Missing warning for bool conversion from pointer

[mkbosmans]

When compiling the code

#include<stdbool.h>

void getBool(bool out);
void getInt(int out);

void test(bool *b, int* i);
void test(bool *b, int* i) {
  getBool(b);
  getInt(i);
}

with clang -std=c99 -Weverything -c bool_pointer_warning.c, I get a warning about the pointer argument of getInt, but not about the pointer argument of getBool.

I guess that is because a pointer is implicitly converted to a boolean, but it would be nice to be able to ask to be warned about the forgotten pointer dereference here.

[shafik]

I think warning on converting a pointer to bool would be difficult but CC @AaronBallman

[AaronBallman]

Well, implementation-wise, it would be easy to do the naive implementation. However, the problem is that implicit conversion from pointer to bool is an incredibly common idiom and there's basically no way we could enable the diagnostic by default. We could maybe reduce the chattiness by restricting it only to diagnosing when a pointer to bool is implicitly converted to a bool, but I'm not certain whether that would be sufficient to allow us to enable the diagnostic by default; someone would have to run the check over a large corpus of code to see how many true positives it finds compared to false positives.