What is a "translation unit" in C++?
I am reading at the time the "Effective C++" written by Scott Meyers and came across the term "translation unit".
Could somebody please give me an explanation of:
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What exactly it is?
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When should I consider using it while programming with C++?
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Is it related to C++ only, or it can be used with other programming languages as well?
I might already use it without knowing the term...
From here: (wayback machine link)
According to standard C++ (wayback machine link) : A translation unit is the basic unit of compilation in C++. It consists of the contents of a single source file, plus the contents of any header files directly or indirectly included by it, minus those lines that were ignored using conditional preprocessing statements.
A single translation unit can be compiled into an object file, library, or executable program.
The notion of a translation unit is most often mentioned in the contexts of the One Definition Rule, and templates.
A translation unit is for all intents and purposes a file (.c/.cpp), after it's finished including all of the header files.
http://msdn.microsoft.com/en-us/library/bxss3ska%28VS.80%29.aspx
A hard question to answer definitively. The C++ standard states:
The text of the program is kept in units called source files in this International Standard. A source file together with all the headers (17.4.1.2) and source files included (16.2) via the preprocessing directive #include, less any source lines skipped by any of the conditional inclusion (16.1) preprocessing directives, is called a translation unit. [Note: a C++ program need not all be translated at the same time. ]
So for most intents and purposes a translation unit is a single C++ source file and the header or other files it includes via the preprocessor #include mechanism.
Regarding your other questions:
- When should I consider using it when programming with C++
You can't not use it - translation units are the basis of a C++ program.
- If it is related only to C++, or it can be used with other programming languages
Other languages have similar concepts, but their semantics will be subtly different. Most other languages don't use a preprocessor, for example.