Perl hasn't! Whenever the returned reference is destroyed, the
463reference count of the original SV is decreased to one and nothing happens.
464The SV will hang around without any way to access it until Perl itself
465terminates. This is a memory leak.
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466
467The correct procedure, then, is to use C<newRV_noinc> instead of
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468C<newRV_inc>. Then, if and when the last reference is destroyed,
469the reference count of the SV will go to zero and it will be destroyed,
07fa94a1 470stopping any memory leak.
55497cff 471
5f05dabc 472There are some convenience functions available that can help with the
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473destruction of xV's. These functions introduce the concept of "mortality".
474An xV that is mortal has had its reference count marked to be decremented,
475but not actually decremented, until "a short time later". Generally the
476term "short time later" means a single Perl statement, such as a call to
477an XSUB function. The actual determinant for when mortal xV's have their
478reference count decremented depends on two macros, SAVETMPS and FREETMPS.
479See L<perlcall> and L<perlxs> for more details on these macros.
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480
481"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
482However, if you mortalize a variable twice, the reference count will
483later be decremented twice.
484
485You should be careful about creating mortal variables. Strange things
486can happen if you make the same value mortal within multiple contexts,
5f05dabc 487or if you make a variable mortal multiple times.
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488
489To create a mortal variable, use the functions:
490
491 SV* sv_newmortal()
492 SV* sv_2mortal(SV*)
493 SV* sv_mortalcopy(SV*)
494
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495The first call creates a mortal SV, the second converts an existing
496SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
497third creates a mortal copy of an existing SV.
a0d0e21e 498
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499The mortal routines are not just for SV's -- AV's and HV's can be
500made mortal by passing their address (type-casted to C<SV*>) to the
07fa94a1 501C<sv_2mortal> or C<sv_mortalcopy> routines.
a0d0e21e 502
5f05dabc 503=head2 Stashes and Globs
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504
505A stash is a hash table (associative array) that contains all of the
506different objects that are contained within a package. Each key of the
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507stash is a symbol name (shared by all the different types of objects
508that have the same name), and each value in the hash table is called a
509GV (for Glob Value). This GV in turn contains references to the various
510objects of that name, including (but not limited to) the following:
cb1a09d0 511
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512 Scalar Value
513 Array Value
514 Hash Value
515 File Handle
516 Directory Handle
517 Format
518 Subroutine
519
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520There is a single stash called "defstash" that holds the items that exist
521in the "main" package. To get at the items in other packages, append the
522string "::" to the package name. The items in the "Foo" package are in
523the stash "Foo::" in defstash. The items in the "Bar::Baz" package are
524in the stash "Baz::" in "Bar::"'s stash.
a0d0e21e 525
d1b91892 526To get the stash pointer for a particular package, use the function:
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527
528 HV* gv_stashpv(char* name, I32 create)
529 HV* gv_stashsv(SV*, I32 create)
530
531The first function takes a literal string, the second uses the string stored
d1b91892 532in the SV. Remember that a stash is just a hash table, so you get back an
cb1a09d0 533C<HV*>. The C<create> flag will create a new package if it is set.
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534
535The name that C<gv_stash*v> wants is the name of the package whose symbol table
536you want. The default package is called C<main>. If you have multiply nested
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537packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
538language itself.
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539
540Alternately, if you have an SV that is a blessed reference, you can find
541out the stash pointer by using:
542
543 HV* SvSTASH(SvRV(SV*));
544
545then use the following to get the package name itself:
546
547 char* HvNAME(HV* stash);
548
5f05dabc
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549If you need to bless or re-bless an object you can use the following
550function:
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551
552 SV* sv_bless(SV*, HV* stash)
553
554where the first argument, an C<SV*>, must be a reference, and the second
555argument is a stash. The returned C<SV*> can now be used in the same way
556as any other SV.
557
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558For more information on references and blessings, consult L<perlref>.
559
5f05dabc 560=head2 Magic
a0d0e21e 561
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562[This section still under construction. Ignore everything here. Post no
563bills. Everything not permitted is forbidden.]
564
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565Any SV may be magical, that is, it has special features that a normal
566SV does not have. These features are stored in the SV structure in a
5f05dabc 567linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
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568
569 struct magic {
570 MAGIC* mg_moremagic;
571 MGVTBL* mg_virtual;
572 U16 mg_private;
573 char mg_type;
574 U8 mg_flags;
575 SV* mg_obj;
576 char* mg_ptr;
577 I32 mg_len;
578 };
579
580Note this is current as of patchlevel 0, and could change at any time.
581
582=head2 Assigning Magic
583
584Perl adds magic to an SV using the sv_magic function:
585
586 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
587
588The C<sv> argument is a pointer to the SV that is to acquire a new magical
589feature.
590
591If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
592set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
593it to the beginning of the linked list of magical features. Any prior
594entry of the same type of magic is deleted. Note that this can be
5fb8527f 595overridden, and multiple instances of the same type of magic can be
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596associated with an SV.
597
598The C<name> and C<namlem> arguments are used to associate a string with
599the magic, typically the name of a variable. C<namlem> is stored in the
55497cff 600C<mg_len> field and if C<name> is non-null and C<namlem> >= 0 a malloc'd
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601copy of the name is stored in C<mg_ptr> field.
602
603The sv_magic function uses C<how> to determine which, if any, predefined
604"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
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605See the "Magic Virtual Table" section below. The C<how> argument is also
606stored in the C<mg_type> field.
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607
608The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
609structure. If it is not the same as the C<sv> argument, the reference
610count of the C<obj> object is incremented. If it is the same, or if
611the C<how> argument is "#", or if it is a null pointer, then C<obj> is
612merely stored, without the reference count being incremented.
613
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614There is also a function to add magic to an C<HV>:
615
616 void hv_magic(HV *hv, GV *gv, int how);
617
618This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
619
620To remove the magic from an SV, call the function sv_unmagic:
621
622 void sv_unmagic(SV *sv, int type);
623
624The C<type> argument should be equal to the C<how> value when the C<SV>
625was initially made magical.
626
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627=head2 Magic Virtual Tables
628
629The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
630C<MGVTBL>, which is a structure of function pointers and stands for
631"Magic Virtual Table" to handle the various operations that might be
632applied to that variable.
633
634The C<MGVTBL> has five pointers to the following routine types:
635
636 int (*svt_get)(SV* sv, MAGIC* mg);
637 int (*svt_set)(SV* sv, MAGIC* mg);
638 U32 (*svt_len)(SV* sv, MAGIC* mg);
639 int (*svt_clear)(SV* sv, MAGIC* mg);
640 int (*svt_free)(SV* sv, MAGIC* mg);
641
642This MGVTBL structure is set at compile-time in C<perl.h> and there are
643currently 19 types (or 21 with overloading turned on). These different
644structures contain pointers to various routines that perform additional
645actions depending on which function is being called.
646
647 Function pointer Action taken
648 ---------------- ------------
649 svt_get Do something after the value of the SV is retrieved.
650 svt_set Do something after the SV is assigned a value.
651 svt_len Report on the SV's length.
652 svt_clear Clear something the SV represents.
653 svt_free Free any extra storage associated with the SV.
654
655For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
656to an C<mg_type> of '\0') contains:
657
658 { magic_get, magic_set, magic_len, 0, 0 }
659
660Thus, when an SV is determined to be magical and of type '\0', if a get
661operation is being performed, the routine C<magic_get> is called. All
662the various routines for the various magical types begin with C<magic_>.
663
664The current kinds of Magic Virtual Tables are:
665
07fa94a1 666 mg_type MGVTBL Type of magical
5f05dabc 667 ------- ------ ----------------------------
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668 \0 vtbl_sv Regexp???
669 A vtbl_amagic Operator Overloading
670 a vtbl_amagicelem Operator Overloading
671 c 0 Used in Operator Overloading
672 B vtbl_bm Boyer-Moore???
673 E vtbl_env %ENV hash
674 e vtbl_envelem %ENV hash element
675 g vtbl_mglob Regexp /g flag???
676 I vtbl_isa @ISA array
677 i vtbl_isaelem @ISA array element
678 L 0 (but sets RMAGICAL) Perl Module/Debugger???
679 l vtbl_dbline Debugger?
44a8e56a 680 o vtbl_collxfrm Locale transformation
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681 P vtbl_pack Tied Array or Hash
682 p vtbl_packelem Tied Array or Hash element
683 q vtbl_packelem Tied Scalar or Handle
684 S vtbl_sig Signal Hash
685 s vtbl_sigelem Signal Hash element
686 t vtbl_taint Taintedness
687 U vtbl_uvar ???
688 v vtbl_vec Vector
689 x vtbl_substr Substring???
e616eb7b 690 y vtbl_itervar Shadow "foreach" iterator variable
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691 * vtbl_glob GV???
692 # vtbl_arylen Array Length
693 . vtbl_pos $. scalar variable
5f05dabc 694 ~ None Used by certain extensions
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695
696When an upper-case and lower-case letter both exist in the table, then the
697upper-case letter is used to represent some kind of composite type (a list
698or a hash), and the lower-case letter is used to represent an element of
699that composite type.
700
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701The '~' magic type is defined specifically for use by extensions and
702will not be used by perl itself. Extensions can use ~ magic to 'attach'
703private information to variables (typically objects). This is especially
704useful because there is no way for normal perl code to corrupt this
705private information (unlike using extra elements of a hash object).
706
707Note that because multiple extensions may be using ~ magic it is
708important for extensions to take extra care with it. Typically only
709using it on objects blessed into the same class as the extension
710is sufficient. It may also be appropriate to add an I32 'signature'
711at the top of the private data area and check that.
712
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713=head2 Finding Magic
714
715 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
716
717This routine returns a pointer to the C<MAGIC> structure stored in the SV.
718If the SV does not have that magical feature, C<NULL> is returned. Also,
719if the SV is not of type SVt_PVMG, Perl may core-dump.
720
721 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
722
723This routine checks to see what types of magic C<sv> has. If the mg_type
724field is an upper-case letter, then the mg_obj is copied to C<nsv>, but
725the mg_type field is changed to be the lower-case letter.
a0d0e21e 726
5f05dabc 727=head2 Double-Typed SV's
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LW
728
729Scalar variables normally contain only one type of value, an integer,
730double, pointer, or reference. Perl will automatically convert the
731actual scalar data from the stored type into the requested type.
732
733Some scalar variables contain more than one type of scalar data. For
734example, the variable C<$!> contains either the numeric value of C<errno>
d1b91892 735or its string equivalent from either C<strerror> or C<sys_errlist[]>.
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736
737To force multiple data values into an SV, you must do two things: use the
738C<sv_set*v> routines to add the additional scalar type, then set a flag
739so that Perl will believe it contains more than one type of data. The
740four macros to set the flags are:
741
742 SvIOK_on
743 SvNOK_on
744 SvPOK_on
745 SvROK_on
746
747The particular macro you must use depends on which C<sv_set*v> routine
748you called first. This is because every C<sv_set*v> routine turns on
749only the bit for the particular type of data being set, and turns off
750all the rest.
751
752For example, to create a new Perl variable called "dberror" that contains
753both the numeric and descriptive string error values, you could use the
754following code:
755
756 extern int dberror;
757 extern char *dberror_list;
758
759 SV* sv = perl_get_sv("dberror", TRUE);
760 sv_setiv(sv, (IV) dberror);
761 sv_setpv(sv, dberror_list[dberror]);
762 SvIOK_on(sv);
763
764If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
765macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
766
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767=head2 XSUB's and the Argument Stack
768
769The XSUB mechanism is a simple way for Perl programs to access C subroutines.
770An XSUB routine will have a stack that contains the arguments from the Perl
771program, and a way to map from the Perl data structures to a C equivalent.
772
773The stack arguments are accessible through the C<ST(n)> macro, which returns
774the C<n>'th stack argument. Argument 0 is the first argument passed in the
775Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
776an C<SV*> is used.
777
778Most of the time, output from the C routine can be handled through use of
779the RETVAL and OUTPUT directives. However, there are some cases where the
780argument stack is not already long enough to handle all the return values.
781An example is the POSIX tzname() call, which takes no arguments, but returns
782two, the local time zone's standard and summer time abbreviations.
783
784To handle this situation, the PPCODE directive is used and the stack is
785extended using the macro:
786
787 EXTEND(sp, num);
788
789where C<sp> is the stack pointer, and C<num> is the number of elements the
790stack should be extended by.
791
792Now that there is room on the stack, values can be pushed on it using the
793macros to push IV's, doubles, strings, and SV pointers respectively:
794
795 PUSHi(IV)
796 PUSHn(double)
797 PUSHp(char*, I32)
798 PUSHs(SV*)
799
800And now the Perl program calling C<tzname>, the two values will be assigned
801as in:
802
803 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
804
805An alternate (and possibly simpler) method to pushing values on the stack is
806to use the macros:
807
808 XPUSHi(IV)
809 XPUSHn(double)
810 XPUSHp(char*, I32)
811 XPUSHs(SV*)
812
813These macros automatically adjust the stack for you, if needed. Thus, you
814do not need to call C<EXTEND> to extend the stack.
815
816For more information, consult L<perlxs> and L<perlxstut>.
817
818=head2 Calling Perl Routines from within C Programs
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819
820There are four routines that can be used to call a Perl subroutine from
821within a C program. These four are:
822
823 I32 perl_call_sv(SV*, I32);
824 I32 perl_call_pv(char*, I32);
825 I32 perl_call_method(char*, I32);
826 I32 perl_call_argv(char*, I32, register char**);
827
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AD
828The routine most often used is C<perl_call_sv>. The C<SV*> argument
829contains either the name of the Perl subroutine to be called, or a
830reference to the subroutine. The second argument consists of flags
831that control the context in which the subroutine is called, whether
832or not the subroutine is being passed arguments, how errors should be
833trapped, and how to treat return values.
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LW
834
835All four routines return the number of arguments that the subroutine returned
836on the Perl stack.
837
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AD
838When using any of these routines (except C<perl_call_argv>), the programmer
839must manipulate the Perl stack. These include the following macros and
840functions:
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LW
841
842 dSP
843 PUSHMARK()
844 PUTBACK
845 SPAGAIN
846 ENTER
847 SAVETMPS
848 FREETMPS
849 LEAVE
850 XPUSH*()
cb1a09d0 851 POP*()
a0d0e21e 852
5f05dabc
PP
853For a detailed description of calling conventions from C to Perl,
854consult L<perlcall>.
a0d0e21e 855
5f05dabc 856=head2 Memory Allocation
a0d0e21e 857
5f05dabc
PP
858It is suggested that you use the version of malloc that is distributed
859with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
860order to satisfy allocation requests more quickly. However, on some
861platforms, it may cause spurious malloc or free errors.
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862
863 New(x, pointer, number, type);
864 Newc(x, pointer, number, type, cast);
865 Newz(x, pointer, number, type);
866
07fa94a1 867These three macros are used to initially allocate memory.
5f05dabc
PP
868
869The first argument C<x> was a "magic cookie" that was used to keep track
870of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
871the current code makes no use of this feature (most Perl developers now
872use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
873
874The second argument C<pointer> should be the name of a variable that will
875point to the newly allocated memory.
d1b91892 876
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AD
877The third and fourth arguments C<number> and C<type> specify how many of
878the specified type of data structure should be allocated. The argument
879C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
880should be used if the C<pointer> argument is different from the C<type>
881argument.
882
883Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
884to zero out all the newly allocated memory.
885
886 Renew(pointer, number, type);
887 Renewc(pointer, number, type, cast);
888 Safefree(pointer)
889
890These three macros are used to change a memory buffer size or to free a
891piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
892match those of C<New> and C<Newc> with the exception of not needing the
893"magic cookie" argument.
894
895 Move(source, dest, number, type);
896 Copy(source, dest, number, type);
897 Zero(dest, number, type);
898
899These three macros are used to move, copy, or zero out previously allocated
900memory. The C<source> and C<dest> arguments point to the source and
901destination starting points. Perl will move, copy, or zero out C<number>
902instances of the size of the C<type> data structure (using the C<sizeof>
903function).
a0d0e21e 904
5f05dabc 905=head2 PerlIO
ce3d39e2 906
5f05dabc
PP
907The most recent development releases of Perl has been experimenting with
908removing Perl's dependency on the "normal" standard I/O suite and allowing
909other stdio implementations to be used. This involves creating a new
910abstraction layer that then calls whichever implementation of stdio Perl
911was compiled with. All XSUB's should now use the functions in the PerlIO
912abstraction layer and not make any assumptions about what kind of stdio
913is being used.
914
915For a complete description of the PerlIO abstraction, consult L<perlapio>.
916
917=head2 Scratchpads
918
8ebc5c01 919=head2 Putting a C value on Perl stack
ce3d39e2
IZ
920
921A lot of opcodes (this is an elementary operation in the internal perl
922stack machine) put an SV* on the stack. However, as an optimization
923the corresponding SV is (usually) not recreated each time. The opcodes
924reuse specially assigned SVs (I<target>s) which are (as a corollary)
925not constantly freed/created.
926
927Each of the targets is created only once (but see
928L<Scratchpads and recursion> below), and when an opcode needs to put
929an integer, a double, or a string on stack, it just sets the
930corresponding parts of its I<target> and puts the I<target> on stack.
931
932The macro to put this target on stack is C<PUSHTARG>, and it is
933directly used in some opcodes, as well as indirectly in zillions of
934others, which use it via C<(X)PUSH[pni]>.
935
8ebc5c01 936=head2 Scratchpads
ce3d39e2 937
5f05dabc
PP
938The question remains on when the SV's which are I<target>s for opcodes
939are created. The answer is that they are created when the current unit --
940a subroutine or a file (for opcodes for statements outside of
941subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
942array is created, which is called a scratchpad for the current
943unit.
944
5f05dabc 945A scratchpad keeps SV's which are lexicals for the current unit and are
ce3d39e2
IZ
946targets for opcodes. One can deduce that an SV lives on a scratchpad
947by looking on its flags: lexicals have C<SVs_PADMY> set, and
948I<target>s have C<SVs_PADTMP> set.
949
5f05dabc
PP
950The correspondence between OP's and I<target>s is not 1-to-1. Different
951OP's in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
952would not conflict with the expected life of the temporary.
953
8ebc5c01 954=head2 Scratchpads and recursions
ce3d39e2
IZ
955
956In fact it is not 100% true that a compiled unit contains a pointer to
957the scratchpad AV. In fact it contains a pointer to an AV of
958(initially) one element, and this element is the scratchpad AV. Why do
959we need an extra level of indirection?
960
961The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
962these can create several execution pointers going into the same
963subroutine. For the subroutine-child not write over the temporaries
964for the subroutine-parent (lifespan of which covers the call to the
965child), the parent and the child should have different
966scratchpads. (I<And> the lexicals should be separate anyway!)
967
5f05dabc
PP
968So each subroutine is born with an array of scratchpads (of length 1).
969On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
970depth of the recursion is not more than the length of this array, and
971if it is, new scratchpad is created and pushed into the array.
972
973The I<target>s on this scratchpad are C<undef>s, but they are already
974marked with correct flags.
975
5f05dabc 976=head2 API LISTING
a0d0e21e 977
cb1a09d0
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978This is a listing of functions, macros, flags, and variables that may be
979useful to extension writers or that may be found while reading other
980extensions.
a0d0e21e 981
cb1a09d0 982=over 8
a0d0e21e 983
cb1a09d0
AD
984=item AvFILL
985
986See C<av_len>.
987
988=item av_clear
989
990Clears an array, making it empty.
991
992 void av_clear _((AV* ar));
993
994=item av_extend
995
996Pre-extend an array. The C<key> is the index to which the array should be
997extended.
998
999 void av_extend _((AV* ar, I32 key));
1000
1001=item av_fetch
1002
1003Returns the SV at the specified index in the array. The C<key> is the
1004index. If C<lval> is set then the fetch will be part of a store. Check
1005that the return value is non-null before dereferencing it to a C<SV*>.
1006
1007 SV** av_fetch _((AV* ar, I32 key, I32 lval));
1008
1009=item av_len
1010
1011Returns the highest index in the array. Returns -1 if the array is empty.
1012
1013 I32 av_len _((AV* ar));
1014
1015=item av_make
1016
5fb8527f
PP
1017Creates a new AV and populates it with a list of SVs. The SVs are copied
1018into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1019will have a reference count of 1.
cb1a09d0
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1020
1021 AV* av_make _((I32 size, SV** svp));
1022
1023=item av_pop
1024
1025Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
1026empty.
1027
1028 SV* av_pop _((AV* ar));
1029
1030=item av_push
1031
5fb8527f
PP
1032Pushes an SV onto the end of the array. The array will grow automatically
1033to accommodate the addition.
cb1a09d0
AD
1034
1035 void av_push _((AV* ar, SV* val));
1036
1037=item av_shift
1038
1039Shifts an SV off the beginning of the array.
1040
1041 SV* av_shift _((AV* ar));
1042
1043=item av_store
1044
1045Stores an SV in an array. The array index is specified as C<key>. The
1046return value will be null if the operation failed, otherwise it can be
1047dereferenced to get the original C<SV*>.
1048
1049 SV** av_store _((AV* ar, I32 key, SV* val));
1050
1051=item av_undef
1052
1053Undefines the array.
1054
1055 void av_undef _((AV* ar));
1056
1057=item av_unshift
1058
5fb8527f
PP
1059Unshift an SV onto the beginning of the array. The array will grow
1060automatically to accommodate the addition.
cb1a09d0
AD
1061
1062 void av_unshift _((AV* ar, I32 num));
1063
1064=item CLASS
1065
1066Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1067constructor. This is always a C<char*>. See C<THIS> and
1068L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1069
1070=item Copy
1071
1072The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1073source, C<d> is the destination, C<n> is the number of items, and C<t> is
1074the type.
1075
1076 (void) Copy( s, d, n, t );
1077
1078=item croak
1079
1080This is the XSUB-writer's interface to Perl's C<die> function. Use this
1081function the same way you use the C C<printf> function. See C<warn>.
1082
1083=item CvSTASH
1084
1085Returns the stash of the CV.
1086
1087 HV * CvSTASH( SV* sv )
1088
1089=item DBsingle
1090
1091When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1092boolean which indicates whether subs are being single-stepped.
5fb8527f
PP
1093Single-stepping is automatically turned on after every step. This is the C
1094variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
cb1a09d0
AD
1095
1096=item DBsub
1097
1098When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f
PP
1099the SV which holds the name of the sub being debugged. This is the C
1100variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
cb1a09d0
AD
1101The sub name can be found by
1102
1103 SvPV( GvSV( DBsub ), na )
1104
5fb8527f
PP
1105=item DBtrace
1106
1107Trace variable used when Perl is run in debugging mode, with the B<-d>
1108switch. This is the C variable which corresponds to Perl's $DB::trace
1109variable. See C<DBsingle>.
1110
cb1a09d0
AD
1111=item dMARK
1112
5fb8527f
PP
1113Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1114C<dORIGMARK>.
cb1a09d0
AD
1115
1116=item dORIGMARK
1117
1118Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1119
5fb8527f
PP
1120=item dowarn
1121
1122The C variable which corresponds to Perl's $^W warning variable.
1123
cb1a09d0
AD
1124=item dSP
1125
5fb8527f 1126Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
cb1a09d0
AD
1127
1128=item dXSARGS
1129
1130Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1131usually handled automatically by C<xsubpp>. Declares the C<items> variable
1132to indicate the number of items on the stack.
1133
5fb8527f
PP
1134=item dXSI32
1135
1136Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1137handled automatically by C<xsubpp>.
1138
1139=item dXSI32
1140
1141Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1142handled automatically by C<xsubpp>.
1143
cb1a09d0
AD
1144=item ENTER
1145
1146Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1147
1148 ENTER;
1149
1150=item EXTEND
1151
1152Used to extend the argument stack for an XSUB's return values.
1153
1154 EXTEND( sp, int x );
1155
1156=item FREETMPS
1157
1158Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1159L<perlcall>.
1160
1161 FREETMPS;
1162
1163=item G_ARRAY
1164
1165Used to indicate array context. See C<GIMME> and L<perlcall>.
1166
1167=item G_DISCARD
1168
1169Indicates that arguments returned from a callback should be discarded. See
1170L<perlcall>.
1171
1172=item G_EVAL
1173
1174Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1175
1176=item GIMME
1177
1178The XSUB-writer's equivalent to Perl's C<wantarray>. Returns C<G_SCALAR> or
1179C<G_ARRAY> for scalar or array context.
1180
1181=item G_NOARGS
1182
1183Indicates that no arguments are being sent to a callback. See L<perlcall>.
1184
1185=item G_SCALAR
1186
1187Used to indicate scalar context. See C<GIMME> and L<perlcall>.
1188
faed5253
JO
1189=item gv_fetchmeth
1190
1191Returns the glob with the given C<name> and a defined subroutine or
1192C<NULL>. The glob lives in the given C<stash>, or in the stashes accessable
1193via @ISA and @<UNIVERSAL>.
1194
1195As a side-effect creates a glob with the given C<name> in the given C<stash>
1196which in the case of success contains an alias for the subroutine, and
1197sets up caching info for this glob. Similarly for all the searched
1198stashes.
1199
1200 GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
1201
1202=item gv_fetchmethod
1203
1204Returns the glob which contains the subroutine to call to invoke the
1205method on the C<stash>. In fact in the presense of autoloading this may
1206be the glob for "AUTOLOAD". In this case the corresponing variable
1207$AUTOLOAD is already setup.
1208
1209Note that if you want to keep this glob for a long time, you need to
1210check for it being "AUTOLOAD", since at the later time the the call
1211may load a different subroutine due to $AUTOLOAD changing its value.
1212Use the glob created via a side effect to do this.
1213
1214This function grants C<"SUPER"> token as prefix of name or postfix of
1215the stash name.
1216
1217Has the same side-effects and as C<gv_fetchmeth()>. C<name> should be
1218writable if contains C<':'> or C<'\''>.
1219
1220 GV* gv_fetchmethod _((HV* stash, char* name));
1221
cb1a09d0
AD
1222=item gv_stashpv
1223
1224Returns a pointer to the stash for a specified package. If C<create> is set
1225then the package will be created if it does not already exist. If C<create>
1226is not set and the package does not exist then NULL is returned.
1227
1228 HV* gv_stashpv _((char* name, I32 create));
1229
1230=item gv_stashsv
1231
1232Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1233
1234 HV* gv_stashsv _((SV* sv, I32 create));
1235
e5581bf4 1236=item GvSV
cb1a09d0 1237
e5581bf4 1238Return the SV from the GV.
44a8e56a
PP
1239
1240=item he_delayfree
1241
1242Releases a hash entry, such as while iterating though the hash, but
1243delays actual freeing of key and value until the end of the current
1244statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>.
cb1a09d0 1245
e5581bf4
JO
1246 void he_delayfree _((HV* hv, HE* hent));
1247
1248=item he_free
1249
1250Releases a hash entry, such as while iterating though the hash. See
1251C<hv_iternext>.
1252
1253 void he_free _((HV* hv, HE* hent));
cb1a09d0
AD
1254
1255=item hv_clear
1256
1257Clears a hash, making it empty.
1258
1259 void hv_clear _((HV* tb));
1260
1261=item hv_delete
1262
1263Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1264and returned to the caller. The C<klen> is the length of the key. The
cb1a09d0
AD
1265C<flags> value will normally be zero; if set to G_DISCARD then null will be
1266returned.
1267
1268 SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
1269
1270=item hv_exists
1271
1272Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1273C<klen> is the length of the key.
cb1a09d0
AD
1274
1275 bool hv_exists _((HV* tb, char* key, U32 klen));
1276
1277=item hv_fetch
1278
1279Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1280C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1281part of a store. Check that the return value is non-null before
1282dereferencing it to a C<SV*>.
1283
1284 SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
1285
1286=item hv_iterinit
1287
1288Prepares a starting point to traverse a hash table.
1289
1290 I32 hv_iterinit _((HV* tb));
1291
1292=item hv_iterkey
1293
1294Returns the key from the current position of the hash iterator. See
1295C<hv_iterinit>.
1296
1297 char* hv_iterkey _((HE* entry, I32* retlen));
1298
1299=item hv_iternext
1300
1301Returns entries from a hash iterator. See C<hv_iterinit>.
1302
1303 HE* hv_iternext _((HV* tb));
1304
1305=item hv_iternextsv
1306
1307Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1308operation.
1309
1310 SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
1311
1312=item hv_iterval
1313
1314Returns the value from the current position of the hash iterator. See
1315C<hv_iterkey>.
1316
1317 SV* hv_iterval _((HV* tb, HE* entry));
1318
1319=item hv_magic
1320
1321Adds magic to a hash. See C<sv_magic>.
1322
1323 void hv_magic _((HV* hv, GV* gv, int how));
1324
1325=item HvNAME
1326
1327Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1328
1329 char *HvNAME (HV* stash)
1330
1331=item hv_store
1332
1333Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
1334the length of the key. The C<hash> parameter is the pre-computed hash
1335value; if it is zero then Perl will compute it. The return value will be
1336null if the operation failed, otherwise it can be dereferenced to get the
1337original C<SV*>.
1338
1339 SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
1340
1341=item hv_undef
1342
1343Undefines the hash.
1344
1345 void hv_undef _((HV* tb));
1346
1347=item isALNUM
1348
1349Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 1350character or digit.
cb1a09d0
AD
1351
1352 int isALNUM (char c)
1353
1354=item isALPHA
1355
5fb8527f 1356Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
1357character.
1358
1359 int isALPHA (char c)
1360
1361=item isDIGIT
1362
1363Returns a boolean indicating whether the C C<char> is an ascii digit.
1364
1365 int isDIGIT (char c)
1366
1367=item isLOWER
1368
1369Returns a boolean indicating whether the C C<char> is a lowercase character.
1370
1371 int isLOWER (char c)
1372
1373=item isSPACE
1374
1375Returns a boolean indicating whether the C C<char> is whitespace.
1376
1377 int isSPACE (char c)
1378
1379=item isUPPER
1380
1381Returns a boolean indicating whether the C C<char> is an uppercase character.
1382
1383 int isUPPER (char c)
1384
1385=item items
1386
1387Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
1388stack. See L<perlxs/"Variable-length Parameter Lists">.
1389
1390=item ix
1391
1392Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
1393was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
1394
1395=item LEAVE
1396
1397Closing bracket on a callback. See C<ENTER> and L<perlcall>.
1398
1399 LEAVE;
1400
1401=item MARK
1402
5fb8527f 1403Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
1404
1405=item mg_clear
1406
1407Clear something magical that the SV represents. See C<sv_magic>.
1408
1409 int mg_clear _((SV* sv));
1410
1411=item mg_copy
1412
1413Copies the magic from one SV to another. See C<sv_magic>.
1414
1415 int mg_copy _((SV *, SV *, char *, STRLEN));
1416
1417=item mg_find
1418
1419Finds the magic pointer for type matching the SV. See C<sv_magic>.
1420
1421 MAGIC* mg_find _((SV* sv, int type));
1422
1423=item mg_free
1424
1425Free any magic storage used by the SV. See C<sv_magic>.
1426
1427 int mg_free _((SV* sv));
1428
1429=item mg_get
1430
1431Do magic after a value is retrieved from the SV. See C<sv_magic>.
1432
1433 int mg_get _((SV* sv));
1434
1435=item mg_len
1436
1437Report on the SV's length. See C<sv_magic>.
1438
1439 U32 mg_len _((SV* sv));
1440
1441=item mg_magical
1442
1443Turns on the magical status of an SV. See C<sv_magic>.
1444
1445 void mg_magical _((SV* sv));
1446
1447=item mg_set
1448
1449Do magic after a value is assigned to the SV. See C<sv_magic>.
1450
1451 int mg_set _((SV* sv));
1452
1453=item Move
1454
1455The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
1456source, C<d> is the destination, C<n> is the number of items, and C<t> is
1457the type.
1458
1459 (void) Move( s, d, n, t );
1460
1461=item na
1462
1463A variable which may be used with C<SvPV> to tell Perl to calculate the
1464string length.
1465
1466=item New
1467
1468The XSUB-writer's interface to the C C<malloc> function.
1469
1470 void * New( x, void *ptr, int size, type )
1471
1472=item Newc
1473
1474The XSUB-writer's interface to the C C<malloc> function, with cast.
1475
1476 void * Newc( x, void *ptr, int size, type, cast )
1477
1478=item Newz
1479
1480The XSUB-writer's interface to the C C<malloc> function. The allocated
1481memory is zeroed with C<memzero>.
1482
1483 void * Newz( x, void *ptr, int size, type )
1484
1485=item newAV
1486
5f05dabc 1487Creates a new AV. The reference count is set to 1.
cb1a09d0
AD
1488
1489 AV* newAV _((void));
1490
1491=item newHV
1492
5f05dabc 1493Creates a new HV. The reference count is set to 1.
cb1a09d0
AD
1494
1495 HV* newHV _((void));
1496
5f05dabc 1497=item newRV_inc
cb1a09d0 1498
5f05dabc 1499Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
1500incremented.
1501
5f05dabc
PP
1502 SV* newRV_inc _((SV* ref));
1503
1504For historical reasons, "newRV" is a synonym for "newRV_inc".
1505
1506=item newRV_noinc
1507
1508Creates an RV wrapper for an SV. The reference count for the original
1509SV is B<not> incremented.
1510
07fa94a1 1511 SV* newRV_noinc _((SV* ref));
cb1a09d0
AD
1512
1513=item newSV
1514
1515Creates a new SV. The C<len> parameter indicates the number of bytes of
07fa94a1
JO
1516pre-allocated string space the SV should have. The reference count for the
1517new SV is set to 1.
cb1a09d0
AD
1518
1519 SV* newSV _((STRLEN len));
1520
1521=item newSViv
1522
07fa94a1
JO
1523Creates a new SV and copies an integer into it. The reference count for the
1524SV is set to 1.
cb1a09d0
AD
1525
1526 SV* newSViv _((IV i));
1527
1528=item newSVnv
1529
07fa94a1
JO
1530Creates a new SV and copies a double into it. The reference count for the
1531SV is set to 1.
cb1a09d0
AD
1532
1533 SV* newSVnv _((NV i));
1534
1535=item newSVpv
1536
07fa94a1
JO
1537Creates a new SV and copies a string into it. The reference count for the
1538SV is set to 1. If C<len> is zero then Perl will compute the length.
cb1a09d0
AD
1539
1540 SV* newSVpv _((char* s, STRLEN len));
1541
1542=item newSVrv
1543
1544Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 1545it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 1546be blessed in the specified package. The new SV is returned and its
5f05dabc 1547reference count is 1.
8ebc5c01 1548
cb1a09d0
AD
1549 SV* newSVrv _((SV* rv, char* classname));
1550
1551=item newSVsv
1552
5fb8527f 1553Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0
AD
1554
1555 SV* newSVsv _((SV* old));
1556
1557=item newXS
1558
1559Used by C<xsubpp> to hook up XSUBs as Perl subs.
1560
1561=item newXSproto
1562
1563Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
1564the subs.
1565
1566=item Nullav
1567
1568Null AV pointer.
1569
1570=item Nullch
1571
1572Null character pointer.
1573
1574=item Nullcv
1575
1576Null CV pointer.
1577
1578=item Nullhv
1579
1580Null HV pointer.
1581
1582=item Nullsv
1583
1584Null SV pointer.
1585
1586=item ORIGMARK
1587
1588The original stack mark for the XSUB. See C<dORIGMARK>.
1589
1590=item perl_alloc
1591
1592Allocates a new Perl interpreter. See L<perlembed>.
1593
1594=item perl_call_argv
1595
1596Performs a callback to the specified Perl sub. See L<perlcall>.
1597
1598 I32 perl_call_argv _((char* subname, I32 flags, char** argv));
1599
1600=item perl_call_method
1601
1602Performs a callback to the specified Perl method. The blessed object must
1603be on the stack. See L<perlcall>.
1604
1605 I32 perl_call_method _((char* methname, I32 flags));
1606
1607=item perl_call_pv
1608
1609Performs a callback to the specified Perl sub. See L<perlcall>.
1610
1611 I32 perl_call_pv _((char* subname, I32 flags));
1612
1613=item perl_call_sv
1614
1615Performs a callback to the Perl sub whose name is in the SV. See
1616L<perlcall>.
1617
1618 I32 perl_call_sv _((SV* sv, I32 flags));
1619
1620=item perl_construct
1621
1622Initializes a new Perl interpreter. See L<perlembed>.
1623
1624=item perl_destruct
1625
1626Shuts down a Perl interpreter. See L<perlembed>.
1627
1628=item perl_eval_sv
1629
1630Tells Perl to C<eval> the string in the SV.
1631
1632 I32 perl_eval_sv _((SV* sv, I32 flags));
1633
1634=item perl_free
1635
1636Releases a Perl interpreter. See L<perlembed>.
1637
1638=item perl_get_av
1639
1640Returns the AV of the specified Perl array. If C<create> is set and the
1641Perl variable does not exist then it will be created. If C<create> is not
1642set and the variable does not exist then null is returned.
1643
1644 AV* perl_get_av _((char* name, I32 create));
1645
1646=item perl_get_cv
1647
1648Returns the CV of the specified Perl sub. If C<create> is set and the Perl
1649variable does not exist then it will be created. If C<create> is not
1650set and the variable does not exist then null is returned.
1651
1652 CV* perl_get_cv _((char* name, I32 create));
1653
1654=item perl_get_hv
1655
1656Returns the HV of the specified Perl hash. If C<create> is set and the Perl
1657variable does not exist then it will be created. If C<create> is not
1658set and the variable does not exist then null is returned.
1659
1660 HV* perl_get_hv _((char* name, I32 create));
1661
1662=item perl_get_sv
1663
1664Returns the SV of the specified Perl scalar. If C<create> is set and the
1665Perl variable does not exist then it will be created. If C<create> is not
1666set and the variable does not exist then null is returned.
1667
1668 SV* perl_get_sv _((char* name, I32 create));
1669
1670=item perl_parse
1671
1672Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
1673
1674=item perl_require_pv
1675
1676Tells Perl to C<require> a module.
1677
1678 void perl_require_pv _((char* pv));
1679
1680=item perl_run
1681
1682Tells a Perl interpreter to run. See L<perlembed>.
1683
1684=item POPi
1685
1686Pops an integer off the stack.
1687
1688 int POPi();
1689
1690=item POPl
1691
1692Pops a long off the stack.
1693
1694 long POPl();
1695
1696=item POPp
1697
1698Pops a string off the stack.
1699
1700 char * POPp();
1701
1702=item POPn
1703
1704Pops a double off the stack.
1705
1706 double POPn();
1707
1708=item POPs
1709
1710Pops an SV off the stack.
1711
1712 SV* POPs();
1713
1714=item PUSHMARK
1715
1716Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
1717
1718 PUSHMARK(p)
1719
1720=item PUSHi
1721
1722Push an integer onto the stack. The stack must have room for this element.
1723See C<XPUSHi>.
1724
1725 PUSHi(int d)
1726
1727=item PUSHn
1728
1729Push a double onto the stack. The stack must have room for this element.
1730See C<XPUSHn>.
1731
1732 PUSHn(double d)
1733
1734=item PUSHp
1735
1736Push a string onto the stack. The stack must have room for this element.
1737The C<len> indicates the length of the string. See C<XPUSHp>.
1738
1739 PUSHp(char *c, int len )
1740
1741=item PUSHs
1742
1743Push an SV onto the stack. The stack must have room for this element. See
1744C<XPUSHs>.
1745
1746 PUSHs(sv)
1747
1748=item PUTBACK
1749
1750Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
1751See C<PUSHMARK> and L<perlcall> for other uses.
1752
1753 PUTBACK;
1754
1755=item Renew
1756
1757The XSUB-writer's interface to the C C<realloc> function.
1758
1759 void * Renew( void *ptr, int size, type )
1760
1761=item Renewc
1762
1763The XSUB-writer's interface to the C C<realloc> function, with cast.
1764
1765 void * Renewc( void *ptr, int size, type, cast )
1766
1767=item RETVAL
1768
1769Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
1770This is always the proper type for the XSUB.
1771See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
1772
1773=item safefree
1774
1775The XSUB-writer's interface to the C C<free> function.
1776
1777=item safemalloc
1778
1779The XSUB-writer's interface to the C C<malloc> function.
1780
1781=item saferealloc
1782
1783The XSUB-writer's interface to the C C<realloc> function.
1784
1785=item savepv
1786
1787Copy a string to a safe spot. This does not use an SV.
1788
1789 char* savepv _((char* sv));
1790
1791=item savepvn
1792
1793Copy a string to a safe spot. The C<len> indicates number of bytes to
1794copy. This does not use an SV.
1795
1796 char* savepvn _((char* sv, I32 len));
1797
1798=item SAVETMPS
1799
1800Opening bracket for temporaries on a callback. See C<FREETMPS> and
1801L<perlcall>.
1802
1803 SAVETMPS;
1804
1805=item SP
1806
1807Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
1808C<SPAGAIN>.
1809
1810=item SPAGAIN
1811
5f05dabc 1812Re-fetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
1813
1814 SPAGAIN;
1815
1816=item ST
1817
1818Used to access elements on the XSUB's stack.
1819
1820 SV* ST(int x)
1821
1822=item strEQ
1823
1824Test two strings to see if they are equal. Returns true or false.
1825
1826 int strEQ( char *s1, char *s2 )
1827
1828=item strGE
1829
1830Test two strings to see if the first, C<s1>, is greater than or equal to the
1831second, C<s2>. Returns true or false.
1832
1833 int strGE( char *s1, char *s2 )
1834
1835=item strGT
1836
1837Test two strings to see if the first, C<s1>, is greater than the second,
1838C<s2>. Returns true or false.
1839
1840 int strGT( char *s1, char *s2 )
1841
1842=item strLE
1843
1844Test two strings to see if the first, C<s1>, is less than or equal to the
1845second, C<s2>. Returns true or false.
1846
1847 int strLE( char *s1, char *s2 )
1848
1849=item strLT
1850
1851Test two strings to see if the first, C<s1>, is less than the second,
1852C<s2>. Returns true or false.
1853
1854 int strLT( char *s1, char *s2 )
1855
1856=item strNE
1857
1858Test two strings to see if they are different. Returns true or false.
1859
1860 int strNE( char *s1, char *s2 )
1861
1862=item strnEQ
1863
1864Test two strings to see if they are equal. The C<len> parameter indicates
1865the number of bytes to compare. Returns true or false.
1866
1867 int strnEQ( char *s1, char *s2 )
1868
1869=item strnNE
1870
1871Test two strings to see if they are different. The C<len> parameter
1872indicates the number of bytes to compare. Returns true or false.
1873
1874 int strnNE( char *s1, char *s2, int len )
1875
1876=item sv_2mortal
1877
1878Marks an SV as mortal. The SV will be destroyed when the current context
1879ends.
1880
1881 SV* sv_2mortal _((SV* sv));
1882
1883=item sv_bless
1884
1885Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
1886must be designated by its stash (see C<gv_stashpv()>). The reference count
1887of the SV is unaffected.
cb1a09d0
AD
1888
1889 SV* sv_bless _((SV* sv, HV* stash));
1890
1891=item sv_catpv
1892
1893Concatenates the string onto the end of the string which is in the SV.
1894
1895 void sv_catpv _((SV* sv, char* ptr));
1896
1897=item sv_catpvn
1898
1899Concatenates the string onto the end of the string which is in the SV. The
1900C<len> indicates number of bytes to copy.
1901
1902 void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
1903
1904=item sv_catsv
1905
5fb8527f 1906Concatenates the string from SV C<ssv> onto the end of the string in SV
cb1a09d0
AD
1907C<dsv>.
1908
1909 void sv_catsv _((SV* dsv, SV* ssv));
1910
5fb8527f
PP
1911=item sv_cmp
1912
1913Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
1914string in C<sv1> is less than, equal to, or greater than the string in
1915C<sv2>.
1916
1917 I32 sv_cmp _((SV* sv1, SV* sv2));
1918
1919=item sv_cmp
1920
1921Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
1922string in C<sv1> is less than, equal to, or greater than the string in
1923C<sv2>.
1924
1925 I32 sv_cmp _((SV* sv1, SV* sv2));
1926
cb1a09d0
AD
1927=item SvCUR
1928
1929Returns the length of the string which is in the SV. See C<SvLEN>.
1930
1931 int SvCUR (SV* sv)
1932
1933=item SvCUR_set
1934
1935Set the length of the string which is in the SV. See C<SvCUR>.
1936
1937 SvCUR_set (SV* sv, int val )
1938
5fb8527f
PP
1939=item sv_dec
1940
5f05dabc 1941Auto-decrement of the value in the SV.
5fb8527f
PP
1942
1943 void sv_dec _((SV* sv));
1944
1945=item sv_dec
1946
5f05dabc 1947Auto-decrement of the value in the SV.
5fb8527f
PP
1948
1949 void sv_dec _((SV* sv));
1950
cb1a09d0
AD
1951=item SvEND
1952
1953Returns a pointer to the last character in the string which is in the SV.
1954See C<SvCUR>. Access the character as
1955
1956 *SvEND(sv)
1957
5fb8527f
PP
1958=item sv_eq
1959
1960Returns a boolean indicating whether the strings in the two SVs are
1961identical.
1962
1963 I32 sv_eq _((SV* sv1, SV* sv2));
1964
cb1a09d0
AD
1965=item SvGROW
1966
5fb8527f
PP
1967Expands the character buffer in the SV. Calls C<sv_grow> to perform the
1968expansion if necessary. Returns a pointer to the character buffer.
cb1a09d0
AD
1969
1970 char * SvGROW( SV* sv, int len )
1971
5fb8527f
PP
1972=item sv_grow
1973
1974Expands the character buffer in the SV. This will use C<sv_unref> and will
1975upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
1976Use C<SvGROW>.
1977
1978=item sv_inc
1979
07fa94a1 1980Auto-increment of the value in the SV.
5fb8527f
PP
1981
1982 void sv_inc _((SV* sv));
1983
cb1a09d0
AD
1984=item SvIOK
1985
1986Returns a boolean indicating whether the SV contains an integer.
1987
1988 int SvIOK (SV* SV)
1989
1990=item SvIOK_off
1991
1992Unsets the IV status of an SV.
1993
1994 SvIOK_off (SV* sv)
1995
1996=item SvIOK_on
1997
1998Tells an SV that it is an integer.
1999
2000 SvIOK_on (SV* sv)
2001
5fb8527f
PP
2002=item SvIOK_only
2003
2004Tells an SV that it is an integer and disables all other OK bits.
2005
2006 SvIOK_on (SV* sv)
2007
2008=item SvIOK_only
2009
2010Tells an SV that it is an integer and disables all other OK bits.
2011
2012 SvIOK_on (SV* sv)
2013
cb1a09d0
AD
2014=item SvIOKp
2015
2016Returns a boolean indicating whether the SV contains an integer. Checks the
2017B<private> setting. Use C<SvIOK>.
2018
2019 int SvIOKp (SV* SV)
2020
2021=item sv_isa
2022
2023Returns a boolean indicating whether the SV is blessed into the specified
2024class. This does not know how to check for subtype, so it doesn't work in
2025an inheritance relationship.
2026
2027 int sv_isa _((SV* sv, char* name));
2028
2029=item SvIV
2030
2031Returns the integer which is in the SV.
2032
2033 int SvIV (SV* sv)
2034
2035=item sv_isobject
2036
2037Returns a boolean indicating whether the SV is an RV pointing to a blessed
2038object. If the SV is not an RV, or if the object is not blessed, then this
2039will return false.
2040
2041 int sv_isobject _((SV* sv));
2042
2043=item SvIVX
2044
2045Returns the integer which is stored in the SV.
2046
2047 int SvIVX (SV* sv);
2048
2049=item SvLEN
2050
2051Returns the size of the string buffer in the SV. See C<SvCUR>.
2052
2053 int SvLEN (SV* sv)
2054
5fb8527f
PP
2055=item sv_len
2056
2057Returns the length of the string in the SV. Use C<SvCUR>.
2058
2059 STRLEN sv_len _((SV* sv));
2060
2061=item sv_len
2062
2063Returns the length of the string in the SV. Use C<SvCUR>.
2064
2065 STRLEN sv_len _((SV* sv));
2066
cb1a09d0
AD
2067=item sv_magic
2068
2069Adds magic to an SV.
2070
2071 void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
2072
2073=item sv_mortalcopy
2074
2075Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2076as mortal.
cb1a09d0
AD
2077
2078 SV* sv_mortalcopy _((SV* oldsv));
2079
2080=item SvOK
2081
2082Returns a boolean indicating whether the value is an SV.
2083
2084 int SvOK (SV* sv)
2085
2086=item sv_newmortal
2087
5f05dabc 2088Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0
AD
2089
2090 SV* sv_newmortal _((void));
2091
2092=item sv_no
2093
2094This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
2095
2096=item SvNIOK
2097
2098Returns a boolean indicating whether the SV contains a number, integer or
2099double.
2100
2101 int SvNIOK (SV* SV)
2102
2103=item SvNIOK_off
2104
2105Unsets the NV/IV status of an SV.
2106
2107 SvNIOK_off (SV* sv)
2108
2109=item SvNIOKp
2110
2111Returns a boolean indicating whether the SV contains a number, integer or
2112double. Checks the B<private> setting. Use C<SvNIOK>.
2113
2114 int SvNIOKp (SV* SV)
2115
2116=item SvNOK
2117
2118Returns a boolean indicating whether the SV contains a double.
2119
2120 int SvNOK (SV* SV)
2121
2122=item SvNOK_off
2123
2124Unsets the NV status of an SV.
2125
2126 SvNOK_off (SV* sv)
2127
2128=item SvNOK_on
2129
2130Tells an SV that it is a double.
2131
2132 SvNOK_on (SV* sv)
2133
5fb8527f
PP
2134=item SvNOK_only
2135
2136Tells an SV that it is a double and disables all other OK bits.
2137
2138 SvNOK_on (SV* sv)
2139
2140=item SvNOK_only
2141
2142Tells an SV that it is a double and disables all other OK bits.
2143
2144 SvNOK_on (SV* sv)
2145
cb1a09d0
AD
2146=item SvNOKp
2147
2148Returns a boolean indicating whether the SV contains a double. Checks the
2149B<private> setting. Use C<SvNOK>.
2150
2151 int SvNOKp (SV* SV)
2152
2153=item SvNV
2154
2155Returns the double which is stored in the SV.
2156
2157 double SvNV (SV* sv);
2158
2159=item SvNVX
2160
2161Returns the double which is stored in the SV.
2162
2163 double SvNVX (SV* sv);
2164
2165=item SvPOK
2166
2167Returns a boolean indicating whether the SV contains a character string.
2168
2169 int SvPOK (SV* SV)
2170
2171=item SvPOK_off
2172
2173Unsets the PV status of an SV.
2174
2175 SvPOK_off (SV* sv)
2176
2177=item SvPOK_on
2178
2179Tells an SV that it is a string.
2180
2181 SvPOK_on (SV* sv)
2182
5fb8527f
PP
2183=item SvPOK_only
2184
2185Tells an SV that it is a string and disables all other OK bits.
2186
2187 SvPOK_on (SV* sv)
2188
2189=item SvPOK_only
2190
2191Tells an SV that it is a string and disables all other OK bits.
2192
2193 SvPOK_on (SV* sv)
2194
cb1a09d0
AD
2195=item SvPOKp
2196
2197Returns a boolean indicating whether the SV contains a character string.
2198Checks the B<private> setting. Use C<SvPOK>.
2199
2200 int SvPOKp (SV* SV)
2201
2202=item SvPV
2203
2204Returns a pointer to the string in the SV, or a stringified form of the SV
2205if the SV does not contain a string. If C<len> is C<na> then Perl will
2206handle the length on its own.
2207
2208 char * SvPV (SV* sv, int len )
2209
2210=item SvPVX
2211
2212Returns a pointer to the string in the SV. The SV must contain a string.
2213
2214 char * SvPVX (SV* sv)
2215
2216=item SvREFCNT
2217
5f05dabc 2218Returns the value of the object's reference count.
cb1a09d0
AD
2219
2220 int SvREFCNT (SV* sv);
2221
2222=item SvREFCNT_dec
2223
5f05dabc 2224Decrements the reference count of the given SV.
cb1a09d0
AD
2225
2226 void SvREFCNT_dec (SV* sv)
2227
2228=item SvREFCNT_inc
2229
5f05dabc 2230Increments the reference count of the given SV.
cb1a09d0
AD
2231
2232 void SvREFCNT_inc (SV* sv)
2233
2234=item SvROK
2235
2236Tests if the SV is an RV.
2237
2238 int SvROK (SV* sv)
2239
2240=item SvROK_off
2241
2242Unsets the RV status of an SV.
2243
2244 SvROK_off (SV* sv)
2245
2246=item SvROK_on
2247
2248Tells an SV that it is an RV.
2249
2250 SvROK_on (SV* sv)
2251
2252=item SvRV
2253
2254Dereferences an RV to return the SV.
2255
2256 SV* SvRV (SV* sv);
2257
2258=item sv_setiv
2259
2260Copies an integer into the given SV.
2261
2262 void sv_setiv _((SV* sv, IV num));
2263
2264=item sv_setnv
2265
2266Copies a double into the given SV.
2267
2268 void sv_setnv _((SV* sv, double num));
2269
2270=item sv_setpv
2271
2272Copies a string into an SV. The string must be null-terminated.
2273
2274 void sv_setpv _((SV* sv, char* ptr));
2275
2276=item sv_setpvn
2277
2278Copies a string into an SV. The C<len> parameter indicates the number of
2279bytes to be copied.
2280
2281 void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
2282
2283=item sv_setref_iv
2284
5fb8527f
PP
2285Copies an integer into a new SV, optionally blessing the SV. The C<rv>
2286argument will be upgraded to an RV. That RV will be modified to point to
2287the new SV. The C<classname> argument indicates the package for the
2288blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2289will be returned and will have a reference count of 1.
cb1a09d0
AD
2290
2291 SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
2292
2293=item sv_setref_nv
2294
5fb8527f
PP
2295Copies a double into a new SV, optionally blessing the SV. The C<rv>
2296argument will be upgraded to an RV. That RV will be modified to point to
2297the new SV. The C<classname> argument indicates the package for the
2298blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2299will be returned and will have a reference count of 1.
cb1a09d0
AD
2300
2301 SV* sv_setref_nv _((SV *rv, char *classname, double nv));
2302
2303=item sv_setref_pv
2304
5fb8527f
PP
2305Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
2306argument will be upgraded to an RV. That RV will be modified to point to
2307the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
2308into the SV. The C<classname> argument indicates the package for the
2309blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2310will be returned and will have a reference count of 1.
cb1a09d0
AD
2311
2312 SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
2313
2314Do not use with integral Perl types such as HV, AV, SV, CV, because those
2315objects will become corrupted by the pointer copy process.
2316
2317Note that C<sv_setref_pvn> copies the string while this copies the pointer.
2318
2319=item sv_setref_pvn
2320
5fb8527f
PP
2321Copies a string into a new SV, optionally blessing the SV. The length of the
2322string must be specified with C<n>. The C<rv> argument will be upgraded to
2323an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
2324argument indicates the package for the blessing. Set C<classname> to
2325C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 2326a reference count of 1.
cb1a09d0
AD
2327
2328 SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
2329
2330Note that C<sv_setref_pv> copies the pointer while this copies the string.
2331
2332=item sv_setsv
2333
2334Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
5f05dabc 2335The source SV may be destroyed if it is mortal.
cb1a09d0
AD
2336
2337 void sv_setsv _((SV* dsv, SV* ssv));
2338
2339=item SvSTASH
2340
2341Returns the stash of the SV.
2342
2343 HV * SvSTASH (SV* sv)
2344
2345=item SVt_IV
2346
2347Integer type flag for scalars. See C<svtype>.
2348
2349=item SVt_PV
2350
2351Pointer type flag for scalars. See C<svtype>.
2352
2353=item SVt_PVAV
2354
2355Type flag for arrays. See C<svtype>.
2356
2357=item SVt_PVCV
2358
2359Type flag for code refs. See C<svtype>.
2360
2361=item SVt_PVHV
2362
2363Type flag for hashes. See C<svtype>.
2364
2365=item SVt_PVMG
2366
2367Type flag for blessed scalars. See C<svtype>.
2368
2369=item SVt_NV
2370
2371Double type flag for scalars. See C<svtype>.
2372
2373=item SvTRUE
2374
2375Returns a boolean indicating whether Perl would evaluate the SV as true or
2376false, defined or undefined.
2377
2378 int SvTRUE (SV* sv)
2379
2380=item SvTYPE
2381
2382Returns the type of the SV. See C<svtype>.
2383
2384 svtype SvTYPE (SV* sv)
2385
2386=item svtype
2387
2388An enum of flags for Perl types. These are found in the file B<sv.h> in the
2389C<svtype> enum. Test these flags with the C<SvTYPE> macro.
2390
2391=item SvUPGRADE
2392
5fb8527f
PP
2393Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
2394the upgrade if necessary. See C<svtype>.
2395
2396 bool SvUPGRADE _((SV* sv, svtype mt));
2397
2398=item sv_upgrade
2399
2400Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
cb1a09d0
AD
2401
2402=item sv_undef
2403
2404This is the C<undef> SV. Always refer to this as C<&sv_undef>.
2405
5fb8527f
PP
2406=item sv_unref
2407
07fa94a1
JO
2408Unsets the RV status of the SV, and decrements the reference count of
2409whatever was being referenced by the RV. This can almost be thought of
2410as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f
PP
2411
2412 void sv_unref _((SV* sv));
2413
cb1a09d0
AD
2414=item sv_usepvn
2415
2416Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
2417stored inside the SV but sv_usepvn allows the SV to use an outside string.
2418The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
2419string length, C<len>, must be supplied. This function will realloc the
2420memory pointed to by C<ptr>, so that pointer should not be freed or used by
2421the programmer after giving it to sv_usepvn.
2422
2423 void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
2424
2425=item sv_yes
2426
2427This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
2428
2429=item THIS
2430
2431Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
2432This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 2433L<perlxs/"Using XS With C++">.
cb1a09d0
AD
2434
2435=item toLOWER
2436
2437Converts the specified character to lowercase.
2438
2439 int toLOWER (char c)
2440
2441=item toUPPER
2442
2443Converts the specified character to uppercase.
2444
2445 int toUPPER (char c)
2446
2447=item warn
2448
2449This is the XSUB-writer's interface to Perl's C<warn> function. Use this
2450function the same way you use the C C<printf> function. See C<croak()>.
2451
2452=item XPUSHi
2453
2454Push an integer onto the stack, extending the stack if necessary. See
2455C<PUSHi>.
2456
2457 XPUSHi(int d)
2458
2459=item XPUSHn
2460
2461Push a double onto the stack, extending the stack if necessary. See
2462C<PUSHn>.
2463
2464 XPUSHn(double d)
2465
2466=item XPUSHp
2467
2468Push a string onto the stack, extending the stack if necessary. The C<len>
2469indicates the length of the string. See C<PUSHp>.
2470
2471 XPUSHp(char *c, int len)
2472
2473=item XPUSHs
2474
2475Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
2476
2477 XPUSHs(sv)
2478
5fb8527f
PP
2479=item XS
2480
2481Macro to declare an XSUB and its C parameter list. This is handled by
2482C<xsubpp>.
2483
cb1a09d0
AD
2484=item XSRETURN
2485
2486Return from XSUB, indicating number of items on the stack. This is usually
2487handled by C<xsubpp>.
2488
5fb8527f 2489 XSRETURN(int x);
cb1a09d0
AD
2490
2491=item XSRETURN_EMPTY
2492
5fb8527f 2493Return an empty list from an XSUB immediately.
cb1a09d0
AD
2494
2495 XSRETURN_EMPTY;
2496
5fb8527f
PP
2497=item XSRETURN_IV
2498
2499Return an integer from an XSUB immediately. Uses C<XST_mIV>.
2500
2501 XSRETURN_IV(IV v);
2502
cb1a09d0
AD
2503=item XSRETURN_NO
2504
5fb8527f 2505Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
2506
2507 XSRETURN_NO;
2508
5fb8527f
PP
2509=item XSRETURN_NV
2510
2511Return an double from an XSUB immediately. Uses C<XST_mNV>.
2512
2513 XSRETURN_NV(NV v);
2514
2515=item XSRETURN_PV
2516
2517Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
2518
2519 XSRETURN_PV(char *v);
2520
cb1a09d0
AD
2521=item XSRETURN_UNDEF
2522
5fb8527f 2523Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
2524
2525 XSRETURN_UNDEF;
2526
2527=item XSRETURN_YES
2528
5fb8527f 2529Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
2530
2531 XSRETURN_YES;
2532
5fb8527f
PP
2533=item XST_mIV
2534
2535Place an integer into the specified position C<i> on the stack. The value is
2536stored in a new mortal SV.
2537
2538 XST_mIV( int i, IV v );
2539
2540=item XST_mNV
2541
2542Place a double into the specified position C<i> on the stack. The value is
2543stored in a new mortal SV.
2544
2545 XST_mNV( int i, NV v );
2546
2547=item XST_mNO
2548
2549Place C<&sv_no> into the specified position C<i> on the stack.
2550
2551 XST_mNO( int i );
2552
2553=item XST_mPV
2554
2555Place a copy of a string into the specified position C<i> on the stack. The
2556value is stored in a new mortal SV.
2557
2558 XST_mPV( int i, char *v );
2559
2560=item XST_mUNDEF
2561
2562Place C<&sv_undef> into the specified position C<i> on the stack.
2563
2564 XST_mUNDEF( int i );
2565
2566=item XST_mYES
2567
2568Place C<&sv_yes> into the specified position C<i> on the stack.
2569
2570 XST_mYES( int i );
2571
2572=item XS_VERSION
2573
2574The version identifier for an XS module. This is usually handled
2575automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
2576
2577=item XS_VERSION_BOOTCHECK
2578
2579Macro to verify that a PM module's $VERSION variable matches the XS module's
2580C<XS_VERSION> variable. This is usually handled automatically by
2581C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
2582
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2583=item Zero
2584
2585The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
2586destination, C<n> is the number of items, and C<t> is the type.
2587
2588 (void) Zero( d, n, t );
2589
2590=back
2591
5f05dabc 2592=head1 EDITOR
cb1a09d0 2593
55497cff 2594Jeff Okamoto <okamoto@corp.hp.com>
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2595
2596With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
2597Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
55497cff 2598Bowers, Matthew Green, Tim Bunce, Spider Boardman, and Ulrich Pfeifer.
cb1a09d0 2599
55497cff 2600API Listing by Dean Roehrich <roehrich@cray.com>.
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2601
2602=head1 DATE
2603
e5581bf4 2604Version 30: 1997/1/17