Asan memory leak detection on x86 platform

[ganeshemb]

Hi,

Change description mentioned as part of "https://reviews.llvm.org/D28609" says memory leaks detection is disabled by default, may i know how to enable it at run time (or) compile time?

Sample C program with memory leak
cat asantest.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main (int argc, char *argv[])
{
   char *name = (char*) malloc(10);
   strcpy(name, argv[1]);
   printf("Hello, %s!\n", name);
   return 0;
}

gcc -g -m32 -fsanitize=address -fno-omit-frame-pointer asantest.c -o asantest

objdump -a asantest

asantest:     file format elf32-i386

 ldd asantest
        linux-gate.so.1 (0xf778a000)
        libasan.so.3 => /usr/lib32/libasan.so.3 (0xf71e0000)

gcc --version
gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516 

when program run as shown below , no leaks were detected.

./asantest world
Hello, world!

when program run with ASAN_OPTIONS , following error is shown.

ASAN_OPTIONS=detect_leaks=1 ./asantest world
==8192==AddressSanitizer: detect_leaks is not supported on this platform.

My system info

 lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit

uname -r
4.9.0-8-amd64

Thanks in advance.

[kcc]

works for current clang:

clang++ ~/misc-c/leak.cc -fsanitize=address -m32  && ./a.out 

=================================================================
==185140==ERROR: LeakSanitizer: detected memory leaks

Doesn't work for my gcc (7.3.0).
Most likely, gcc didn't update the sanitizer run-time for a while.
Please check the current gcc head, then ask in the gcc bugtracker.

[kcc]

(closing since there is nothing to fix in the LLVM trunk)

[ganeshemb]

i tried using clang6.0 to compile my test app but it does not seem to work either, may i know which version of clang are you using ?

clang-6.0 -g -fsanitize=address -fno-omit-frame-pointer -m32 -o asantest asantest.c && ./asantest hi
Hello, hi!

[kcc]

I am using the current clang trunk (9.0), pretty sure it will work the same in 8.0 and 7.0, but please verify.

[lygstate]

On ubuntu 20.04 clang -m32 not works

lygstate@yonggang-ubuntu2004:~/work/iotjs$ clang --version
clang version 10.0.0-4ubuntu1 
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
lygstate@yonggang-ubuntu2004:~/work/iotjs$ clang -m32 -g3 -fsanitize=address -o asantest asantest.c
lygstate@yonggang-ubuntu2004:~/work/iotjs$ ./asantest abc
Hello, abc!
lygstate@yonggang-ubuntu2004:~/work/iotjs$ cat asantest.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main (int argc, char *argv[])
{
   char *name = (char*) malloc(10);
   strcpy(name, argv[1]);
   printf("Hello, %s!\n", name);
   return 0;
}lygstate@yonggang-ubuntu2004:~/work/iotjs$ clang -g3 -fsanitize=address -o asantest asantest.c
lygstate@yonggang-ubuntu2004:~/work/iotjs$ ./asantest abc
Hello, abc!

=================================================================
==69746==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 10 byte(s) in 1 object(s) allocated from:
    #0 0x493a1d in malloc (/home/lygstate/work/iotjs/asantest+0x493a1d)
    #1 0x4c312f in main /home/lygstate/work/iotjs/asantest.c:7:25
    #2 0x7ffb671ab0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16

SUMMARY: AddressSanitizer: 10 byte(s) leaked in 1 allocation(s).
lygstate@yonggang-ubuntu2004:~/work/iotjs$ 

[vitalybuka]

lsan does not detect 100% of leaks. after return from main() pointer still can be on the stack in some uninitialized stack variable and be visible to the lsan long after leak happens from the c++ perspective.
If you try to do the same in some loop, it's likely will be detected.
Also ASAN_OPTIONS=detect_stack_use_after_return=1 can help