How Can I Debug 'Double Free or Corruption' Errors in C using glibc?

Tracking Down "Double Free or Corruption" Errors in C using glibc

When running a C program, you might encounter the frustrating error message "glibc detected ...: double free or corruption (!prev).*" This error indicates that glibc has detected an attempt to free a memory address that has already been freed or has become corrupted.

To track down this enigmatic error, setting the MALLOC_CHECK_ environment variable to 2 can be a valuable tool. This action instructs glibc to employ an error-tolerant version of malloc, causing your program to cease execution precisely when the double free occurs.

By setting this environment variable within gdb, you can gain a more precise understanding of the error. Use the following command in gdb before executing your program:

set environment MALLOC_CHECK_ 2

This action should trigger the termination of your program, displaying the offending free() call in the backtrace.

By examining the backtrace, you can pinpoint the source of the double free and take steps to resolve it. Remember to consult the malloc() man page for additional information on this error and its potential resolutions.

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