formline() could wipe out readonly-ness, freeing constants

prematurely, or affect cloning of pad constants

p4raw-id: //depot/perl@5056

2 files changed, 21 insertions, 5 deletions

diff --git a/pp_ctl.c b/pp_ctl.c
index 972c21d30c..7b4cbfea49 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -302,8 +302,13 @@ PP(pp_formline)
     bool item_is_utf = FALSE;
 
     if (!SvMAGICAL(tmpForm) || !SvCOMPILED(tmpForm)) {
-	SvREADONLY_off(tmpForm);
-	doparseform(tmpForm);
+	if (SvREADONLY(tmpForm)) {
+	    SvREADONLY_off(tmpForm);
+	    doparseform(tmpForm);
+	    SvREADONLY_on(tmpForm);
+	}
+	else
+	    doparseform(tmpForm);
     }
 
     SvPV_force(PL_formtarget, len);
diff --git a/t/op/write.t b/t/op/write.t
index 9918b2f57f..87d50429f4 100755
--- a/t/op/write.t
+++ b/t/op/write.t
@@ -1,8 +1,6 @@
 #!./perl
 
-# $RCSfile: write.t,v $$Revision: 4.1 $$Date: 92/08/07 18:28:38 $
-
-print "1..6\n";
+print "1..8\n";
 
 my $CAT = ($^O eq 'MSWin32') ? 'type' : 'cat';
 
@@ -190,3 +188,16 @@ if (`$CAT Op_write.tmp` eq $right)
 else
     { print "not ok 6\n"; }
 
+# test lexicals and globals
+{
+    my $this = "ok";
+    our $that = 7;
+    format LEX =
+@<<@|
+$this,$that
+.
+    open(LEX, ">&STDOUT") or die;
+    write LEX;
+    $that = 8;
+    write LEX;
+}