Fields with the same name across different anonymous unions inside one union

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Is it legal to have fields with the same name across different anonymous unions inside one union?

union Foo
{
    union
    {
        int bar;
    };

    union
    {
        int bar;
    };
};

This code fails to compile by GCC but works fine in MSVC.

type-definition language-lawyer unions c++
1 Answers

This is not allowed by C++ standard. Any compiler which compiles this code is non-conformant.

See 10.4.1/1:

The names of the members of an anonymous union shall be distinct from the names of any other entity in the scope in which the anonymous union is declared.

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