Re: [avr-gcc-list] GCC native bool compile on mega8

[Ned Konz]

On Wednesday 12 January 2005 10:33 pm, A Day wrote:
> What does the AVR-GCC compile bools down to? It would be great if a
> bool compiled down to a single bit, but I suspect bools actually take
> up a full byte. I couldn't find this in the FAQ. Thanks ahead of time
> for your insight :-)

Depends on how you define a bool.

If you define it as something int-ish or pass it to a function or do math with 
it, it becomes an int. That's C, not GCC.

There's nothing keeping you from defining multiple boolean flags in a single 
byte, though:

typedef struct {
uint8_t bool0: 1;
uint8_t bool1: 1;
uint8_t bool2: 1;
uint8_t bool3: 1;
uint8_t bool4: 1;
uint8_t bool5: 1;
uint8_t bool6: 1;
uint8_t bool7: 1;
} eightBool_t;

#define true 1
#define false 0

eightBool_t someBools = { true, false, false, true, false, true, false, 
false };

/* but ... */

someFunction(someBools.bool4); /* promotes to an int */

-- 
Ned Konz
http://bike-nomad.com