Compiler Support

Feature	GCC	Clang	MSVC
[[fallthrough]]	7.0	3.9	15.0
[[nodiscard]]	7.0	3.9	15.3
[[maybe_unused]]	7.0	3.9	15.3
Attributes for namespaces and enumerators	4.9/6[^gccnote]	3.4	14.0
Ignore unknown attributes	All versions	3.9	14.0
Using attribute namespaces without repetition	7.0	3.9	15.3

All of the above compilers also support C++11/14 attributes.

[^gccnote]: GCC 4.9 (namespaces) / GCC 6 (enumerations)

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In the next chapter, we will explore the changes in std::optional.