Debugging Core Files Using HP WDB (5900-1573; WDB 6.2; January 2011)

7. To determine the value of the variables, you must analyze the contents of the required

memory location.

In this example, the value of arg1 is an integer, and hence this value is 32(0x20).

The argument, arg0, is a pointer to a structure. To arrive at the value of arg0, the

offsets for the variables in the structure must be determined manually.

Following are the offsets for the variables in the structure st_one (in case of the

PA-RISC 32–bit binary):

struct st_one {

int one; +0x0

char *two; +0x4

struct st_two *three; +0x8

int *four; +0xC

char *five; +0x10

};

Following are two methods to determine the values in the structure:

NOTE: If the debug information is available, these offsets can be displayed by

using the ptype -v struct st_one command.

• Method 1:

In this method, the memory location of the fields in the structure st_one are

calculated by determining the offsets for each field relative to the address

location of arg0. The contents of the calculated address locations are displayed

by using the x command.

The following debugging session illustrates how to determine the values in the

structure, st_one:

◦ To display the char* value at the second field in the structure, enter the

following command at the gdb prompt:

(gdb) x/x 0x7f7e6688+0x4

0x7f7e668c: 0x40001140

To display the string value at the displayed address, enter the following

command at the gdb prompt:

(gdb) x/s 0x40001140

0x40001140 <__d_trap_fptr+292>: "NOT!"

◦ To display the int* value in the fourth field, enter the following command

at the gdb prompt:

(gdb) x/x 0x7f7e6688+0xc

0x7f7e6694: 0x7f7e6688

To display the int value at this address, enter the following command at

the gdb prompt: