Fix Encode 2.60 with g++

The recently added Encode 2.60 won't compile with g++, due to assigning
a const char * const pointer to a char* struct field.

The intent of the code itself is a bit unclear, but it appears to be
to set SvPVX as a read-only alias of a const string, using the SvLEN()=0
trick to avoid it being freed.

Fix the g++ builds by casting away the constness, and add some asserts and
comments to make it less unclear what's going on.

1 files changed, 4 insertions, 1 deletions

diff --git a/cpan/Encode/Encode.xs b/cpan/Encode/Encode.xs
index 18c982ac47..e08101add5 100644
--- a/cpan/Encode/Encode.xs
+++ b/cpan/Encode/Encode.xs
@@ -47,8 +47,11 @@ Encode_XSEncoding(pTHX_ encode_t * enc)
     SV *iv    = newSViv(PTR2IV(enc));
     SV *sv    = sv_bless(newRV_noinc(iv),stash);
     int i = 0;
+    /* with the SvLEN() == 0 hack, PVX won't be freed. We cast away name's
+    constness, in the hope that perl won't mess with it. */
+    assert(SvTYPE(iv) >= SVt_PV); assert(SvLEN(iv) == 0);
     SvFLAGS(iv) |= SVp_POK;
-    SvPVX(iv) = enc->name[0];
+    SvPVX(iv) = (char*) enc->name[0];
     PUSHMARK(sp);
     XPUSHs(sv);
     while (enc->name[i]) {