Outputting to stderr whenever malloc/free is called

Question

With Linux/GCC/C++, I'd like to record something to stderr whenever malloc/free/new/delete are called. I'm trying to understand a library's memory allocations, and so I'd like to generate this output while I'm running unit tests. I use valgrind for mem leak detection, but I can't find an option to make it just log allocations.

Any ideas? I'm looking for the simplest possible solution. Recompiling the library is not an option.

Answer 1

You can trace calls to malloc/free with ltrace:

#include <stdlib.h>

int main (void)
{
  void *ptr = malloc(10);
  free(ptr);

  return 0;
}


$ g++ test.cpp -o test
$ ltrace -e malloc,free ./test
malloc(10)                                       = 0x804a008
free(0x804a008)                                  = <void>
+++ exited (status 0) +++

To trace new/delete calls without recompiling you will probably need to use something like LD_PRELOAD to override the calls with your own versions, this is precisely what LeakTracer does which might do what you want.