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Two phase lookup – explanation needed

Posted by: admin November 30, 2017 Leave a comment

Questions:

What does it mean that compiler is using two phase lookup in order to compile template class?

Answers:

Templates are compiled (atleast) twice:

  1. Without Instantiation the template code itself is checked for syntax.
    Eg: Any syntax errors errors such as ; etc.

  2. At the time of instantiation(when the exact type is known), the template code is checked again to ensure all calls are valid for that particular type.
    Eg: The template might inturn call to functions which might not be present for that particular type.

This is called as Two Phase Lookup.