[PATCH] Fix a NULL pointer dereference when looking for a DESTROY method

[Niko Tyni]

The empty DESTROY method optimization introduced by commit
fbb3ee5af3d would crash the interpreter if a DESTROY method
was declared but not actually defined.

This is seen in the real world with AutoLoader / AutoSplit,
where the crash defeats autoloading a DESTROY method.
---
 sv.c          |    3 ++-
 t/op/method.t |   11 ++++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/sv.c b/sv.c
index fb82caf..ed4be5f 100644
--- a/sv.c
+++ b/sv.c
@@ -5658,7 +5658,8 @@ Perl_sv_clear(pTHX_ register SV *const sv)
 			&& !CvCONST(destructor)
 			/* Don't bother calling an empty destructor */
 			&& (CvISXSUB(destructor)
-			|| CvSTART(destructor)->op_next->op_type != OP_LEAVESUB))
+			|| (CvSTART(destructor)
+			    && (CvSTART(destructor)->op_next->op_type != OP_LEAVESUB))))
 		{
 		    SV* const tmpref = newRV(sv);
 	            SvREADONLY_on(tmpref);   /* DESTROY() could be naughty */
diff --git a/t/op/method.t b/t/op/method.t
index afa8cfb..d2914c4 100644
--- a/t/op/method.t
+++ b/t/op/method.t
@@ -10,7 +10,7 @@ BEGIN {
     require "test.pl";
 }
 
-print "1..78\n";
+print "1..79\n";
 
 @A::ISA = 'B';
 @B::ISA = 'C';
@@ -292,3 +292,12 @@ EOT
 	"check if UNIVERSAL::AUTOLOAD works",
     );
 }
+{
+    fresh_perl_is(<<'EOT',
+sub M::DESTROY; bless {}, "M" ; print "survived\n";
+EOT
+    "survived",
+    {},
+	"no crash with a declared but missing DESTROY method"
+    );
+}
-- 
1.6.6


--IS0zKkzwUGydFO0o--