gcc - Static assert in C

Question

What's the best way to achieve compile time static asserts in C (not C++), with particular emphasis on GCC?

Answer 1

C11 standard adds the _Static_assert keyword.

This is implemented since gcc-4.6:

_Static_assert (0, "assert1"); /* { dg-error "static assertion failed: "assert1"" } */

The first slot needs to be an integral constant expression. The second slot is a constant string literal which can be long (_Static_assert(0, L"assertion of doom!")).

I should note that this is also implemented in recent versions of clang.