Compiler version and platform:
Intel(R) C Intel(R) 64 Compiler for applications running on Intel(R) 64, Version 17.0.1.132 Build 20161005
$ icc -O1 small.c; ./a.out; echo $?
0
$
$ icc -Os small.c; ./a.out; echo $?
255
$
$ cat small.c
short a = 2;
int main ()
{
while (a)
a -= 3;
return a;
}
$