SVf_IsCOW

As discussed in ticket #114820, instead of using READONLY+FAKE to mark
a copy-on-write string, we should make it a separate flag.

There are many modules in CPAN (and 1 in core, Compress::Raw::Zlib)
that assume that SvREADONLY means read-only.  Only one CPAN module,
POSIX::pselect will definitely be broken by this.  Others may need to
be tweaked.  But I believe this is for the better.

It causes all tests except ext/Devel-Peek/t/Peek.t (which needs a tiny
tweak still) to pass under PERL_OLD_COPY_ON_WRITE, which is a prereq-
uisite for any new COW scheme that creates COWs under the same cir-
cumstances.

1 files changed, 3 insertions, 5 deletions

diff --git a/pp.c b/pp.c
index 6088a11394..52f5d39d87 100644
--- a/pp.c
+++ b/pp.c
@@ -772,13 +772,11 @@ S_do_chomp(pTHX_ SV *retval, SV *sv, bool chomping)
 	return;
     }
     else if (SvREADONLY(sv)) {
-        if (SvFAKE(sv)) {
-            /* SV is copy-on-write */
-	    sv_force_normal_flags(sv, 0);
-        }
-        else
             Perl_croak_no_modify();
     }
+    else if (SvIsCOW(sv)) {
+	sv_force_normal_flags(sv, 0);
+    }
 
     if (PL_encoding) {
 	if (!SvUTF8(sv)) {