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Diffstat (limited to 'absl/base/attributes.h')
-rw-r--r-- | absl/base/attributes.h | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/absl/base/attributes.h b/absl/base/attributes.h index c4fd81b0..2cf4b1e8 100644 --- a/absl/base/attributes.h +++ b/absl/base/attributes.h @@ -594,6 +594,85 @@ #define ABSL_ATTRIBUTE_FUNC_ALIGN(bytes) #endif +// ABSL_FALLTHROUGH_INTENDED +// +// Annotates implicit fall-through between switch labels, allowing a case to +// indicate intentional fallthrough and turn off warnings about any lack of a +// `break` statement. The ABSL_FALLTHROUGH_INTENDED macro should be followed by +// a semicolon and can be used in most places where `break` can, provided that +// no statements exist between it and the next switch label. +// +// Example: +// +// switch (x) { +// case 40: +// case 41: +// if (truth_is_out_there) { +// ++x; +// ABSL_FALLTHROUGH_INTENDED; // Use instead of/along with annotations +// // in comments +// } else { +// return x; +// } +// case 42: +// ... +// +// Notes: when compiled with clang in C++11 mode, the ABSL_FALLTHROUGH_INTENDED +// macro is expanded to the [[clang::fallthrough]] attribute, which is analysed +// when performing switch labels fall-through diagnostic +// (`-Wimplicit-fallthrough`). See clang documentation on language extensions +// for details: +// https://clang.llvm.org/docs/AttributeReference.html#fallthrough-clang-fallthrough +// +// When used with unsupported compilers, the ABSL_FALLTHROUGH_INTENDED macro +// has no effect on diagnostics. In any case this macro has no effect on runtime +// behavior and performance of code. +#ifdef ABSL_FALLTHROUGH_INTENDED +#error "ABSL_FALLTHROUGH_INTENDED should not be defined." +#endif + +// TODO(zhangxy): Use c++17 standard [[fallthrough]] macro, when supported. +#if defined(__clang__) && defined(__has_warning) +#if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough") +#define ABSL_FALLTHROUGH_INTENDED [[clang::fallthrough]] +#endif +#elif defined(__GNUC__) && __GNUC__ >= 7 +#define ABSL_FALLTHROUGH_INTENDED [[gnu::fallthrough]] +#endif + +#ifndef ABSL_FALLTHROUGH_INTENDED +#define ABSL_FALLTHROUGH_INTENDED \ + do { \ + } while (0) +#endif + +// ABSL_DEPRECATED() +// +// Marks a deprecated class, struct, enum, function, method and variable +// declarations. The macro argument is used as a custom diagnostic message (e.g. +// suggestion of a better alternative). +// +// Examples: +// +// class ABSL_DEPRECATED("Use Bar instead") Foo {...}; +// +// ABSL_DEPRECATED("Use Baz() instead") void Bar() {...} +// +// template <typename T> +// ABSL_DEPRECATED("Use DoThat() instead") +// void DoThis(); +// +// Every usage of a deprecated entity will trigger a warning when compiled with +// clang's `-Wdeprecated-declarations` option. This option is turned off by +// default, but the warnings will be reported by clang-tidy. +#if defined(__clang__) && __cplusplus >= 201103L +#define ABSL_DEPRECATED(message) __attribute__((deprecated(message))) +#endif + +#ifndef ABSL_DEPRECATED +#define ABSL_DEPRECATED(message) +#endif + // ABSL_CONST_INIT // // A variable declaration annotated with the `ABSL_CONST_INIT` attribute will |