stop using &PL_sv_yes as no-op method

Method lookup yields a fake method for ->import or ->unimport if there's
no actual method, for historical reasons so that "use" doesn't barf
if there's no import method.  This fake method used to be &PL_sv_yes
being used as a magic placeholder, recognised specially by pp_entersub.
But &PL_sv_yes is a string, which we'd expect to serve as a symbolic
CV ref.  Change method lookup to yield an actual CV with a body in this
case, and remove the special case from pp_entersub.  This fixes the
remaining part of [perl #126042].

2 files changed, 10 insertions, 2 deletions

diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index 5ceb7fe939..891b7e71d4 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -2339,9 +2339,17 @@ CODE:
        only current internal behavior, these tests can be changed in the
        future if necessery */
     PUSHMARK(SP);
-    retcnt = call_sv(&PL_sv_yes, 0); /* does nothing */
+    retcnt = call_sv(&PL_sv_yes, G_EVAL);
     SPAGAIN;
     SP -= retcnt;
+    errsv = ERRSV;
+    errstr = SvPV(errsv, errlen);
+    if(memBEGINs(errstr, errlen, "Undefined subroutine &main::1 called at")) {
+        PUSHMARK(SP);
+        retcnt = call_sv((SV*)i_sub, 0); /* call again to increase counter */
+        SPAGAIN;
+        SP -= retcnt;
+    }
     PUSHMARK(SP);
     retcnt = call_sv(&PL_sv_no, G_EVAL);
     SPAGAIN;
diff --git a/ext/XS-APItest/t/call.t b/ext/XS-APItest/t/call.t
index 355e49886e..8192b9bd36 100644
--- a/ext/XS-APItest/t/call.t
+++ b/ext/XS-APItest/t/call.t
@@ -33,7 +33,7 @@ sub i {
     $call_sv_count++;
 }
 call_sv_C();
-is($call_sv_count, 6, "call_sv_C passes");
+is($call_sv_count, 7, "call_sv_C passes");
 
 sub d {
     die "its_dead_jim\n";