Well first, you can do pattern matching with the preprocessor using the ##. This is how an IIF macro could be defined: #define IIF(cond) IIF_ ## cond #define IIF_0(t, f) f #define IIF_1(t, f) t However there is one problem with this approach. A subtle side effect of the ## operator is that it inhibits … Read more
Use gcc -E to only run the preprocessor part, e.g. give a file in.c #if 0 0; #endif #if 1 1; #endif running $ gcc -E in.c -o in.i yields a file in.i # 1 “in.cpp” # 1 “<built-in>” # 1 “<command-line>” # 1 “in.cpp” 1; i.e. the parts behind the #if 0 got removed. … Read more
#define STRINGIFY2(X) #X #define STRINGIFY(X) STRINGIFY2(X) #define A 2 Then STRINGIFY(A) will give you “2”. You can concatenate it with other string literals by putting them side by side. “I have the number ” STRINGIFY(A) “.” gives you “I have the number 2.”.
Project properties -> C/C++ -> Preprocessing -> Preprocess to a file: Yes (/P) The files will be called .i and will be created in the build directory. Also see the msdn page.
You can choose the “Show the Assistant editor” view in the top right set of buttons in the toolbar. Then, at the top of the right-hand editor you can click the little Related Files button and then either choose Preprocess or Assembly. You can see an example of both the preprocessor output and generated assembly … Read more
In MSVC you could use push_macro pragma, GCC supports it for compatibility with Microsoft Windows compilers. #pragma push_macro(“MACRONAME”) #undef MACRONAME // some actions #pragma pop_macro(“MACRONAME”)
The C++ Standard says (16.3.4.3): The resulting completely macro-replaced preprocessing token sequence [… of the macro expansion…] is not processed as a preprocessing directive even if it resembles one… So no, there is no ‘official’ way of achieving what you want with macros.
Place anywhere: #ifndef DEBUG #error “Only Debug builds are supported” #endif For reference: Diagnostics
It is used if you want to replace a default header with one of your own making, for example, let’s say you want to replace “stdlib.h”. You would create a file called stdlib.h in your project, and that would be included instead of the default header. #include_next is used if you want to add some … Read more
On systems with gnu linker and compiler or something compatible, it’s possible to put certain objects in different sections. The linker will then generate symbols for the start and end of the section. Using that you can put all your structs into that section in different objects, the linker will consolidate those sections when linking … Read more