string eval turns off readonlyness on lexicals #6160
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From @nwc10Created by @nwc10Without ithreads, a lexical stays readonly when it is referenced inside $ perl5.8.0-32 -MDevel::Peek -wle 'my $k = "!"; Internals::SvREADONLY $k, 1; Dump $k; eval "print \$k"; Dump $k' With ithreads it loses its readonlyness: perl5.8.0-32-i -MDevel::Peek -wle 'my $k = "!"; Inter This is still true in blead. It seems wrong. (It's also the source of a I think it's the code at the line /* could be a freed constant */ in Perl Info |
From @schwernConfirmed to still exist in 5.8.6 and blead. |
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The RT System itself - Status changed from 'new' to 'open' |
From @chornySame result on 5.12.0 with ithreads. On Sat Dec 14 11:15:57 2002, nicholas wrote:
-- |
From [Unknown Contact. See original ticket]Same result on 5.12.0 with ithreads. On Sat Dec 14 11:15:57 2002, nicholas wrote:
-- |
From @cpansproutThe readonliness is turned off explicitly in pad_free under ithreads. See also bug #19022, which resulted from the same change. There is some discussion there, too, but nobody seemed to know exactly why the readonliness needed to be turned off. Change 4761/2aa1bed, from January of 2000, added that SvREADONLY_off. It is supposed to make sure that pad entries that were constants will not be constants the next time they are used. My question is: When the addresses of those scalars are reused, won’t the scalars be wiped clean? (In case it’s not obvious, I have very little idea how pads actually work.) I tried simply deleting that SvREADONLY_off, and all tests pass (see the first attached patch). Then I thought that maybe I should check that the SV is freed, and only then do SvREADONLY_off, to preserve the original intent of change 4761/2aa1bed. That worked too. So, here are two patches. Take your pick. |
From @cpansproutFrom: Father Chrysostomos <sprout@cpan.org> [perl #19135] string eval turns off readonlyness on lexicals Don’t turn off readonliness on lexicals when freeing pad entries. Inline Patchdiff -up blead/pad.c blead-19135-readonly-lexicals/pad.c
--- blead/pad.c 2010-09-12 04:32:10.000000000 -0700
+++ blead-19135-readonly-lexicals/pad.c 2010-09-14 16:13:03.000000000 -0700
@@ -1386,11 +1386,6 @@ Perl_pad_free(pTHX_ PADOFFSET po)
if (PL_curpad[po] && PL_curpad[po] != &PL_sv_undef) {
SvPADTMP_off(PL_curpad[po]);
-#ifdef USE_ITHREADS
- /* SV could be a shared hash key (eg bugid #19022) */
- if (!SvIsCOW(PL_curpad[po]))
- SvREADONLY_off(PL_curpad[po]); /* could be a freed constant */
-#endif
}
if ((I32)po < PL_padix)
PL_padix = po - 1;
diff -rup blead/t/op/eval.t blead-19135-readonly-lexicals/t/op/eval.t
--- blead/t/op/eval.t 2010-07-03 08:47:11.000000000 -0700
+++ blead-19135-readonly-lexicals/t/op/eval.t 2010-09-14 16:23:18.000000000 -0700
@@ -6,7 +6,7 @@ BEGIN {
require './test.pl';
}
-print "1..107\n";
+print "1..108\n";
eval 'print "ok 1\n";';
@@ -611,3 +611,10 @@ eval $ov;
print "ok\n";
EOP
+{
+ my $k = "!";
+ Internals::SvREADONLY $k, 1;
+ eval 'my $do_something_with = $k';
+ eval { $k = 'mon' };
+ is $k, "!", "string eval leaves readonly lexicals readonly [perl #19135]";
+} |
From @cpansproutFrom: Father Chrysostomos <sprout@cpan.org> [perl #19135] string eval turns off readonlyness on lexicals Don’t turn of readonliness on lexicals when freeing pad entries, Inline Patchdiff -up blead/pad.c blead-19135-readonly-lexicals/pad.c
--- blead/pad.c 2010-09-12 04:32:10.000000000 -0700
+++ blead-19135-readonly-lexicals/pad.c 2010-09-14 16:13:59.000000000 -0700
@@ -1387,8 +1387,7 @@ Perl_pad_free(pTHX_ PADOFFSET po)
if (PL_curpad[po] && PL_curpad[po] != &PL_sv_undef) {
SvPADTMP_off(PL_curpad[po]);
#ifdef USE_ITHREADS
- /* SV could be a shared hash key (eg bugid #19022) */
- if (!SvIsCOW(PL_curpad[po]))
+ if (SvIS_FREED(PL_curpad[po]))
SvREADONLY_off(PL_curpad[po]); /* could be a freed constant */
#endif
}
diff -rup blead/t/op/eval.t blead-19135-readonly-lexicals/t/op/eval.t
--- blead/t/op/eval.t 2010-07-03 08:47:11.000000000 -0700
+++ blead-19135-readonly-lexicals/t/op/eval.t 2010-09-14 16:23:18.000000000 -0700
@@ -6,7 +6,7 @@ BEGIN {
require './test.pl';
}
-print "1..107\n";
+print "1..108\n";
eval 'print "ok 1\n";';
@@ -611,3 +611,10 @@ eval $ov;
print "ok\n";
EOP
+{
+ my $k = "!";
+ Internals::SvREADONLY $k, 1;
+ eval 'my $do_something_with = $k';
+ eval { $k = 'mon' };
+ is $k, "!", "string eval leaves readonly lexicals readonly [perl #19135]";
+} |
From @cpansproutOn Sun Sep 19 12:10:11 2010, sprout wrote:
Has anyone in the know had a chance to review these yet? |
From @cpansproutOn Sun Sep 26 12:46:49 2010, sprout wrote:
Well...? :-) Here is a better test case, with no Internals:: stuff: $ perl5.13.5 -wle 'for my $k(!0) { eval "\$k"; eval { $k = 7 }; print |
From [Unknown Contact. See original ticket]On Sun Sep 26 12:46:49 2010, sprout wrote:
Well...? :-) Here is a better test case, with no Internals:: stuff: $ perl5.13.5 -wle 'for my $k(!0) { eval "\$k"; eval { $k = 7 }; print |
From @iabynOn Sun, Nov 28, 2010 at 01:39:18PM -0800, Father Chrysostomos via RT wrote:
I think the first fix is correct (just removing the SvREADONLY_off). The second fix is wrong, in that the SVs in the pad aren't freed in the -- |
From @cpansproutOn Mon Dec 06 07:40:09 2010, davem wrote:
I’ve just applied a slightly modified version as 3aadd5c. |
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@cpansprout - Status changed from 'open' to 'resolved' |
Migrated from rt.perl.org#19135 (status was 'resolved')
Searchable as RT19135$
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