Consider the following example:
enum w {
// c=-1,
a,
b
};
whattodo (
char option
) {
static
struct todo {
enum w what;
char option;
} todos[]= {
{a,'a'},
{b,'b'},
{-1}
};
struct todo *p= todos;
do if (
(option && !option)
) break;
while ((++p)->what >= 0);
return p->what;
}
Compiling with -O[>0] and -Wall for x86 we have that code for
whattodo:
whattodo:
.L2:
jmp .L2
a) Formally, the code is correct. As p->what can never be < 0
according to its type.
b) GCC _silently_ allows the {-1} initialization for that type, even
with -Wall.
Uncommenting the c= -1 member of enum, or explicit casting p->what to
int solves the problem, of course. But maybe some warning would be
appropriate in such a situation? It takes some time for me to
recognize what leads me to that cool .L2: jmp .L2 from seemengly
harmless C code... Or maybe I don't know some healthy compiler
option?
