diff options
Diffstat (limited to 'third_party/abseil-cpp/absl/base/attributes.h')
| -rw-r--r-- | third_party/abseil-cpp/absl/base/attributes.h | 67 |
1 files changed, 43 insertions, 24 deletions
diff --git a/third_party/abseil-cpp/absl/base/attributes.h b/third_party/abseil-cpp/absl/base/attributes.h index cf2cb5501e..52139556f2 100644 --- a/third_party/abseil-cpp/absl/base/attributes.h +++ b/third_party/abseil-cpp/absl/base/attributes.h @@ -131,14 +131,14 @@ // ABSL_ATTRIBUTE_WEAK // // Tags a function as weak for the purposes of compilation and linking. -// Weak attributes currently do not work properly in LLVM's Windows backend, -// so disable them there. See https://bugs.llvm.org/show_bug.cgi?id=37598 +// Weak attributes did not work properly in LLVM's Windows backend before +// 9.0.0, so disable them there. See https://bugs.llvm.org/show_bug.cgi?id=37598 // for further information. // The MinGW compiler doesn't complain about the weak attribute until the link // step, presumably because Windows doesn't use ELF binaries. #if (ABSL_HAVE_ATTRIBUTE(weak) || \ (defined(__GNUC__) && !defined(__clang__))) && \ - !(defined(__llvm__) && defined(_WIN32)) && !defined(__MINGW32__) + (!defined(_WIN32) || __clang_major__ < 9) && !defined(__MINGW32__) #undef ABSL_ATTRIBUTE_WEAK #define ABSL_ATTRIBUTE_WEAK __attribute__((weak)) #define ABSL_HAVE_ATTRIBUTE_WEAK 1 @@ -281,10 +281,7 @@ // ABSL_ATTRIBUTE_RETURNS_NONNULL // // Tells the compiler that a particular function never returns a null pointer. -#if ABSL_HAVE_ATTRIBUTE(returns_nonnull) || \ - (defined(__GNUC__) && \ - (__GNUC__ > 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)) && \ - !defined(__clang__)) +#if ABSL_HAVE_ATTRIBUTE(returns_nonnull) #define ABSL_ATTRIBUTE_RETURNS_NONNULL __attribute__((returns_nonnull)) #else #define ABSL_ATTRIBUTE_RETURNS_NONNULL @@ -524,6 +521,13 @@ // ABSL_ATTRIBUTE_UNUSED // // Prevents the compiler from complaining about variables that appear unused. +// +// For code or headers that are assured to only build with C++17 and up, prefer +// just using the standard '[[maybe_unused]]' directly over this macro. +// +// Due to differences in positioning requirements between the old, compiler +// specific __attribute__ syntax and the now standard [[maybe_unused]], this +// macro does not attempt to take advantage of '[[maybe_unused]]'. #if ABSL_HAVE_ATTRIBUTE(unused) || (defined(__GNUC__) && !defined(__clang__)) #undef ABSL_ATTRIBUTE_UNUSED #define ABSL_ATTRIBUTE_UNUSED __attribute__((__unused__)) @@ -595,31 +599,24 @@ // 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: +// Notes: When supported, GCC and Clang can issue a warning on switch labels +// with unannotated fallthrough using the warning `-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 +// 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") +#elif ABSL_HAVE_CPP_ATTRIBUTE(fallthrough) +#define ABSL_FALLTHROUGH_INTENDED [[fallthrough]] +#elif ABSL_HAVE_CPP_ATTRIBUTE(clang::fallthrough) #define ABSL_FALLTHROUGH_INTENDED [[clang::fallthrough]] -#endif -#elif defined(__GNUC__) && __GNUC__ >= 7 +#elif ABSL_HAVE_CPP_ATTRIBUTE(gnu::fallthrough) #define ABSL_FALLTHROUGH_INTENDED [[gnu::fallthrough]] -#endif - -#ifndef ABSL_FALLTHROUGH_INTENDED +#else #define ABSL_FALLTHROUGH_INTENDED \ do { \ } while (0) @@ -699,4 +696,26 @@ #define ABSL_ATTRIBUTE_PURE_FUNCTION #endif +// ABSL_ATTRIBUTE_LIFETIME_BOUND indicates that a resource owned by a function +// parameter or implicit object parameter is retained by the return value of the +// annotated function (or, for a parameter of a constructor, in the value of the +// constructed object). This attribute causes warnings to be produced if a +// temporary object does not live long enough. +// +// When applied to a reference parameter, the referenced object is assumed to be +// retained by the return value of the function. When applied to a non-reference +// parameter (for example, a pointer or a class type), all temporaries +// referenced by the parameter are assumed to be retained by the return value of +// the function. +// +// See also the upstream documentation: +// https://clang.llvm.org/docs/AttributeReference.html#lifetimebound +#if ABSL_HAVE_CPP_ATTRIBUTE(clang::lifetimebound) +#define ABSL_ATTRIBUTE_LIFETIME_BOUND [[clang::lifetimebound]] +#elif ABSL_HAVE_ATTRIBUTE(lifetimebound) +#define ABSL_ATTRIBUTE_LIFETIME_BOUND __attribute__((lifetimebound)) +#else +#define ABSL_ATTRIBUTE_LIFETIME_BOUND +#endif + #endif // ABSL_BASE_ATTRIBUTES_H_ |