LeakSanitizer is a run-time memory leak detector. It can be combined with AddressSanitizer to get both memory error and leak detection, or used in a stand-alone mode. LSan adds almost no performance overhead until the very end of the process, at which point there is an extra leak detection phase.


LeakSanitizer is supported on x86_64 Linux and OS X. In order to use it, simply build your program with AddressSanitizer:

$ cat memory-leak.c
#include <stdlib.h>
void *p;
int main() {
  p = malloc(7);
  p = 0; // The memory is leaked here.
  return 0;
% clang -fsanitize=address -g memory-leak.c ; ASAN_OPTIONS=detect_leaks=1 ./a.out
==23646==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 7 byte(s) in 1 object(s) allocated from:
    #0 0x4af01b in __interceptor_malloc /projects/compiler-rt/lib/asan/asan_malloc_linux.cc:52:3
    #1 0x4da26a in main memory-leak.c:4:7
    #2 0x7f076fd9cec4 in __libc_start_main libc-start.c:287
SUMMARY: AddressSanitizer: 7 byte(s) leaked in 1 allocation(s).

To use LeakSanitizer in stand-alone mode, link your program with -fsanitize=leak flag. Make sure to use clang (not ld) for the link step, so that it would link in proper LeakSanitizer run-time library into the final executable.