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Re: backtrace/1476: Empty stack.


The following reply was made to PR backtrace/1476; it has been noted by GNATS.

From: "Peter.Schauer" <Peter.Schauer@regent.e-technik.tu-muenchen.de>
To: chastain@sourceware.org, gdb-prs@sources.redhat.com,
        gdb-gnats@sources.redhat.com
Cc: skarab@kemsu.ru, kettenis@gnu.org
Subject: Re: backtrace/1476: Empty stack.
Date: Mon, 8 Dec 2003 12:40:38 MET

 I strongly suspect that this is caused by a zero function pointer call,
 and the example below indeed shows a regression with backtracing from
 zero function pointer calls between gdb-5.3 and gdb-6.0.
 
 I am not familiar enough with the new frame code to propose a fix though,
 sorry.
 
 pes@xxxx_7$ cat zerofun.c
 void x()
 {
   void (*fp)() = 0;
   fp();
 }
 int
 main()
 {
   x();
   return 0;
 }
 pes@xxxx_8$ gcc -g zerofun.c
 pes@xxxx_9$ gdb-5.3 a.out
 GNU gdb 5.3
 Copyright 2002 Free Software Foundation, Inc.
 GDB is free software, covered by the GNU General Public License, and you are
 welcome to change it and/or distribute copies of it under certain conditions.
 Type "show copying" to see the conditions.
 There is absolutely no warranty for GDB.  Type "show warranty" for details.
 This GDB was configured as "i686-pc-linux-gnu"...
 (gdb) r
 Starting program: ..../a.out 
 
 Program received signal SIGSEGV, Segmentation fault.
 0x00000000 in ?? ()
 (gdb) bt
 #0  0x00000000 in ?? ()
 #1  0x08048306 in x () at zerofun.c:4
 #2  0x0804831d in main () at zerofun.c:9
 #3  0x420158d4 in __libc_start_main () from /lib/i686/libc.so.6
 (gdb) q
 The program is running.  Exit anyway? (y or n) y
 pes@xxxx_10$ gdb-6.0 a.out
 GNU gdb 6.0
 Copyright 2003 Free Software Foundation, Inc.
 GDB is free software, covered by the GNU General Public License, and you are
 welcome to change it and/or distribute copies of it under certain conditions.
 Type "show copying" to see the conditions.
 There is absolutely no warranty for GDB.  Type "show warranty" for details.
 This GDB was configured as "i686-pc-linux-gnu"...
 (gdb) r
 Starting program: ..../a.out 
 
 Program received signal SIGSEGV, Segmentation fault.
 0x00000000 in ?? ()
 (gdb) bt
 #0  0x00000000 in ?? ()
 (gdb) q
 The program is running.  Exit anyway? (y or n) y
 
 -- 
 Peter Schauer			pes@regent.e-technik.tu-muenchen.de


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