Add a macro MUTABLE_PTR(p), which on (non-pedantic) gcc will not cast

away const, returning a void *. Add MUTABLE_SV(sv) which uses this, and
replace all (SV *) casts either with MUTABLE_SV(sv), or (const SV *).

This probably still needs some work - assigning to SvPVX() and SvRV()
is now likely to generate a casting error. The core doesn't do this.
But as-is it's finding bugs that can be fixed.

p4raw-id: //depot/perl@34605

1 files changed, 7 insertions, 0 deletions

diff --git a/handy.h b/handy.h
index d51b75dc81..d6a9026740 100644
--- a/handy.h
+++ b/handy.h
@@ -48,6 +48,13 @@ Null SV pointer. (No longer available when C<PERL_CORE> is defined.)
 #define TRUE (1)
 #define FALSE (0)
 
+#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
+#  define MUTABLE_PTR(p) ({ void *_p = (p); (void *) _p; })
+#else
+#  define MUTABLE_PTR(p) ((void *) (p))
+#endif
+
+#define MUTABLE_SV(p)	((SV *)MUTABLE_PTR(p))
 
 /* XXX Configure ought to have a test for a boolean type, if I can
    just figure out all the headers such a test needs.