In the C<SvPV> macro, the length of the string returned is placed into the
variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
-care what the length of the data is, use the global variable C<PL_na>. Remember,
+care what the length of the data is, use the global variable C<PL_na>, though
+this is rather less efficient than using a local variable. Remember,
however, that Perl allows arbitrary strings of data that may both contain
NULs and might not be terminated by a NUL.
I<pseudo-block>, and arrange for some changes to be automatically
undone at the end of it, either explicit, or via a non-local exit (via
die()). A I<block>-like construct is created by a pair of
-C<ENTER>/C<LEAVE> macros (see L<perlcall/EXAMPLE/"Returning a
-Scalar">). Such a construct may be created specially for some
-important localized task, or an existing one (like boundaries of
-enclosing Perl subroutine/block, or an existing pair for freeing TMPs)
-may be used. (In the second case the overhead of additional
-localization must be almost negligible.) Note that any XSUB is
-automatically enclosed in an C<ENTER>/C<LEAVE> pair.
+C<ENTER>/C<LEAVE> macros (see L<perlcall/"Returning a Scalar">).
+Such a construct may be created specially for some important localized
+task, or an existing one (like boundaries of enclosing Perl
+subroutine/block, or an existing pair for freeing TMPs) may be
+used. (In the second case the overhead of additional localization must
+be almost negligible.) Note that any XSUB is automatically enclosed in
+an C<ENTER>/C<LEAVE> pair.
Inside such a I<pseudo-block> the following service is available:
with C<perl> be referenced with an explicit C<Perl_> prefix.
The sort order of the listing is case insensitive, with any
-occurrences of '_' ignored for the the purpose of sorting.
+occurrences of '_' ignored for the purpose of sorting.
=over 8
variable which corresponds to Perl's $DB::sub variable. See C<PL_DBsingle>.
The sub name can be found by
- SvPV( GvSV( PL_DBsub ), PL_na )
+ SvPV( GvSV( PL_DBsub ), len )
=item PL_DBtrace
necessary dereferencing of possibly C<SV*> keys. The length of
the string is placed in C<len> (this is a macro, so do I<not> use
C<&len>). If you do not care about what the length of the key is,
-you may use the global variable C<PL_na>. Remember though, that hash
+you may use the global variable C<PL_na>, though this is rather less
+efficient than using a local variable. Remember though, that hash
keys in perl are free to contain embedded nulls, so using C<strlen()>
or similar is not a good way to find the length of hash keys.
This is very similar to the C<SvPV()> macro described elsewhere in
int mg_set (SV* sv)
+=item modglobal
+
+C<modglobal> is a general purpose, interpreter global HV for use by
+extensions. While it could hold extension specific information, it is
+meant primarily for information that needs to be shared between
+extensions. Moreover, while it could be used for any kind of
+information, it is meant for information that should be not accessible
+in the usual way from the perl symbol table.
+
=item Move
The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
=item PL_na
-A variable which may be used with C<SvPV> to tell Perl to calculate the
-string length.
+A convenience variable which is typically used with C<SvPV> when one doesn't
+care about the length of the string. It is usually more efficient to
+declare a local variable and use that instead.
=item New
=item SvPV
Returns a pointer to the string in the SV, or a stringified form of the SV
-if the SV does not contain a string. If C<len> is C<PL_na> then Perl will
-handle the length on its own. Handles 'get' magic.
+if the SV does not contain a string. Handles 'get' magic.
char* SvPV (SV* sv, int len )
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