[perl #119169] index with __PACKAGE__ for 2nd argument

The refactoring of fbm_compile in 66379c06cd to prepare for
c72a4eedff1 put in an SvIsCOW check before doing SvPV_force.  I sim-
ply changed the logic there so that SvPV_force would continue to have
its effect but without tripping up on read-only variables for which
SvPV_force would not need to make any changes anyway.

Now, if a COW scalar is read-only, we can’t call SvPV_force on it,
because it will die.

It turns out that we don’t actually need to call SvPV_force on COWs.
We can just go ahead and attach the BM magic and continue sharing
the buffer.

2 files changed, 5 insertions, 2 deletions

diff --git a/t/op/index.t b/t/op/index.t
index d53405383e..eaed4b3d65 100644
--- a/t/op/index.t
+++ b/t/op/index.t
@@ -7,7 +7,7 @@ BEGIN {
 }
 
 use strict;
-plan( tests => 120 );
+plan( tests => 121 );
 
 run_tests() unless caller;
 
@@ -248,4 +248,7 @@ use constant u => undef;
 }
 is u, undef, 'undef constant is still undef';
 
+is index('the main road', __PACKAGE__), 4,
+    '[perl #119169] __PACKAGE__ as 2nd argument';
+
 } # end of sub run_tests
diff --git a/util.c b/util.c
index be75796eda..316f45d5fe 100644
--- a/util.c
+++ b/util.c
@@ -539,7 +539,7 @@ Perl_fbm_compile(pTHX_ SV *sv, U32 flags)
 	if (mg && mg->mg_len >= 0)
 	    mg->mg_len++;
     }
-    if (!SvPOK(sv) || SvNIOKp(sv) || SvIsCOW(sv))
+    if (!SvPOK(sv) || SvNIOKp(sv))
 	s = (U8*)SvPV_force_mutable(sv, len);
     else s = (U8 *)SvPV_mutable(sv, len);
     if (len == 0)		/* TAIL might be on a zero-length string. */