First, I found that its not possible to define the type of the constant using #define, why is that? Why is what? It’s not true: #define MY_INT_CONSTANT ((int) 12345) Second, are there any advantages to use one of them over the another one? Yes. #define defines a macro which is replaced even before compilation starts. … Read more
I end up having to remember what the macro is and substitute it in my head as I read. That seems to reflect poorly on the naming of the macros. I would assume you wouldn’t have to emulate the preprocessor if it were a log_function_entry() macro. The ones that I have encountered that were intuitive … Read more
No, because there’s no precompiler. However, in your case you could achieve the same thing as follows: class MyClass { private static final int PROTEINS = 0; … MyArray[] foo = new MyArray[PROTEINS]; } The compiler will notice that PROTEINS can never, ever change and so will inline it, which is more or less what … Read more
gcc -E file.c or g++ -E file.cpp will do this for you. The -E switch forces the compiler to stop after the preprocessing phase, spitting all it’s got at the moment to standard output. Note: Surely you must have some #include directives. The included files get preprocessed, too, so you might get lots of output. … Read more
#if defined _DEBUG || defined _UNIT_TEST //Code here #endif You could use AND and NOT operators as well. For instance: #if !defined _DEBUG && defined _UNIT_TEST //Code here #endif
I discovered X-macros a couple of years ago when I started making use of function pointers in my code. I am an embedded programmer and I use state machines frequently. Often I would write code like this: /* declare an enumeration of state codes */ enum{ STATE0, STATE1, STATE2, … , STATEX, NUM_STATES}; /* declare … Read more
C language define execution environment in two categories: freestanding and hosted. In both execution environment a function is called by the environment for program startup. In a freestanding environment program startup function can be implementation defined while in hosted environment it should be main. No program in C can run without program startup function on … Read more
Well macros don’t directly expand recursively, but there are ways we can work around this. The easiest way of doing recursion in the preprocessor is to use a deferred expression. A deferred expression is an expression that requires more scans to fully expand: #define EMPTY() #define DEFER(id) id EMPTY() #define OBSTRUCT(…) __VA_ARGS__ DEFER(EMPTY)() #define EXPAND(…) … Read more
Here is my homework of the day, it’s based on macro tricks and today I particularly learnt about __VA_NARG__ invented by Laurent Deniau. Anyway, the following sample code works up to 8 fields for the sake of clarity. Just extend the code by duplicating if you need more (this is because the preprocessor doesn’t feature … Read more
To elaborate (Neil Butterworth and blue.tuxedo have already given the correct answer): WIN32 is defined by the SDK or the build environment, so it does not use the implementation reserved namespace _WIN32 is defined by the compiler so it uses the underscore to place it in the implementation-reserved namespace You’ll find a similar set of … Read more