llvm-project/clang/docs/LeakSanitizer.rst

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LeakSanitizer
================

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Introduction
============

LeakSanitizer is a run-time memory leak detector. It can be combined with
:doc:`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.

Usage
=====

LeakSanitizer is supported on x86\_64 Linux and macOS. In order to use it,
simply build your program with :doc:`AddressSanitizer`:

.. code-block:: console

    $ 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.

More Information
================

`<https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer>`_