An example to illustrate the surprising precedence of `<<` in action.

prec.c

#include <stdio.h>

int main(int argc, char *argv[]) {
    printf("1 << 1 + 2      = %d\n", 1 << 1 + 2);
    printf("1 << 1 * 3      = %d\n", 1 << 1 * 3);
    printf("1 << 1 + 1 << 1 = %d\n", 1 << 1 + 1 << 1);

    return 0;
}

Build and run:

% gcc -Wall -o prec prec.c && ./prec
prec.c: In function ‘main’:
prec.c:4:5: warning: suggest parentheses around ‘+’ inside ‘<<’ [-Wparentheses]
prec.c:6:5: warning: suggest parentheses around ‘+’ inside ‘<<’ [-Wparentheses]
1 << 1 + 2      = 8
1 << 1 * 3      = 8
1 << 1 + 1 << 1 = 8