Fix clang -Wunused-member-function warnings with FMT_MAYBE_UNUSED. #1576
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include/fmt/core.h
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| @@ -132,6 +132,14 @@ | |||
| # define FMT_NORETURN | |||
| #endif | |||
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| #ifndef FMT_MAYBE_UNUSED | |||
| # if (__cplusplus >= 201703L) | |||
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I suggest replacing this check with FMT_HAS_CPP_ATTRIBUTE(maybe_unused).
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Updated to use FMT_HAS_CPP_ATTRIBUTE as requested.
However this fails the Travis C++14 build; although __has_cpp_attribute returns false it also triggers a warning that this attribute requires C++17.
That's a useful warning to have, to avoid accidental usage, so this could be something like __cplusplus >= 201703L && FMT_HAS_CPP_ATTRIBUTE(maybe_unused) as per FMT_FALLTHROUGH.
Perhaps a more general approach, to test both language version and compiler support within that version, could be:
#define FMT_HAS_CPP17_ATTRIBUTE(_attribute) (__cplusplus >= 201703L && FMT_HAS_CPP_ATTRIBUTE(_attribute))
And then use that for FMT_MAYBE_UNUSED and FMT_FALLTHROUGH.
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Perhaps a more general approach, to test both language version and compiler support within that version
Good idea.
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Great, thanks - I've added a FMT_HAS_CPP14_ATTRIBUTE to cover FMT_DEPRECATED as well so all of the version+attribute checks now use this approach.
include/fmt/core.h
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| @@ -36,6 +36,9 @@ | |||
| # define FMT_HAS_CPP_ATTRIBUTE(x) 0 | |||
| #endif | |||
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| #define FMT_HAS_CPP14_ATTRIBUTE(_attribute) (__cplusplus >= 201402L && FMT_HAS_CPP_ATTRIBUTE(_attribute)) | |||
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Why underscore in _attribute?
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I normally underscore macro parameters to help distinguish them from regular variable names.
That's not the normal fmt style though so I've removed them and run clang-format as requested.
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LGTM but please apply clang-format to your changes. Thanks! |
…guage-specific attributes. FMT_DEPRECATED is now defined as FMT_HAS_CPP14_ATTRIBUTE(deprecated), as this attribute was introduced in C++14. FMT_FALLTHROUGH is now defined as FMT_HAS_CPP17_ATTRIBUTE(fallthrough), as this attribute was introduced in C++17. FMT_MAYBE_UNUSED is defined as FMT_HAS_CPP17_ATTRIBUTE(maybe_unused), as this attribute was introduced in C++17. FMT_MAYBE_UNUSED has been applied to fix a couple of -Wunused-member-function warnings from clang.
FMT_MAYBE_UNUSED currently expands to the [[maybe_unused]] attribute on C++17.
It could be extended to previous language versions with a compiler-specific attribute if required.