Backport of C23's typeof_unqual using GNU extensions

gnuc_typeof_unqual.c

/* If you compile with clang and `-Weverything' you'll probably want
 * to use `-Wno-gnu-statement-expression-from-macro-expansion', too.
 *
 * Plain C18 version:
 *   https://gist.github.com/imaami/92b38f45142f8a8390fefa2d972bc63d
 */
#define typeof_unqual(x) __typeof__(({ *(__typeof__(x) *)(void *)0; }))

int main(void)
{
	const int ci = 1;
	typeof_unqual(ci)        i1 = ci;
	typeof_unqual(const int) i2 = ci;
	i1 = 0;
	i2 = 0;
	return i1 + i2;
}