Incomplete array type with internal linkage: missing diagnostics under -pedantic

[llvmbot]

Bugzilla Link	51319
Version	12.0
OS	Windows NT
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@zygoloid

Extended Description

Sample code (t0.c):

static int arr[ ];

int main( void )
{
return arr[ 0 ];
}

static int arr[ ] = { 0 };

Invocation: clang t0.c -std=c11 -Wall -Wextra -pedantic

Expected diagnostics: t0.c:1:12: error: array size missing in ‘arr’

Actual diagnostics:

Tool version: 12.0.0

[AaronBallman]

C23 6.9.3 (External object definitions) is what covers this. static int arr[]; is a tentative definition, and p3 makes it UB because int[] is an incomplete type. This same wording exists in all versions of C.