WebThis macro name can be used with the conditional preprocessor #ifdef directive or #if with the defined () operator to tell whether a source code or include file is being compiled as C++ or C. #ifdef __cplusplus printf ("C++\n"); #else printf ("C\n"); #endif Or you could use #if defined (__cplusplus) printf ("C++\n"); #else printf ("C\n"); #endif WebFeb 19, 2009 · Not only should you use a unique and predictable (internal) include guard but you should also consider using (external) include guards around each preprocessor include directive in header files. The following is a small example, both a.h and b.h include base.h but preprocessor will have information to not even visit base.h a second time.
Header files (C++) Microsoft Learn
WebAug 2, 2024 · The identifier can be passed from the command line using the /D option. Up to 30 macros can be specified with /D. The #ifdef directive is useful for checking whether a definition exists, because a definition can be passed from the command line. For example: C++ // ifdef_ifndef.CPP // compile with: /Dtest /c #ifndef test #define final #endif Web跨平台C++;代码和单头-多个实现 我听说编写跨平台C++代码的方法是定义类如下(例如,窗口类):,c++,cross-platform,header-files,C++,Cross Platform,Header Files,然后相应地选 … biogenetics scam
How can I determine in a C++ header file whether C++/CX is …
WebMar 30, 2024 · Header files, which typically contain declarations of functions, classes, and other data types, are included in other source files that need to use them. When a header … WebJun 10, 2024 · This is defined to a string literal representing the version of C++/WinRT that is active. In addition to serving as a feature detector, this macro is used to ensure that all of the C++/WinRT header files you use are compatible with each other. (If not, you will get a compile-time assertion failure.) WebJan 27, 2024 · This type of preprocessor directive tells the compiler to include a file in the source code program. There are two types of files that can be included by the user in the program: Header files or Standard files: These files contain definitions of pre-defined functions like printf (), scanf (), etc. bio genetics pills