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c++staticglobal-variablesconstantsdefault-value

Default value as Global const vs. Function return value

In the book Programming Principles and Practice Using C++ by Bjarne Stroustrup in section 8.6.2 Global initialization, it is recommended to define default values (e.g. for date in a calendar) as follows:

const Date& default_date()
{
  static const Date dd(1970,1,1);
  return dd;
}

How does this method compare to simply having a global constant as follows?

static const Date dd(1970,1,1);
Solution

  • The default_date function is declared with external linkage which means it can be used from any translation unit which have a suitable declaration.

    The global variable have internal linkage, and thus can only be used in the translation unit it's defined in.