Here is the program which gdb is attached to:


#include <stdio.h>

void dummy(char* s)


int main()
    char buf[512];
    scanf("%s", buf);
    printf("%s\n", buf);
    return 0;

It is compiled with:

gcc prog.c o prog

This is the script which drives the program:

from pwn import *

p = process("./prog")

Here's the sequence of operation I perform:

  1. Run the script in one bash tab. It launches prog
  2. In another bash tab: sudo gdb -p `pgrep prog` . gdb attaches itself to the running process
  3. Set a breakpoint on dummy call in gdb: b dummy
  4. Press c in gdb to continue
  5. Hit Enter in the script to continue
  6. gdb gives up by saying: 0x000056446a5af764 <dummy+4>: Cannot access memory at address 0x56446a5af764

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If instead of feeding the input programmatically, I launch the program manually, attach gdb and feed the input myself, the breakpoint is correctly hit.

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What is the problem in the script?

1 Answer 1


The process dies before/while gdb connects to it, as your python script finishes. Use the following line at the end of your script to keep it running.


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