Reserved Identifiers

Identifiers with two initial underscores or an initial underscore followed by an uppercase letter are reserved globally for use by the compiler.

C Identifiers that begin with an underscore are reserved as identifiers with file scope in both the ordinary and tag name spaces.

C++C++ extends the C reservations to include more identifiers in a larger name space. Any name that contains double underscores anywhere is reserved. Any identifier that begins with an underscore is reserved in the global namespace.

Related References

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