Question

Suppose I 宣布了一个宏观名称,xyz()。

现在,我在第二次会议上正在创建另一个宏观<代码>xyz1()和参照第1个宏观(即xyz(<>)。

最后,Ill还创立了另一个宏观xyz2()和第三版第二版。

Now my question is: is this correct (it s executing without any problem)? Macro xyz() is defined twice. Why its not giving an error? What is the solution?

Answer 1

无,只有一度界定第一个宏观wiil。页: 1

#define Symbol SymbolResolution

预处理器将取代<代码>Symbol>>。凡是见Symbol。如果Symbol Resolution is a #define , or includes some sign that have #define s within same will be used to them, they will all be amended. 直到没有在整个翻译单位有<代码>#define的符号。

因此,你可以像你所希望的那样,参考其他宏观。然而,你可以追溯性地参照宏观。你们也应谨慎从事这项工作——如果你滥用宏观方法,这很容易导致难以读懂的很多东西,而且很难减少编码。

Answer 2

如果你指其他宏观,就是合法的。

When the preprocessor expands a macro name, the macro s expansion replaces the macro invocation, then the expansion is examined for more macros to expand.

#define hello() (12)
#define test() (1+hello())

然而,宏观呼吁本身并非合法。

A self-referential macro is one whose name appears in its definition. Recall that all macro definitions are rescanned for more macros to replace. If the self-reference were considered a use of the macro, it would produce an infinitely large expansion. To prevent this, the self-reference is not considered a macro call.

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