Re: Bug in reversible GDB

[Hui Zhu <teawater at gmail dot com>]

Hi Michael,

I have reproduce this issue.  Looks like it just affect AMD64.

infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0x400398
infrun: stepped into subroutine
infrun: inserting step-resume breakpoint at 0x400398
infrun: resume (step=0, signal=0), trap_expected=0
infrun: prepare_to_wait
infrun: target_wait (-1, status) =
infrun:   21937 [process 21937],
infrun:   status->kind = stopped, signal = SIGTRAP

We meet this issue in i386 in before and you have fix it.  But looks
like it still affect AMD64.

Thanks,
Hui


On Tue, Jul 7, 2009 at 14:25, Hui Zhu<teawater@gmail.com> wrote:
> ---------- Forwarded message ----------
> From: Colin Paul Gloster <Colin_Paul_Gloster@acm.org>
> Date: Mon, Jul 6, 2009 at 20:33
> Subject: Bug in reversible GDB
> To: Hui Zhu <teawater@gmail.com>
>
>
> On Fri, 3 Jul 2009, Hui Zhu wrote:
>
> |--------------------------------------------------------------------------------|
> |"[..]
> ? ? ? ? ? |
> |
> ?? ? ? ? ?|
> |Process record and replay target (This is the new name ) ?is already
> ?? ? ? ? ?|
> |in the gdb-cve-head.
> ?? ? ? ? ?|
> |You can get more message from
> http://sourceware.org/gdb/wiki/ReversibleDebugging|
> |
> ?? ? ? ? ?|
> |BTW, The AMD64 patch ?still not in, you can get it from the link in
> ? ? ? ? ? |
> |this wiki page.
> ? ? ? ? ? |
> |
> ?? ? ? ? ?|
> |[..]"
> ? ? ? ? ? |
> |--------------------------------------------------------------------------------|
>
>
> Hi Hui,
>
> Thank you for the work. It seems that it may become excellent. I am
> yet to see it being perfect though.
>
> I give an example of buggy behavior based on
> HTTP://SourceForge.net/forum/forum.php?forum_id=832141
> ...
>
> #include<stdio.h>
> int a = 0;
> void
> cool2 ()
> {
> printf ("a = %d\n", a);
> }
> int
> cool ()
> {
> a += 3;
>
> cool2();
>
> return (a);
> }
> int
> main()
> {
> int b = 0;
> int c = 1;
>
> printf ("a = %d b = %d c = %d\n", a, b, c);
> b = cool ();
> printf ("a = %d b = %d c = %d\n", a, b, c);
>
> /*Line 27.*/c += 1;
> /*Line 28.*/printf ("a = %d b = %d c = %d\n", a, b, c);
> /*Line 29.*/a -= 2;
> /*Line 30.*/printf ("a = %d b = %d c = %d\n", a, b, c);
>
> /*Line 32.*/return (0);
> }
>
>
> gdb ./C_program_for_testing_reversible_debugging
> GNU gdb (GDB) 6.8.50.20090629-cvs (actually
> gdb-weekly-CVS-6.8.50.20090630.tar.bz2 patched as per
> HTTP://Sourceware.org/ml/gdb-patches/2009-06/msg00797.html
> and
> HTTP://Sourceware.org/ml/gdb-patches/2009-06/msg00798.html
> and
> HTTP://Sourceware.org/ml/gdb-patches/2009-06/msg00799.html
> )
> Copyright (C) 2009 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law. ?Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-unknown-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> (gdb) break main
> Breakpoint 1 at 0x401050: file
> C_program_for_testing_reversible_debugging.c, line 20.
> (gdb) run
> Starting program: /home/Colin_Paul/C_program_for_testing_reversible_debugging
>
> Breakpoint 1, main () at C_program_for_testing_reversible_debugging.c:20
> 20 ? ? ?int b = 0;
> (gdb) record
> (gdb) break C_program_for_testing_reversible_debugging.c:32
> Breakpoint 2 at 0x4010ea: file
> C_program_for_testing_reversible_debugging.c, line 32.
> (gdb) continue
> Continuing.
> a = 0 b = 0 c = 1
> a = 3
> a = 3 b = 3 c = 1
> a = 3 b = 3 c = 2
> a = 1 b = 3 c = 2
>
> Breakpoint 2, main () at C_program_for_testing_reversible_debugging.c:32
> 32 ? ? ?return (0);
> (gdb) reverse-step
> 28 ? ? ?printf ("a = %d b = %d c = %d\n", a, b, c);
> (gdb) reverse-step
> 27 ? ? ?c += 1;
> (gdb)
>
>
> I would have hoped that reverse-step from the 32nd line would reach
> the 30th line instead of the 27th line, and that the second
> reverse-step would reach the 29th line instead of the 28th line.
>
> I noticed that reverse-next behaved exactly the same as reverse-step...
> gdb ./C_program_for_testing_reversible_debugging
> GNU gdb (GDB) 6.8.50.20090629-cvs
> Copyright (C) 2009 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law. ?Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-unknown-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> (gdb) break main
> Breakpoint 1 at 0x401050: file
> C_program_for_testing_reversible_debugging.c, line 20.
> (gdb) run
> Starting program: /home/Colin_Paul/C_program_for_testing_reversible_debugging
>
> Breakpoint 1, main () at C_program_for_testing_reversible_debugging.c:20
> 20 ? ? ?int b = 0;
> (gdb) record
> (gdb) break C_program_for_testing_reversible_debugging.c:32
> Breakpoint 2 at 0x4010ea: file
> C_program_for_testing_reversible_debugging.c, line 32.
> (gdb) continue
> Continuing.
> a = 0 b = 0 c = 1
> a = 3
> a = 3 b = 3 c = 1
> a = 3 b = 3 c = 2
> a = 1 b = 3 c = 2
>
> Breakpoint 2, main () at C_program_for_testing_reversible_debugging.c:32
> 32 ? ? ?return (0);
> (gdb) reverse-
> reverse-continue ?reverse-next ? ? ?reverse-search ? ?reverse-stepi
> reverse-finish ? ?reverse-nexti ? ? reverse-step
> (gdb) reverse-next
> 28 ? ? ?printf ("a = %d b = %d c = %d\n", a, b, c);
> (gdb) reverse-next
> 27 ? ? ?c += 1;
> (gdb) quit
> The program is running. ?Quit anyway (and kill it)? (y or n) y
>
> The operating system I used was Bluewhite64 GNU/Linux 12.2 (
> uname -a
> Linux bluewhite64 2.6.27.7 #1 SMP Fri Dec 5 01:27:18 EET 2008 x86_64
> Intel(R) Core(TM)2 Quad ?CPU ? Q9450 ?@ 2.66GHz GenuineIntel GNU/Linux
> ). I used that operating system's default compiler (
> gcc -v
> Reading specs from /usr/lib/gcc/x86_64-pc-linux/4.2.4/specs
> Target: x86_64-pc-linux
> Configured with: ../gcc-4.2.4/configure --prefix=/usr --enable-shared
> --enable-languages=ada,c,c++,fortran,java,objc --disable-multilib
> --enable-threads=posix --enable-__cxa_atexit --disable-checking
> --with-gnu-ld --verbose --build=x86_64-pc-linux
> --target=x86_64-pc-linux --host=x86_64-pc-linux
> Thread model: posix
> gcc version 4.2.4
> ). I compiled with
> gcc -g C_program_for_testing_reversible_debugging.c -o
> C_program_for_testing_reversible_debugging
>
> Good luck.
>
> With best regards,
> Colin Paul
>