Incorrect math when reading a padded number from shared memory #11634
Comments
From markgr@online.noCreated by markgr@online.noSynopsis When reading a number from shared memory that is padded with /0`s and then doing Detail If the fourth field in shmwrite is larger than the value being written, the Work arounds I have posted this on perl monks http://www.perlmonks.org/?node_id=924278 and Example code The following code does nothing sensible (not even error checking) but it does Thanks Mark #!/usr/bin/perl use IPC::SysV qw(IPC_STAT IPC_PRIVATE IPC_CREAT IPC_EXCL S_IRUSR S_IWUSR IPC_RMID); $key=shmget(IPC_PRIVATE,100,IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR); my $ret=fork(); if($ret>0){ Perl Info |
From zefram@fysh.orgMark Grant wrote:
Yes, it will. Perl maintains a scalar's numeric value separately from I recommend that you always explicitly stringify the scalar when reading -zefram |
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The RT System itself - Status changed from 'new' to 'open' |
From @LeontOn Mon, Sep 5, 2011 at 10:32 PM, Mark Grant <perlbug-followup@perl.org> wrote:
It seems shmread doesn't turn off SvIOK on the variable when writing The patch attached is a quick fix, but I'm wondering if there aren't Leon |
From @Leontshmread.patchdiff --git a/doio.c b/doio.c
index cecc574..1759fea 100644
--- a/doio.c
+++ b/doio.c
@@ -2304,7 +2304,7 @@ Perl_do_shmio(pTHX_ I32 optype, SV **mark, SV **sp)
/* suppress warning when reading into undef var (tchrist 3/Mar/00) */
if (! SvOK(mstr))
sv_setpvs(mstr, "");
- SvPV_force_nolen(mstr);
+ SvPOK_only(mstr);
mbuf = SvGROW(mstr, (STRLEN)msize+1);
Copy(shm + mpos, mbuf, msize, char);
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From @LeontOn Tue, Sep 6, 2011 at 10:40 AM, Zefram <zefram@fysh.org> wrote:
No, shmread copies the data, it does not map it into a scalar. My Leon |
From @cpansproutOn Tue Sep 06 04:44:45 2011, LeonT wrote:
Is it possible to write tests for this sort of thing? |
From @LeontOn Tue, Sep 6, 2011 at 5:31 PM, Father Chrysostomos via RT
Sure. I've updated my patch and attached a test for this issue, but I Leon |
From @Leontshmread.patchdiff --git a/doio.c b/doio.c
index cecc574..6f6d6b8 100644
--- a/doio.c
+++ b/doio.c
@@ -2304,7 +2304,8 @@ Perl_do_shmio(pTHX_ I32 optype, SV **mark, SV **sp)
/* suppress warning when reading into undef var (tchrist 3/Mar/00) */
if (! SvOK(mstr))
sv_setpvs(mstr, "");
- SvPV_force_nolen(mstr);
+ sv_upgrade(mstr, SVt_PV);
+ SvPOK_only(mstr);
mbuf = SvGROW(mstr, (STRLEN)msize+1);
Copy(shm + mpos, mbuf, msize, char);
|
From @LeontOn Tue, Sep 6, 2011 at 5:31 PM, Father Chrysostomos via RT
Fix with tests attached Leon |
From @Leont0001-Added-SysV-shared-memory-tests.patchFrom 2395d6ca00592a30ca1a71d0539471816293883f Mon Sep 17 00:00:00 2001
From: Leon Timmermans <fawaka@gmail.com>
Date: Tue, 13 Sep 2011 18:34:28 +0200
Subject: [PATCH 1/2] Added SysV shared memory tests
Tests are based on IPC-SysV's tests, though I had to remove a lot for it
not to rely on IPC::SharedMem.
---
MANIFEST | 1 +
t/io/shm.t | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 76 insertions(+), 0 deletions(-)
create mode 100644 t/io/shm.t
diff --git a/MANIFEST b/MANIFEST
index 16121f8..a52d7a7 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -4810,6 +4810,7 @@ t/io/print.t See if print commands work
t/io/pvbm.t See if PVBMs break IO commands
t/io/read.t See if read works
t/io/say.t See if say works
+t/io/shm.t See if SysV shared memory works
t/io/tell.t See if file seeking works
t/io/through.t See if pipe passes data intact
t/io/utf8.t See if file seeking works
diff --git a/t/io/shm.t b/t/io/shm.t
new file mode 100644
index 0000000..a450679
--- /dev/null
+++ b/t/io/shm.t
@@ -0,0 +1,75 @@
+################################################################################
+#
+# $Revision: 6 $
+# $Author: mhx $
+# $Date: 2010/03/07 16:01:42 +0100 $
+#
+################################################################################
+#
+# Version 2.x, Copyright (C) 2007-2010, Marcus Holland-Moritz <mhx@cpan.org>.
+# Version 1.x, Copyright (C) 1999, Graham Barr <gbarr@pobox.com>.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the same terms as Perl itself.
+#
+################################################################################
+
+BEGIN {
+ if ($ENV{'PERL_CORE'}) {
+ chdir 't' if -d 't';
+ @INC = '../lib' if -d '../lib' && -d '../ext';
+ }
+
+ require Test::More; import Test::More;
+ require Config; import Config;
+
+ if ($ENV{'PERL_CORE'} && $Config{'extensions'} !~ m[\bIPC/SysV\b]) {
+ plan(skip_all => 'IPC::SysV was not built');
+ }
+}
+
+if ($Config{'d_shm'} ne 'define') {
+ plan(skip_all => '$Config{d_shm} undefined');
+}
+
+use sigtrap qw/die normal-signals error-signals/;
+use IPC::SysV qw/ IPC_PRIVATE S_IRWXU IPC_RMID /;
+
+my $key;
+END { shmctl $key, IPC_RMID, 0 if defined $key }
+
+{
+ local $SIG{SYS} = sub { plan(skip_all => "SIGSYS caught") } if exists $SIG{SYS};
+ $key = shmget IPC_PRIVATE, 8, S_IRWXU;
+}
+
+if (not defined $key) {
+ my $info = "IPC::SharedMem->new failed: $!";
+ if ($! == &IPC::SysV::ENOSPC || $! == &IPC::SysV::ENOSYS ||
+ $! == &IPC::SysV::ENOMEM || $! == &IPC::SysV::EACCES) {
+ plan(skip_all => $info);
+ }
+ else {
+ die $info;
+ }
+}
+else {
+ plan(tests => 11);
+ pass('acquired shared mem');
+}
+
+ok(shmwrite($key, pack("N", 4711), 0, 4), 'write(offs=0)');
+ok(shmwrite($key, pack("N", 210577), 4, 4), 'write(offs=4)');
+
+my $var;
+ok(shmread($key, $var, 0, 4), 'read(offs=0) returned ok');
+is($var, pack("N", 4711), 'read(offs=0) correct');
+ok(shmread($key, $var, 4, 4), 'read(offs=4) returned ok');
+is($var, pack("N", 210577), 'read(offs=4) correct');
+
+ok(shmwrite($key, "Shared", 1, 6), 'write(offs=1)');
+
+ok(shmread($key, $var, 1, 6), 'read(offs=1) returned ok');
+is($var, 'Shared', 'read(offs=1) correct');
+ok(shmwrite($key,"Memory", 0, 6), 'write(offs=0)');
+
--
1.7.4.1
|
From @Leont0002-Fix-98480-math-when-reading-shared-memory.patchFrom 38c932d1f18ff2003ccac01607311506b81e1714 Mon Sep 17 00:00:00 2001
From: Leon Timmermans <fawaka@gmail.com>
Date: Tue, 13 Sep 2011 20:13:22 +0200
Subject: [PATCH 2/2] Fix #98480 math when reading shared memory
shmread didn't unset SvIOK properly, causing a read into a SVIV to have
an incorrect numeric value. This patch fixes that and adds tests.
---
doio.c | 3 ++-
t/io/shm.t | 8 +++++++-
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/doio.c b/doio.c
index cb77cf6..1edf8d2 100644
--- a/doio.c
+++ b/doio.c
@@ -2278,7 +2278,8 @@ Perl_do_shmio(pTHX_ I32 optype, SV **mark, SV **sp)
/* suppress warning when reading into undef var (tchrist 3/Mar/00) */
if (! SvOK(mstr))
sv_setpvs(mstr, "");
- SvPV_force_nolen(mstr);
+ sv_upgrade(mstr, SVt_PV);
+ SvPOK_only(mstr);
mbuf = SvGROW(mstr, (STRLEN)msize+1);
Copy(shm + mpos, mbuf, msize, char);
diff --git a/t/io/shm.t b/t/io/shm.t
index a450679..46bb2e1 100644
--- a/t/io/shm.t
+++ b/t/io/shm.t
@@ -54,7 +54,7 @@ if (not defined $key) {
}
}
else {
- plan(tests => 11);
+ plan(tests => 13);
pass('acquired shared mem');
}
@@ -73,3 +73,9 @@ ok(shmread($key, $var, 1, 6), 'read(offs=1) returned ok');
is($var, 'Shared', 'read(offs=1) correct');
ok(shmwrite($key,"Memory", 0, 6), 'write(offs=0)');
+my $number = 1;
+my $int = 2;
+shmwrite $key, $int, 0, 1;
+shmread $key, $number, 0, 1;
+is("$number", $int, qq{"\$id" eq "$int"});
+cmp_ok($number + 0, '==', $int, "\$id + 0 == $int");
--
1.7.4.1
|
From @LeontOn Tue, Sep 6, 2011 at 5:31 PM, Father Chrysostomos via RT
Fix with tests attached Leon |
From @cpansproutOn Wed Sep 14 08:12:07 2011, LeonT wrote:
It seems you’ve submitted one of those ‘stealth’ patches. For some |
From @cpansproutOn Wed Sep 14 08:11:13 2011, LeonT wrote:
*That’s* odd! Your message showed up twice in RT, once without the |
From @LeontOn Wed, Sep 14, 2011 at 6:56 PM, Father Chrysostomos via RT
It seems gmail screwed up, it appears in my mailbox twice too, once Leon |
From @cpansproutOn Wed Sep 14 08:11:13 2011, LeonT wrote:
|
|
@cpansprout - Status changed from 'open' to 'resolved' |
Migrated from rt.perl.org#98480 (status was 'resolved')
Searchable as RT98480$
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