From: Gurusamy Sarathy <gsar@cpan.org>
Date: Fri, 28 Apr 2000 03:07:54 +0000 (+0000)
Subject: under useithreads, constant pad entries could inadvertently be
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=6a7129a1faa6d28064c474b8f21af7ca723db9bf;p=p5sagit%2Fp5-mst-13.2.git

under useithreads, constant pad entries could inadvertently be
shared across threads (from Eric Blood <eblood@xmission.com>);
added Eric's test case to testsuite

p4raw-id: //depot/perl@5979
---

diff --git a/op.c b/op.c
index 7ca60ae..681efae 100644
--- a/op.c
+++ b/op.c
@@ -6433,9 +6433,18 @@ Perl_peep(pTHX_ register OP *o)
 	     * for reference counts, sv_upgrade() etc. */
 	    if (cSVOP->op_sv) {
 		PADOFFSET ix = pad_alloc(OP_CONST, SVs_PADTMP);
-		SvREFCNT_dec(PL_curpad[ix]);
-		SvPADTMP_on(cSVOPo->op_sv);
-		PL_curpad[ix] = cSVOPo->op_sv;
+		if (SvPADTMP(cSVOPo->op_sv)) {
+		    /* If op_sv is already a PADTMP then it is being used by
+		     * another pad, so make a copy. */
+		    sv_setsv(PL_curpad[ix],cSVOPo->op_sv);
+		    SvREADONLY_on(PL_curpad[ix]);
+		    SvREFCNT_dec(cSVOPo->op_sv);
+		}
+		else {
+		    SvREFCNT_dec(PL_curpad[ix]);
+		    SvPADTMP_on(cSVOPo->op_sv);
+		    PL_curpad[ix] = cSVOPo->op_sv;
+		}
 		cSVOPo->op_sv = Nullsv;
 		o->op_targ = ix;
 	    }
diff --git a/t/op/misc.t b/t/op/misc.t
index ef3be30..55f459d 100755
--- a/t/op/misc.t
+++ b/t/op/misc.t
@@ -551,3 +551,10 @@ my $x = "foo";
 { f } continue { print $x, "\n" }
 EXPECT
 foo
+########
+sub C () { 1 }
+sub M { $_[0] = 2; }
+eval "C";
+M(C);
+EXPECT
+Modification of a read-only value attempted at - line 2.