[PATCH] crash in join OP if __get_string returns null

[Jens Rieks]

Hi,

make_COW_reference in src/string.c does not check for a NULL string.
Due to this, parrot crashes if the join OP is used and a PMC's __get_string 
method returns a null string.

A test case (patch against t/op/string.t) as well as a patch (against 
src/string.c) is attached to the message.

jens

Index: src/string.c
===================================================================
RCS file: /cvs/public/parrot/src/string.c,v
retrieving revision 1.191
diff -u -w -r1.191 string.c
--- src/string.c	15 Apr 2004 11:11:50 -0000	1.191
+++ src/string.c	16 Apr 2004 10:26:35 -0000
@@ -146,6 +146,9 @@
 make_COW_reference(struct Parrot_Interp *interpreter, STRING *s)
 {
     STRING *d;
+    if (s == NULL) {
+        return NULL;
+    }
     if (PObj_constant_TEST(s)) {
         PObj_constant_CLEAR(s);
         d = new_string_header(interpreter, PObj_get_FLAGS(s));
Index: t/op/string.t
===================================================================
RCS file: /cvs/public/parrot/t/op/string.t,v
retrieving revision 1.73
diff -u -w -r1.73 string.t
--- t/op/string.t	13 Apr 2004 14:18:33 -0000	1.73
+++ t/op/string.t	16 Apr 2004 10:26:39 -0000
@@ -16,7 +16,7 @@
 
 =cut
 
-use Parrot::Test tests => 131;
+use Parrot::Test tests => 132;
 use Test::More;
 
 output_is( <<'CODE', <<OUTPUT, "set_s_s|sc" );
@@ -2386,6 +2386,40 @@
 a--b
 OUTPUT
 
+output_is( <<'CODE', <<OUTPUT, "join: __get_string returns a null string");
+##PIR##
+.sub _main
+    newclass P0, "Foo"
+
+    new P0, .PerlArray
+
+    find_type I0, "Foo"
+    new P1, I0
+
+    push P0, P1
+
+    print "a"
+    join S0, "", P0
+    print "b"
+    print S0
+    print "c\n"
+    end
+.end
+
+.namespace ["Foo"]
+
+.sub __get_string method
+    .local string ret
+
+    null ret
+    .pcc_begin_return
+    .return ret
+    .pcc_end_return
+.end
+CODE
+abc
+OUTPUT
+
 output_is( <<'CODE', <<OUTPUT, "eq_addr/ne_addr");
         set S0, "Test"
         set S1, S0
@@ -2430,4 +2464,3 @@
 OUTPUT
 
 1;
-