void aaalib_trim(char *in) {
size_t n = strlen(in);
if(n != 0) {
while(isspace(in[--n]))
;
in[n+1] = 0;
}
return;
}

The compiler is probably buggy.
If the for loop is the issue, the above code will
compile with no errors.
But i wouldn't use a compiler that cannot properly
parse and check C code..