Why is 'int' used as just int and why not as std::int in C++?

Question

Unlike everything is standardized in current C++, are there any specific reasons to leave int, char, ...., main() and others from it. (Not talking of +,-,%,.. because they aren't language-specific)

Why is it not like:

std::int std::main(std::int argc, std::char *argv[])
{
    //Sample C++ code (incorrect with current standards though)
    std::return 0;
}

Isn't standardization incomplete with them out of std scope?

What I believe is, they are basic components which occurs everywhere when writing a program, whether simple or complex. They are not included in the standardization, just to follow the DRY principle.

Answer 1

Keywords such as int and return and the main() function are all included in the C++ standard. std does not mean that only those things are standardized. Instead, it refers to the things that are in the standard library (which, like keywords, is a part of the standard). Include files such as #include <vector> are needed to use the standard library, but keywords can be used without any #includes.

Answer 2

std:: is the namespace name of the Standard Library. But C++ has built-in types, and those are more fundamental. In fact, significant parts of the Standard Library are built using types like int. You can see the chicken-and-egg problem if the Standard Library would depend on itself.

Answer 3

The types you mention are keywords. Keywords are not identifiers and therefore cannot belong to scopes or namespaces. During parsing of the program , keywords are found at an earlier stage than identifiers.

Changing the namespace of the program entry point (::main currently) would mean all linkers everywhere have to be updated and so I doubt there would be any support for such a move. Also it would go against the principle that std is for the standard library and not for user code, whereas the user writes the code that goes in main.