Brian Paul wrote:
>
> I've seen this before but I can't recall the reasoning for it.
> When defining a multi-statement macro people use this construct:
>
> #define MY_MACRO(FOO) \
> do { \
> statement1(FOO); \
> statement2(FOO); \
> statement3(FOO); \
> } while(0)
>
> Why is the do/while loop used?
>
> I'm asking here so everyone can be educated.
To force the compound statements to behave as a single statement, eg in if/else
statements:
if (1)
MY_MACRO(_foo);
works as expected with the do/while, but gives some funny results without. More
complicated examples can be constructed.
It also _forces_ the coder to place a semicolon after the statement, as in:
MY_MACRO(1);
MY_MACRO(2);
which isn't anything to do with correctness, but it does mean that emacs
auto-indent will continue to work correctly for these lines.
Keith
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