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gdb breakpoint problem
- From: kdsfinger at gmail dot com
- To: gdb at sourceware dot org
- Date: Mon, 11 Jun 2007 12:59:57 -0400
- Subject: gdb breakpoint problem
hi, all
I am new to gdb and have trouble in setting the breakpoint. The
problem is, the program does not stop at some of the breakpoints. I am
using gdb6.6 in centos4.4. Here is the detail.
===================================
/* sample.c -- Sample C program to be debugged with ddd
*/
#include <stdio.h>
#include <stdlib.h>
static void shell_sort(int a[], int size){
int i, j;
int h = 1;
do {
h = h * 3 + 1;
} while (h <= size);
do {
h /= 3;
for (i = h; i < size; i++){
int v = a[i];
for (j = i; j >= h && a[j - h] > v; j -= h)
a[j] = a[j - h];
if (i != j)
a[j] = v;
}
} while (h != 1);
}
int main(int argc, char *argv[]){
int *a; //line 24
int i; //line 25
a = (int *)malloc((argc - 1) * sizeof(int)); // line 26
for (i = 0; i < argc - 1; i++)
a[i] = atoi(argv[i + 1]);
shell_sort(a, argc);
for (i = 0; i < argc - 1; i++)
printf("%d ", a[i]);
printf("\n");
free(a);
return 0;
}
========================================
gcc -g -o sample sample.c
gdb sample
GNU gdb 6.6
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GDB is free software, covered by the GNU General Public License, and you are
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Type "show copying" to see the conditions.
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This GDB was configured as "i686-pc-linux-gnu"...
Using host libthread_db library "/lib/tls/libthread_db.so.1".
(gdb) break 24
Breakpoint 1 at 0x804850b: file sample.c, line 24.
(gdb) info break 1
Num Type Disp Enb Address What
1 breakpoint keep y 0x0804850b in main at sample.c:24
(gdb) run 2 4 6 3 5 7
Starting program: /home/amdx2/drive2/cpp/testddd/sample 2 4 6 3 5 7
Breakpoint 1, main (argc=7, argv=0xbff515c4) at sample.c:26
26 a = (int *)malloc((argc - 1) * sizeof(int));
-------------------------
As you can see, the program did not stop at the breakpoint on line24.
It stops at line26. If I add another breakpoint on line25, this 2nd
breakpoint is skipped as well and the program stops at line26. Why is
that? How can I correct it?
On my own program which is rather big, it got the same problem. When I
use info break xxx, it sometimes point to a different place in "What".
For example, I placed the breakpoint in main line 100, but the "what"
points to other functions in different line. As the result, these
breakpoints never work. I changed my gcc flags with combinations of
-glevel -olevel, the problem did not solve. Thanks for your comments.
zl2k