Re: pthread_t ids of threads not showed by "thread info"

[Stefano Sabatini <stefano dot sabatini-lala at poste dot it>]

On Friday 2010-04-23 17:46:29 +0200, Jan Kratochvil wrote:
> On Fri, 23 Apr 2010 17:35:54 +0200, Stefano Sabatini wrote:
> > On date Friday 2010-04-23 16:25:11 +0200, Jan Kratochvil wrote:
> > > You must have debug symbols from glibc.  On Fedora `debuginfo-install glibc',
> > > some similar command on other distros.
> > 
> > OK now I have this problem:
> > 
> > (gdb) threads __stack_user
> > Attempt to extract a component of a value that is not a structure.
> > (gdb) threads stack_used
> 
> > (gdb) p __stack_user
> > $1 = -1221236944
> $1 = {next = 0x7ffff7fd19c0, prev = 0x7ffff7fd19c0}
> 
> > (gdb) p &__stack_user
> > $4 = (<data variable, no debug info> *) 0xb7970160
> $4 = (list_t *) 0x379501b280
> 
> > (gdb) p (void *)&__stack_user
> > $5 = (void *) 0xb7970160
> $5 = (void *) 0x379501b280
> 
> > (gdb) p (void *)&__stack_user.next
> > Attempt to extract a component of a value that is not a structure.
> $6 = (void *) 0x379501b280
> 
> 
> > I have debug symbols installed (installed libc6-dbg on Debian).
> 
> You should bugreport it to libc6-dbg, __stack_user must have its type.

$ cat thrids.c 
#include <pthread.h>
#include <unistd.h>

void *fn(void *p)
{
  sleep(180);
  return 0;
}

int main(void)
{
    char *str = 0;

    pthread_t pth1, pth2;

    pthread_create(&pth1, 0, fn, 0);
    pthread_create(&pth2, 0, fn, 0);
    *str = 0;
    pthread_join(pth1, 0);

    return 0;
}

$ make thrids 
gcc -I/home/stefano/include -g -O0 -pg -D_ISOC9X_SOURCE -Wall -Wno-switch -Wdisabled-optimization -Wpointer-arith -Wredundant-decls -Wno-pointer-sign -Wcast-qual -Wwrite-strings -fno-math-errno -lm -I/home/stefano/include -L/home/stefano/lib -pthread  thrids.c   -o thrids
$ ldd thrids
	linux-gate.so.1 =>  (0xb78c6000)
	libm.so.6 => /lib/i686/cmov/libm.so.6 (0xb788b000)
	libpthread.so.0 => /lib/i686/cmov/libpthread.so.0 (0xb7872000)
	libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb772a000)
	/lib/ld-linux.so.2 (0xb78c7000)

$ gdb thrids
GNU gdb (GDB) 7.0.1-debian
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 "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/stefano/src/Sandbox/C/thrids...done.
(gdb) b main
Breakpoint 1 at 0x8048630: file thrids.c, line 12.
(gdb) r
[Thread debugging using libthread_db enabled]
 
Breakpoint 1, main () at thrids.c:12
12        char *str = 0;
(gdb) p stack_user
No symbol "stack_user" in current context.
(gdb) p __stack_user
$1 = -1209776352
(gdb) p &__stack_user
$2 = (<data variable, no debug info> *) 0xb7fa5160 
(gdb) quit

$ cd /usr/lib/debug/lib
$ cd
$ nm -S libpthread-2.10.2.so | grep __stack_user
00017160 00000008 b __GI___stack_user
00017160 00000008 b __stack_user
$ nm -S libpthread-2.10.2.so | grep stack_used
0001511c 00000008 d stack_used

I'm currently stucked with this, I really cannot say if it is a
problem with what I'm doing or with some debian specific issue.

I'll be grateful for any advice.
 
> One could hack it more using just offsets without any struct definitions but
> it was just a proof-of-concept hack the info is in the core file.  One should
> just apply libthread_db even on the core files.

Best regards.