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#ifdef __cplusplus
// C++ code
#else
// C code
#endif
The structure is this.
My question is, how to actually trigger the #ifdef on?
I mean, in program? What code I write can turn #ifdef on?
For example, in this case. is that
#define __cplusplus
will turn it on?
526
__cplusplus. This macro is defined when the C++ compiler is in use. You can use __cplusplus to test whether a header is compiled by a C compiler or a C++ compiler. This macro is similar to __STDC_VERSION__ , in that it expands to a version number.
The meaning of #ifdef is that the code inside the block will be included in the compilation only if the mentioned preprocessor macro is defined. Similarily #if means that the block will be included only if the expression evaluates to true (when replacing undefined macros that appears in the expression with 0).
C++ preprocessor macro __cplusplus The __cplusplus preprocessor macro is defined if the compilation unit is compiled with a C++ compiler. Its value corresponds to the C++ standard that the compiler uses to compile a compilation unit.
To see if your compiler has C++11 support, run it with just the --version option to get a print out of the version number. Do this for whichever compiler(s) you wish to use with Rosetta. Acceptable versions: GCC/g++: Version 4.8 or later.
"#define __cplusplus"
will let it on?
Yes, it will "let it on".
__cplusplus should be automatically defined by C++ compiler. C++ uses different name mangling and the macro often used to make C headers compatible with C++:
#ifdef __cplusplus
extern "C" {
#endif
...
#ifdef __cplusplus
}
#endif
Just compile it with a C++ compiler and __cplusplus is defined automatically in that case.
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