Wrong "warning: subtraction of pointers to type 'int [n]' of zero size has undefined behavior [-Wpointer-arith]"

[llvmbot]

Bugzilla Link	27954
Version	trunk
OS	Linux
Reporter	LLVM Bugzilla Contributor

Extended Description

Source code:

---

#include <stdio.h>

int main()
{
int n = 1;
int a[n];
(void)(&a + 1 - &a);

printf("sizeof(int [n]) = %zu\n", sizeof(int [n]));
}

Results:

---

$ clang -std=c11 -Weverything -Wno-vla -O3 test.c && ./a.out
test.c:7:17: warning: subtraction of pointers to type 'int [n]' of zero size has undefined behavior [-Wpointer-arith]
(void)(&a + 1 - &a);
~~~~~~ ^ ~~
1 warning generated.
sizeof(int [n]) = 4

clang version: clang version 3.9.0 (trunk 271312)

The warning talks about zero size but the size of type 'int [n]' is not zero as illustrated by the result of printf. The warning is wrong.