Little Update Some compilers might support __has_include ( header-name ). The extension was added to the C++17 standard (P0061R1). Compiler Support Clang GCC from 5.X Visual Studio from VS2015 Update 2 (?) Example (from clang website): // Note the two possible file name string formats. #if __has_include(“myinclude.h”) && __has_include(<stdint.h>) # include “myinclude.h” #endif Sources SD-6: … Read more
One thing to be aware of when you’re using the token-paste (‘##‘) or stringizing (‘#‘) preprocessing operators is that you have to use an extra level of indirection for them to work properly in all cases. If you don’t do this and the items passed to the token-pasting operator are macros themselves, you’ll get results … Read more
Yes, it’s guaranteed. It works because arguments to macros are themselves macro-expanded, except where the macro argument name appears in the macro body with the stringifier # or the token-paster ##. 6.10.3.1/1: … After the arguments for the invocation of a function-like macro have been identified, argument substitution takes place. A parameter in the replacement … Read more
They are not the same. The first one doesn’t work (I tested in gcc 4.4.1). Error message was: test.cc:1:15: warning: extra tokens at end of #ifdef directive If you want to check if multiple things are defined, use the second one.
NB: The steps below will solve 90% of your Xcode archive issues however, from the comments it is suggested you try quitting Xcode first. This may save you hours of setting tweaking. Check the “user header paths” are correct (Add “” to paths for spaces, both in your project and dependencies) Set “Always search user … Read more
The technique from Making something both a C identifier and a string? can be used here. As usual with such preprocessor stuff, writing and understanding the preprocessor part can be hard, and includes passing macros to other macros and involves using # and ## operators, but using it is real easy. I find this style … Read more
This allows you to override the macros when you’re compiling: gcc -DMACRONAME=value The definitions in the header file are used as defaults.
Not possible. Do it the other way around: #ifdef COVERAGE_TOOL #define COV_ON(x) _Pragma (COVERAGE #x) #else #define COV_ON(x) #endif
Yes, we can. The #endif statement matches to the previous #if #ifdef or #ifndef etc for which there hasn’t been a corresponding #endif. e.g. #if ———-| #if —–| | #endif —| | #endif ——–|
The command echo | gcc -E -Wp,-v – will show the include path in use.