Variable length arg lists for macros

[Larry Jones]

In article <362 at island.uu.net>, walker at island.uu.net (Richard Walker) writes:
> The problem illustrated above is caused by the bad usage of the macro. The
> macro call should be formed as a statement to avoid the flow control problem.
> In other words, the errors above are caused by the missing ';' at the end
> of the trace macro call.
> 
> Especially, macros which expand into code with flow control
> should be formed such that the semicolon cleanly terminates
> the flow, e.g.:
> 
> #define COMPLEX_MACRO(foo) (if(SOME_TEST(foo)) {statements;}else)

Well, it's a good idea, but the example could be better - it could be valid
C if the replacement text didn't have the parentheses around a partial
statement!  In any case, the preferred definition of statement macros is:

#define COMPLEX_MACRO(foo) do { whatever } while (0)

That way the macro expands into a single statement, eats the following semi-
colon, and causes a syntax error if there isn't one instead of accidentally
swallowing the following statement.

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