You can see the list of all macros gcc/g++ defines for any combination of flags like that: $ g++ -E -dD -xc++ /dev/null For example: [max@truth ~]$ g++ -E -dD -xc++ /dev/null > a [max@truth ~]$ g++ -E -dD -xc++ -g -O3 /dev/null > b [max@truth ~]$ diff a b 1a2 > # 1 “/home/max//” … Read more
Like this: #include <stdio.h> #define QUOTE(str) #str #define EXPAND_AND_QUOTE(str) QUOTE(str) #define TEST thisisatest #define TESTE EXPAND_AND_QUOTE(TEST) int main() { printf(TESTE); } The reason is that when macro arguments are substituted into the macro body, they are expanded unless they appear with the # or ## preprocessor operators in that macro. So, str (with value TEST … Read more
from the C# faq. http://blogs.msdn.com/CSharpFAQ/archive/2004/03/09/86979.aspx Why doesn’t C# support #define macros? In C++, I can define a macro such as: #define PRODUCT(x, y, z) x * y * z and then use it in code: int a = PRODUCT(3, 2, 1); C# doesn’t allow you to do this. Why? There are a few reasons why. … Read more
The C/C++ preprocessor acts in units of tokens, and a string literal is a single token. As such, you can’t intervene in the middle of a string literal like that. You could preprocess script.py into something like: “some code\n” “some more code that will be appended\n” and #include that, however. Or you can use xxd … Read more
Macros can’t expand into preprocessing directives. From C99 6.10.3.4/3 “Rescanning and further replacement”: The resulting completely macro-replaced preprocessing token sequence is not processed as a preprocessing directive even if it resembles one,
You can’t do that. You have to do something like this: #ifdef DEBUG #define DO(WHAT) MyObj->WHAT() #else #define DO(WHAT) do { } while(0) #endif The do { } while(0) avoids empty statements. See this question, for example.
__cplusplus should be defined as 199711L in pre-C++11 compilers, 201103L in those suporting C++11. Whether this is much help in practice is another question: most compilers are only halfway there, so shouldn’t be defining it as 201103L, even if they support the features you are interested in. And it’s not unheard of for a compiler … Read more
You can make use of: #ifdef __GNUC__ #ifdef __MINGW32__ For additional macros you might be interested in this page which shows other compiler macros.
An occurrence of a parameter in a function-like macro, unless it is the operand of # or ##, is expanded before substituting it and rescanning the whole for further expansion. Because g‘s parameter is the operand of #, the argument is not expanded but instead immediately stringified (“f(1,2)”). Because h‘s parameter is not the operand … Read more
The file includes itself so the same source code can be used to generate 4 different sets of functions for specific values of the macro USIZE. The #include directives are actually enclosed in an #ifndef, which limits the recursion to a single level: #ifndef USIZE // common definitions … // #define VSENC vsenc #define VSDEC … Read more