Is it correct way to write a multiple statements in one Macro?
#define AB() do { printf("hi"); } while(0)
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1A macro is just text replacement. I don't think the question makes sense. You don't generally have something *in* a macro because a macro is not a syntactic unit. – Kerrek SB Sep 30 '16 at 09:57
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Now that depends on how you want to use the macro – Simon Black Sep 30 '16 at 09:57
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The macro in question has the advantage that the use can be written as a function call, i.e. `AB();` – Paul Ogilvie Sep 30 '16 at 10:03
2 Answers
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Yes.
Although the correct way is most often to not have any function-like macro at all.
Please note that the do-while(0) trick is only relevant in code bases with sloppy brace style, such as
if(x)
AB();
else
The do-while(0) trick will prevent compiler errors caused by the stray semi-colon, if there is an else statement following. Had the macro only used braces, you'd get if(){}; else which is a syntax error.
Note that the above brace style caused one of the most expensive software bugs in history, known as the Apple "goto-fail" bug. So there are very sound reasons never to use it. If you always use {} after every statement, the do-while(0) trick also turns irrelevant.
Lundin
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Yes this is the correct way.
Ideally you want a macro to expand into a single statement, not a compound statement. Yours satisfies that.
You can safely use this macro in an if, else block.
Bathsheba
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