Re: [patch] Fix a crash due to a VALUE double free

[Luis Machado <luisgpm at linux dot vnet dot ibm dot com>]

FYI

The failures was due to a async-related regression introduced in PPC.

Regards,
Luis
On Mon, 2008-07-14 at 12:11 -0300, Luis Machado wrote:
> Hi Jan,
> 
> 
> This testcase is currently failing for PPC64.
> 
> Running /home/luis/src/gdb/gdb-head/HEAD/gdb/testsuite/gdb.base/value-double-free.exp ...
> FAIL: gdb.base/value-double-free.exp: continue
> FAIL: gdb.base/value-double-free.exp: print empty()
> 
> More complete log:
> 
> (gdb) run ^M
> Starting
> program: /home/luis/builds/gdb-head/DFP/gdb/testsuite/gdb.base/value-double-free ^M
> ^M
> Breakpoint 1, main ()
> at /home/luis/src/gdb/gdb-head/HEAD/gdb/testsuite/gdb.base/value-double-free.c:31^M
> 31        var = 1;^M
> (gdb) watch var^M
> Hardware watchpoint 2: var^M
> (gdb) PASS: gdb.base/value-double-free.exp: watch var
> continue^M
> Continuing.^M
> Target is executing.^M
> (gdb) FAIL: gdb.base/value-double-free.exp: continue
> print empty()^M
> Target is executing.^M
> (gdb) FAIL: gdb.base/value-double-free.exp: print empty()
> help help^M
> Print list of commands.^M
> (gdb) PASS: gdb.base/value-double-free.exp: help help
> testcase /home/luis/src/gdb/gdb-head/HEAD/gdb/testsuite/gdb.base/value-double-free.exp completed in 1 seconds
> 
> 
> On Mon, 2008-07-07 at 23:18 +0200, Jan Kratochvil wrote:
> > Hi,
> > 
> > it crashes if you call an inferior function right after a watchpoint hit.
> > 
> > Bugreported with a reproducer by Jakub Jelinek.
> > 
> > 
> > Regards,
> > Jan
> > plain text document attachment (gdb-value-double-free.patch)
> > gdb/
> > 2008-07-07  Jan Kratochvil  <jan.kratochvil@redhat.com>
> > 
> > 	* breakpoint.c (bpstat_copy): Call RELEASE_VALUE on the new OLD_VAL.
> > 
> > gdb/testsuite/
> > 2008-07-07  Jan Kratochvil  <jan.kratochvil@redhat.com>
> > 
> > 	* gdb.base/value-double-free.exp, gdb.base/value-double-free.c: New.
> > 
> > --- gdb/breakpoint.c	28 Jun 2008 09:42:15 -0000	1.327
> > +++ gdb/breakpoint.c	7 Jul 2008 21:12:14 -0000
> > @@ -1996,7 +1996,10 @@ bpstat_copy (bpstat bs)
> >        if (bs->commands != NULL)
> >  	tmp->commands = copy_command_lines (bs->commands);
> >        if (bs->old_val != NULL)
> > -	tmp->old_val = value_copy (bs->old_val);
> > +	{
> > +	  tmp->old_val = value_copy (bs->old_val);
> > +	  release_value (tmp->old_val);
> > +	}
> > 
> >        if (p == NULL)
> >  	/* This is the first thing in the chain.  */
> > --- /dev/null	1 Jan 1970 00:00:00 -0000
> > +++ gdb/testsuite/gdb.base/value-double-free.c	7 Jul 2008 21:12:17 -0000
> > @@ -0,0 +1,36 @@
> > +/* This testcase is part of GDB, the GNU debugger.
> > +
> > +   Copyright 2008 Free Software Foundation, Inc.
> > +
> > +   This program is free software; you can redistribute it and/or modify
> > +   it under the terms of the GNU General Public License as published by
> > +   the Free Software Foundation; either version 3 of the License, or
> > +   (at your option) any later version.
> > +
> > +   This program is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +   GNU General Public License for more details.
> > +
> > +   You should have received a copy of the GNU General Public License
> > +   along with this program.  If not, see <http://www.gnu.org/licenses/>.
> > +
> > +   Please email any bugs, comments, and/or additions to this file to:
> > +   bug-gdb@prep.ai.mit.edu  */
> > +
> > +volatile int var;
> > +
> > +void
> > +empty (void)
> > +{
> > +}
> > +
> > +int
> > +main (void)
> > +{
> > +  var = 1;
> > +  /* Workaround PR 38: We may miss the first watchpoint hit as we stop on the
> > +     exact instruction which would cause the watchpoint hit.  */
> > +  var = 2;
> > +  return 0;
> > +}
> > --- /dev/null	1 Jan 1970 00:00:00 -0000
> > +++ gdb/testsuite/gdb.base/value-double-free.exp	7 Jul 2008 21:12:17 -0000
> > @@ -0,0 +1,38 @@
> > +# Copyright 2008 Free Software Foundation, Inc.
> > +
> > +# This program is free software; you can redistribute it and/or modify
> > +# it under the terms of the GNU General Public License as published by
> > +# the Free Software Foundation; either version 3 of the License, or
> > +# (at your option) any later version.
> > +#
> > +# This program is distributed in the hope that it will be useful,
> > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +# GNU General Public License for more details.
> > +#
> > +# You should have received a copy of the GNU General Public License
> > +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> > +
> > +set testfile value-double-free
> > +set srcfile ${testfile}.c
> > +set binfile ${objdir}/${subdir}/${testfile}
> > +if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
> > +    untested "Couldn't compile test program"
> > +    return -1
> > +}
> > +
> > +# Get things started.
> > +
> > +gdb_exit
> > +gdb_start
> > +gdb_reinitialize_dir $srcdir/$subdir
> > +gdb_load ${binfile}
> > +
> > +if ![runto_main] {
> > +    return -1
> > +}
> > +gdb_test "watch var" "atchpoint \[0-9\]+: var"
> > +gdb_test "continue" "atchpoint \[0-9\]+: var.*Old value = 0.*New value = \[12\].*"
> > +gdb_test "print empty()" " = void"
> > +# We did segfault here.
> > +gdb_test "help help"