May 14, 2011 · Most compilers will allow you to define a macro from the command line (e.g. g++ -DDEBUG something.cpp), but you can also just put a define in your code like so: #define …

As far as I know, what you're trying to do (use if statement and then return a value from a macro) isn't possible in ISO C... but it is somewhat possible with statement expressions (GNU …

In other words, when the compiler starts building your code, no #define statements or anything like that is left. A good way to understand what the preprocessor does to your code is to get …

Oct 28, 2009 · #define is a compiler pre processor directive and should be used as such, for conditional compilation etc.. E.g. where low level code needs to define some possible …

Nov 27, 2015 · In the normal C or C++ build process the first thing that happens is that the PreProcessor runs, the preprocessor looks though the source files for preprocessor directives …

Mar 4, 2017 · #define simply substitutes a name with its value. Furthermore, a #define'd constant may be used in the preprocessor: you can use it with #ifdef to do conditional compilation …

Aug 19, 2008 · #define is used to define compile-time constants that you can use with #if to include or exclude bits of code. #define USEFOREACH #if USEFOREACH foreach(var item in …

Aug 24, 2010 · Macros (created with #define) are always replaced as written, and can have double-evaluation problems. inline on the other hand, is purely advisory - the compiler is free …

#define is a special "before compile" directive in C# (it derives from the old C preprocessor directives) that defines a preprocessor symbol. Coupled with #if , depending on what symbols …

Jun 18, 2012 · The scope of #define is limited to the file in which it is defined. So, #defines which are created in one source file are NOT available in a different source file. In short, #defines …