unexpected success with restrict keyword punning

restrict_punning.c

// I expect this to generate errors on mismatched prototypes but apparently it does not. I should probably figure out why.

// gcc -std=c1x -Wstrict-aliasing -Wall -Wno-unused-but-set-variable restrict_punning.c
// clang -std=c1x -Wstrict-aliasing -Wall restrict_punning.c

void f1(char * restrict a, char * b)
{
  return;
}

void f2(char * a, char * b)
{
  return;
}

int main() {

  void (*fp1)(char * restrict a, char * b);
  void (*fp2)(char * a, char * b);

  fp1 = f1; // match
  fp1 = f2; // fc missing restrict
  fp2 = f1; // fc extra restrict
  fp2 = f2; // match

  return 0;
}