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I don't understand why this doesn't work


From: Ray Hurst
Subject: I don't understand why this doesn't work
Date: Sat, 09 Feb 2008 11:21:34 -0800
User-agent: Thunderbird 2.0.0.9 (Windows/20071031)

I'm running under Windows XP and Cygwin.

I ran GDB on a simple C program and captured the output (below).
I have a few questions:

Why can I run the program several times with no errors but as soon as I set a breakpoint at main it gets a SIGSEGV fault?

Why does the backtrace show only addresses?


C:\Documents and Settings\Ray Hurst\workspace\CDT\HelloWorld-ANSIC\Debug>gdb Hel
loWorld-ANSIC.exe
GNU gdb 6.5.50.20060706-cvs (cygwin-special)
Copyright (C) 2006 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-cygwin"...
(gdb) list
5        Version     :
6        Copyright   : Your copyright notice
7        Description : Hello World in C, Ansi-style
8 =======================================================================
=====
9        */
10
11      #include <stdio.h>
12      #include <stdlib.h>
13
14      int main(void) {
(gdb) list 20
15              puts("!!!Hello World!!!"); /* prints !!!Hello World!!! */
16              return EXIT_SUCCESS;
17      }
(gdb) run
Starting program: /cygdrive/c/Documents and Settings/Ray Hurst/workspace/CDT/Hel
loWorld-ANSIC/Debug/HelloWorld-ANSIC.exe
Loaded symbols for /cygdrive/c/WINDOWS/system32/ntdll.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/kernel32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/cygwin1.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/advapi32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/rpcrt4.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/secur32.dll
!!!Hello World!!!

Program exited normally.
(gdb) run
Starting program: /cygdrive/c/Documents and Settings/Ray Hurst/workspace/CDT/Hel
loWorld-ANSIC/Debug/HelloWorld-ANSIC.exe
Loaded symbols for /cygdrive/c/WINDOWS/system32/ntdll.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/kernel32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/cygwin1.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/advapi32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/rpcrt4.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/secur32.dll
!!!Hello World!!!

Program exited normally.
(gdb) b main
Breakpoint 1 at 0x401050: file ../src/HelloWorld-ANSIC.c, line 14.
(gdb) run
Starting program: /cygdrive/c/Documents and Settings/Ray Hurst/workspace/CDT/Hel
loWorld-ANSIC/Debug/HelloWorld-ANSIC.exe
Loaded symbols for /cygdrive/c/WINDOWS/system32/ntdll.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/kernel32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/cygwin1.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/advapi32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/rpcrt4.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/secur32.dll

Program received signal SIGSEGV, Segmentation fault.
[Switching to thread 4896.0x1314]
0x000007f4 in ?? ()
(gdb) bt
#0  0x000007f4 in ?? ()
#1  0x00000000 in ?? ()
(gdb)

Ray





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