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The static keyword (static and extern are mutually exclusive), applied to the definition of an external variable, changes this a bit: the variable can only be accessed by the functions in the same module where it was defined. But it is possible for a function in the same module to pass a reference (pointer) of the variable to another function ...
stdarg.h is a header in the C standard library of the C programming language that allows functions to accept an indefinite number of arguments. [1] It provides facilities for stepping through a list of function arguments of unknown number and type. C++ provides this functionality in the header cstdarg.
In the C and C++ programming languages, an inline function is one qualified with the keyword inline; this serves two purposes: . It serves as a compiler directive that suggests (but does not require) that the compiler substitute the body of the function inline by performing inline expansion, i.e. by inserting the function code at the address of each function call, thereby saving the overhead ...
Such extern declarations are often placed in a shared header file, since it is common practice for all .c files in a project to include at least one .h file: the standard header file errno.h is an example, making the errno variable accessible to all modules in a project.
In C++, classes can be forward-declared if you only need to use the pointer-to-that-class type (since all object pointers are the same size, and this is what the compiler cares about). This is especially useful inside class definitions, e.g. if a class contains a member that is a pointer (or a reference) to another class.
The primary effect of the extern "C" declaration in C++ is to disable C++ name mangling. With other languages, separate utils or middleware are used, examples include: GNOME project: GObject Introspection; SWIG; Chromium project: Blink and V8 engine use an interface description language (IDL) compiler for standard JavaScript interfaces; Other ...
This is also valid in C++. (C++ 98/03 deprecated this usage in favor of anonymous namespaces, but is no longer deprecated in C++ 11.) Also, C++ implicitly treats any const namespace-scope variable as having internal linkage unless it is explicitly declared extern, unlike C. A name's linkage is related to, but distinct from, its scope. The scope ...
While a variable or function may be declared many times, it is typically defined once (in C++, this is known as the One Definition Rule or ODR). Dynamic languages such as JavaScript or Python generally allow functions to be redefined, that is, re-bound; a function is a variable much like any other, with a name and a value (the definition).