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.

11 files changed, 41 insertions, 11 deletions

diff --git a/cpan/Encode/Byte/Makefile.PL b/cpan/Encode/Byte/Makefile.PL
index 58deaf39a6..0cc5ece4fb 100644
--- a/cpan/Encode/Byte/Makefile.PL
+++ b/cpan/Encode/Byte/Makefile.PL
@@ -120,8 +120,11 @@ 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])
diff --git a/cpan/Encode/CN/Makefile.PL b/cpan/Encode/CN/Makefile.PL
index efd2edb90f..5e689cb75b 100644
--- a/cpan/Encode/CN/Makefile.PL
+++ b/cpan/Encode/CN/Makefile.PL
@@ -96,8 +96,11 @@ 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])
diff --git a/cpan/Encode/EBCDIC/Makefile.PL b/cpan/Encode/EBCDIC/Makefile.PL
index 7a3a4cb89c..50ae0df257 100644
--- a/cpan/Encode/EBCDIC/Makefile.PL
+++ b/cpan/Encode/EBCDIC/Makefile.PL
@@ -77,8 +77,11 @@ 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])
diff --git a/cpan/Encode/Encode.pm b/cpan/Encode/Encode.pm
index 9dc970b299..5d477f6bde 100644
--- a/cpan/Encode/Encode.pm
+++ b/cpan/Encode/Encode.pm
@@ -4,7 +4,7 @@
 package Encode;
 use strict;
 use warnings;
-our $VERSION = sprintf "%d.%02d", q$Revision: 2.60 $ =~ /(\d+)/g;
+our $VERSION = sprintf "%d.%02d", q$Revision: 2.60_01 $ =~ /(\d+)/g;
 use constant DEBUG => !!$ENV{PERL_ENCODE_DEBUG};
 use XSLoader ();
 XSLoader::load( __PACKAGE__, $VERSION );
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]) {
diff --git a/cpan/Encode/Encode/Makefile_PL.e2x b/cpan/Encode/Encode/Makefile_PL.e2x
index b78656769d..c17a5096f7 100644
--- a/cpan/Encode/Encode/Makefile_PL.e2x
+++ b/cpan/Encode/Encode/Makefile_PL.e2x
@@ -113,8 +113,11 @@ 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])
diff --git a/cpan/Encode/JP/Makefile.PL b/cpan/Encode/JP/Makefile.PL
index cb671b60d4..6ec73eac35 100644
--- a/cpan/Encode/JP/Makefile.PL
+++ b/cpan/Encode/JP/Makefile.PL
@@ -96,8 +96,11 @@ 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])
diff --git a/cpan/Encode/KR/Makefile.PL b/cpan/Encode/KR/Makefile.PL
index fa6f0d8042..0790ed08b4 100644
--- a/cpan/Encode/KR/Makefile.PL
+++ b/cpan/Encode/KR/Makefile.PL
@@ -94,8 +94,11 @@ 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])
diff --git a/cpan/Encode/Symbol/Makefile.PL b/cpan/Encode/Symbol/Makefile.PL
index b525610369..2dec60d53f 100644
--- a/cpan/Encode/Symbol/Makefile.PL
+++ b/cpan/Encode/Symbol/Makefile.PL
@@ -82,8 +82,11 @@ 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])
diff --git a/cpan/Encode/TW/Makefile.PL b/cpan/Encode/TW/Makefile.PL
index c7711d9655..69b3e96242 100644
--- a/cpan/Encode/TW/Makefile.PL
+++ b/cpan/Encode/TW/Makefile.PL
@@ -92,8 +92,11 @@ 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])
diff --git a/cpan/Encode/bin/enc2xs b/cpan/Encode/bin/enc2xs
index 966c456765..c44487d0c2 100644
--- a/cpan/Encode/bin/enc2xs
+++ b/cpan/Encode/bin/enc2xs
@@ -316,8 +316,11 @@ 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])