AddressSanitizer blacklist in c++ not working

Question

I'm trying to get address sanitizer blacklist working in a C++ project but its not working as expected. I tried the example on their website, if I compile with clang, it works fine.

build % cat suppress.txt
fun:bad_foo

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

build % clang -fsanitize=address -fsanitize-blacklist=suppress.txt foo.c ; ./a.out
Exit code: 0

But as soon as I use clang++, its ignored.

build % cp foo.c foo.cpp
build % clang++ -fsanitize=address -fsanitize-blacklist=suppress.txt foo.cpp ; ./a.out
=================================================================
==9943==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6040000003f8 at pc 0x00010ff93ee8 bp 0x7ffedfc6c340 sp 0x7ffedfc6c338
WRITE of size 4 at 0x6040000003f8 thread T0
Provided dSYM: [/Users/.../build/./a.out.dSYM/Contents/Resources/DWARF/a.out] does not match symbol owner 0x7fe1b060edc0
    #0 0x10ff93ee7 in bad_foo() (a.out:x86_64+0x100000ee7)
    #1 0x10ff93f08 in main (a.out:x86_64+0x100000f08)
    #2 0x7fff7940508c in start (libdyld.dylib:x86_64+0x1708c)

0x6040000003f8 is located 0 bytes to the right of 40-byte region [0x6040000003d0,0x6040000003f8)
allocated by thread T0 here:
    #0 0x10fff2173 in wrap_malloc (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x5c173)
    #1 0x10ff93e93 in bad_foo() (a.out:x86_64+0x100000e93)
    #2 0x10ff93f08 in main (a.out:x86_64+0x100000f08)
    #3 0x7fff7940508c in start (libdyld.dylib:x86_64+0x1708c)

SUMMARY: AddressSanitizer: heap-buffer-overflow (a.out:x86_64+0x100000ee7) in bad_foo()
Shadow bytes around the buggy address:
  0x1c0800000020: fa fa 00 00 00 00 00 fa fa fa 00 00 00 00 00 05
  0x1c0800000030: fa fa 00 00 00 00 00 fa fa fa 00 00 00 00 00 05
  0x1c0800000040: fa fa 00 00 00 00 00 fa fa fa 00 00 00 00 00 07
  0x1c0800000050: fa fa 00 00 00 00 00 fa fa fa 00 00 00 00 00 fa
  0x1c0800000060: fa fa 00 00 00 00 00 fa fa fa 00 00 00 00 00 fa
=>0x1c0800000070: fa fa 00 00 00 00 00 05 fa fa 00 00 00 00 00[fa]
  0x1c0800000080: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0800000090: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c08000000a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c08000000b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c08000000c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==9943==ABORTING
[1]    9943 abort      ./a.out
Exit code: 134

I'm using clang-7 from releases.llvm.org

build % clang --version
clang version 7.0.0 (tags/RELEASE_700/final)
Target: x86_64-apple-darwin18.2.0
Thread model: posix
InstalledDir: /Users/.../clang+llvm-7.0.0-x86_64-apple-darwin/bin

Is this not supported under C++?

Answer 1

In C++ function names will be mangled and it looks like the blacklist requires us to use mangled names, for example:

fun:_Z7bad_foov

then it will works for me. We can see form the example I think you are using they have an example of using a mangled name as well but they don't explain it:

# Turn off checks for a particular functions (use mangled names):
fun:MyFooBar
fun:_Z8MyFooBarv

You can use a utility like nm to find the mangled name, for example for your exmaple when I do:

nm a.out

I see something like this:

0000000100000e80 T __Z7bad_foov
...

Not sure why we obtain an extra _ but we do.