do{..}while(0) macro substitutions

From: Yan (rottled_at_gmail.com)
Date: 12/31/04 

Date: Thu, 30 Dec 2004 23:29:27 GMT

A lot of times when reading open software, i come across macros that are
defined as follows:

#define CALL_FUNCS(x) \
do { \
    func1(x); \
    func2(x); \
    func3(x); \
} while (0);

now, of course this will work but how is this any better than:

#define CALL_FUNCS(x) \
{ \
    func1(x); \
    func2(x); \
    func3(x); \
}

i can't see how the compiler can optimize (a) any better than (b) or in
any case can (b) break what (a) won't. Any input will be appreciated.

tia

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