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The C preprocessor (CPP) is a text file processor that is used with C, C++ and other programming tools.The preprocessor provides for file inclusion (often header files), macro expansion, conditional compilation, and line control.
A variadic macro is a feature of some computer programming languages, especially the C preprocessor, whereby a macro may be declared to accept a varying number of arguments. Variable-argument macros were introduced in 1999 in the ISO/IEC 9899:1999 ( C99 ) revision of the C language standard, and in 2011 in ISO/IEC 14882:2011 ( C++11 ) revision ...
For #include guards to work properly, each guard must test and conditionally set a different preprocessor macro. Therefore, a project using #include guards must work out a coherent naming scheme for its include guards, and make sure its scheme doesn't conflict with that of any third-party headers it uses, or with the names of any globally visible macros.
In computer science, a preprocessor (or precompiler) [1] is a program that processes its input data to produce output that is used as input in another program. The output is said to be a preprocessed form of the input data, which is often used by some subsequent programs like compilers .
This example aims to improve the readability of the X macro usage by: Prefix the name of the macro that defines the list with "FOR_". Pass name of the worker macro into the list macro. This both avoids defining an obscurely named macro (X), and alleviates the need to undefine it. Use the syntax for variadic macro arguments "..." in the worker ...
Note that the preprocessor is in principle language agnostic, and is a lexical preprocessor, working at the lexical analysis level – it does not do parsing, and thus is unable to do any processing specific to C syntax. The input to the compiler is the translation unit, and thus it does not see any preprocessor directives, which have all been ...
Using #pragma once allows the C preprocessor to include a header file when it is needed and to ignore an #include directive otherwise. This has the effect of altering the behavior of the C preprocessor itself, and allows programmers to express file dependencies in a simple fashion, obviating the need for manual management.
It defines the C preprocessor macro assert and implements runtime assertion in C. assert.h is defined in ANSI C as part of the C standard library. In the C++ programming language, assert.h and < cassert > are available; both are functionally equivalent.