Disable PL_sawampersand

PL_sawampersand actually causes bugs (e.g., perl #4289), because the
behaviour changes.  eval '$&' after a match will produce different
results depending on whether $& was seen before the match.

Using copy-on-write for the pre-match copy (preceding patches do that)
alleviates the slowdown caused by mentioning $&.  The copy doesn’t
happen unless the string is modified after the match.  It’s now a
post- match copy.  So we no longer need to do things differently
depending on whether $& has been seen.

PL_sawampersand is now #defined to be equal to what it would be if
every program began with $',$&,$`.

I left the PL_sawampersand code in place, in case this commit proves
immature.  Running Configure with -Accflags=PERL_SAWAMPERSAND will
reënable the PL_sawampersand mechanism.

1 files changed, 4 insertions, 0 deletions

diff --git a/makedef.pl b/makedef.pl
index 7afc35ff04..0593342462 100644
--- a/makedef.pl
+++ b/makedef.pl
@@ -279,6 +279,10 @@ unless ($define{'PERL_OLD_COPY_ON_WRITE'}
     ++$skip{Perl_sv_setsv_cow};
 }
 
+unless ($define{PERL_SAW_AMPERSAND}) {
+    ++$skip{PL_sawampersand};
+}
+
 unless ($define{'USE_REENTRANT_API'}) {
     ++$skip{PL_reentrant_buffer};
 }