C++ 布尔运算符可以与预处理器一起使用吗？
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Can boolean operators be used with the preprocessor?
提问by Wesley
I wondering if it possible to have a preprocessor OR or AND statement? I have this code where I want to run under _DEBUGor _UNIT_TESTtags(?).
我想知道是否有可能有一个预处理器 OR 或 AND 语句？我有这个代码，我想在_DEBUG或_UNIT_TEST标签下运行（？）。
What I want is something like the following:
我想要的是以下内容：
#if _DEBUG || _UNIT_TEST
//Code here
#endif
If this is not possible, is there a workaround to achieve the same thing without having to duplicate the code using a #elseif?
如果这是不可能的，是否有一种解决方法可以实现相同的目的而不必使用#elseif?
回答by Kirill V. Lyadvinsky
#if defined _DEBUG || defined _UNIT_TEST
//Code here
#endif
You could use AND and NOT operators as well. For instance:
您也可以使用 AND 和 NOT 运算符。例如：
#if !defined _DEBUG && defined _UNIT_TEST
//Code here
#endif
回答by Roman Starkov
#iftakes anyC++ expression of integral type(1) that the compiler manages to evaluate at compile time. So yes, you can use ||and &&, as long as you use defined(SOMETHING)to test for definedness.
#if接受编译器在编译时设法计算的任何整数类型 (1) 的 C++ 表达式。所以是的，你可以使用||and &&，只要你defined(SOMETHING)用来测试定义性。
(1): well, it's a bit more restricted than that; for the nitty-gritty see the restrictions here(at "with these additional restrictions").
(1)：嗯，它比那更受限制；有关细节，请参阅此处的限制（在“带有这些附加限制”）。
回答by AshleysBrain
#if defined(_DEBUG) || defined(_UNIT_TEST)
//Code here
#endif
Also for the record, it's #elif, not #elseif.
另外为了记录，它是#elif，不是#elseif。
