Better version of change #19069

Subject: [PATCH] Re: [PATCH] Re: [perl #21614] 5.8.0 Unbalanced string table refcount
Message-ID: <20030326230145.GC279@Bagpuss.unfortu.net>
p4raw-link: @19069 on //depot/perl: 10bcdfd6e8d70ea5a2c02616001cf97fce7f3e17

p4raw-id: //depot/perl@19071

3 files changed, 36 insertions, 11 deletions

diff --git a/pp_hot.c b/pp_hot.c
index 15ba94c041..a622c53548 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1509,7 +1509,7 @@ Perl_do_readline(pTHX)
 	    sv_unref(sv);
 	(void)SvUPGRADE(sv, SVt_PV);
 	tmplen = SvLEN(sv);	/* remember if already alloced */
-	if (!tmplen)
+	if (!tmplen && !SvREADONLY(sv))
 	    Sv_Grow(sv, 80);	/* try short-buffering it */
 	offset = 0;
 	if (type == OP_RCATLINE && SvOK(sv)) {
diff --git a/sv.c b/sv.c
index a1b44cf8e1..1fdd0c2e33 100644
--- a/sv.c
+++ b/sv.c
@@ -1585,15 +1585,8 @@ Perl_sv_grow(pTHX_ register SV *sv, register STRLEN newlen)
 	    newlen = 0xFFFF;
 #endif
     }
-    else {
-	/* This is annoying, because sv_force_normal_flags will fix the flags,
-	   recurse into sv_grow to malloc a buffer of SvCUR(sv) + 1, then
-	   return back to us, only for us to potentially realloc the buffer.
-	*/
-	if (SvIsCOW(sv))
-	    sv_force_normal_flags(sv, 0);
+    else
 	s = SvPVX(sv);
-    }
 
     if (newlen > SvLEN(sv)) {		/* need more room? */
 	if (SvLEN(sv) && s) {
@@ -6296,7 +6289,8 @@ Perl_sv_gets(pTHX_ register SV *sv, register PerlIO *fp, I32 append)
     I32 rspara = 0;
     I32 recsize;
 
-    SV_CHECK_THINKFIRST_COW_DROP(sv);
+    if (SvTHINKFIRST(sv))
+	sv_force_normal_flags(sv, append ? 0 : SV_COW_DROP_PV);
     /* XXX. If you make this PVIV, then copy on write can copy scalars read
        from <>.
        However, perlbench says it's slower, because the existing swipe code
diff --git a/t/op/readline.t b/t/op/readline.t
index 8936022b2e..d127d583a5 100644
--- a/t/op/readline.t
+++ b/t/op/readline.t
@@ -6,7 +6,7 @@ BEGIN {
     require './test.pl';
 }
 
-plan tests => 5;
+plan tests => 11;
 
 eval { for (\2) { $_ = <FH> } };
 like($@, 'Modification of a read-only value attempted', '[perl #19566]');
@@ -27,3 +27,34 @@ foreach my $k ('k', 'k'x82) {
 	      );
   is ($result, "end", '[perl #21614] for length ' . length $k);
 }
+
+
+foreach my $k ('perl', 'perl'x21) {
+  my $result
+    = runperl (switches => '-l', stdin => ' rules', stderr => 1,
+	       prog => "%a = qw($k v); foreach (keys %a) {\$_ .= <>; print}",
+	      );
+  is ($result, "$k rules", 'rcatline to shared sv for length ' . length $k);
+}
+
+foreach my $l (1, 82) {
+  my $k = $l;
+  $k = 'k' x $k;
+  my $copy = $k;
+  $k = <DATA>;
+  is ($k, "moo\n", 'catline to COW sv for length ' . length $copy);
+}
+
+
+foreach my $l (1, 21) {
+  my $k = $l;
+  $k = 'perl' x $k;
+  my $perl = $k;
+  $k .= <DATA>;
+  is ($k, "$perl rules\n", 'rcatline to COW sv for length ' . length $perl);
+}
+__DATA__
+moo
+moo
+ rules
+ rules