len);>. It might work with your compiler, but it won't work for everyone.
Break this sort of statement up into separate assignments:
- SV *s;
- STRLEN len;
- char * ptr;
- ptr = SvPV(s, len);
- foo(ptr, len);
+ SV *s;
+ STRLEN len;
+ char * ptr;
+ ptr = SvPV(s, len);
+ foo(ptr, len);
If you want to know if the scalar value is TRUE, you can use:
For example, a tied SV may have a valid underlying value in the IV slot
(so SvIOKp is true), but the data should be accessed via the FETCH
routine rather than directly, so SvIOK is false. Another is when
-numeric conversion has occured and precision has been lost: only the
+numeric conversion has occurred and precision has been lost: only the
private flag is set on 'lossy' values. So when an NV is converted to an
IV with loss, SvIOKp, SvNOKp and SvNOK will be set, while SvIOK wont be.
"Magic Virtual Table" to handle the various operations that might be
applied to that variable.
-The C<MGVTBL> has five pointers to the following routine types:
+The C<MGVTBL> has five (or sometimes eight) pointers to the following
+routine types:
int (*svt_get)(SV* sv, MAGIC* mg);
int (*svt_set)(SV* sv, MAGIC* mg);
int (*svt_clear)(SV* sv, MAGIC* mg);
int (*svt_free)(SV* sv, MAGIC* mg);
+ int (*svt_copy)(SV *sv, MAGIC* mg, SV *nsv, const char *name, int namlen);
+ int (*svt_dup)(MAGIC *mg, CLONE_PARAMS *param);
+ int (*svt_local)(SV *nsv, MAGIC *mg);
+
+
This MGVTBL structure is set at compile-time in F<perl.h> and there are
currently 19 types (or 21 with overloading turned on). These different
structures contain pointers to various routines that perform additional
svt_clear Clear something the SV represents.
svt_free Free any extra storage associated with the SV.
+ svt_copy copy tied variable magic to a tied element
+ svt_dup duplicate a magic structure during thread cloning
+ svt_local copy magic to local value during 'local'
+
For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
to an C<mg_type> of C<PERL_MAGIC_sv>) contains:
with C<magic_>. NOTE: the magic routines are not considered part of
the Perl API, and may not be exported by the Perl library.
+The last three slots are a recent addition, and for source code
+compatibility they are only checked for if one of the three flags
+MGf_COPY, MGf_DUP or MGf_LOCAL is set in mg_flags. This means that most
+code can continue declaring a vtable as a 5-element value. These three are
+currently used exclusively by the threading code, and are highly subject
+to change.
+
The current kinds of Magic Virtual Tables are:
mg_type
y PERL_MAGIC_defelem vtbl_defelem Shadow "foreach" iterator
variable / smart parameter
vivification
- * PERL_MAGIC_glob vtbl_glob GV (typeglob)
# 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
=item A
-This function is a part of the public API.
+This function is a part of the public API. All such functions should also
+have 'd', very few do not.
=item p
-This function has a C<Perl_> prefix; ie, it is defined as C<Perl_av_fetch>
+This function has a C<Perl_> prefix; i.e. it is defined as
+C<Perl_av_fetch>.
=item d
This function has documentation using the C<apidoc> feature which we'll
-look at in a second.
+look at in a second. Some functions have 'd' but not 'A'; docs are good.
=back
=item s
-This is a static function and is defined as C<S_whatever>, and usually
-called within the sources as C<whatever(...)>.
+This is a static function and is defined as C<STATIC S_whatever>, and
+usually called within the sources as C<whatever(...)>.
=item n
-This does not use C<aTHX_> and C<pTHX> to pass interpreter context. (See
+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>.)
=item r
Binary backward compatibility; this function is a macro but also has
a C<Perl_> implementation (which is exported).
+=item others
+
+See the comments at the top of C<embed.fnc> for others.
+
=back
If you edit F<embed.pl> or F<embed.fnc>, you will need to run
You can use these macros if you call code that may croak, but you need
to do some cleanup before giving control back to Perl. For example:
- dXCPT; /* set up neccessary variables */
+ dXCPT; /* set up necessary variables */
XCPT_TRY_START {
code_that_may_croak();
interpreters for other languages in the Perl core, but it also allows
optimizations through the creation of "macro-ops" (ops which perform the
functions of multiple ops which are usually executed together, such as
-C<gvsv, gvsv, add>.)
+C<gvsv, gvsv, add>.)
This feature is implemented as a new op type, C<OP_CUSTOM>. The Perl
core does not "know" anything special about this op type, and so it will
place in the C<PL_custom_op_names> and C<PL_custom_op_descs> hashes.
Forthcoming versions of C<B::Generate> (version 1.0 and above) should
-directly support the creation of custom ops by name; C<Opcodes::Custom>
-will provide functions which make it trivial to "register" custom ops to
-the Perl interpreter.
+directly support the creation of custom ops by name.
=head1 AUTHORS