[llvm-dev] partial instrumentation seems broken

[adi t via llvm-dev]

Hi all,

I used the instruction from here:
https://clang.llvm.org/docs/SanitizerCoverage.html#partially-disabling-instrumentation

to compile the following c file

#include <stdint.h>
#include <stdio.h>
#include <sanitizer/coverage_interface.h>


void __sanitizer_cov_trace_pc_guard_init(uint32_t *start,
                                                    uint32_t *stop) {
  static uint64_t N;  // Counter for the guards.
  if (start == stop || *start) return;  // Initialize only once.
  printf("INIT: %p %p\n", start, stop);
  for (uint32_t *x = start; x < stop; x++)
    *x = ++N;  // Guards should start from 1.
}

 void __sanitizer_cov_trace_pc_guard(uint32_t *guard) {
  if (!*guard) return;  // Duplicate the guard check.

  void *PC = __builtin_return_address(0);
  char PcDescr[1024];

}


int addition(int num1, int num2)
{
     int sum;
     sum = num1+num2;
     if(sum)
      return sum;
     else
      return 0;

}

int substraction(int num1, int num2)
{
     int sum;
     sum = num1-num2;

     if(sum)
    return sum;
     else
      return -1;
}

int main()
{
     int var1, var2,res;
     printf("Enter number 1: ");
     scanf("%d",&var1);
     printf("Enter number 2: ");
     scanf("%d",&var2);

     if(var1 >1){

      res = addition(var1, var2);
      printf ("Output: %d", res);
     }
     if(var2 > 2){
      res = substraction(var1, var2);
      printf ("Output2: %d", res);
      }

     return 0;
}

test.sh

export CC=clang
export LDFLAGS="-O0 -g -fsanitize-coverage=trace-pc-guard
-fsanitize-coverage-allowlist=./whitelist.txt
-fsanitize-coverage-blocklist=./blacklist.txt"

$CC  $LD_LFAGS test.c -o test

blacklist.txt contains:
fun:addition*

and whitelist.txt contains
src:*
fun:*

Basically I want everything to be instrumented except function addition.
I'm using clang 11.

The problem is if I look in the disassembly of the binary
sanitizer_cov_trace_pc_guard in any of the 3 functions:
main/addition/substraction. It should instrument all , except addition.
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