Debugging Dynamic Memory Usage Errors Using HP WDB (5900-1474; WDB 6.2; January 2011)

Example 12 Bounds-checking to detect out-of-bounds writes

Sample Program

bash-2.05b$ cat bounds.c

1 #include<stdio.h>

3 int main()

4 {

5 char *cp = (char*)malloc(100);

6 cp[-1] = 100;

7 strcpy(cp,"Hello");

8 cp[100] = 100;

9 free(cp);

10 exit(0);

11 }

Sample Debugging Session

bash-2.05b$ gdb bounds

HP gdb 5.5.0 for PA-RISC 1.1 or 2.0 (narrow), HP-UX 11.00

and target hppa1.1-hp-hpux11.00.

Hewlett-Packard Wildebeest 5.5.0 (based on GDB) is covered

by the GNU General Public License. Type "show copying" to

see the conditions to change it and/or distribute copies.

Type "show warranty" for warranty/support.

(gdb) set heap-check bounds on

(gdb) b main

Breakpoint 1 at 0x2c04: file bounds.c, line 5 from bounds.

(gdb) b 10

Breakpoint 2 at 0x2c58: file bounds.c, line 10 from bounds.

(gdb) r

Starting program: bounds

Breakpoint 1, main () at bounds.c:5

5 char *cp = (char*)malloc(100);

(gdb) c

Continuing.

warning: Memory block (size = 100 address = 0x4042a3c8)

appears to be corrupted at the beginning.

Allocation context not found

#1 main() at bounds.c:5

#2 _start() from /usr/lib/libc.2

#3 _start() from /opt/langtools/lib/librtc.sl

#4 $START$() from

warning: Use command backtrace (bt) to see the current context.

Ignore top 4 frames belonging to leak detection library of gdb.

0x70e78d7c in __rtc_event+0 () from /opt/langtools/lib/librtc.sl

Memory-Debugging Features of WDB 49