From c6fb3f6e3e5160581b78d87d4c62f42ef3cc0db5 Mon Sep 17 00:00:00 2001
From: Father Chrysostomos <sprout@cpan.org>
Date: Tue, 17 Jan 2012 18:22:16 -0800
Subject: [PATCH] =?UTF-8?q?[perl=20#106726]=20Don=E2=80=99t=20crash=20on?=
 =?UTF-8?q?=20length(@arr)=20warning?=
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The RT ticket blames this on 676a678ac, but it was actually commit
579333ee9e3.  676a678ac extended this problem to evals (and modules),
but it already occurred in the main program.

This crashes:

    ./miniperl -Ilib -we 'sub {length my @forecasts}'

because it is trying to find the variable name for the warning in the
CV returned by find_runcv, but this is a *compile-time* warning, so
using find_runcv is just wrong.

It ends up looking for the array in PL_main_cv’s pad, instead of
PL_compcv.
---
 op.c          | 3 ++-
 sv.c          | 6 ++++--
 t/op/length.t | 9 ++++++++-
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/op.c b/op.c
index 12f0cbc95107..a1f5d25cd428 100644
--- a/op.c
+++ b/op.c
@@ -9720,7 +9720,8 @@ Perl_ck_length(pTHX_ OP *o)
                 case OP_PADHV:
                 case OP_PADAV:
                     name = varname(
-                        NULL, hash ? '%' : '@', kid->op_targ, NULL, 0, 1
+                        (GV *)PL_compcv, hash ? '%' : '@', kid->op_targ,
+                        NULL, 0, 1
                     );
                     break;
                 case OP_RV2HV:
diff --git a/sv.c b/sv.c
index dff16078b4f7..d116996e77b1 100644
--- a/sv.c
+++ b/sv.c
@@ -13859,7 +13859,7 @@ Perl_varname(pTHX_ const GV *const gv, const char gvtype, PADOFFSET targ,
 {
 
     SV * const name = sv_newmortal();
-    if (gv) {
+    if (gv && isGV(gv)) {
 	char buffer[2];
 	buffer[0] = gvtype;
 	buffer[1] = 0;
@@ -13878,10 +13878,12 @@ Perl_varname(pTHX_ const GV *const gv, const char gvtype, PADOFFSET targ,
 	}
     }
     else {
-	CV * const cv = find_runcv(NULL);
+	CV * const cv = gv ? (CV *)gv : find_runcv(NULL);
 	SV *sv;
 	AV *av;
 
+	assert(!cv || SvTYPE(cv) == SVt_PVCV);
+
 	if (!cv || !CvPADLIST(cv))
 	    return NULL;
 	av = MUTABLE_AV((*av_fetch(CvPADLIST(cv), 0, FALSE)));
diff --git a/t/op/length.t b/t/op/length.t
index 0288bec57f38..55260d32b830 100644
--- a/t/op/length.t
+++ b/t/op/length.t
@@ -6,7 +6,7 @@ BEGIN {
     @INC = '../lib';
 }
 
-plan (tests => 37);
+plan (tests => 38);
 
 print "not " unless length("")    == 0;
 print "ok 1\n";
@@ -224,4 +224,11 @@ is($ul, undef, "Assigned length of overloaded undef with result in TARG");
     print length undef;
 }
 
+{
+    local $SIG{__WARN__} = sub {
+	pass '[perl #106726] no crash with length @lexical warning'
+    };
+    eval ' sub { length my @forecasts } ';
+}
+
 is($warnings, 0, "There were no other warnings");