GDB creating a core file

Question

Alright so don't ask why, but I want to create a core file of a test program I made. It's not corrupted and it doesn't screw up, but I want to generate a core file of it. Heres the code:

#include <stdio.h>
int main(){
printf("TEST");
}

As I said its really simple, but I want to be able to dump a core of it. How can I do it? BTW I'm on Ubuntu 10.04

Do want to do this by change the program itself or externally? — CB Bailey, Jan 05 '11 at 22:51
Do you want to change the program so it generates a core dump, or do you want to keep the program the same and trigger the core dump externally? — CB Bailey, Jan 05 '11 at 22:53
possible duplicate of [How to programatically cause a core dump in C/C++](http://stackoverflow.com/questions/979141/how-to-programatically-cause-a-core-dump-in-c-c) — Chris J, Jan 05 '11 at 22:57
How could I find the PID of the program? I've looked on TOP's list but its not there. — Jack Jacobsen, Jan 05 '11 at 22:57
@Jack Jacobsen: It's probably not there any more. Your program will exit fast. — CB Bailey, Jan 05 '11 at 23:05

score 12 · Answer 1 · answered Jan 05 '11 at 22:57

12

From the gdb command prompt with your executable loaded, issue the generate-core-file command.

answered Jan 05 '11 at 22:57

Karl Bielefeldt

47,314
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+1, but should note that this isn't supported on Windows (at least without Cygwin) for whatever reason. – Michael Burr Jan 05 '11 at 23:03
Ugh... GCC 6.6 on OpenBSD: *`Undefined command: "generate-core-file". Try "help".`* – jww Nov 24 '19 at 06:54

score 6 · Answer 2 · edited Nov 08 '18 at 15:20

~~If you can change the program adding a call to abort() will generate a core dump in many unix environments.~~

You need to make sure that you have core files enabled. The most common reason for core files not being generated is a zero size core ulimit. Check with the command ulimit -c and reset if zero with ulimit -c unlimited.

If you don't want to change the program you can send an abort signal with the kill command: kill -SIGABRT <pid> but with such a short program you are probably going to have to used a script and even then you may not be able to get the signal in before the process exits.

With bash you can try something like this (assuming that your program is called a.out and is in the current directory):

./a.out & kill -SIGABRT $!

& says run this in the background and $! is the PID of the most recently executed background command.

(-1) Is it possible that the application exit before the SIGABRT signal is send? You would need a sleep() or scanf() to wait for. — Raphael Bossek, Jan 05 '11 at 23:21
@Raphael B.: Yes, this is what I said: "even then you may not be able to get the signal in before the process exits". I'm not sure I understand your (-1) explanation? — CB Bailey, Jan 05 '11 at 23:27

score 6 · Answer 3 · answered Jan 05 '11 at 22:58

6

Load your program in gdb, set a breakpoint, run to the break point and then

(gdb) generate-core-file

answered Jan 05 '11 at 22:58

jcopenha

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Ugh... GCC 6.6 on OpenBSD: *`Undefined command: "generate-core-file". Try "help".`* – jww Nov 24 '19 at 06:53

score 0 · Answer 4 · answered Mar 29 '17 at 16:30

0

Another option is to use - gcore command.

answered Mar 29 '17 at 16:30

dev

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GDB creating a core file

4 Answers4