[clang] lsan is ignored when used with ubsan

[jonathanpoelen]

https://godbolt.org/z/dcj4hh73h

With the following code, which has a memory leak:

#include <stdio.h>

int main(int argc, char** argv) {
  int* a = new int[10];
  a[5] = 0;
  volatile int b = a[argc];
  if (b)
    printf("xx\n");
  // bool bb = *reinterpret_cast<bool*>(argv); // ubsan ok
  // if (bb)
  //  printf("xx\n");
  return 0;
}

Compiling with -fsanitize=address,undefined does not detect the memory leak, whereas it is detected with -fsanitize=address or -fsanitize=leak alone.

Furthermore, compiling with -fsanitize=leak,undefined gives link errors which are magically fixed by adding -fsanitize=address or -lubsan:

/usr/bin/ld: /home/jonathan/rawdisk/test-c09389.o: in function `main':
test.cpp:(.text+0x53): undefined reference to `__ubsan_handle_type_mismatch_v1'
/usr/bin/ld: test.cpp:(.text+0xa7): undefined reference to `__ubsan_handle_pointer_overflow'
/usr/bin/ld: test.cpp:(.text+0xd3): undefined reference to `__ubsan_handle_type_mismatch_v1'
/usr/bin/ld: test.cpp:(.text+0x140): undefined reference to `__ubsan_handle_pointer_overflow'
/usr/bin/ld: test.cpp:(.text+0x16c): undefined reference to `__ubsan_handle_type_mismatch_v1

clang version 19.1.7

Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-pc-linux-gnu/13.3.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-pc-linux-gnu/14.2.1
Found candidate GCC installation: /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/13.3.1
Found candidate GCC installation: /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/14.2.1
Selected GCC installation: /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/14.2.1
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64