diff options
Diffstat (limited to 'absl/base/internal/inline_variable.h')
| -rw-r--r-- | absl/base/internal/inline_variable.h | 30 |
1 files changed, 25 insertions, 5 deletions
diff --git a/absl/base/internal/inline_variable.h b/absl/base/internal/inline_variable.h index f7bb8c56..a65fe893 100644 --- a/absl/base/internal/inline_variable.h +++ b/absl/base/internal/inline_variable.h @@ -53,7 +53,24 @@ // it will likely be a reference type). //////////////////////////////////////////////////////////////////////////////// -#ifdef __cpp_inline_variables +// ABSL_INTERNAL_HAS_WARNING() +// +// If the compiler supports the `__has_warning` extension for detecting +// warnings, then this macro is defined to be `__has_warning`. +// +// If the compiler does not support `__has_warning`, invocations expand to 0. +// +// For clang's documentation of `__has_warning`, see +// https://clang.llvm.org/docs/LanguageExtensions.html#has-warning +#if defined(__has_warning) +#define ABSL_INTERNAL_HAS_WARNING __has_warning +#else // Otherwise, be optimistic and assume the warning is not enabled. +#define ABSL_INTERNAL_HAS_WARNING(warning) 0 +#endif // defined(__has_warning) + +// If the compiler supports inline variables and does not warn when used... +#if defined(__cpp_inline_variables) && \ + !ABSL_INTERNAL_HAS_WARNING("-Wc++98-c++11-c++14-compat") // Clang's -Wmissing-variable-declarations option erroneously warned that // inline constexpr objects need to be pre-declared. This has now been fixed, @@ -66,19 +83,21 @@ // identity_t is used here so that the const and name are in the // appropriate place for pointer types, reference types, function pointer // types, etc.. -#if defined(__clang__) +#if defined(__clang__) && \ + ABSL_INTERNAL_HAS_WARNING("-Wmissing-variable-declarations") #define ABSL_INTERNAL_EXTERN_DECL(type, name) \ extern const ::absl::internal::identity_t<type> name; #else // Otherwise, just define the macro to do nothing. #define ABSL_INTERNAL_EXTERN_DECL(type, name) -#endif // defined(__clang__) +#endif // defined(__clang__) && + // ABSL_INTERNAL_HAS_WARNING("-Wmissing-variable-declarations") // See above comment at top of file for details. #define ABSL_INTERNAL_INLINE_CONSTEXPR(type, name, init) \ ABSL_INTERNAL_EXTERN_DECL(type, name) \ inline constexpr ::absl::internal::identity_t<type> name = init -#else +#else // Otherwise, we need to emulate inline variables... // See above comment at top of file for details. // @@ -102,6 +121,7 @@ static_assert(sizeof(void (*)(decltype(name))) != 0, \ "Silence unused variable warnings.") -#endif // __cpp_inline_variables +#endif // defined(__cpp_inline_variables) && + // !ABSL_INTERNAL_HAS_WARNING("-Wc++98-c++11-c++14-compat") #endif // ABSL_BASE_INTERNAL_INLINE_VARIABLE_EMULATION_H_ |