when iterating over the hash or when checking for the keys
with the C<hv_exists> function.
-You can run into similar problems when you store C<&PL_sv_true> or
-C<&PL_sv_false> into AVs or HVs. Trying to modify such elements
+You can run into similar problems when you store C<&PL_sv_yes> or
+C<&PL_sv_no> into AVs or HVs. Trying to modify such elements
will give you the following error:
Modification of a read-only value attempted
To make a long story short, you can use the special variables
-C<&PL_sv_undef>, C<&PL_sv_true> and C<&PL_sv_false> with AVs and
+C<&PL_sv_undef>, C<&PL_sv_yes> and C<&PL_sv_no> with AVs and
HVs, but you have to make sure you know what you're doing.
Generally, if you want to store an undefined value in an AV
/* Still under construction */
-Upgrades rv to reference if not already one. Creates new SV for rv to
-point to. If C<classname> is non-null, the SV is blessed into the specified
-class. SV is returned.
+The following function upgrades rv to reference if not already one.
+Creates a new SV for rv to point to. If C<classname> is non-null, the SV
+is blessed into the specified class. SV is returned.
SV* newSVrv(SV* rv, const char* classname);
-Copies integer, unsigned integer or double into an SV whose reference is C<rv>. SV is blessed
-if C<classname> is non-null.
+The following three functions copy integer, unsigned integer or double
+into an SV whose reference is C<rv>. SV is blessed if C<classname> is
+non-null.
SV* sv_setref_iv(SV* rv, const char* classname, IV iv);
SV* sv_setref_uv(SV* rv, const char* classname, UV uv);
SV* sv_setref_nv(SV* rv, const char* classname, NV iv);
-Copies the pointer value (I<the address, not the string!>) into an SV whose
-reference is rv. SV is blessed if C<classname> is non-null.
+The following function copies the pointer value (I<the address, not the
+string!>) into an SV whose reference is rv. SV is blessed if C<classname>
+is non-null.
- SV* sv_setref_pv(SV* rv, const char* classname, PV iv);
+ SV* sv_setref_pv(SV* rv, const char* classname, void* pv);
-Copies string into an SV whose reference is C<rv>. Set length to 0 to let
-Perl calculate the string length. SV is blessed if C<classname> is non-null.
+The following function copies string into an SV whose reference is C<rv>.
+Set length to 0 to let Perl calculate the string length. SV is blessed if
+C<classname> is non-null.
- SV* sv_setref_pvn(SV* rv, const char* classname, PV iv, STRLEN length);
+ SV* sv_setref_pvn(SV* rv, const char* classname, char* pv, STRLEN length);
-Tests whether the SV is blessed into the specified class. It does not
-check inheritance relationships.
+The following function tests whether the SV is blessed into the specified
+class. It does not check inheritance relationships.
int sv_isa(SV* sv, const char* name);
-Tests whether the SV is a reference to a blessed object.
+The following function tests whether the SV is a reference to a blessed object.
int sv_isobject(SV* sv);
-Tests whether the SV is derived from the specified class. SV can be either
-a reference to a blessed object or a string containing a class name. This
-is the function implementing the C<UNIVERSAL::isa> functionality.
+The following function tests whether the SV is derived from the specified
+class. SV can be either a reference to a blessed object or a string
+containing a class name. This is the function implementing the
+C<UNIVERSAL::isa> functionality.
bool sv_derived_from(SV* sv, const char* name);
AV* get_av("package::varname", GV_ADD);
HV* get_hv("package::varname", GV_ADD);
-Notice the use of TRUE as the second parameter. The new variable can now
+Notice the use of GV_ADD as the second parameter. The new variable can now
be set, using the routines appropriate to the data type.
There are additional macros whose values may be bitwise OR'ed with the
-C<TRUE> argument to enable certain extra features. Those bits are:
+C<GV_ADD> argument to enable certain extra features. Those bits are:
=over
If you are not sure then doing an C<SvREFCNT_inc> and C<sv_2mortal>, or
making a C<sv_mortalcopy> is safer.
-The mortal routines are not just for SVs -- AVs and HVs can be
+The mortal routines are not just for SVs; AVs and HVs can be
made mortal by passing their address (type-casted to C<SV*>) to the
C<sv_2mortal> or C<sv_mortalcopy> routines.
To remove the magic from an SV, call the function sv_unmagic:
- void sv_unmagic(SV *sv, int type);
+ int sv_unmagic(SV *sv, int type);
The C<type> argument should be equal to the C<how> value when the C<SV>
was initially made magical.
+However, note that C<sv_unmagic> removes all magic of a certain C<type> from the
+C<SV>. If you want to remove only certain magic of a C<type> based on the magic
+virtual table, use C<sv_unmagicext> instead:
+
+ int sv_unmagicext(SV *sv, int type, MGVTBL *vtbl);
+
=head2 Magic Virtual Tables
The C<mg_virtual> field in the C<MAGIC> structure is a pointer to an
(old-style char and macro) MGVTBL Type of magic
-------------------------- ------ -------------
\0 PERL_MAGIC_sv vtbl_sv Special scalar variable
+ # PERL_MAGIC_arylen vtbl_arylen Array length ($#ary)
+ % PERL_MAGIC_rhash (none) extra data for restricted
+ hashes
+ . PERL_MAGIC_pos vtbl_pos pos() lvalue
+ : PERL_MAGIC_symtab (none) extra data for symbol tables
+ < PERL_MAGIC_backref vtbl_backref for weak ref data
+ @ PERL_MAGIC_arylen_p (none) to move arylen out of XPVAV
A PERL_MAGIC_overload vtbl_amagic %OVERLOAD hash
a PERL_MAGIC_overload_elem vtbl_amagicelem %OVERLOAD hash element
- c PERL_MAGIC_overload_table (none) Holds overload table (AMT)
- on stash
- B PERL_MAGIC_bm vtbl_bm Boyer-Moore (fast string search)
- D PERL_MAGIC_regdata vtbl_regdata Regex match position data
+ B PERL_MAGIC_bm vtbl_regexp Boyer-Moore
+ (fast string search)
+ c PERL_MAGIC_overload_table vtbl_ovrld Holds overload table
+ (AMT) on stash
+ D PERL_MAGIC_regdata vtbl_regdata Regex match position data
(@+ and @- vars)
d PERL_MAGIC_regdatum vtbl_regdatum Regex match position data
element
E PERL_MAGIC_env vtbl_env %ENV hash
e PERL_MAGIC_envelem vtbl_envelem %ENV hash element
- f PERL_MAGIC_fm vtbl_fm Formline ('compiled' format)
- g PERL_MAGIC_regex_global vtbl_mglob m//g target / study()ed string
+ f PERL_MAGIC_fm vtbl_regdata Formline ('compiled' format)
+ G PERL_MAGIC_study vtbl_regdata study()ed string
+ g PERL_MAGIC_regex_global vtbl_mglob m//g target
H PERL_MAGIC_hints vtbl_hints %^H hash
h PERL_MAGIC_hintselem vtbl_hintselem %^H hash element
I PERL_MAGIC_isa vtbl_isa @ISA array
k PERL_MAGIC_nkeys vtbl_nkeys scalar(keys()) lvalue
L PERL_MAGIC_dbfile (none) Debugger %_<filename
l PERL_MAGIC_dbline vtbl_dbline Debugger %_<filename element
- o PERL_MAGIC_collxfrm vtbl_collxfrm Locale collate transformation
+ N PERL_MAGIC_shared (none) Shared between threads
+ n PERL_MAGIC_shared_scalar (none) Shared between threads
+ o PERL_MAGIC_collxfrm vtbl_collxfrm Locale transformation
P PERL_MAGIC_tied vtbl_pack Tied array or hash
p PERL_MAGIC_tiedelem vtbl_packelem Tied array or hash element
q PERL_MAGIC_tiedscalar vtbl_packelem Tied scalar or handle
- r PERL_MAGIC_qr vtbl_qr precompiled qr// regex
- S PERL_MAGIC_sig vtbl_sig %SIG hash
+ r PERL_MAGIC_qr vtbl_regexp precompiled qr// regex
+ S PERL_MAGIC_sig (none) %SIG hash
s PERL_MAGIC_sigelem vtbl_sigelem %SIG hash element
t PERL_MAGIC_taint vtbl_taint Taintedness
U PERL_MAGIC_uvar vtbl_uvar Available for use by extensions
+ u PERL_MAGIC_uvar_elem (none) Reserved for use by extensions
+ V PERL_MAGIC_vstring (none) SV was vstring literal
v PERL_MAGIC_vec vtbl_vec vec() lvalue
- V PERL_MAGIC_vstring (none) v-string scalars
- w PERL_MAGIC_utf8 vtbl_utf8 UTF-8 length+offset cache
+ w PERL_MAGIC_utf8 vtbl_utf8 Cached UTF-8 information
x PERL_MAGIC_substr vtbl_substr substr() lvalue
y PERL_MAGIC_defelem vtbl_defelem Shadow "foreach" iterator
variable / smart parameter
vivification
- # PERL_MAGIC_arylen vtbl_arylen Array length ($#ary)
- . PERL_MAGIC_pos vtbl_pos pos() lvalue
- < PERL_MAGIC_backref vtbl_backref back pointer to a weak ref
+ ] PERL_MAGIC_checkcall (none) inlining/mutation of call to
+ this CV
~ PERL_MAGIC_ext (none) Available for use by extensions
- : PERL_MAGIC_symtab (none) hash used as symbol table
- % PERL_MAGIC_rhash (none) hash used as restricted hash
- @ PERL_MAGIC_arylen_p vtbl_arylen_p pointer to $#a from @a
When an uppercase and lowercase letter both exist in the table, then the
an C<SV> through the functions C<hv_store_ent>, C<hv_fetch_ent>,
C<hv_delete_ent>, and C<hv_exists_ent>. Accessing the key as a string
through the functions without the C<..._ent> suffix circumvents the
-hook. See L<Hash::Util::Fieldhash/Guts> for a detailed description.
+hook. See L<Hash::Util::FieldHash/GUTS> for a detailed description.
Note that because multiple extensions may be using C<PERL_MAGIC_ext>
or C<PERL_MAGIC_uvar> magic, it is important for extensions to take
extra care to avoid conflict. Typically only using the magic on
objects blessed into the same class as the extension is sufficient.
-For C<PERL_MAGIC_ext> magic, it may also be appropriate to add an I32
-'signature' at the top of the private data area and check that.
+For C<PERL_MAGIC_ext> magic, it is usually a good idea to define an
+C<MGVTBL>, even if all its fields will be C<0>, so that individual
+C<MAGIC> pointers can be identified as a particular kind of magic
+using their magic virtual table. C<mg_findext> provides an easy way
+to do that:
+
+ STATIC MGVTBL my_vtbl = { 0, 0, 0, 0, 0, 0, 0, 0 };
+
+ MAGIC *mg;
+ if ((mg = mg_findext(sv, PERL_MAGIC_ext, &my_vtbl))) {
+ /* this is really ours, not another module's PERL_MAGIC_ext */
+ my_priv_data_t *priv = (my_priv_data_t *)mg->mg_ptr;
+ ...
+ }
Also note that the C<sv_set*()> and C<sv_cat*()> functions described
earlier do B<not> invoke 'set' magic on their targets. This must
=head2 Finding Magic
- MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
+ MAGIC *mg_find(SV *sv, int type); /* Finds the magic pointer of that type */
+
+This routine returns a pointer to a C<MAGIC> structure stored in the SV.
+If the SV does not have that magical feature, C<NULL> is returned. If the
+SV has multiple instances of that magical feature, the first one will be
+returned. C<mg_findext> can be used to find a C<MAGIC> structure of an SV
+based on both it's magic type and it's magic virtual table:
+
+ MAGIC *mg_findext(SV *sv, int type, MGVTBL *vtbl);
-This routine returns a pointer to the C<MAGIC> structure stored in the SV.
-If the SV does not have that magical feature, C<NULL> is returned. Also,
-if the SV is not of type SVt_PVMG, Perl may core dump.
+Also, if the SV passed to C<mg_find> or C<mg_findext> is not of type
+SVt_PVMG, Perl may core dump.
int mg_copy(SV* sv, SV* nsv, const char* key, STRLEN klen);
PUSHs(sv_2mortal(newSVuv(an_unsigned_integer)))
PUSHs(sv_2mortal(newSVnv(a_double)))
PUSHs(sv_2mortal(newSVpv("Some String",0)))
+ /* Although the last example is better written as the more efficient: */
+ PUSHs(newSVpvs_flags("Some String", SVs_TEMP))
And now the Perl program calling C<tzname>, the two values will be assigned
as in:
=head2 Scratchpads
The question remains on when the SVs which are I<target>s for opcodes
-are created. The answer is that they are created when the current unit --
-a subroutine or a file (for opcodes for statements outside of
-subroutines) -- is compiled. During this time a special anonymous Perl
-array is created, which is called a scratchpad for the current
-unit.
+are created. The answer is that they are created when the current
+unit--a subroutine or a file (for opcodes for statements outside of
+subroutines)--is compiled. During this time a special anonymous Perl
+array is created, which is called a scratchpad for the current unit.
A scratchpad keeps SVs which are lexicals for the current unit and are
targets for opcodes. One can deduce that an SV lives on a scratchpad
After the compile tree for a subroutine (or for an C<eval> or a file)
is created, an additional pass over the code is performed. This pass
is neither top-down or bottom-up, but in the execution order (with
-additional complications for conditionals). These optimizations are
-done in the subroutine peep(). Optimizations performed at this stage
-are subject to the same restrictions as in the pass 2.
+additional complications for conditionals). Optimizations performed
+at this stage are subject to the same restrictions as in the pass 2.
+
+Peephole optimizations are done by calling the function pointed to
+by the global variable C<PL_peepp>. By default, C<PL_peepp> just
+calls the function pointed to by the global variable C<PL_rpeepp>.
+By default, that performs some basic op fixups and optimisations along
+the execution-order op chain, and recursively calls C<PL_rpeepp> for
+each side chain of ops (resulting from conditionals). Extensions may
+provide additional optimisations or fixups, hooking into either the
+per-subroutine or recursive stage, like this:
+
+ static peep_t prev_peepp;
+ static void my_peep(pTHX_ OP *o)
+ {
+ /* custom per-subroutine optimisation goes here */
+ prev_peepp(o);
+ /* custom per-subroutine optimisation may also go here */
+ }
+ BOOT:
+ prev_peepp = PL_peepp;
+ PL_peepp = my_peep;
+
+ static peep_t prev_rpeepp;
+ static void my_rpeep(pTHX_ OP *o)
+ {
+ OP *orig_o = o;
+ for(; o; o = o->op_next) {
+ /* custom per-op optimisation goes here */
+ }
+ prev_rpeepp(orig_o);
+ }
+ BOOT:
+ prev_rpeepp = PL_rpeepp;
+ PL_rpeepp = my_rpeep;
=head2 Pluggable runops
This function should be as efficient as possible to keep your programs
running as fast as possible.
+=head2 Compile-time scope hooks
+
+As of perl 5.14 it is possible to hook into the compile-time lexical
+scope mechanism using C<Perl_blockhook_register>. This is used like
+this:
+
+ STATIC void my_start_hook(pTHX_ int full);
+ STATIC BHK my_hooks;
+
+ BOOT:
+ BhkENTRY_set(&my_hooks, bhk_start, my_start_hook);
+ Perl_blockhook_register(aTHX_ &my_hooks);
+
+This will arrange to have C<my_start_hook> called at the start of
+compiling every lexical scope. The available hooks are:
+
+=over 4
+
+=item C<void bhk_start(pTHX_ int full)>
+
+This is called just after starting a new lexical scope. Note that Perl
+code like
+
+ if ($x) { ... }
+
+creates two scopes: the first starts at the C<(> and has C<full == 1>,
+the second starts at the C<{> and has C<full == 0>. Both end at the
+C<}>, so calls to C<start> and C<pre/post_end> will match. Anything
+pushed onto the save stack by this hook will be popped just before the
+scope ends (between the C<pre_> and C<post_end> hooks, in fact).
+
+=item C<void bhk_pre_end(pTHX_ OP **o)>
+
+This is called at the end of a lexical scope, just before unwinding the
+stack. I<o> is the root of the optree representing the scope; it is a
+double pointer so you can replace the OP if you need to.
+
+=item C<void bhk_post_end(pTHX_ OP **o)>
+
+This is called at the end of a lexical scope, just after unwinding the
+stack. I<o> is as above. Note that it is possible for calls to C<pre_>
+and C<post_end> to nest, if there is something on the save stack that
+calls string eval.
+
+=item C<void bhk_eval(pTHX_ OP *const o)>
+
+This is called just before starting to compile an C<eval STRING>, C<do
+FILE>, C<require> or C<use>, after the eval has been set up. I<o> is the
+OP that requested the eval, and will normally be an C<OP_ENTEREVAL>,
+C<OP_DOFILE> or C<OP_REQUIRE>.
+
+=back
+
+Once you have your hook functions, you need a C<BHK> structure to put
+them in. It's best to allocate it statically, since there is no way to
+free it once it's registered. The function pointers should be inserted
+into this structure using the C<BhkENTRY_set> macro, which will also set
+flags indicating which entries are valid. If you do need to allocate
+your C<BHK> dynamically for some reason, be sure to zero it before you
+start.
+
+Once registered, there is no mechanism to switch these hooks off, so if
+that is necessary you will need to do this yourself. An entry in C<%^H>
+is probably the best way, so the effect is lexically scoped; however it
+is also possible to use the C<BhkDISABLE> and C<BhkENABLE> macros to
+temporarily switch entries on and off. You should also be aware that
+generally speaking at least one scope will have opened before your
+extension is loaded, so you will see some C<pre/post_end> pairs that
+didn't have a matching C<start>.
+
=head1 Examining internal data structures with the C<dump> functions
To aid debugging, the source file F<dump.c> contains a number of
Similarly, all global variables begin with C<PL_>. (By convention,
static functions start with C<S_>.)
-Inside the Perl core, you can get at the functions either with or
-without the C<Perl_> prefix, thanks to a bunch of defines that live in
-F<embed.h>. This header file is generated automatically from
+Inside the Perl core (C<PERL_CORE> defined), you can get at the functions
+either with or without the C<Perl_> prefix, thanks to a bunch of defines
+that live in F<embed.h>. Note that extension code should I<not> set
+C<PERL_CORE>; this exposes the full perl internals, and is likely to cause
+breakage of the XS in each new perl release.
+
+The file F<embed.h> is generated automatically from
F<embed.pl> and F<embed.fnc>. F<embed.pl> also creates the prototyping
header files for the internal functions, generates the documentation
and a lot of other bits and pieces. It's important that when you add
This does not need a interpreter context, so the definition has no
C<pTHX>, and it follows that callers don't use C<aTHX>. (See
-L<perlguts/Background and PERL_IMPLICIT_CONTEXT>.)
+L</Background and PERL_IMPLICIT_CONTEXT>.)
=item r
You should also "register" your op with the Perl interpreter so that it
can produce sensible error and warning messages. Since it is possible to
have multiple custom ops within the one "logical" op type C<OP_CUSTOM>,
-Perl uses the value of C<< o->op_ppaddr >> as a key into the
-C<PL_custom_op_descs> and C<PL_custom_op_names> hashes. This means you
-need to enter a name and description for your op at the appropriate
-place in the C<PL_custom_op_names> and C<PL_custom_op_descs> hashes.
+Perl uses the value of C<< o->op_ppaddr >> to determine which custom op
+it is dealing with. You should create an C<XOP> structure for each
+ppaddr you use, set the properties of the custom op with
+C<XopENTRY_set>, and register the structure against the ppaddr using
+C<Perl_custom_op_register>. A trivial example might look like:
+
+ static XOP my_xop;
+ static OP *my_pp(pTHX);
+
+ BOOT:
+ XopENTRY_set(&my_xop, xop_name, "myxop");
+ XopENTRY_set(&my_xop, xop_desc, "Useless custom op");
+ Perl_custom_op_register(aTHX_ my_pp, &my_xop);
+
+The available fields in the structure are:
+
+=over 4
+
+=item xop_name
+
+A short name for your op. This will be included in some error messages,
+and will also be returned as C<< $op->name >> by the L<B|B> module, so
+it will appear in the output of module like L<B::Concise|B::Concise>.
+
+=item xop_desc
+
+A short description of the function of the op.
+
+=item xop_class
+
+Which of the various C<*OP> structures this op uses. This should be one of
+the C<OA_*> constants from F<op.h>, namely
+
+=over 4
+
+=item OA_BASEOP
+
+=item OA_UNOP
+
+=item OA_BINOP
+
+=item OA_LOGOP
+
+=item OA_LISTOP
+
+=item OA_PMOP
+
+=item OA_SVOP
+
+=item OA_PADOP
+
+=item OA_PVOP_OR_SVOP
+
+This should be interpreted as 'C<PVOP>' only. The C<_OR_SVOP> is because
+the only core C<PVOP>, C<OP_TRANS>, can sometimes be a C<SVOP> instead.
+
+=item OA_LOOP
+
+=item OA_COP
+
+=back
+
+The other C<OA_*> constants should not be used.
+
+=item xop_peep
+
+This member is of type C<Perl_cpeep_t>, which expands to C<void
+(*Perl_cpeep_t)(aTHX_ OP *o, OP *oldop)>. If it is set, this function
+will be called from C<Perl_rpeep> when ops of this type are encountered
+by the peephole optimizer. I<o> is the OP that needs optimizing;
+I<oldop> is the previous OP optimized, whose C<op_next> points to I<o>.
+
+=back
C<B::Generate> directly supports the creation of custom ops by name.
=head1 SEE ALSO
-perlapi(1), perlintern(1), perlxs(1), perlembed(1)
+L<perlapi>, L<perlintern>, L<perlxs>, L<perlembed>
https://perl5.git.perl.org / perl5.git / blobdiff