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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 ...
Some things, like types, templates, and extern inline functions, can be defined in more than one translation unit. For a given entity, each definition must have the same sequence of tokens. Non-extern objects and functions in different translation units are different entities, even if their names and types are the same.
A common practice for header files to maintain both C and C++ compatibility is to make its declaration be extern "C" for the scope of the header: [21] /* Header file foo.h */ #ifdef __cplusplus /* If this is a C++ compiler, use C linkage */ extern "C" { #endif /* These functions get C linkage */ void foo (); struct bar { /* ... */ }; #ifdef ...
The declaration informs the compiler that a variable by that name and type exists, but the compiler does not need to allocate memory for it since it is allocated elsewhere. The extern keyword means "declare without defining". In other words, it is a way to explicitly declare a variable, or to force a declaration without a definition.
In C and C++, the line above represents a forward declaration of a function and is the function's prototype. After processing this declaration, the compiler would allow the program code to refer to the entity printThisInteger in the rest of the program. The definition for a function must be provided somewhere (same file or other, where it would ...
C++ has a trivial FFI with C, as the languages share a significant common subset. 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
A newer language construct (since C++11 and C23), constexpr allows for declaring a compile-time constant value that need not consume runtime memory. [20] Inline function. For a long time, a function-like macro was the only way to define function-like behavior that did not incur runtime function call overhead.
In computer programming, a declaration is a language construct specifying identifier properties: it declares a word's (identifier's) meaning. [1] Declarations are most commonly used for functions, variables, constants, and classes, but can also be used for other entities such as enumerations and type definitions. [1]