Uhh, perhaps I'm not parsing your claim correctly, but that warning most certainly does exist in gcc.
$ gcc -Wall test.c
test.c: In function ‘main’:
test.c:6:5: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
if (a = b) {
^
Parentheses here would be superfluous, but would perhaps confirm you really intended to assign (i.e. used = instead of ==).
Parentheses here would be superfluous, but would perhaps confirm you really intended to assign (i.e. used = instead of ==).