CODEWITHSUNDEEP
c++c++20c++-faq
Akib Azmain Turja
Akib Azmain Turja

Reputation: 1180

Difference between preprocessor macros and std::source_location

There are some predefined preprocessor macros (specified in C and C++ standard) like __line__ and __file__ which are replaced by line number and file name during preprocessing respectively. In C++20, a new class std::source_location is introduced which does more or less the same thing.

So, my questions are...

Upvotes: 4

Views: 334

Answers (1)

ComicSansMS
ComicSansMS

Reputation: 54737

Preprocessor macros live outside the type system. Preprocessor macro substitution happens outside the rest of the language. See this answer and this answer for a comprehensive discussion of the disadvantages of using the preprocessor.

std::source_location on the other hand behaves like any other C++ struct. It has plain value fields that are typed and behave like any other values in the language.

Besides that, functionality-wise the two mechanisms are equivalent. There is nothing that the one can achieve that cannot be done by the other (apart from the column field in source_location, which has no equivalent in the preprocessor). It's just that the new approach achieves its goals more nicely.

Upvotes: 4

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