Re: [patch 1/1] consolidate TRUE and FALSE

Jan Engelhardt
2006-03-18T21:57:37Z

>
>Isn't there a runtime cost converting all "non-false" values to a unique "true" (i.e. converting non-zero values to one) ?
>

Somewhat. The answer is "yes, but depends on usage". If you just
write

_Bool x = filthy_action();
if(x)

Then the compiler is smart enough to optimize 'x' away if it is not used
somewhere else, therefore we do not pay a price for converting the return
type of filthy_action (=int) to a _Bool.

The asm output for storing the result of filthy_action() [requires
'volatile int x' in this small example]

call strxcmp
mov [ebp-4], eax

While making that a 'volatile _Bool x' makes it:

call strxcmp
test eax, eax
setnz al
mov [ebp-1], al

Makes me prefer typedef int bool over _Bool.

Jan Engelhardt
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