Hi!

This is a simple test demonstrating false-negative memory leak detection when two functions stack frames overlay; here the first function allocates memory and stores pointer in the stack, and the second function invokes lsan to detect memory leak

$ uname -a

Linux machine_name 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt11-1+deb8u4 (2015-09-19) x86_64 GNU/Linux

$ clang --version | head -1

clang version 5.0.1 (tags/RELEASE_501/final)

$ cat t.c

#include <sanitizer/lsan_interface.h>
#include <stdlib.h>
#include <assert.h>

#define NOINLINE __attribute__((noinline))

NOINLINE
void foo( size_t size )
{
    volatile char * a[128];

    a[0] = (volatile char *)malloc( size );
    assert( a[0] );
}

NOINLINE
void bar( void )
{
#ifdef ENABLE_LSAN_FALSE_NEGATIVE
    volatile char * a[128];
#endif

    __lsan_do_leak_check();
}

int main( int argc, char ** argv )
{
    foo( argc );
    bar();

    return 0;
}

$ clang t.c -fsanitize=leak -DENABLE_LSAN_FALSE_NEGATIVE && ./a.out
$ echo $?

0

if we unset the macro ENABLE_LSAN_FALSE_NEGATIVE then lsan will detect memory leak as expected

$ clang t.c -fsanitize=leak && ./a.out

=================================================================
==4778==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 1 byte(s) in 1 object(s) allocated from
#0 0x4097c7 in __interceptor_malloc ...
...