Add PERL_REENTRANT for XS modules

This allows them to get the reentrant versions of libc functions
automatically.  Previously if they wanted to do this, they had to
declare themselves (shudder) as PERL_CORE or PERL_EXT.

1 files changed, 12 insertions, 5 deletions

diff --git a/dist/ExtUtils-ParseXS/lib/perlxs.pod b/dist/ExtUtils-ParseXS/lib/perlxs.pod
index e887d33ca7..6b21d966a9 100644
--- a/dist/ExtUtils-ParseXS/lib/perlxs.pod
+++ b/dist/ExtUtils-ParseXS/lib/perlxs.pod
@@ -2051,11 +2051,18 @@ you need to do is to instantiate a Perl interpreter.
 
 This wrapping happens always when compiling Perl core source
 (PERL_CORE is defined) or the Perl core extensions (PERL_EXT is
-defined).  When compiling XS code outside of Perl core the wrapping
-does not take place.  Note, however, that intermixing the _r-forms
-(as Perl compiled for multithreaded operation will do) and the _r-less
-forms is neither well-defined (inconsistent results, data corruption,
-or even crashes become more likely), nor is it very portable.
+defined).  When compiling XS code outside of the Perl core, the wrapping
+does not take place before Perl 5.28.  Starting in that release you can
+
+ #define PERL_REENTRANT
+
+in your code to enable the wrapping.  It is advisable to do so if you
+are using such functions, as intermixing the C<_r>-forms (as Perl compiled
+for multithreaded operation will do) and the C<_r>-less forms is neither
+well-defined (inconsistent results, data corruption, or even crashes
+become more likely), nor is it very portable.  Unfortunately, not all
+systems have all the C<_r> forms, but using this C<#define> gives you
+whatever protection that Perl is aware is available on each system.
 
 =head1 EXAMPLES