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From: "daniel.parkinson1 at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug gdb/17676] New: gdb cannot print the address a pointer is
 pointing to returned by malloc
Date: Wed, 03 Dec 2014 17:36:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=17676

            Bug ID: 17676
           Summary: gdb cannot print the address a pointer is pointing to
                    returned by malloc
           Product: gdb
           Version: 7.7
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: daniel.parkinson1 at gmail dot com

Overview

After making a call to malloc to assign a memory address to a pointer that is a
parameter of the function, gdb will print 0x0 as the address pointed to.

Steps to reproduce

Compiling the following code...

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

void create_stack(int *other_name_stack);

int *stack;

int main(void) {
    create_stack(stack);
    return 0;
}

void create_stack(int *other_name_stack) {

        other_name_stack = malloc(sizeof(int)*10);
        if(other_name_stack == NULL)
                printf("Malloc failed: %s\n", strerror(errno));

        printf("%p\n", (void *)other_name_stack);
}

Command: gcc -O0 -Wall -g teststack.c -o teststack
Command: gdb ./teststack

break create_stack
n
p other_name_stack

Actual results.

p other_name_stack will always return 0x0, but the if statement will never
return true.

Expected results

I would expect to be able to see the memory address returned by malloc.

Build Date & Hardware

Linux jim-vm-ubuntu 3.16.0-031600-generic #201408031935 SMP Sun Aug 3 23:56:17
UTC 2014 i686 i686 i686 GNU/Linux

Additional Info

GNU gdb (Ubuntu 7.7-0ubuntu3.1) 7.7

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