C ifdef 或
WebMar 8, 2024 · or-. #if defined (LINUX) defined (ANDROID) // your code here #endif /* LINUX ANDROID */. Both above are the same, which one you use simply depends on … WebOct 14, 2015 · 2. #ifdef checks whether the name following is #define d before it. The code between the #ifdef and #endif will be ignored if the check fails. The check can be fulfilled by writing #define TEST_PURPOSE explicitly before that #ifdef, or passing /D "TEST_PURPOSE" as an argument to the MSVC compiler.
C ifdef 或
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Web如果使用 `define定义了 称为 `FLAG `的宏,那么关键字 `ifdef会告诉编译器包含这段代码 , 直到下一个 `else或`endif 。 关键字 `ifndef只是告诉编译器 ,如果给定的名为 FLAG的宏没有使用 `define指令定义,则将这段代码包含在下一个`else "或`endif之前。 WebOct 26, 2012 · 1.头文件中的#ifndef头件的中的#ifndef,这是一个很关键的东西。比如你有两个C文件,这两个C文件都include了同一个头文件。而编译时,这两个C文件要一同编译 …
WebSep 26, 2024 · 可以在任何可以使用 #if 的地方使用 #ifdef 和 #ifndef 指令。 如果定义了 identifier,#ifdefidentifier 语句等效于 #if 1。 如果 identifier 尚未定义或未被 #undef 指令 … http://c.biancheng.net/view/449.html
WebAug 2, 2024 · The #ifdef identifier statement is equivalent to #if 1 when identifier has been defined. It's equivalent to #if 0 when identifier hasn't been defined, or has been undefined by the #undef directive. These directives check only for the presence or absence of identifiers defined with #define, not for identifiers declared in the C or C++ source code.
WebMar 9, 2024 · OR condition in #ifdef. #if defined LINUX defined ANDROID // your code here #endif /* LINUX ANDROID */. #if defined (LINUX) defined (ANDROID) // your code here #endif /* LINUX ANDROID */. Both above are the same, which one you use simply depends on your taste. P.S.: #ifdef is simply the short form of #if defined, however, does …
Web#ifdef 的用法 #ifdef 用法的一般格式为: #ifdef 宏名 程序段1 #else 程序段2 #endif. 它的意思是,如果当前的宏已被定义过,则对“程序段1”进行编译,否则对“程序段2”进行编译。 … how to take care of special placesWebMar 30, 2015 · 结论:通过使用#ifdef指示符,我们可以区隔一些与特定头文件、程序库和其他文件版本有关的代码 #if, #ifdef, #ifndef, #else, #elif, #endif的用法: 这些命令可以让 … ready or not server browserWebApr 2, 2024 · 每個巢狀 #else 、 #elif 或 #endif 指示詞都屬於最接近的上述 #if 指示詞。. 所有條件式編譯指示詞,例如 #if 和 #ifdef ,都必須符合檔案結尾之前的結尾 #endif 指示詞。. 否則會產生錯誤訊息。. 當 Include 檔包含條件式編譯指示詞時,這些指示詞必須滿足相同的條 … how to take care of tadpoles and frogsWeb#ifdef, #ifndef 检查标识符是否被定义为宏名 这就是”标识符“的意思,这两个预处理条件用来判断这个宏是否被定义,而不是宏的值。 第二个例子的错误就在于,#ifdef OPEN_AUTH 是判断OPEN_AUTH这个宏是否被定义,但从上下文看, OPEN_AUTH被定义为0,语义上就 … ready or not smotret onlineWebMar 2, 2024 · Explanation. The conditional preprocessing block starts with #if, #ifdef or #ifndef directive, then optionally includes any number of #elif, #elifdef, or #elifndef (since C++23) directives, then optionally includes at most one #else directive and is terminated with #endif directive. Any inner conditional preprocessing blocks are processed separately. … ready or not shotgunWebMay 14, 2024 · C source file. In your src_file.c you need neither #ifndef nor #define.What you are implementing that way is an include guard, which is not what you want, what you actually need is:. #ifdef WITH_ATS #include "ats.h" #endif That is, to include ats.h if WITH_ATS is defined.. Note that, in your C source file, WITH_ATS is just an empty … how to take care of spidersWebJul 23, 2024 · #可以用命令行传递变量 RELEASE = abc #ifdef 变量名称不能加$() ifdef RELEASE $(warning RELEASE defined) else $(warning RELEASE not defined) endif #ifeq 后面参数要叫$(), 因为是值引用, 值可以为数值或字符串 ifeq ($(RELEASE),abc) $(warning RELEASE eqal abc) else $(warning RELEASE not equal abc) endif all: @echo ok! ready or not siterutracker.org