[ASAN] ignorelist example in documentation unnecessary leaks memory.

[JackyWoo]

Description

ASan ignorelist not work in doc

$ cat foo.c
#include <stdlib.h>
void bad_foo() {
  int *a = (int*)malloc(40);
  a[10] = 1;
}
int main() { bad_foo(); }

$ cat ignorelist.txt
# Ignore reports from bad_foo function.
fun:bad_foo

$ clang -fsanitize=address foo.c ; ./a.out
# AddressSanitizer prints an error report.

$ clang -fsanitize=address -fsanitize-ignorelist=ignorelist.txt foo.c ; ./a.out
=================================================================
==2593520==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x55f61e60ee3e in __interceptor_malloc (/data1/home/wujianchao/project/test/tsan/a.out+0xb6e3e) (BuildId: 3fe97814135ec7f296a218cbc2c358ccc05a4109)
    #1 0x55f61e649711 in bad_foo (/data1/home/wujianchao/project/test/tsan/a.out+0xf1711) (BuildId: 3fe97814135ec7f296a218cbc2c358ccc05a4109)
    #2 0x55f61e649738 in main (/data1/home/wujianchao/project/test/tsan/a.out+0xf1738) (BuildId: 3fe97814135ec7f296a218cbc2c358ccc05a4109)
    #3 0x7f2b5ea69082 in __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:308:16

SUMMARY: AddressSanitizer: 40 byte(s) leaked in 1 allocation(s).

env

$ clang -v
Ubuntu clang version 16.0.3 (++20230420083033+12f17d196eff-1~exp1~20230420083138.77)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/11
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/11
Candidate multilib: .;@m64
Selected multilib: .;@m64

[deafwolf]

the problem can be reproduced with clang 17

$ clang -v
clang version 17.0.6 (Fedora 17.0.6-1.fc39)
Target: x86_64-redhat-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/13
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/13
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64

[vitalybuka]

For leaks you need to follow https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#suppressions

[slabko]

Hi @MaskRay ,

The documentation at https://clang.llvm.org/docs/SanitizerSpecialCaseList.html still mentions the exact example from the issue. I am a bit confused. This is marked as not planned, but what exactly is not planned? The documentation? The fact that it still throws an error? If this is a bug in documentation, then shouldn't this page be removed?

Just to be sure, this is an exact copy from the documentation; however, it does not work as described.

[vitalybuka]

Thanks.
It's bad example in documentation.
Example has 2 issues: buffer overflow and memory leak.
ignorelist here to suppress overflow.

Maybe it was written when lsan was not a part of asan.
It needs to be updated.