$ cat umr.cc
#include <stdio.h>

int main(int argc, char** argv) {
  int* a = new int[10];
  a[5] = 0;
  if (a[argc])
    printf("xx\n");
  return 0;
}

$ cat blacklist.txt
# Maybe comments breaks something?
fun:main

# Maybe comments breaks something?

$ clang++-16 -fsanitize=memory -fno-omit-frame-pointer -g -O2 umr.cc -o umr && ./umr
==25090==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x5555555fd336 in main /tmp/test-msan/umr.cc:6:7
    #1 0x7ffff7a3984f  (/usr/lib/libc.so.6+0x2384f) (BuildId: 2f005a79cd1a8e385972f5a102f16adba414d75e)
    #2 0x7ffff7a39909 in __libc_start_main (/usr/lib/libc.so.6+0x23909) (BuildId: 2f005a79cd1a8e385972f5a102f16adba414d75e)
    #3 0x555555573294 in _start (/tmp/test-msan/umr+0x1f294)

SUMMARY: MemorySanitizer: use-of-uninitialized-value /tmp/test-msan/umr.cc:6:7 in main
Exiting

$ clang++-16 -fsanitize-blacklist=blacklist.txt -fsanitize=memory -fno-omit-frame-pointer -g -O2 umr.cc -o umr && ./umr