- Prefix header
computer programming, a prefix headeris a feature found in some C or C++ compilersused to simplify code and/or to reduce compilation time.
In the C and
C++programming languages, a header fileis a file whose text is automatically included in another source file by the compiler, usually by the use of compiler directives at the beginning of the source file. A prefix header differs from a normal header file in that it is "automatically" included at the beginning of every source file by the compiler, without the use of any compiler directives.
Prefix headers are usually pre-compiled in order to reduce compilation times.
Mac OS X, the Xcodebuild system generates prefix headers automatically for new projects. A new Cocoa project, for instance, gets a prefix header that looks like this:
As a result, it is unnecessary to explicitly include any of the above files in any
Objective-Ccode in the program, although doing so is harmless, in the case of Objective-C because of the semantics of the
#importdirective, but more generally with
#includebecause of the use of
Similar prefix headers are generated for other types of project.
* [http://developer.apple.com/documentation/DeveloperTools/Conceptual/XcodeBuildSystem/800_bs_speed_up_build/chapter_8_section_2.html Xcode User Guide: Using a Precompiled Prefix Header]
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