On Jun 10, 2005, at 05:15:15, Pavel Machek wrote:
Hi!
do {} while (0)
, else you are preparing trap for someone.
Can you please explain what the difference between these two are?
Some compiler version specific thing?
It took me quite some remembering. Problem is that with your macros,
someone can write
dyn_tick_reprogram_timer()
printk();
[notice missing ; at first line], and still get it compile. If you
replace {} with do {} while (0), he'll get compile error as he should.
Actually, the real reason is for something like this:
#define myfunc1() {}
#define myfunc2() {}
if (a && b) myfunc1();
else myfunc2();
This would be translated as:
if (a && b) {};
else {};
Which would generate a syntax error:
zeus:~ kyle$ gcc -c `y -e .c` -o tmp.o <<'EOF'
> #define myfunc1() {}
> #define myfunc2() {}
> void x() {
> int a = 0, b = 1;
> if (a && b) myfunc1();
> else myfunc2();
> }
> EOF
/tmp/y.c8F08d.c: In function ‘x’:
/tmp/y.c8F08d.c:4: error: parse error before "else"
Cheers,
Kyle Moffett
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