3 perlguts - Perl's Internal Functions
7 This document attempts to describe some of the internal functions of the
8 Perl executable. It is far from complete and probably contains many errors.
9 Please refer any questions or comments to the author below.
15 Perl has three typedefs that handle Perl's three main data types:
21 Each typedef has specific routines that manipulate the various data types.
23 =head2 What is an "IV"?
25 Perl uses a special typedef IV which is a simple integer type that is
26 guaranteed to be large enough to hold a pointer (as well as an integer).
28 Perl also uses two special typedefs, I32 and I16, which will always be at
29 least 32-bits and 16-bits long, respectively.
31 =head2 Working with SVs
33 An SV can be created and loaded with one command. There are four types of
34 values that can be loaded: an integer value (IV), a double (NV), a string,
35 (PV), and another scalar (SV).
41 SV* newSVpv(char*, int);
42 SV* newSVpvn(char*, int);
43 SV* newSVpvf(const char*, ...);
46 To change the value of an *already-existing* SV, there are seven routines:
48 void sv_setiv(SV*, IV);
49 void sv_setuv(SV*, UV);
50 void sv_setnv(SV*, double);
51 void sv_setpv(SV*, const char*);
52 void sv_setpvn(SV*, const char*, int)
53 void sv_setpvf(SV*, const char*, ...);
54 void sv_setpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
55 void sv_setsv(SV*, SV*);
57 Notice that you can choose to specify the length of the string to be
58 assigned by using C<sv_setpvn>, C<newSVpvn>, or C<newSVpv>, or you may
59 allow Perl to calculate the length by using C<sv_setpv> or by specifying
60 0 as the second argument to C<newSVpv>. Be warned, though, that Perl will
61 determine the string's length by using C<strlen>, which depends on the
62 string terminating with a NUL character.
64 The arguments of C<sv_setpvf> are processed like C<sprintf>, and the
65 formatted output becomes the value.
67 C<sv_setpvfn> is an analogue of C<vsprintf>, but it allows you to specify
68 either a pointer to a variable argument list or the address and length of
69 an array of SVs. The last argument points to a boolean; on return, if that
70 boolean is true, then locale-specific information has been used to format
71 the string, and the string's contents are therefore untrustworthy (see
72 L<perlsec>). This pointer may be NULL if that information is not
73 important. Note that this function requires you to specify the length of
76 The C<sv_set*()> functions are not generic enough to operate on values
77 that have "magic". See L<Magic Virtual Tables> later in this document.
79 All SVs that contain strings should be terminated with a NUL character.
80 If it is not NUL-terminated there is a risk of
81 core dumps and corruptions from code which passes the string to C
82 functions or system calls which expect a NUL-terminated string.
83 Perl's own functions typically add a trailing NUL for this reason.
84 Nevertheless, you should be very careful when you pass a string stored
85 in an SV to a C function or system call.
87 To access the actual value that an SV points to, you can use the macros:
93 which will automatically coerce the actual scalar type into an IV, double,
96 In the C<SvPV> macro, the length of the string returned is placed into the
97 variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
98 care what the length of the data is, use the global variable C<PL_na> or a
99 local variable of type C<STRLEN>. However using C<PL_na> can be quite
100 inefficient because C<PL_na> must be accessed in thread-local storage in
101 threaded Perl. In any case, remember that Perl allows arbitrary strings of
102 data that may both contain NULs and might not be terminated by a NUL.
104 Also remember that C doesn't allow you to safely say C<foo(SvPV(s, len),
105 len);>. It might work with your compiler, but it won't work for everyone.
106 Break this sort of statement up into separate assignments:
113 If you want to know if the scalar value is TRUE, you can use:
117 Although Perl will automatically grow strings for you, if you need to force
118 Perl to allocate more memory for your SV, you can use the macro
120 SvGROW(SV*, STRLEN newlen)
122 which will determine if more memory needs to be allocated. If so, it will
123 call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
124 decrease, the allocated memory of an SV and that it does not automatically
125 add a byte for the a trailing NUL (perl's own string functions typically do
126 C<SvGROW(sv, len + 1)>).
128 If you have an SV and want to know what kind of data Perl thinks is stored
129 in it, you can use the following macros to check the type of SV you have.
135 You can get and set the current length of the string stored in an SV with
136 the following macros:
139 SvCUR_set(SV*, I32 val)
141 You can also get a pointer to the end of the string stored in the SV
146 But note that these last three macros are valid only if C<SvPOK()> is true.
148 If you want to append something to the end of string stored in an C<SV*>,
149 you can use the following functions:
151 void sv_catpv(SV*, char*);
152 void sv_catpvn(SV*, char*, STRLEN);
153 void sv_catpvf(SV*, const char*, ...);
154 void sv_catpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
155 void sv_catsv(SV*, SV*);
157 The first function calculates the length of the string to be appended by
158 using C<strlen>. In the second, you specify the length of the string
159 yourself. The third function processes its arguments like C<sprintf> and
160 appends the formatted output. The fourth function works like C<vsprintf>.
161 You can specify the address and length of an array of SVs instead of the
162 va_list argument. The fifth function extends the string stored in the first
163 SV with the string stored in the second SV. It also forces the second SV
164 to be interpreted as a string.
166 The C<sv_cat*()> functions are not generic enough to operate on values that
167 have "magic". See L<Magic Virtual Tables> later in this document.
169 If you know the name of a scalar variable, you can get a pointer to its SV
170 by using the following:
172 SV* perl_get_sv("package::varname", FALSE);
174 This returns NULL if the variable does not exist.
176 If you want to know if this variable (or any other SV) is actually C<defined>,
181 The scalar C<undef> value is stored in an SV instance called C<PL_sv_undef>. Its
182 address can be used whenever an C<SV*> is needed.
184 There are also the two values C<PL_sv_yes> and C<PL_sv_no>, which contain Boolean
185 TRUE and FALSE values, respectively. Like C<PL_sv_undef>, their addresses can
186 be used whenever an C<SV*> is needed.
188 Do not be fooled into thinking that C<(SV *) 0> is the same as C<&PL_sv_undef>.
192 if (I-am-to-return-a-real-value) {
193 sv = sv_2mortal(newSViv(42));
197 This code tries to return a new SV (which contains the value 42) if it should
198 return a real value, or undef otherwise. Instead it has returned a NULL
199 pointer which, somewhere down the line, will cause a segmentation violation,
200 bus error, or just weird results. Change the zero to C<&PL_sv_undef> in the first
201 line and all will be well.
203 To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
204 call is not necessary (see L<Reference Counts and Mortality>).
206 =head2 What's Really Stored in an SV?
208 Recall that the usual method of determining the type of scalar you have is
209 to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
210 usually these macros will always return TRUE and calling the C<Sv*V>
211 macros will do the appropriate conversion of string to integer/double or
212 integer/double to string.
214 If you I<really> need to know if you have an integer, double, or string
215 pointer in an SV, you can use the following three macros instead:
221 These will tell you if you truly have an integer, double, or string pointer
222 stored in your SV. The "p" stands for private.
224 In general, though, it's best to use the C<Sv*V> macros.
226 =head2 Working with AVs
228 There are two ways to create and load an AV. The first method creates an
233 The second method both creates the AV and initially populates it with SVs:
235 AV* av_make(I32 num, SV **ptr);
237 The second argument points to an array containing C<num> C<SV*>'s. Once the
238 AV has been created, the SVs can be destroyed, if so desired.
240 Once the AV has been created, the following operations are possible on AVs:
242 void av_push(AV*, SV*);
245 void av_unshift(AV*, I32 num);
247 These should be familiar operations, with the exception of C<av_unshift>.
248 This routine adds C<num> elements at the front of the array with the C<undef>
249 value. You must then use C<av_store> (described below) to assign values
250 to these new elements.
252 Here are some other functions:
255 SV** av_fetch(AV*, I32 key, I32 lval);
256 SV** av_store(AV*, I32 key, SV* val);
258 The C<av_len> function returns the highest index value in array (just
259 like $#array in Perl). If the array is empty, -1 is returned. The
260 C<av_fetch> function returns the value at index C<key>, but if C<lval>
261 is non-zero, then C<av_fetch> will store an undef value at that index.
262 The C<av_store> function stores the value C<val> at index C<key>, and does
263 not increment the reference count of C<val>. Thus the caller is responsible
264 for taking care of that, and if C<av_store> returns NULL, the caller will
265 have to decrement the reference count to avoid a memory leak. Note that
266 C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s as their
271 void av_extend(AV*, I32 key);
273 The C<av_clear> function deletes all the elements in the AV* array, but
274 does not actually delete the array itself. The C<av_undef> function will
275 delete all the elements in the array plus the array itself. The
276 C<av_extend> function extends the array so that it contains at least C<key+1>
277 elements. If C<key+1> is less than the currently allocated length of the array,
278 then nothing is done.
280 If you know the name of an array variable, you can get a pointer to its AV
281 by using the following:
283 AV* perl_get_av("package::varname", FALSE);
285 This returns NULL if the variable does not exist.
287 See L<Understanding the Magic of Tied Hashes and Arrays> for more
288 information on how to use the array access functions on tied arrays.
290 =head2 Working with HVs
292 To create an HV, you use the following routine:
296 Once the HV has been created, the following operations are possible on HVs:
298 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
299 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
301 The C<klen> parameter is the length of the key being passed in (Note that
302 you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
303 length of the key). The C<val> argument contains the SV pointer to the
304 scalar being stored, and C<hash> is the precomputed hash value (zero if
305 you want C<hv_store> to calculate it for you). The C<lval> parameter
306 indicates whether this fetch is actually a part of a store operation, in
307 which case a new undefined value will be added to the HV with the supplied
308 key and C<hv_fetch> will return as if the value had already existed.
310 Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
311 C<SV*>. To access the scalar value, you must first dereference the return
312 value. However, you should check to make sure that the return value is
313 not NULL before dereferencing it.
315 These two functions check if a hash table entry exists, and deletes it.
317 bool hv_exists(HV*, char* key, U32 klen);
318 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
320 If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
321 create and return a mortal copy of the deleted value.
323 And more miscellaneous functions:
328 Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
329 table but does not actually delete the hash table. The C<hv_undef> deletes
330 both the entries and the hash table itself.
332 Perl keeps the actual data in linked list of structures with a typedef of HE.
333 These contain the actual key and value pointers (plus extra administrative
334 overhead). The key is a string pointer; the value is an C<SV*>. However,
335 once you have an C<HE*>, to get the actual key and value, use the routines
338 I32 hv_iterinit(HV*);
339 /* Prepares starting point to traverse hash table */
340 HE* hv_iternext(HV*);
341 /* Get the next entry, and return a pointer to a
342 structure that has both the key and value */
343 char* hv_iterkey(HE* entry, I32* retlen);
344 /* Get the key from an HE structure and also return
345 the length of the key string */
346 SV* hv_iterval(HV*, HE* entry);
347 /* Return a SV pointer to the value of the HE
349 SV* hv_iternextsv(HV*, char** key, I32* retlen);
350 /* This convenience routine combines hv_iternext,
351 hv_iterkey, and hv_iterval. The key and retlen
352 arguments are return values for the key and its
353 length. The value is returned in the SV* argument */
355 If you know the name of a hash variable, you can get a pointer to its HV
356 by using the following:
358 HV* perl_get_hv("package::varname", FALSE);
360 This returns NULL if the variable does not exist.
362 The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
366 hash = (hash * 33) + *key++;
368 See L<Understanding the Magic of Tied Hashes and Arrays> for more
369 information on how to use the hash access functions on tied hashes.
371 =head2 Hash API Extensions
373 Beginning with version 5.004, the following functions are also supported:
375 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
376 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
378 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
379 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
381 SV* hv_iterkeysv (HE* entry);
383 Note that these functions take C<SV*> keys, which simplifies writing
384 of extension code that deals with hash structures. These functions
385 also allow passing of C<SV*> keys to C<tie> functions without forcing
386 you to stringify the keys (unlike the previous set of functions).
388 They also return and accept whole hash entries (C<HE*>), making their
389 use more efficient (since the hash number for a particular string
390 doesn't have to be recomputed every time). See L<API LISTING> later in
391 this document for detailed descriptions.
393 The following macros must always be used to access the contents of hash
394 entries. Note that the arguments to these macros must be simple
395 variables, since they may get evaluated more than once. See
396 L<API LISTING> later in this document for detailed descriptions of these
399 HePV(HE* he, STRLEN len)
403 HeSVKEY_force(HE* he)
404 HeSVKEY_set(HE* he, SV* sv)
406 These two lower level macros are defined, but must only be used when
407 dealing with keys that are not C<SV*>s:
412 Note that both C<hv_store> and C<hv_store_ent> do not increment the
413 reference count of the stored C<val>, which is the caller's responsibility.
414 If these functions return a NULL value, the caller will usually have to
415 decrement the reference count of C<val> to avoid a memory leak.
419 References are a special type of scalar that point to other data types
420 (including references).
422 To create a reference, use either of the following functions:
424 SV* newRV_inc((SV*) thing);
425 SV* newRV_noinc((SV*) thing);
427 The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
428 functions are identical except that C<newRV_inc> increments the reference
429 count of the C<thing>, while C<newRV_noinc> does not. For historical
430 reasons, C<newRV> is a synonym for C<newRV_inc>.
432 Once you have a reference, you can use the following macro to dereference
437 then call the appropriate routines, casting the returned C<SV*> to either an
438 C<AV*> or C<HV*>, if required.
440 To determine if an SV is a reference, you can use the following macro:
444 To discover what type of value the reference refers to, use the following
445 macro and then check the return value.
449 The most useful types that will be returned are:
458 SVt_PVGV Glob (possible a file handle)
459 SVt_PVMG Blessed or Magical Scalar
461 See the sv.h header file for more details.
463 =head2 Blessed References and Class Objects
465 References are also used to support object-oriented programming. In the
466 OO lexicon, an object is simply a reference that has been blessed into a
467 package (or class). Once blessed, the programmer may now use the reference
468 to access the various methods in the class.
470 A reference can be blessed into a package with the following function:
472 SV* sv_bless(SV* sv, HV* stash);
474 The C<sv> argument must be a reference. The C<stash> argument specifies
475 which class the reference will belong to. See
476 L<Stashes and Globs> for information on converting class names into stashes.
478 /* Still under construction */
480 Upgrades rv to reference if not already one. Creates new SV for rv to
481 point to. If C<classname> is non-null, the SV is blessed into the specified
482 class. SV is returned.
484 SV* newSVrv(SV* rv, char* classname);
486 Copies integer or double into an SV whose reference is C<rv>. SV is blessed
487 if C<classname> is non-null.
489 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
490 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
492 Copies the pointer value (I<the address, not the string!>) into an SV whose
493 reference is rv. SV is blessed if C<classname> is non-null.
495 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
497 Copies string into an SV whose reference is C<rv>. Set length to 0 to let
498 Perl calculate the string length. SV is blessed if C<classname> is non-null.
500 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, STRLEN length);
502 Tests whether the SV is blessed into the specified class. It does not
503 check inheritance relationships.
505 int sv_isa(SV* sv, char* name);
507 Tests whether the SV is a reference to a blessed object.
509 int sv_isobject(SV* sv);
511 Tests whether the SV is derived from the specified class. SV can be either
512 a reference to a blessed object or a string containing a class name. This
513 is the function implementing the C<UNIVERSAL::isa> functionality.
515 bool sv_derived_from(SV* sv, char* name);
517 To check if you've got an object derived from a specific class you have
520 if (sv_isobject(sv) && sv_derived_from(sv, class)) { ... }
522 =head2 Creating New Variables
524 To create a new Perl variable with an undef value which can be accessed from
525 your Perl script, use the following routines, depending on the variable type.
527 SV* perl_get_sv("package::varname", TRUE);
528 AV* perl_get_av("package::varname", TRUE);
529 HV* perl_get_hv("package::varname", TRUE);
531 Notice the use of TRUE as the second parameter. The new variable can now
532 be set, using the routines appropriate to the data type.
534 There are additional macros whose values may be bitwise OR'ed with the
535 C<TRUE> argument to enable certain extra features. Those bits are:
537 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
538 "Name <varname> used only once: possible typo" warning.
539 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
540 the variable did not exist before the function was called.
542 If you do not specify a package name, the variable is created in the current
545 =head2 Reference Counts and Mortality
547 Perl uses an reference count-driven garbage collection mechanism. SVs,
548 AVs, or HVs (xV for short in the following) start their life with a
549 reference count of 1. If the reference count of an xV ever drops to 0,
550 then it will be destroyed and its memory made available for reuse.
552 This normally doesn't happen at the Perl level unless a variable is
553 undef'ed or the last variable holding a reference to it is changed or
554 overwritten. At the internal level, however, reference counts can be
555 manipulated with the following macros:
557 int SvREFCNT(SV* sv);
558 SV* SvREFCNT_inc(SV* sv);
559 void SvREFCNT_dec(SV* sv);
561 However, there is one other function which manipulates the reference
562 count of its argument. The C<newRV_inc> function, you will recall,
563 creates a reference to the specified argument. As a side effect,
564 it increments the argument's reference count. If this is not what
565 you want, use C<newRV_noinc> instead.
567 For example, imagine you want to return a reference from an XSUB function.
568 Inside the XSUB routine, you create an SV which initially has a reference
569 count of one. Then you call C<newRV_inc>, passing it the just-created SV.
570 This returns the reference as a new SV, but the reference count of the
571 SV you passed to C<newRV_inc> has been incremented to two. Now you
572 return the reference from the XSUB routine and forget about the SV.
573 But Perl hasn't! Whenever the returned reference is destroyed, the
574 reference count of the original SV is decreased to one and nothing happens.
575 The SV will hang around without any way to access it until Perl itself
576 terminates. This is a memory leak.
578 The correct procedure, then, is to use C<newRV_noinc> instead of
579 C<newRV_inc>. Then, if and when the last reference is destroyed,
580 the reference count of the SV will go to zero and it will be destroyed,
581 stopping any memory leak.
583 There are some convenience functions available that can help with the
584 destruction of xVs. These functions introduce the concept of "mortality".
585 An xV that is mortal has had its reference count marked to be decremented,
586 but not actually decremented, until "a short time later". Generally the
587 term "short time later" means a single Perl statement, such as a call to
588 an XSUB function. The actual determinant for when mortal xVs have their
589 reference count decremented depends on two macros, SAVETMPS and FREETMPS.
590 See L<perlcall> and L<perlxs> for more details on these macros.
592 "Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
593 However, if you mortalize a variable twice, the reference count will
594 later be decremented twice.
596 You should be careful about creating mortal variables. Strange things
597 can happen if you make the same value mortal within multiple contexts,
598 or if you make a variable mortal multiple times.
600 To create a mortal variable, use the functions:
604 SV* sv_mortalcopy(SV*)
606 The first call creates a mortal SV, the second converts an existing
607 SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
608 third creates a mortal copy of an existing SV.
610 The mortal routines are not just for SVs -- AVs and HVs can be
611 made mortal by passing their address (type-casted to C<SV*>) to the
612 C<sv_2mortal> or C<sv_mortalcopy> routines.
614 =head2 Stashes and Globs
616 A "stash" is a hash that contains all of the different objects that
617 are contained within a package. Each key of the stash is a symbol
618 name (shared by all the different types of objects that have the same
619 name), and each value in the hash table is a GV (Glob Value). This GV
620 in turn contains references to the various objects of that name,
621 including (but not limited to) the following:
630 There is a single stash called "PL_defstash" that holds the items that exist
631 in the "main" package. To get at the items in other packages, append the
632 string "::" to the package name. The items in the "Foo" package are in
633 the stash "Foo::" in PL_defstash. The items in the "Bar::Baz" package are
634 in the stash "Baz::" in "Bar::"'s stash.
636 To get the stash pointer for a particular package, use the function:
638 HV* gv_stashpv(char* name, I32 create)
639 HV* gv_stashsv(SV*, I32 create)
641 The first function takes a literal string, the second uses the string stored
642 in the SV. Remember that a stash is just a hash table, so you get back an
643 C<HV*>. The C<create> flag will create a new package if it is set.
645 The name that C<gv_stash*v> wants is the name of the package whose symbol table
646 you want. The default package is called C<main>. If you have multiply nested
647 packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
650 Alternately, if you have an SV that is a blessed reference, you can find
651 out the stash pointer by using:
653 HV* SvSTASH(SvRV(SV*));
655 then use the following to get the package name itself:
657 char* HvNAME(HV* stash);
659 If you need to bless or re-bless an object you can use the following
662 SV* sv_bless(SV*, HV* stash)
664 where the first argument, an C<SV*>, must be a reference, and the second
665 argument is a stash. The returned C<SV*> can now be used in the same way
668 For more information on references and blessings, consult L<perlref>.
670 =head2 Double-Typed SVs
672 Scalar variables normally contain only one type of value, an integer,
673 double, pointer, or reference. Perl will automatically convert the
674 actual scalar data from the stored type into the requested type.
676 Some scalar variables contain more than one type of scalar data. For
677 example, the variable C<$!> contains either the numeric value of C<errno>
678 or its string equivalent from either C<strerror> or C<sys_errlist[]>.
680 To force multiple data values into an SV, you must do two things: use the
681 C<sv_set*v> routines to add the additional scalar type, then set a flag
682 so that Perl will believe it contains more than one type of data. The
683 four macros to set the flags are:
690 The particular macro you must use depends on which C<sv_set*v> routine
691 you called first. This is because every C<sv_set*v> routine turns on
692 only the bit for the particular type of data being set, and turns off
695 For example, to create a new Perl variable called "dberror" that contains
696 both the numeric and descriptive string error values, you could use the
700 extern char *dberror_list;
702 SV* sv = perl_get_sv("dberror", TRUE);
703 sv_setiv(sv, (IV) dberror);
704 sv_setpv(sv, dberror_list[dberror]);
707 If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
708 macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
710 =head2 Magic Variables
712 [This section still under construction. Ignore everything here. Post no
713 bills. Everything not permitted is forbidden.]
715 Any SV may be magical, that is, it has special features that a normal
716 SV does not have. These features are stored in the SV structure in a
717 linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
730 Note this is current as of patchlevel 0, and could change at any time.
732 =head2 Assigning Magic
734 Perl adds magic to an SV using the sv_magic function:
736 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
738 The C<sv> argument is a pointer to the SV that is to acquire a new magical
741 If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
742 set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
743 it to the beginning of the linked list of magical features. Any prior
744 entry of the same type of magic is deleted. Note that this can be
745 overridden, and multiple instances of the same type of magic can be
746 associated with an SV.
748 The C<name> and C<namlen> arguments are used to associate a string with
749 the magic, typically the name of a variable. C<namlen> is stored in the
750 C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
751 copy of the name is stored in C<mg_ptr> field.
753 The sv_magic function uses C<how> to determine which, if any, predefined
754 "Magic Virtual Table" should be assigned to the C<mg_virtual> field.
755 See the "Magic Virtual Table" section below. The C<how> argument is also
756 stored in the C<mg_type> field.
758 The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
759 structure. If it is not the same as the C<sv> argument, the reference
760 count of the C<obj> object is incremented. If it is the same, or if
761 the C<how> argument is "#", or if it is a NULL pointer, then C<obj> is
762 merely stored, without the reference count being incremented.
764 There is also a function to add magic to an C<HV>:
766 void hv_magic(HV *hv, GV *gv, int how);
768 This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
770 To remove the magic from an SV, call the function sv_unmagic:
772 void sv_unmagic(SV *sv, int type);
774 The C<type> argument should be equal to the C<how> value when the C<SV>
775 was initially made magical.
777 =head2 Magic Virtual Tables
779 The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
780 C<MGVTBL>, which is a structure of function pointers and stands for
781 "Magic Virtual Table" to handle the various operations that might be
782 applied to that variable.
784 The C<MGVTBL> has five pointers to the following routine types:
786 int (*svt_get)(SV* sv, MAGIC* mg);
787 int (*svt_set)(SV* sv, MAGIC* mg);
788 U32 (*svt_len)(SV* sv, MAGIC* mg);
789 int (*svt_clear)(SV* sv, MAGIC* mg);
790 int (*svt_free)(SV* sv, MAGIC* mg);
792 This MGVTBL structure is set at compile-time in C<perl.h> and there are
793 currently 19 types (or 21 with overloading turned on). These different
794 structures contain pointers to various routines that perform additional
795 actions depending on which function is being called.
797 Function pointer Action taken
798 ---------------- ------------
799 svt_get Do something after the value of the SV is retrieved.
800 svt_set Do something after the SV is assigned a value.
801 svt_len Report on the SV's length.
802 svt_clear Clear something the SV represents.
803 svt_free Free any extra storage associated with the SV.
805 For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
806 to an C<mg_type> of '\0') contains:
808 { magic_get, magic_set, magic_len, 0, 0 }
810 Thus, when an SV is determined to be magical and of type '\0', if a get
811 operation is being performed, the routine C<magic_get> is called. All
812 the various routines for the various magical types begin with C<magic_>.
814 The current kinds of Magic Virtual Tables are:
816 mg_type MGVTBL Type of magic
817 ------- ------ ----------------------------
818 \0 vtbl_sv Special scalar variable
819 A vtbl_amagic %OVERLOAD hash
820 a vtbl_amagicelem %OVERLOAD hash element
821 c (none) Holds overload table (AMT) on stash
822 B vtbl_bm Boyer-Moore (fast string search)
824 e vtbl_envelem %ENV hash element
825 f vtbl_fm Formline ('compiled' format)
826 g vtbl_mglob m//g target / study()ed string
827 I vtbl_isa @ISA array
828 i vtbl_isaelem @ISA array element
829 k vtbl_nkeys scalar(keys()) lvalue
830 L (none) Debugger %_<filename
831 l vtbl_dbline Debugger %_<filename element
832 o vtbl_collxfrm Locale transformation
833 P vtbl_pack Tied array or hash
834 p vtbl_packelem Tied array or hash element
835 q vtbl_packelem Tied scalar or handle
837 s vtbl_sigelem %SIG hash element
838 t vtbl_taint Taintedness
839 U vtbl_uvar Available for use by extensions
840 v vtbl_vec vec() lvalue
841 x vtbl_substr substr() lvalue
842 y vtbl_defelem Shadow "foreach" iterator variable /
843 smart parameter vivification
844 * vtbl_glob GV (typeglob)
845 # vtbl_arylen Array length ($#ary)
846 . vtbl_pos pos() lvalue
847 ~ (none) Available for use by extensions
849 When an uppercase and lowercase letter both exist in the table, then the
850 uppercase letter is used to represent some kind of composite type (a list
851 or a hash), and the lowercase letter is used to represent an element of
854 The '~' and 'U' magic types are defined specifically for use by
855 extensions and will not be used by perl itself. Extensions can use
856 '~' magic to 'attach' private information to variables (typically
857 objects). This is especially useful because there is no way for
858 normal perl code to corrupt this private information (unlike using
859 extra elements of a hash object).
861 Similarly, 'U' magic can be used much like tie() to call a C function
862 any time a scalar's value is used or changed. The C<MAGIC>'s
863 C<mg_ptr> field points to a C<ufuncs> structure:
866 I32 (*uf_val)(IV, SV*);
867 I32 (*uf_set)(IV, SV*);
871 When the SV is read from or written to, the C<uf_val> or C<uf_set>
872 function will be called with C<uf_index> as the first arg and a
873 pointer to the SV as the second. A simple example of how to add 'U'
874 magic is shown below. Note that the ufuncs structure is copied by
875 sv_magic, so you can safely allocate it on the stack.
883 uf.uf_val = &my_get_fn;
884 uf.uf_set = &my_set_fn;
886 sv_magic(sv, 0, 'U', (char*)&uf, sizeof(uf));
888 Note that because multiple extensions may be using '~' or 'U' magic,
889 it is important for extensions to take extra care to avoid conflict.
890 Typically only using the magic on objects blessed into the same class
891 as the extension is sufficient. For '~' magic, it may also be
892 appropriate to add an I32 'signature' at the top of the private data
895 Also note that the C<sv_set*()> and C<sv_cat*()> functions described
896 earlier do B<not> invoke 'set' magic on their targets. This must
897 be done by the user either by calling the C<SvSETMAGIC()> macro after
898 calling these functions, or by using one of the C<sv_set*_mg()> or
899 C<sv_cat*_mg()> functions. Similarly, generic C code must call the
900 C<SvGETMAGIC()> macro to invoke any 'get' magic if they use an SV
901 obtained from external sources in functions that don't handle magic.
902 L<API LISTING> later in this document identifies such functions.
903 For example, calls to the C<sv_cat*()> functions typically need to be
904 followed by C<SvSETMAGIC()>, but they don't need a prior C<SvGETMAGIC()>
905 since their implementation handles 'get' magic.
909 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
911 This routine returns a pointer to the C<MAGIC> structure stored in the SV.
912 If the SV does not have that magical feature, C<NULL> is returned. Also,
913 if the SV is not of type SVt_PVMG, Perl may core dump.
915 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
917 This routine checks to see what types of magic C<sv> has. If the mg_type
918 field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
919 the mg_type field is changed to be the lowercase letter.
921 =head2 Understanding the Magic of Tied Hashes and Arrays
923 Tied hashes and arrays are magical beasts of the 'P' magic type.
925 WARNING: As of the 5.004 release, proper usage of the array and hash
926 access functions requires understanding a few caveats. Some
927 of these caveats are actually considered bugs in the API, to be fixed
928 in later releases, and are bracketed with [MAYCHANGE] below. If
929 you find yourself actually applying such information in this section, be
930 aware that the behavior may change in the future, umm, without warning.
932 The perl tie function associates a variable with an object that implements
933 the various GET, SET etc methods. To perform the equivalent of the perl
934 tie function from an XSUB, you must mimic this behaviour. The code below
935 carries out the necessary steps - firstly it creates a new hash, and then
936 creates a second hash which it blesses into the class which will implement
937 the tie methods. Lastly it ties the two hashes together, and returns a
938 reference to the new tied hash. Note that the code below does NOT call the
939 TIEHASH method in the MyTie class -
940 see L<Calling Perl Routines from within C Programs> for details on how
951 tie = newRV_noinc((SV*)newHV());
952 stash = gv_stashpv("MyTie", TRUE);
953 sv_bless(tie, stash);
954 hv_magic(hash, tie, 'P');
955 RETVAL = newRV_noinc(hash);
959 The C<av_store> function, when given a tied array argument, merely
960 copies the magic of the array onto the value to be "stored", using
961 C<mg_copy>. It may also return NULL, indicating that the value did not
962 actually need to be stored in the array. [MAYCHANGE] After a call to
963 C<av_store> on a tied array, the caller will usually need to call
964 C<mg_set(val)> to actually invoke the perl level "STORE" method on the
965 TIEARRAY object. If C<av_store> did return NULL, a call to
966 C<SvREFCNT_dec(val)> will also be usually necessary to avoid a memory
969 The previous paragraph is applicable verbatim to tied hash access using the
970 C<hv_store> and C<hv_store_ent> functions as well.
972 C<av_fetch> and the corresponding hash functions C<hv_fetch> and
973 C<hv_fetch_ent> actually return an undefined mortal value whose magic
974 has been initialized using C<mg_copy>. Note the value so returned does not
975 need to be deallocated, as it is already mortal. [MAYCHANGE] But you will
976 need to call C<mg_get()> on the returned value in order to actually invoke
977 the perl level "FETCH" method on the underlying TIE object. Similarly,
978 you may also call C<mg_set()> on the return value after possibly assigning
979 a suitable value to it using C<sv_setsv>, which will invoke the "STORE"
980 method on the TIE object. [/MAYCHANGE]
983 In other words, the array or hash fetch/store functions don't really
984 fetch and store actual values in the case of tied arrays and hashes. They
985 merely call C<mg_copy> to attach magic to the values that were meant to be
986 "stored" or "fetched". Later calls to C<mg_get> and C<mg_set> actually
987 do the job of invoking the TIE methods on the underlying objects. Thus
988 the magic mechanism currently implements a kind of lazy access to arrays
991 Currently (as of perl version 5.004), use of the hash and array access
992 functions requires the user to be aware of whether they are operating on
993 "normal" hashes and arrays, or on their tied variants. The API may be
994 changed to provide more transparent access to both tied and normal data
995 types in future versions.
998 You would do well to understand that the TIEARRAY and TIEHASH interfaces
999 are mere sugar to invoke some perl method calls while using the uniform hash
1000 and array syntax. The use of this sugar imposes some overhead (typically
1001 about two to four extra opcodes per FETCH/STORE operation, in addition to
1002 the creation of all the mortal variables required to invoke the methods).
1003 This overhead will be comparatively small if the TIE methods are themselves
1004 substantial, but if they are only a few statements long, the overhead
1005 will not be insignificant.
1007 =head2 Localizing changes
1009 Perl has a very handy construction
1016 This construction is I<approximately> equivalent to
1025 The biggest difference is that the first construction would
1026 reinstate the initial value of $var, irrespective of how control exits
1027 the block: C<goto>, C<return>, C<die>/C<eval> etc. It is a little bit
1028 more efficient as well.
1030 There is a way to achieve a similar task from C via Perl API: create a
1031 I<pseudo-block>, and arrange for some changes to be automatically
1032 undone at the end of it, either explicit, or via a non-local exit (via
1033 die()). A I<block>-like construct is created by a pair of
1034 C<ENTER>/C<LEAVE> macros (see L<perlcall/"Returning a Scalar">).
1035 Such a construct may be created specially for some important localized
1036 task, or an existing one (like boundaries of enclosing Perl
1037 subroutine/block, or an existing pair for freeing TMPs) may be
1038 used. (In the second case the overhead of additional localization must
1039 be almost negligible.) Note that any XSUB is automatically enclosed in
1040 an C<ENTER>/C<LEAVE> pair.
1042 Inside such a I<pseudo-block> the following service is available:
1046 =item C<SAVEINT(int i)>
1048 =item C<SAVEIV(IV i)>
1050 =item C<SAVEI32(I32 i)>
1052 =item C<SAVELONG(long i)>
1054 These macros arrange things to restore the value of integer variable
1055 C<i> at the end of enclosing I<pseudo-block>.
1057 =item C<SAVESPTR(s)>
1059 =item C<SAVEPPTR(p)>
1061 These macros arrange things to restore the value of pointers C<s> and
1062 C<p>. C<s> must be a pointer of a type which survives conversion to
1063 C<SV*> and back, C<p> should be able to survive conversion to C<char*>
1066 =item C<SAVEFREESV(SV *sv)>
1068 The refcount of C<sv> would be decremented at the end of
1069 I<pseudo-block>. This is similar to C<sv_2mortal>, which should (?) be
1072 =item C<SAVEFREEOP(OP *op)>
1074 The C<OP *> is op_free()ed at the end of I<pseudo-block>.
1076 =item C<SAVEFREEPV(p)>
1078 The chunk of memory which is pointed to by C<p> is Safefree()ed at the
1079 end of I<pseudo-block>.
1081 =item C<SAVECLEARSV(SV *sv)>
1083 Clears a slot in the current scratchpad which corresponds to C<sv> at
1084 the end of I<pseudo-block>.
1086 =item C<SAVEDELETE(HV *hv, char *key, I32 length)>
1088 The key C<key> of C<hv> is deleted at the end of I<pseudo-block>. The
1089 string pointed to by C<key> is Safefree()ed. If one has a I<key> in
1090 short-lived storage, the corresponding string may be reallocated like
1093 SAVEDELETE(PL_defstash, savepv(tmpbuf), strlen(tmpbuf));
1095 =item C<SAVEDESTRUCTOR(f,p)>
1097 At the end of I<pseudo-block> the function C<f> is called with the
1098 only argument (of type C<void*>) C<p>.
1100 =item C<SAVESTACK_POS()>
1102 The current offset on the Perl internal stack (cf. C<SP>) is restored
1103 at the end of I<pseudo-block>.
1107 The following API list contains functions, thus one needs to
1108 provide pointers to the modifiable data explicitly (either C pointers,
1109 or Perlish C<GV *>s). Where the above macros take C<int>, a similar
1110 function takes C<int *>.
1114 =item C<SV* save_scalar(GV *gv)>
1116 Equivalent to Perl code C<local $gv>.
1118 =item C<AV* save_ary(GV *gv)>
1120 =item C<HV* save_hash(GV *gv)>
1122 Similar to C<save_scalar>, but localize C<@gv> and C<%gv>.
1124 =item C<void save_item(SV *item)>
1126 Duplicates the current value of C<SV>, on the exit from the current
1127 C<ENTER>/C<LEAVE> I<pseudo-block> will restore the value of C<SV>
1128 using the stored value.
1130 =item C<void save_list(SV **sarg, I32 maxsarg)>
1132 A variant of C<save_item> which takes multiple arguments via an array
1133 C<sarg> of C<SV*> of length C<maxsarg>.
1135 =item C<SV* save_svref(SV **sptr)>
1137 Similar to C<save_scalar>, but will reinstate a C<SV *>.
1139 =item C<void save_aptr(AV **aptr)>
1141 =item C<void save_hptr(HV **hptr)>
1143 Similar to C<save_svref>, but localize C<AV *> and C<HV *>.
1147 The C<Alias> module implements localization of the basic types within the
1148 I<caller's scope>. People who are interested in how to localize things in
1149 the containing scope should take a look there too.
1153 =head2 XSUBs and the Argument Stack
1155 The XSUB mechanism is a simple way for Perl programs to access C subroutines.
1156 An XSUB routine will have a stack that contains the arguments from the Perl
1157 program, and a way to map from the Perl data structures to a C equivalent.
1159 The stack arguments are accessible through the C<ST(n)> macro, which returns
1160 the C<n>'th stack argument. Argument 0 is the first argument passed in the
1161 Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
1164 Most of the time, output from the C routine can be handled through use of
1165 the RETVAL and OUTPUT directives. However, there are some cases where the
1166 argument stack is not already long enough to handle all the return values.
1167 An example is the POSIX tzname() call, which takes no arguments, but returns
1168 two, the local time zone's standard and summer time abbreviations.
1170 To handle this situation, the PPCODE directive is used and the stack is
1171 extended using the macro:
1175 where C<SP> is the macro that represents the local copy of the stack pointer,
1176 and C<num> is the number of elements the stack should be extended by.
1178 Now that there is room on the stack, values can be pushed on it using the
1179 macros to push IVs, doubles, strings, and SV pointers respectively:
1186 And now the Perl program calling C<tzname>, the two values will be assigned
1189 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
1191 An alternate (and possibly simpler) method to pushing values on the stack is
1199 These macros automatically adjust the stack for you, if needed. Thus, you
1200 do not need to call C<EXTEND> to extend the stack.
1202 For more information, consult L<perlxs> and L<perlxstut>.
1204 =head2 Calling Perl Routines from within C Programs
1206 There are four routines that can be used to call a Perl subroutine from
1207 within a C program. These four are:
1209 I32 perl_call_sv(SV*, I32);
1210 I32 perl_call_pv(char*, I32);
1211 I32 perl_call_method(char*, I32);
1212 I32 perl_call_argv(char*, I32, register char**);
1214 The routine most often used is C<perl_call_sv>. The C<SV*> argument
1215 contains either the name of the Perl subroutine to be called, or a
1216 reference to the subroutine. The second argument consists of flags
1217 that control the context in which the subroutine is called, whether
1218 or not the subroutine is being passed arguments, how errors should be
1219 trapped, and how to treat return values.
1221 All four routines return the number of arguments that the subroutine returned
1224 When using any of these routines (except C<perl_call_argv>), the programmer
1225 must manipulate the Perl stack. These include the following macros and
1240 For a detailed description of calling conventions from C to Perl,
1241 consult L<perlcall>.
1243 =head2 Memory Allocation
1245 All memory meant to be used with the Perl API functions should be manipulated
1246 using the macros described in this section. The macros provide the necessary
1247 transparency between differences in the actual malloc implementation that is
1250 It is suggested that you enable the version of malloc that is distributed
1251 with Perl. It keeps pools of various sizes of unallocated memory in
1252 order to satisfy allocation requests more quickly. However, on some
1253 platforms, it may cause spurious malloc or free errors.
1255 New(x, pointer, number, type);
1256 Newc(x, pointer, number, type, cast);
1257 Newz(x, pointer, number, type);
1259 These three macros are used to initially allocate memory.
1261 The first argument C<x> was a "magic cookie" that was used to keep track
1262 of who called the macro, to help when debugging memory problems. However,
1263 the current code makes no use of this feature (most Perl developers now
1264 use run-time memory checkers), so this argument can be any number.
1266 The second argument C<pointer> should be the name of a variable that will
1267 point to the newly allocated memory.
1269 The third and fourth arguments C<number> and C<type> specify how many of
1270 the specified type of data structure should be allocated. The argument
1271 C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
1272 should be used if the C<pointer> argument is different from the C<type>
1275 Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
1276 to zero out all the newly allocated memory.
1278 Renew(pointer, number, type);
1279 Renewc(pointer, number, type, cast);
1282 These three macros are used to change a memory buffer size or to free a
1283 piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
1284 match those of C<New> and C<Newc> with the exception of not needing the
1285 "magic cookie" argument.
1287 Move(source, dest, number, type);
1288 Copy(source, dest, number, type);
1289 Zero(dest, number, type);
1291 These three macros are used to move, copy, or zero out previously allocated
1292 memory. The C<source> and C<dest> arguments point to the source and
1293 destination starting points. Perl will move, copy, or zero out C<number>
1294 instances of the size of the C<type> data structure (using the C<sizeof>
1299 The most recent development releases of Perl has been experimenting with
1300 removing Perl's dependency on the "normal" standard I/O suite and allowing
1301 other stdio implementations to be used. This involves creating a new
1302 abstraction layer that then calls whichever implementation of stdio Perl
1303 was compiled with. All XSUBs should now use the functions in the PerlIO
1304 abstraction layer and not make any assumptions about what kind of stdio
1307 For a complete description of the PerlIO abstraction, consult L<perlapio>.
1309 =head2 Putting a C value on Perl stack
1311 A lot of opcodes (this is an elementary operation in the internal perl
1312 stack machine) put an SV* on the stack. However, as an optimization
1313 the corresponding SV is (usually) not recreated each time. The opcodes
1314 reuse specially assigned SVs (I<target>s) which are (as a corollary)
1315 not constantly freed/created.
1317 Each of the targets is created only once (but see
1318 L<Scratchpads and recursion> below), and when an opcode needs to put
1319 an integer, a double, or a string on stack, it just sets the
1320 corresponding parts of its I<target> and puts the I<target> on stack.
1322 The macro to put this target on stack is C<PUSHTARG>, and it is
1323 directly used in some opcodes, as well as indirectly in zillions of
1324 others, which use it via C<(X)PUSH[pni]>.
1328 The question remains on when the SVs which are I<target>s for opcodes
1329 are created. The answer is that they are created when the current unit --
1330 a subroutine or a file (for opcodes for statements outside of
1331 subroutines) -- is compiled. During this time a special anonymous Perl
1332 array is created, which is called a scratchpad for the current
1335 A scratchpad keeps SVs which are lexicals for the current unit and are
1336 targets for opcodes. One can deduce that an SV lives on a scratchpad
1337 by looking on its flags: lexicals have C<SVs_PADMY> set, and
1338 I<target>s have C<SVs_PADTMP> set.
1340 The correspondence between OPs and I<target>s is not 1-to-1. Different
1341 OPs in the compile tree of the unit can use the same target, if this
1342 would not conflict with the expected life of the temporary.
1344 =head2 Scratchpads and recursion
1346 In fact it is not 100% true that a compiled unit contains a pointer to
1347 the scratchpad AV. In fact it contains a pointer to an AV of
1348 (initially) one element, and this element is the scratchpad AV. Why do
1349 we need an extra level of indirection?
1351 The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1352 these can create several execution pointers going into the same
1353 subroutine. For the subroutine-child not write over the temporaries
1354 for the subroutine-parent (lifespan of which covers the call to the
1355 child), the parent and the child should have different
1356 scratchpads. (I<And> the lexicals should be separate anyway!)
1358 So each subroutine is born with an array of scratchpads (of length 1).
1359 On each entry to the subroutine it is checked that the current
1360 depth of the recursion is not more than the length of this array, and
1361 if it is, new scratchpad is created and pushed into the array.
1363 The I<target>s on this scratchpad are C<undef>s, but they are already
1364 marked with correct flags.
1366 =head1 Compiled code
1370 Here we describe the internal form your code is converted to by
1371 Perl. Start with a simple example:
1375 This is converted to a tree similar to this one:
1383 (but slightly more complicated). This tree reflects the way Perl
1384 parsed your code, but has nothing to do with the execution order.
1385 There is an additional "thread" going through the nodes of the tree
1386 which shows the order of execution of the nodes. In our simplified
1387 example above it looks like:
1389 $b ---> $c ---> + ---> $a ---> assign-to
1391 But with the actual compile tree for C<$a = $b + $c> it is different:
1392 some nodes I<optimized away>. As a corollary, though the actual tree
1393 contains more nodes than our simplified example, the execution order
1394 is the same as in our example.
1396 =head2 Examining the tree
1398 If you have your perl compiled for debugging (usually done with C<-D
1399 optimize=-g> on C<Configure> command line), you may examine the
1400 compiled tree by specifying C<-Dx> on the Perl command line. The
1401 output takes several lines per node, and for C<$b+$c> it looks like
1406 FLAGS = (SCALAR,KIDS)
1408 TYPE = null ===> (4)
1410 FLAGS = (SCALAR,KIDS)
1412 3 TYPE = gvsv ===> 4
1418 TYPE = null ===> (5)
1420 FLAGS = (SCALAR,KIDS)
1422 4 TYPE = gvsv ===> 5
1428 This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1429 not optimized away (one per number in the left column). The immediate
1430 children of the given node correspond to C<{}> pairs on the same level
1431 of indentation, thus this listing corresponds to the tree:
1439 The execution order is indicated by C<===E<gt>> marks, thus it is C<3
1440 4 5 6> (node C<6> is not included into above listing), i.e.,
1441 C<gvsv gvsv add whatever>.
1443 =head2 Compile pass 1: check routines
1445 The tree is created by the I<pseudo-compiler> while yacc code feeds it
1446 the constructions it recognizes. Since yacc works bottom-up, so does
1447 the first pass of perl compilation.
1449 What makes this pass interesting for perl developers is that some
1450 optimization may be performed on this pass. This is optimization by
1451 so-called I<check routines>. The correspondence between node names
1452 and corresponding check routines is described in F<opcode.pl> (do not
1453 forget to run C<make regen_headers> if you modify this file).
1455 A check routine is called when the node is fully constructed except
1456 for the execution-order thread. Since at this time there are no
1457 back-links to the currently constructed node, one can do most any
1458 operation to the top-level node, including freeing it and/or creating
1459 new nodes above/below it.
1461 The check routine returns the node which should be inserted into the
1462 tree (if the top-level node was not modified, check routine returns
1465 By convention, check routines have names C<ck_*>. They are usually
1466 called from C<new*OP> subroutines (or C<convert>) (which in turn are
1467 called from F<perly.y>).
1469 =head2 Compile pass 1a: constant folding
1471 Immediately after the check routine is called the returned node is
1472 checked for being compile-time executable. If it is (the value is
1473 judged to be constant) it is immediately executed, and a I<constant>
1474 node with the "return value" of the corresponding subtree is
1475 substituted instead. The subtree is deleted.
1477 If constant folding was not performed, the execution-order thread is
1480 =head2 Compile pass 2: context propagation
1482 When a context for a part of compile tree is known, it is propagated
1483 down through the tree. At this time the context can have 5 values
1484 (instead of 2 for runtime context): void, boolean, scalar, list, and
1485 lvalue. In contrast with the pass 1 this pass is processed from top
1486 to bottom: a node's context determines the context for its children.
1488 Additional context-dependent optimizations are performed at this time.
1489 Since at this moment the compile tree contains back-references (via
1490 "thread" pointers), nodes cannot be free()d now. To allow
1491 optimized-away nodes at this stage, such nodes are null()ified instead
1492 of free()ing (i.e. their type is changed to OP_NULL).
1494 =head2 Compile pass 3: peephole optimization
1496 After the compile tree for a subroutine (or for an C<eval> or a file)
1497 is created, an additional pass over the code is performed. This pass
1498 is neither top-down or bottom-up, but in the execution order (with
1499 additional complications for conditionals). These optimizations are
1500 done in the subroutine peep(). Optimizations performed at this stage
1501 are subject to the same restrictions as in the pass 2.
1505 This is a listing of functions, macros, flags, and variables that may be
1506 useful to extension writers or that may be found while reading other
1509 Note that all Perl API global variables must be referenced with the C<PL_>
1510 prefix. Some macros are provided for compatibility with the older,
1511 unadorned names, but this support will be removed in a future release.
1513 It is strongly recommended that all Perl API functions that don't begin
1514 with C<perl> be referenced with an explicit C<Perl_> prefix.
1516 The sort order of the listing is case insensitive, with any
1517 occurrences of '_' ignored for the purpose of sorting.
1523 Clears an array, making it empty. Does not free the memory used by the
1526 void av_clear (AV* ar)
1530 Pre-extend an array. The C<key> is the index to which the array should be
1533 void av_extend (AV* ar, I32 key)
1537 Returns the SV at the specified index in the array. The C<key> is the
1538 index. If C<lval> is set then the fetch will be part of a store. Check
1539 that the return value is non-null before dereferencing it to a C<SV*>.
1541 See L<Understanding the Magic of Tied Hashes and Arrays> for more
1542 information on how to use this function on tied arrays.
1544 SV** av_fetch (AV* ar, I32 key, I32 lval)
1548 Same as C<av_len()>. Deprecated, use C<av_len()> instead.
1552 Returns the highest index in the array. Returns -1 if the array is empty.
1558 Creates a new AV and populates it with a list of SVs. The SVs are copied
1559 into the array, so they may be freed after the call to av_make. The new AV
1560 will have a reference count of 1.
1562 AV* av_make (I32 size, SV** svp)
1566 Pops an SV off the end of the array. Returns C<&PL_sv_undef> if the array is
1573 Pushes an SV onto the end of the array. The array will grow automatically
1574 to accommodate the addition.
1576 void av_push (AV* ar, SV* val)
1580 Shifts an SV off the beginning of the array.
1582 SV* av_shift (AV* ar)
1586 Stores an SV in an array. The array index is specified as C<key>. The
1587 return value will be NULL if the operation failed or if the value did not
1588 need to be actually stored within the array (as in the case of tied arrays).
1589 Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1590 caller is responsible for suitably incrementing the reference count of C<val>
1591 before the call, and decrementing it if the function returned NULL.
1593 See L<Understanding the Magic of Tied Hashes and Arrays> for more
1594 information on how to use this function on tied arrays.
1596 SV** av_store (AV* ar, I32 key, SV* val)
1600 Undefines the array. Frees the memory used by the array itself.
1602 void av_undef (AV* ar)
1606 Unshift the given number of C<undef> values onto the beginning of the
1607 array. The array will grow automatically to accommodate the addition.
1608 You must then use C<av_store> to assign values to these new elements.
1610 void av_unshift (AV* ar, I32 num)
1614 Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
1615 constructor. This is always a C<char*>. See C<THIS> and
1616 L<perlxs/"Using XS With C++">.
1620 The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1621 source, C<d> is the destination, C<n> is the number of items, and C<t> is
1622 the type. May fail on overlapping copies. See also C<Move>.
1624 void Copy( s, d, n, t )
1628 This is the XSUB-writer's interface to Perl's C<die> function. Use this
1629 function the same way you use the C C<printf> function. See C<warn>.
1633 Returns the stash of the CV.
1635 HV* CvSTASH( SV* sv )
1639 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1640 boolean which indicates whether subs are being single-stepped.
1641 Single-stepping is automatically turned on after every step. This is the C
1642 variable which corresponds to Perl's $DB::single variable. See C<PL_DBsub>.
1646 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
1647 the SV which holds the name of the sub being debugged. This is the C
1648 variable which corresponds to Perl's $DB::sub variable. See C<PL_DBsingle>.
1649 The sub name can be found by
1651 SvPV( GvSV( PL_DBsub ), len )
1655 Trace variable used when Perl is run in debugging mode, with the B<-d>
1656 switch. This is the C variable which corresponds to Perl's $DB::trace
1657 variable. See C<PL_DBsingle>.
1661 Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1666 Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1670 The C variable which corresponds to Perl's $^W warning variable.
1674 Declares a local copy of perl's stack pointer for the XSUB, available via
1675 the C<SP> macro. See C<SP>.
1679 Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1680 usually handled automatically by C<xsubpp>. Declares the C<items> variable
1681 to indicate the number of items on the stack.
1685 Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1686 handled automatically by C<xsubpp>.
1690 Switches filehandle to binmode. C<iotype> is what C<IoTYPE(io)> would
1693 do_binmode(fp, iotype, TRUE);
1697 Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1703 Used to extend the argument stack for an XSUB's return values.
1709 Analyses the string in order to make fast searches on it using fbm_instr() --
1710 the Boyer-Moore algorithm.
1712 void fbm_compile(SV* sv, U32 flags)
1716 Returns the location of the SV in the string delimited by C<str> and
1717 C<strend>. It returns C<Nullch> if the string can't be found. The
1718 C<sv> does not have to be fbm_compiled, but the search will not be as
1721 char* fbm_instr(char *str, char *strend, SV *sv, U32 flags)
1725 Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1732 Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
1736 Indicates that arguments returned from a callback should be discarded. See
1741 Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1745 A backward-compatible version of C<GIMME_V> which can only return
1746 C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1750 The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1751 C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1752 context, respectively.
1756 Indicates that no arguments are being sent to a callback. See L<perlcall>.
1760 Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1764 Returns the glob with the given C<name> and a defined subroutine or
1765 C<NULL>. The glob lives in the given C<stash>, or in the stashes
1766 accessible via @ISA and @UNIVERSAL.
1768 The argument C<level> should be either 0 or -1. If C<level==0>, as a
1769 side-effect creates a glob with the given C<name> in the given
1770 C<stash> which in the case of success contains an alias for the
1771 subroutine, and sets up caching info for this glob. Similarly for all
1772 the searched stashes.
1774 This function grants C<"SUPER"> token as a postfix of the stash name.
1776 The GV returned from C<gv_fetchmeth> may be a method cache entry,
1777 which is not visible to Perl code. So when calling C<perl_call_sv>,
1778 you should not use the GV directly; instead, you should use the
1779 method's CV, which can be obtained from the GV with the C<GvCV> macro.
1781 GV* gv_fetchmeth (HV* stash, char* name, STRLEN len, I32 level)
1783 =item gv_fetchmethod
1785 =item gv_fetchmethod_autoload
1787 Returns the glob which contains the subroutine to call to invoke the
1788 method on the C<stash>. In fact in the presence of autoloading this may
1789 be the glob for "AUTOLOAD". In this case the corresponding variable
1790 $AUTOLOAD is already setup.
1792 The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1793 lookup is performed if the given method is not present: non-zero means
1794 yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1795 C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1796 non-zero C<autoload> parameter.
1798 These functions grant C<"SUPER"> token as a prefix of the method name.
1800 Note that if you want to keep the returned glob for a long time, you
1801 need to check for it being "AUTOLOAD", since at the later time the call
1802 may load a different subroutine due to $AUTOLOAD changing its value.
1803 Use the glob created via a side effect to do this.
1805 These functions have the same side-effects and as C<gv_fetchmeth> with
1806 C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
1807 The warning against passing the GV returned by C<gv_fetchmeth> to
1808 C<perl_call_sv> apply equally to these functions.
1810 GV* gv_fetchmethod (HV* stash, char* name)
1811 GV* gv_fetchmethod_autoload (HV* stash, char* name, I32 autoload)
1815 Used to indicate void context. See C<GIMME_V> and L<perlcall>.
1819 Returns a pointer to the stash for a specified package. If C<create> is set
1820 then the package will be created if it does not already exist. If C<create>
1821 is not set and the package does not exist then NULL is returned.
1823 HV* gv_stashpv (char* name, I32 create)
1827 Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1829 HV* gv_stashsv (SV* sv, I32 create)
1833 Return the SV from the GV.
1837 This flag, used in the length slot of hash entries and magic
1838 structures, specifies the structure contains a C<SV*> pointer where a
1839 C<char*> pointer is to be expected. (For information only--not to be used).
1843 Returns the computed hash stored in the hash entry.
1849 Returns the actual pointer stored in the key slot of the hash entry.
1850 The pointer may be either C<char*> or C<SV*>, depending on the value of
1851 C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1852 are usually preferable for finding the value of a key.
1858 If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1859 holds an C<SV*> key. Otherwise, holds the actual length of the key.
1860 Can be assigned to. The C<HePV()> macro is usually preferable for finding
1867 Returns the key slot of the hash entry as a C<char*> value, doing any
1868 necessary dereferencing of possibly C<SV*> keys. The length of
1869 the string is placed in C<len> (this is a macro, so do I<not> use
1870 C<&len>). If you do not care about what the length of the key is,
1871 you may use the global variable C<PL_na>, though this is rather less
1872 efficient than using a local variable. Remember though, that hash
1873 keys in perl are free to contain embedded nulls, so using C<strlen()>
1874 or similar is not a good way to find the length of hash keys.
1875 This is very similar to the C<SvPV()> macro described elsewhere in
1878 char* HePV(HE* he, STRLEN len)
1882 Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1883 does not contain an C<SV*> key.
1889 Returns the key as an C<SV*>. Will create and return a temporary
1890 mortal C<SV*> if the hash entry contains only a C<char*> key.
1892 HeSVKEY_force(HE* he)
1896 Sets the key to a given C<SV*>, taking care to set the appropriate flags
1897 to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1899 HeSVKEY_set(HE* he, SV* sv)
1903 Returns the value slot (type C<SV*>) stored in the hash entry.
1909 Clears a hash, making it empty.
1911 void hv_clear (HV* tb)
1915 Deletes a key/value pair in the hash. The value SV is removed from the hash
1916 and returned to the caller. The C<klen> is the length of the key. The
1917 C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
1920 SV* hv_delete (HV* tb, char* key, U32 klen, I32 flags)
1924 Deletes a key/value pair in the hash. The value SV is removed from the hash
1925 and returned to the caller. The C<flags> value will normally be zero; if set
1926 to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1927 hash value, or 0 to ask for it to be computed.
1929 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash)
1933 Returns a boolean indicating whether the specified hash key exists. The
1934 C<klen> is the length of the key.
1936 bool hv_exists (HV* tb, char* key, U32 klen)
1940 Returns a boolean indicating whether the specified hash key exists. C<hash>
1941 can be a valid precomputed hash value, or 0 to ask for it to be computed.
1943 bool hv_exists_ent (HV* tb, SV* key, U32 hash)
1947 Returns the SV which corresponds to the specified key in the hash. The
1948 C<klen> is the length of the key. If C<lval> is set then the fetch will be
1949 part of a store. Check that the return value is non-null before
1950 dereferencing it to a C<SV*>.
1952 See L<Understanding the Magic of Tied Hashes and Arrays> for more
1953 information on how to use this function on tied hashes.
1955 SV** hv_fetch (HV* tb, char* key, U32 klen, I32 lval)
1959 Returns the hash entry which corresponds to the specified key in the hash.
1960 C<hash> must be a valid precomputed hash number for the given C<key>, or
1961 0 if you want the function to compute it. IF C<lval> is set then the
1962 fetch will be part of a store. Make sure the return value is non-null
1963 before accessing it. The return value when C<tb> is a tied hash
1964 is a pointer to a static location, so be sure to make a copy of the
1965 structure if you need to store it somewhere.
1967 See L<Understanding the Magic of Tied Hashes and Arrays> for more
1968 information on how to use this function on tied hashes.
1970 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash)
1974 Prepares a starting point to traverse a hash table.
1976 I32 hv_iterinit (HV* tb)
1978 Returns the number of keys in the hash (i.e. the same as C<HvKEYS(tb)>).
1979 The return value is currently only meaningful for hashes without tie
1982 NOTE: Before version 5.004_65, C<hv_iterinit> used to return the number
1983 of hash buckets that happen to be in use. If you still need that
1984 esoteric value, you can get it through the macro C<HvFILL(tb)>.
1988 Returns the key from the current position of the hash iterator. See
1991 char* hv_iterkey (HE* entry, I32* retlen)
1995 Returns the key as an C<SV*> from the current position of the hash
1996 iterator. The return value will always be a mortal copy of the
1997 key. Also see C<hv_iterinit>.
1999 SV* hv_iterkeysv (HE* entry)
2003 Returns entries from a hash iterator. See C<hv_iterinit>.
2005 HE* hv_iternext (HV* tb)
2009 Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
2012 SV* hv_iternextsv (HV* hv, char** key, I32* retlen)
2016 Returns the value from the current position of the hash iterator. See
2019 SV* hv_iterval (HV* tb, HE* entry)
2023 Adds magic to a hash. See C<sv_magic>.
2025 void hv_magic (HV* hv, GV* gv, int how)
2029 Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
2031 char* HvNAME (HV* stash)
2035 Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
2036 the length of the key. The C<hash> parameter is the precomputed hash
2037 value; if it is zero then Perl will compute it. The return value will be
2038 NULL if the operation failed or if the value did not need to be actually
2039 stored within the hash (as in the case of tied hashes). Otherwise it can
2040 be dereferenced to get the original C<SV*>. Note that the caller is
2041 responsible for suitably incrementing the reference count of C<val>
2042 before the call, and decrementing it if the function returned NULL.
2044 See L<Understanding the Magic of Tied Hashes and Arrays> for more
2045 information on how to use this function on tied hashes.
2047 SV** hv_store (HV* tb, char* key, U32 klen, SV* val, U32 hash)
2051 Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
2052 parameter is the precomputed hash value; if it is zero then Perl will
2053 compute it. The return value is the new hash entry so created. It will be
2054 NULL if the operation failed or if the value did not need to be actually
2055 stored within the hash (as in the case of tied hashes). Otherwise the
2056 contents of the return value can be accessed using the C<He???> macros
2057 described here. Note that the caller is responsible for suitably
2058 incrementing the reference count of C<val> before the call, and decrementing
2059 it if the function returned NULL.
2061 See L<Understanding the Magic of Tied Hashes and Arrays> for more
2062 information on how to use this function on tied hashes.
2064 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash)
2070 void hv_undef (HV* tb)
2074 Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
2077 int isALNUM (char c)
2081 Returns a boolean indicating whether the C C<char> is an ascii alphabetic
2084 int isALPHA (char c)
2088 Returns a boolean indicating whether the C C<char> is an ascii digit.
2090 int isDIGIT (char c)
2094 Returns a boolean indicating whether the C C<char> is a lowercase character.
2096 int isLOWER (char c)
2100 Returns a boolean indicating whether the C C<char> is whitespace.
2102 int isSPACE (char c)
2106 Returns a boolean indicating whether the C C<char> is an uppercase character.
2108 int isUPPER (char c)
2112 Variable which is setup by C<xsubpp> to indicate the number of items on the
2113 stack. See L<perlxs/"Variable-length Parameter Lists">.
2117 Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
2118 was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
2122 Closing bracket on a callback. See C<ENTER> and L<perlcall>.
2126 =item looks_like_number
2128 Test if an the content of an SV looks like a number (or is a number).
2130 int looks_like_number(SV*)
2135 Stack marker variable for the XSUB. See C<dMARK>.
2139 Clear something magical that the SV represents. See C<sv_magic>.
2141 int mg_clear (SV* sv)
2145 Copies the magic from one SV to another. See C<sv_magic>.
2147 int mg_copy (SV *, SV *, char *, STRLEN)
2151 Finds the magic pointer for type matching the SV. See C<sv_magic>.
2153 MAGIC* mg_find (SV* sv, int type)
2157 Free any magic storage used by the SV. See C<sv_magic>.
2159 int mg_free (SV* sv)
2163 Do magic after a value is retrieved from the SV. See C<sv_magic>.
2169 Report on the SV's length. See C<sv_magic>.
2175 Turns on the magical status of an SV. See C<sv_magic>.
2177 void mg_magical (SV* sv)
2181 Do magic after a value is assigned to the SV. See C<sv_magic>.
2187 C<modglobal> is a general purpose, interpreter global HV for use by
2188 extensions that need to keep information on a per-interpreter basis.
2189 In a pinch, it can also be used as a symbol table for extensions
2190 to share data among each other. It is a good idea to use keys
2191 prefixed by the package name of the extension that owns the data.
2195 The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
2196 source, C<d> is the destination, C<n> is the number of items, and C<t> is
2197 the type. Can do overlapping moves. See also C<Copy>.
2199 void Move( s, d, n, t )
2203 A convenience variable which is typically used with C<SvPV> when one doesn't
2204 care about the length of the string. It is usually more efficient to
2205 declare a local variable and use that instead.
2209 The XSUB-writer's interface to the C C<malloc> function.
2211 void* New( x, void *ptr, int size, type )
2215 Creates a new AV. The reference count is set to 1.
2221 The XSUB-writer's interface to the C C<malloc> function, with cast.
2223 void* Newc( x, void *ptr, int size, type, cast )
2227 Creates a constant sub equivalent to Perl C<sub FOO () { 123 }>
2228 which is eligible for inlining at compile-time.
2230 void newCONSTSUB(HV* stash, char* name, SV* sv)
2234 Creates a new HV. The reference count is set to 1.
2240 Creates an RV wrapper for an SV. The reference count for the original SV is
2243 SV* newRV_inc (SV* ref)
2245 For historical reasons, "newRV" is a synonym for "newRV_inc".
2249 Creates an RV wrapper for an SV. The reference count for the original
2250 SV is B<not> incremented.
2252 SV* newRV_noinc (SV* ref)
2256 Creates a new SV. A non-zero C<len> parameter indicates the number of
2257 bytes of preallocated string space the SV should have. An extra byte
2258 for a tailing NUL is also reserved. (SvPOK is not set for the SV even
2259 if string space is allocated.) The reference count for the new SV is
2260 set to 1. C<id> is an integer id between 0 and 1299 (used to identify
2263 SV* NEWSV (int id, STRLEN len)
2267 Creates a new SV and copies an integer into it. The reference count for the
2274 Creates a new SV and copies a double into it. The reference count for the
2281 Creates a new SV and copies a string into it. The reference count for the
2282 SV is set to 1. If C<len> is zero then Perl will compute the length.
2284 SV* newSVpv (char* s, STRLEN len)
2288 Creates a new SV an initialize it with the string formatted like
2291 SV* newSVpvf(const char* pat, ...);
2295 Creates a new SV and copies a string into it. The reference count for the
2296 SV is set to 1. If C<len> is zero then Perl will create a zero length
2299 SV* newSVpvn (char* s, STRLEN len)
2303 Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
2304 it will be upgraded to one. If C<classname> is non-null then the new SV will
2305 be blessed in the specified package. The new SV is returned and its
2306 reference count is 1.
2308 SV* newSVrv (SV* rv, char* classname)
2312 Creates a new SV which is an exact duplicate of the original SV.
2314 SV* newSVsv (SV* old)
2318 Used by C<xsubpp> to hook up XSUBs as Perl subs.
2322 Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
2327 The XSUB-writer's interface to the C C<malloc> function. The allocated
2328 memory is zeroed with C<memzero>.
2330 void* Newz( x, void *ptr, int size, type )
2338 Null character pointer.
2354 The original stack mark for the XSUB. See C<dORIGMARK>.
2358 Allocates a new Perl interpreter. See L<perlembed>.
2360 =item perl_call_argv
2362 Performs a callback to the specified Perl sub. See L<perlcall>.
2364 I32 perl_call_argv (char* subname, I32 flags, char** argv)
2366 =item perl_call_method
2368 Performs a callback to the specified Perl method. The blessed object must
2369 be on the stack. See L<perlcall>.
2371 I32 perl_call_method (char* methname, I32 flags)
2375 Performs a callback to the specified Perl sub. See L<perlcall>.
2377 I32 perl_call_pv (char* subname, I32 flags)
2381 Performs a callback to the Perl sub whose name is in the SV. See
2384 I32 perl_call_sv (SV* sv, I32 flags)
2386 =item perl_construct
2388 Initializes a new Perl interpreter. See L<perlembed>.
2392 Shuts down a Perl interpreter. See L<perlembed>.
2396 Tells Perl to C<eval> the string in the SV.
2398 I32 perl_eval_sv (SV* sv, I32 flags)
2402 Tells Perl to C<eval> the given string and return an SV* result.
2404 SV* perl_eval_pv (char* p, I32 croak_on_error)
2408 Releases a Perl interpreter. See L<perlembed>.
2412 Returns the AV of the specified Perl array. If C<create> is set and the
2413 Perl variable does not exist then it will be created. If C<create> is not
2414 set and the variable does not exist then NULL is returned.
2416 AV* perl_get_av (char* name, I32 create)
2420 Returns the CV of the specified Perl sub. If C<create> is set and the Perl
2421 variable does not exist then it will be created. If C<create> is not
2422 set and the variable does not exist then NULL is returned.
2424 CV* perl_get_cv (char* name, I32 create)
2428 Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2429 variable does not exist then it will be created. If C<create> is not
2430 set and the variable does not exist then NULL is returned.
2432 HV* perl_get_hv (char* name, I32 create)
2436 Returns the SV of the specified Perl scalar. If C<create> is set and the
2437 Perl variable does not exist then it will be created. If C<create> is not
2438 set and the variable does not exist then NULL is returned.
2440 SV* perl_get_sv (char* name, I32 create)
2444 Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2446 =item perl_require_pv
2448 Tells Perl to C<require> a module.
2450 void perl_require_pv (char* pv)
2454 Tells a Perl interpreter to run. See L<perlembed>.
2458 Pops an integer off the stack.
2464 Pops a long off the stack.
2470 Pops a string off the stack.
2476 Pops a double off the stack.
2482 Pops an SV off the stack.
2488 Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2494 Push an integer onto the stack. The stack must have room for this element.
2495 Handles 'set' magic. See C<XPUSHi>.
2501 Push a double onto the stack. The stack must have room for this element.
2502 Handles 'set' magic. See C<XPUSHn>.
2504 void PUSHn(double d)
2508 Push a string onto the stack. The stack must have room for this element.
2509 The C<len> indicates the length of the string. Handles 'set' magic. See
2512 void PUSHp(char *c, int len )
2516 Push an SV onto the stack. The stack must have room for this element. Does
2517 not handle 'set' magic. See C<XPUSHs>.
2523 Push an unsigned integer onto the stack. The stack must have room for
2524 this element. See C<XPUSHu>.
2526 void PUSHu(unsigned int d)
2531 Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2532 See C<PUSHMARK> and L<perlcall> for other uses.
2538 The XSUB-writer's interface to the C C<realloc> function.
2540 void* Renew( void *ptr, int size, type )
2544 The XSUB-writer's interface to the C C<realloc> function, with cast.
2546 void* Renewc( void *ptr, int size, type, cast )
2550 Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
2551 This is always the proper type for the XSUB.
2552 See L<perlxs/"The RETVAL Variable">.
2556 The XSUB-writer's interface to the C C<free> function.
2560 The XSUB-writer's interface to the C C<malloc> function.
2564 The XSUB-writer's interface to the C C<realloc> function.
2568 Copy a string to a safe spot. This does not use an SV.
2570 char* savepv (char* sv)
2574 Copy a string to a safe spot. The C<len> indicates number of bytes to
2575 copy. This does not use an SV.
2577 char* savepvn (char* sv, I32 len)
2581 Opening bracket for temporaries on a callback. See C<FREETMPS> and
2588 Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2593 Refetch the stack pointer. Used after a callback. See L<perlcall>.
2599 Used to access elements on the XSUB's stack.
2605 Test two strings to see if they are equal. Returns true or false.
2607 int strEQ( char *s1, char *s2 )
2611 Test two strings to see if the first, C<s1>, is greater than or equal to the
2612 second, C<s2>. Returns true or false.
2614 int strGE( char *s1, char *s2 )
2618 Test two strings to see if the first, C<s1>, is greater than the second,
2619 C<s2>. Returns true or false.
2621 int strGT( char *s1, char *s2 )
2625 Test two strings to see if the first, C<s1>, is less than or equal to the
2626 second, C<s2>. Returns true or false.
2628 int strLE( char *s1, char *s2 )
2632 Test two strings to see if the first, C<s1>, is less than the second,
2633 C<s2>. Returns true or false.
2635 int strLT( char *s1, char *s2 )
2639 Test two strings to see if they are different. Returns true or false.
2641 int strNE( char *s1, char *s2 )
2645 Test two strings to see if they are equal. The C<len> parameter indicates
2646 the number of bytes to compare. Returns true or false.
2648 int strnEQ( char *s1, char *s2 )
2652 Test two strings to see if they are different. The C<len> parameter
2653 indicates the number of bytes to compare. Returns true or false.
2655 int strnNE( char *s1, char *s2, int len )
2659 Marks an SV as mortal. The SV will be destroyed when the current context
2662 SV* sv_2mortal (SV* sv)
2666 Blesses an SV into a specified package. The SV must be an RV. The package
2667 must be designated by its stash (see C<gv_stashpv()>). The reference count
2668 of the SV is unaffected.
2670 SV* sv_bless (SV* sv, HV* stash)
2674 Concatenates the string onto the end of the string which is in the SV.
2675 Handles 'get' magic, but not 'set' magic. See C<sv_catpv_mg>.
2677 void sv_catpv (SV* sv, char* ptr)
2681 Like C<sv_catpv>, but also handles 'set' magic.
2683 void sv_catpv_mg (SV* sv, const char* ptr)
2687 Concatenates the string onto the end of the string which is in the SV. The
2688 C<len> indicates number of bytes to copy. Handles 'get' magic, but not
2689 'set' magic. See C<sv_catpvn_mg>.
2691 void sv_catpvn (SV* sv, char* ptr, STRLEN len)
2695 Like C<sv_catpvn>, but also handles 'set' magic.
2697 void sv_catpvn_mg (SV* sv, char* ptr, STRLEN len)
2701 Processes its arguments like C<sprintf> and appends the formatted output
2702 to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
2703 typically be called after calling this function to handle 'set' magic.
2705 void sv_catpvf (SV* sv, const char* pat, ...)
2709 Like C<sv_catpvf>, but also handles 'set' magic.
2711 void sv_catpvf_mg (SV* sv, const char* pat, ...)
2715 Concatenates the string from SV C<ssv> onto the end of the string in SV
2716 C<dsv>. Handles 'get' magic, but not 'set' magic. See C<sv_catsv_mg>.
2718 void sv_catsv (SV* dsv, SV* ssv)
2722 Like C<sv_catsv>, but also handles 'set' magic.
2724 void sv_catsv_mg (SV* dsv, SV* ssv)
2728 Efficient removal of characters from the beginning of the string
2729 buffer. SvPOK(sv) must be true and the C<ptr> must be a pointer to
2730 somewhere inside the string buffer. The C<ptr> becomes the first
2731 character of the adjusted string.
2733 void sv_chop(SV* sv, char *ptr)
2738 Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2739 string in C<sv1> is less than, equal to, or greater than the string in
2742 I32 sv_cmp (SV* sv1, SV* sv2)
2746 Returns the length of the string which is in the SV. See C<SvLEN>.
2752 Set the length of the string which is in the SV. See C<SvCUR>.
2754 void SvCUR_set (SV* sv, int val)
2758 Auto-decrement of the value in the SV.
2760 void sv_dec (SV* sv)
2762 =item sv_derived_from
2764 Returns a boolean indicating whether the SV is derived from the specified
2765 class. This is the function that implements C<UNIVERSAL::isa>. It works
2766 for class names as well as for objects.
2768 bool sv_derived_from _((SV* sv, char* name));
2772 Returns a pointer to the last character in the string which is in the SV.
2773 See C<SvCUR>. Access the character as
2779 Returns a boolean indicating whether the strings in the two SVs are
2782 I32 sv_eq (SV* sv1, SV* sv2)
2786 Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
2787 its argument more than once.
2789 void SvGETMAGIC(SV *sv)
2793 Expands the character buffer in the SV so that it has room for the
2794 indicated number of bytes (remember to reserve space for an extra
2795 trailing NUL character). Calls C<sv_grow> to perform the expansion if
2796 necessary. Returns a pointer to the character buffer.
2798 char* SvGROW(SV* sv, STRLEN len)
2802 Expands the character buffer in the SV. This will use C<sv_unref> and will
2803 upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2808 Auto-increment of the value in the SV.
2810 void sv_inc (SV* sv)
2814 Inserts a string at the specified offset/length within the SV.
2815 Similar to the Perl substr() function.
2817 void sv_insert(SV *sv, STRLEN offset, STRLEN len,
2818 char *str, STRLEN strlen)
2822 Returns a boolean indicating whether the SV contains an integer.
2828 Unsets the IV status of an SV.
2830 void SvIOK_off (SV* sv)
2834 Tells an SV that it is an integer.
2836 void SvIOK_on (SV* sv)
2840 Tells an SV that it is an integer and disables all other OK bits.
2842 void SvIOK_only (SV* sv)
2846 Returns a boolean indicating whether the SV contains an integer. Checks the
2847 B<private> setting. Use C<SvIOK>.
2853 Returns a boolean indicating whether the SV is blessed into the specified
2854 class. This does not check for subtypes; use C<sv_derived_from> to verify
2855 an inheritance relationship.
2857 int sv_isa (SV* sv, char* name)
2861 Returns a boolean indicating whether the SV is an RV pointing to a blessed
2862 object. If the SV is not an RV, or if the object is not blessed, then this
2865 int sv_isobject (SV* sv)
2869 Coerces the given SV to an integer and returns it.
2875 Returns the integer which is stored in the SV, assuming SvIOK is true.
2881 Returns the size of the string buffer in the SV. See C<SvCUR>.
2887 Returns the length of the string in the SV. Use C<SvCUR>.
2889 STRLEN sv_len (SV* sv)
2893 Adds magic to an SV.
2895 void sv_magic (SV* sv, SV* obj, int how, char* name, I32 namlen)
2899 Creates a new SV which is a copy of the original SV. The new SV is marked
2902 SV* sv_mortalcopy (SV* oldsv)
2906 Creates a new SV which is mortal. The reference count of the SV is set to 1.
2908 SV* sv_newmortal (void)
2912 Returns a boolean indicating whether the SV contains a number, integer or
2919 Unsets the NV/IV status of an SV.
2921 void SvNIOK_off (SV* sv)
2925 Returns a boolean indicating whether the SV contains a number, integer or
2926 double. Checks the B<private> setting. Use C<SvNIOK>.
2928 int SvNIOKp (SV* SV)
2932 This is the C<false> SV. See C<PL_sv_yes>. Always refer to this as C<&PL_sv_no>.
2936 Returns a boolean indicating whether the SV contains a double.
2942 Unsets the NV status of an SV.
2944 void SvNOK_off (SV* sv)
2948 Tells an SV that it is a double.
2950 void SvNOK_on (SV* sv)
2954 Tells an SV that it is a double and disables all other OK bits.
2956 void SvNOK_only (SV* sv)
2960 Returns a boolean indicating whether the SV contains a double. Checks the
2961 B<private> setting. Use C<SvNOK>.
2967 Coerce the given SV to a double and return it.
2969 double SvNV (SV* sv)
2973 Returns the double which is stored in the SV, assuming SvNOK is true.
2975 double SvNVX (SV* sv)
2979 Returns a boolean indicating whether the value is an SV.
2985 Returns a boolean indicating whether the SvIVX is a valid offset value
2986 for the SvPVX. This hack is used internally to speed up removal of
2987 characters from the beginning of a SvPV. When SvOOK is true, then the
2988 start of the allocated string buffer is really (SvPVX - SvIVX).
2994 Returns a boolean indicating whether the SV contains a character string.
3000 Unsets the PV status of an SV.
3002 void SvPOK_off (SV* sv)
3006 Tells an SV that it is a string.
3008 void SvPOK_on (SV* sv)
3012 Tells an SV that it is a string and disables all other OK bits.
3014 void SvPOK_only (SV* sv)
3018 Returns a boolean indicating whether the SV contains a character string.
3019 Checks the B<private> setting. Use C<SvPOK>.
3025 Returns a pointer to the string in the SV, or a stringified form of the SV
3026 if the SV does not contain a string. Handles 'get' magic.
3028 char* SvPV (SV* sv, STRLEN len)
3032 Like <SvPV> but will force the SV into becoming a string (SvPOK). You
3033 want force if you are going to update the SvPVX directly.
3035 char* SvPV_force(SV* sv, STRLEN len)
3039 Returns a pointer to the string in the SV. The SV must contain a string.
3041 char* SvPVX (SV* sv)
3045 Returns the value of the object's reference count.
3047 int SvREFCNT (SV* sv)
3051 Decrements the reference count of the given SV.
3053 void SvREFCNT_dec (SV* sv)
3057 Increments the reference count of the given SV.
3059 void SvREFCNT_inc (SV* sv)
3063 Tests if the SV is an RV.
3069 Unsets the RV status of an SV.
3071 void SvROK_off (SV* sv)
3075 Tells an SV that it is an RV.
3077 void SvROK_on (SV* sv)
3081 Dereferences an RV to return the SV.
3087 Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
3088 its argument more than once.
3090 void SvSETMAGIC( SV *sv )
3094 Copies an integer into the given SV. Does not handle 'set' magic.
3097 void sv_setiv (SV* sv, IV num)
3101 Like C<sv_setiv>, but also handles 'set' magic.
3103 void sv_setiv_mg (SV* sv, IV num)
3107 Copies a double into the given SV. Does not handle 'set' magic.
3110 void sv_setnv (SV* sv, double num)
3114 Like C<sv_setnv>, but also handles 'set' magic.
3116 void sv_setnv_mg (SV* sv, double num)
3120 Copies a string into an SV. The string must be null-terminated.
3121 Does not handle 'set' magic. See C<sv_setpv_mg>.
3123 void sv_setpv (SV* sv, const char* ptr)
3127 Like C<sv_setpv>, but also handles 'set' magic.
3129 void sv_setpv_mg (SV* sv, const char* ptr)
3133 Copies an integer into the given SV, also updating its string value.
3134 Does not handle 'set' magic. See C<sv_setpviv_mg>.
3136 void sv_setpviv (SV* sv, IV num)
3140 Like C<sv_setpviv>, but also handles 'set' magic.
3142 void sv_setpviv_mg (SV* sv, IV num)
3146 Copies a string into an SV. The C<len> parameter indicates the number of
3147 bytes to be copied. Does not handle 'set' magic. See C<sv_setpvn_mg>.
3149 void sv_setpvn (SV* sv, const char* ptr, STRLEN len)
3153 Like C<sv_setpvn>, but also handles 'set' magic.
3155 void sv_setpvn_mg (SV* sv, const char* ptr, STRLEN len)
3159 Processes its arguments like C<sprintf> and sets an SV to the formatted
3160 output. Does not handle 'set' magic. See C<sv_setpvf_mg>.
3162 void sv_setpvf (SV* sv, const char* pat, ...)
3166 Like C<sv_setpvf>, but also handles 'set' magic.
3168 void sv_setpvf_mg (SV* sv, const char* pat, ...)
3172 Copies an integer into a new SV, optionally blessing the SV. The C<rv>
3173 argument will be upgraded to an RV. That RV will be modified to point to
3174 the new SV. The C<classname> argument indicates the package for the
3175 blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
3176 will be returned and will have a reference count of 1.
3178 SV* sv_setref_iv (SV *rv, char *classname, IV iv)
3182 Copies a double into a new SV, optionally blessing the SV. The C<rv>
3183 argument will be upgraded to an RV. That RV will be modified to point to
3184 the new SV. The C<classname> argument indicates the package for the
3185 blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
3186 will be returned and will have a reference count of 1.
3188 SV* sv_setref_nv (SV *rv, char *classname, double nv)
3192 Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
3193 argument will be upgraded to an RV. That RV will be modified to point to
3194 the new SV. If the C<pv> argument is NULL then C<PL_sv_undef> will be placed
3195 into the SV. The C<classname> argument indicates the package for the
3196 blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
3197 will be returned and will have a reference count of 1.
3199 SV* sv_setref_pv (SV *rv, char *classname, void* pv)
3201 Do not use with integral Perl types such as HV, AV, SV, CV, because those
3202 objects will become corrupted by the pointer copy process.
3204 Note that C<sv_setref_pvn> copies the string while this copies the pointer.
3208 Copies a string into a new SV, optionally blessing the SV. The length of the
3209 string must be specified with C<n>. The C<rv> argument will be upgraded to
3210 an RV. That RV will be modified to point to the new SV. The C<classname>
3211 argument indicates the package for the blessing. Set C<classname> to
3212 C<Nullch> to avoid the blessing. The new SV will be returned and will have
3213 a reference count of 1.
3215 SV* sv_setref_pvn (SV *rv, char *classname, char* pv, I32 n)
3217 Note that C<sv_setref_pv> copies the pointer while this copies the string.
3221 Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
3224 void SvSetSV (SV* dsv, SV* ssv)
3226 =item SvSetSV_nosteal
3228 Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
3229 May evaluate arguments more than once.
3231 void SvSetSV_nosteal (SV* dsv, SV* ssv)
3235 Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
3236 The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
3237 See the macro forms C<SvSetSV>, C<SvSetSV_nosteal> and C<sv_setsv_mg>.
3239 void sv_setsv (SV* dsv, SV* ssv)
3243 Like C<sv_setsv>, but also handles 'set' magic.
3245 void sv_setsv_mg (SV* dsv, SV* ssv)
3249 Copies an unsigned integer into the given SV. Does not handle 'set' magic.
3252 void sv_setuv (SV* sv, UV num)
3256 Like C<sv_setuv>, but also handles 'set' magic.
3258 void sv_setuv_mg (SV* sv, UV num)
3262 Returns the stash of the SV.
3264 HV* SvSTASH (SV* sv)
3268 Taints an SV if tainting is enabled
3270 void SvTAINT (SV* sv)
3274 Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
3276 int SvTAINTED (SV* sv)
3280 Untaints an SV. Be I<very> careful with this routine, as it short-circuits
3281 some of Perl's fundamental security features. XS module authors should
3282 not use this function unless they fully understand all the implications
3283 of unconditionally untainting the value. Untainting should be done in
3284 the standard perl fashion, via a carefully crafted regexp, rather than
3285 directly untainting variables.
3287 void SvTAINTED_off (SV* sv)
3291 Marks an SV as tainted.
3293 void SvTAINTED_on (SV* sv)
3297 Integer type flag for scalars. See C<svtype>.
3301 Pointer type flag for scalars. See C<svtype>.
3305 Type flag for arrays. See C<svtype>.
3309 Type flag for code refs. See C<svtype>.
3313 Type flag for hashes. See C<svtype>.
3317 Type flag for blessed scalars. See C<svtype>.
3321 Double type flag for scalars. See C<svtype>.
3325 Returns a boolean indicating whether Perl would evaluate the SV as true or
3326 false, defined or undefined. Does not handle 'get' magic.
3332 Returns the type of the SV. See C<svtype>.
3334 svtype SvTYPE (SV* sv)
3338 An enum of flags for Perl types. These are found in the file B<sv.h> in the
3339 C<svtype> enum. Test these flags with the C<SvTYPE> macro.
3343 This is the C<undef> SV. Always refer to this as C<&PL_sv_undef>.
3347 Unsets the RV status of the SV, and decrements the reference count of
3348 whatever was being referenced by the RV. This can almost be thought of
3349 as a reversal of C<newSVrv>. See C<SvROK_off>.
3351 void sv_unref (SV* sv)
3355 Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
3356 the upgrade if necessary. See C<svtype>.
3358 bool SvUPGRADE (SV* sv, svtype mt)
3362 Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
3366 Tells an SV to use C<ptr> to find its string value. Normally the string is
3367 stored inside the SV but sv_usepvn allows the SV to use an outside string.
3368 The C<ptr> should point to memory that was allocated by C<malloc>. The
3369 string length, C<len>, must be supplied. This function will realloc the
3370 memory pointed to by C<ptr>, so that pointer should not be freed or used by
3371 the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
3372 See C<sv_usepvn_mg>.
3374 void sv_usepvn (SV* sv, char* ptr, STRLEN len)
3378 Like C<sv_usepvn>, but also handles 'set' magic.
3380 void sv_usepvn_mg (SV* sv, char* ptr, STRLEN len)
3382 =item sv_vcatpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
3384 Processes its arguments like C<vsprintf> and appends the formatted output
3385 to an SV. Uses an array of SVs if the C style variable argument list is
3386 missing (NULL). Indicates if locale information has been used for formatting.
3388 void sv_catpvfn _((SV* sv, const char* pat, STRLEN patlen,
3389 va_list *args, SV **svargs, I32 svmax,
3390 bool *used_locale));
3392 =item sv_vsetpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
3394 Works like C<vcatpvfn> but copies the text into the SV instead of
3397 void sv_setpvfn _((SV* sv, const char* pat, STRLEN patlen,
3398 va_list *args, SV **svargs, I32 svmax,
3399 bool *used_locale));
3403 Coerces the given SV to an unsigned integer and returns it.
3409 Returns the unsigned integer which is stored in the SV, assuming SvIOK is true.
3415 This is the C<true> SV. See C<PL_sv_no>. Always refer to this as C<&PL_sv_yes>.
3419 Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
3420 This is always the proper type for the C++ object. See C<CLASS> and
3421 L<perlxs/"Using XS With C++">.
3425 Converts the specified character to lowercase.
3427 int toLOWER (char c)
3431 Converts the specified character to uppercase.
3433 int toUPPER (char c)
3437 This is the XSUB-writer's interface to Perl's C<warn> function. Use this
3438 function the same way you use the C C<printf> function. See C<croak()>.
3442 Push an integer onto the stack, extending the stack if necessary. Handles
3443 'set' magic. See C<PUSHi>.
3449 Push a double onto the stack, extending the stack if necessary. Handles 'set'
3450 magic. See C<PUSHn>.
3456 Push a string onto the stack, extending the stack if necessary. The C<len>
3457 indicates the length of the string. Handles 'set' magic. See C<PUSHp>.
3459 XPUSHp(char *c, int len)
3463 Push an SV onto the stack, extending the stack if necessary. Does not
3464 handle 'set' magic. See C<PUSHs>.
3470 Push an unsigned integer onto the stack, extending the stack if
3471 necessary. See C<PUSHu>.
3475 Macro to declare an XSUB and its C parameter list. This is handled by
3480 Return from XSUB, indicating number of items on the stack. This is usually
3481 handled by C<xsubpp>.
3485 =item XSRETURN_EMPTY
3487 Return an empty list from an XSUB immediately.
3493 Return an integer from an XSUB immediately. Uses C<XST_mIV>.
3499 Return C<&PL_sv_no> from an XSUB immediately. Uses C<XST_mNO>.
3505 Return an double from an XSUB immediately. Uses C<XST_mNV>.
3511 Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
3513 XSRETURN_PV(char *v)
3515 =item XSRETURN_UNDEF
3517 Return C<&PL_sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
3523 Return C<&PL_sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
3529 Place an integer into the specified position C<i> on the stack. The value is
3530 stored in a new mortal SV.
3532 XST_mIV( int i, IV v )
3536 Place a double into the specified position C<i> on the stack. The value is
3537 stored in a new mortal SV.
3539 XST_mNV( int i, NV v )
3543 Place C<&PL_sv_no> into the specified position C<i> on the stack.
3549 Place a copy of a string into the specified position C<i> on the stack. The
3550 value is stored in a new mortal SV.
3552 XST_mPV( int i, char *v )
3556 Place C<&PL_sv_undef> into the specified position C<i> on the stack.
3562 Place C<&PL_sv_yes> into the specified position C<i> on the stack.
3568 The version identifier for an XS module. This is usually handled
3569 automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
3571 =item XS_VERSION_BOOTCHECK
3573 Macro to verify that a PM module's $VERSION variable matches the XS module's
3574 C<XS_VERSION> variable. This is usually handled automatically by
3575 C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
3579 The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
3580 destination, C<n> is the number of items, and C<t> is the type.
3582 void Zero( d, n, t )
3588 Until May 1997, this document was maintained by Jeff Okamoto
3589 <okamoto@corp.hp.com>. It is now maintained as part of Perl itself.
3591 With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
3592 Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
3593 Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
3594 Stephen McCamant, and Gurusamy Sarathy.
3596 API Listing originally by Dean Roehrich <roehrich@cray.com>.