From @arc

When S_opmethod_stash() determines that the LHS is an unblessed reference, it generates an error message containing the method name. However, it was calling SvPVX() on the method name without ensuring that it's SvPOK(). The fix is straightforward, and is now in blead; see below.

That said, I'm wondering whether we should special-case undefined method names, so as to produce better error messages. If we want to do that before 5.26, we've got about two weeks left before the "user-visible changes" freeze.

commit 323dbd0
Author: Aaron Crane <arc@cpan.org>
Date: Wed Jan 4 20:02:45 2017 +0000

RT#130496: assertion failure for '{}->$x' on undefined $x

Inline Patch

diff --git a/pp_hot.c b/pp_hot.c
index dd2c611e1f..97d46f6511 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -4465,7 +4465,7 @@ S_opmethod_stash(pTHX_ SV* meth)
                     && SvOBJECT(ob))))
     {
        Perl_croak(aTHX_ "Can't call method \"%" SVf "\" on unblessed reference",
-                  SVfARG((SvPVX(meth) == PL_isa_DOES)
+                  SVfARG((SvPOK(meth) && SvPVX(meth) == PL_isa_DOES)
                                         ? newSVpvs_flags("DOES", SVs_TEMP)
                                         : meth));
     }
diff --git a/t/op/method.t b/t/op/method.t
index 8795734ae4..ef181c4ce0 100644
--- a/t/op/method.t
+++ b/t/op/method.t
@@ -13,7 +13,7 @@ BEGIN {
 use strict;
 no warnings 'once';

-plan(tests => 150);
+plan(tests => 151);

 @A::ISA = 'B';
 @B::ISA = 'C';
@@ -704,6 +704,13 @@ SKIP: {
                   "check unknown import() methods don't corrupt the stack");
 }

+# RT#130496: assertion failure when looking for a method of undefined name
+# on an unblessed reference
+fresh_perl_is('eval { {}->$x }; print $@;',
+              "Can't call method \"\" on unblessed reference at - line 1.",
+              {},
+              "no crash with undef method name on unblessed ref");
+
 __END__
 #FF9900
 #F78C08

--

Aaron Crane ** http://aaroncrane.co.uk/

pp_hot.c:4468: HV *S_opmethod_stash(SV *) Assertion Failed. #15791

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pp_hot.c:4468: HV S_opmethod_stash(SV ) Assertion Failed. #15791