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#include <stdio.h>
 
#define STATIC_ASSERT(COND) typedef char static_assertion_##__LINE__[(COND) ? 1 : -1]
#define ENSURE_SIZE(structure, size) STATIC_ASSERT(sizeof(structure) == size)
 
typedef struct
{
	unsigned a;
	unsigned b;
} foo;
ENSURE_SIZE(foo, sizeof(unsigned));
 
int main(void) {
	unsigned local_a = 0;
	foo *f = (foo *)(&local_a);
	printf("address local_a: %X, f->a: %X\n", &local_a, &f->a);
	return 0;
}
 

prog.c:3:42: error: size of array 'static_assertion___LINE__' is negative
 #define STATIC_ASSERT(COND) typedef char static_assertion_##__LINE__[(COND) ? 1 : -1]
                                          ^
prog.c:4:38: note: in expansion of macro 'STATIC_ASSERT'
 #define ENSURE_SIZE(structure, size) STATIC_ASSERT(sizeof(structure) == size)
                                      ^
prog.c:11:1: note: in expansion of macro 'ENSURE_SIZE'
 ENSURE_SIZE(foo, sizeof(unsigned));
 ^
prog.c: In function 'main':
prog.c:16:9: warning: format '%X' expects argument of type 'unsigned int', but argument 2 has type 'unsigned int *' [-Wformat=]
  printf("address local_a: %X, f->a: %X\n", &local_a, &f->a);
         ^
prog.c:16:9: warning: format '%X' expects argument of type 'unsigned int', but argument 3 has type 'unsigned int *' [-Wformat=]

Standard output is empty