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C++ Tips : Translation Unit

Translation unit, internal linkage, external linkage.

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By Haluk Oral
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C++ Tips : Translation Unit

My C++ Notes

Translation Unit

Translation Unit

  • Consist of SOURCE file after it has processed by PREPROCESSOR.
  • Header files are literally included.
  • All macros are expanded and conditional compilation is resolved.
  • Each translation unit is compiled independently.

External Linkage

  • function or global variable is accessible throughout your program

Internal Linkage

  • ONLY accessible in 1 translation unit

You can explicitly control the linkage by using extern and static keyword. Default linkage:

  • non-const -> extern
  • const -> intern
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// global scope.

int i; // extern
extern const int j; // explicitly extern

const int x; // intern 
static int y; // explicitly intern

int f(); // extern 
static int sf(); // explicitly intern

It is better to use unnamed namespace for making explicitly intern.

Stack overflow: What is external linkage and internal linkage?.

programming, cpp
cpp translation unit internal linkage external linkage
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