こういうのだな
$ gcc -x c -std=c90 -Wpedantic - <<EOF
int main() {
int a = 0;
a += 1;
int c;
c = a;
return 0;
}
EOF
<stdin>: In function ‘main’:
<stdin>:4:9: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
$