index_out_of_bounds.c

// Example compilation:
// gcc index_out_of_bounds.c -std=c99 -Wall -Wextra
//
// Compiles with ZERO warnings/errors on gcc 10.2.0
//
// Adding -O2 or above causes 2 warnings
//  for the printf line (this is by design of gcc, not a bug):
// array subscript -80 is below array bounds of ‘const int[5]’ [-Warray-bounds]
// array subscript 80 is above array bounds of ‘const int[5]’ [-Warray-bounds]
//
// -Warray-bounds is enabled by -Wall
//
// Info on gcc warnings:
// https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

#include <stdio.h>

int main(void) {
	const int pos_foo = 80;
	const int neg_foo = -80;
	const int numbers[] = {575757, 111, 222, 333, 444};

	printf("pos: %d neg: %d\n", numbers[pos_foo], numbers[neg_foo]);

	return 0;
}