malloc-failer

malloc-failer is a custom memory allocation wrapper that logs memory allocation failures. It tracks the file, function, and line number where the allocation fails and can write the logs to a specified log file (default: xmalloc.log). The project also allows the user to specify certain lines in the code to always log memory allocation attempts, providing better insight into memory management issues during debugging.

Usage

Clone the repo and navigate into the project:

git clone https://github.com/droubarka/malloc-failer.git
cd malloc-failer

Compile with custom macros for specific lines and log file:

make MACROS='-D SPECIFICLINES=7,8 -D LOGFILE=\"logfile.log\"'

Link your project with the xmalloc static library:

gcc YOURPROJECT.c xmalloc -o YOURPROJECT

Example Output for YOURPROJECT

#include <stdio.h>
#include <stdlib.h>
#include "xmalloc.h"

int main() {
    char *ptr1 = malloc(100); // Normal allocation
    char *ptr2 = malloc(50);  // Assume this is line 7
    char *ptr3 = malloc(200); // Assume this is line 8

    // No NULL check, leading to a segmentation fault if malloc fails
    ptr2[0] = 'A';
    ptr3[0] = 'B';

    free(ptr1);
    free(ptr2);
    free(ptr3);

    return 0;
}

And you compile with:

make MACROS='-D SPECIFICLINES=7,8 -D LOGFILE=\"logfile.log\"'
gcc YOURPROJECT.c xmalloc -o YOURPROJECT
./YOURPROJECT

Expected Terminal Output (stderr):

xmalloc: YOURPROJECT.c:main:7: unable to allocate 50 Bytes
xmalloc: YOURPROJECT.c:main:8: unable to allocate 200 Bytes
Segmentation fault (core dumped)

xmalloc: note: Log has been successfully saved to logfile.log

Contents of logfile.log:

xmalloc: YOURPROJECT.c:main:7: unable to allocate 50 Bytes
xmalloc: YOURPROJECT.c:main:8: unable to allocate 200 Bytes

Explanation:

• Lines 7 and 8 fail due to SPECIFICLINES, so malloc returns NULL.
• No NULL check means the program tries to access ptr2[0] and ptr3[0], causing a segmentation fault.
• Log file still records the failures, providing a clue for debugging.
• The final log message appears before the crash, ensuring logs are saved.

License

malloc-failer is licensed under the GPLv3 License. See LICENSE for details.