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139 lines
4.8 KiB
139 lines
4.8 KiB
/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef LIBTEXTCLASSIFIER_UTILS_BASE_MACROS_H_
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#define LIBTEXTCLASSIFIER_UTILS_BASE_MACROS_H_
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#include "utils/base/config.h"
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namespace libtextclassifier3 {
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#define TC3_ARRAYSIZE(a) \
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((sizeof(a) / sizeof(*(a))) / (size_t)(!(sizeof(a) % sizeof(*(a)))))
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#if LANG_CXX11
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#define TC3_DISALLOW_COPY_AND_ASSIGN(TypeName) \
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TypeName(const TypeName &) = delete; \
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TypeName &operator=(const TypeName &) = delete
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#else // C++98 case follows
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// Note that these C++98 implementations cannot completely disallow copying,
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// as members and friends can still accidentally make elided copies without
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// triggering a linker error.
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#define TC3_DISALLOW_COPY_AND_ASSIGN(TypeName) \
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TypeName(const TypeName &); \
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TypeName &operator=(const TypeName &)
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#endif // LANG_CXX11
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// The TC3_FALLTHROUGH_INTENDED macro can be used to annotate implicit
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// fall-through between switch labels:
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//
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// switch (x) {
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// case 40:
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// case 41:
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// if (truth_is_out_there) {
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// ++x;
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// TC3_FALLTHROUGH_INTENDED; // Use instead of/along with annotations in
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// // comments.
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// } else {
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// return x;
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// }
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// case 42:
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// ...
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//
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// As shown in the example above, the TC3_FALLTHROUGH_INTENDED macro should be
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// followed by a semicolon. It is designed to mimic control-flow statements
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// like 'break;', so it can be placed in most places where 'break;' can, but
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// only if there are no statements on the execution path between it and the
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// next switch label.
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//
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// When compiled with clang in C++11 mode, the TC3_FALLTHROUGH_INTENDED macro
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// is expanded to [[clang::fallthrough]] attribute, which is analysed when
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// performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough').
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// See clang documentation on language extensions for details:
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// http://clang.llvm.org/docs/AttributeReference.html#fallthrough-clang-fallthrough
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//
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// When used with unsupported compilers, the TC3_FALLTHROUGH_INTENDED macro has
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// no effect on diagnostics.
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//
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// In either case this macro has no effect on runtime behavior and performance
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// of code.
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#if defined(__clang__) && defined(__has_warning)
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#if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
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#define TC3_FALLTHROUGH_INTENDED [[clang::fallthrough]]
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#endif
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#elif defined(__GNUC__) && __GNUC__ >= 7
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#define TC3_FALLTHROUGH_INTENDED [[gnu::fallthrough]]
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#endif
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#ifndef TC3_FALLTHROUGH_INTENDED
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#define TC3_FALLTHROUGH_INTENDED \
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do { \
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} while (0)
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#endif
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#ifdef __has_builtin
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#define TC3_HAS_BUILTIN(x) __has_builtin(x)
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#else
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#define TC3_HAS_BUILTIN(x) 0
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#endif
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// Compilers can be told that a certain branch is not likely to be taken
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// (for instance, a CHECK failure), and use that information in static
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// analysis. Giving it this information can help it optimize for the
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// common case in the absence of better information (ie.
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// -fprofile-arcs).
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//
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// We need to disable this for GPU builds, though, since nvcc8 and older
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// don't recognize `__builtin_expect` as a builtin, and fail compilation.
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#if (!defined(__NVCC__)) && (TC3_HAS_BUILTIN(__builtin_expect) || \
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(defined(__GNUC__) && __GNUC__ >= 3))
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#define TC3_PREDICT_FALSE(x) (__builtin_expect(x, 0))
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#define TC3_PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
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#else
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#define TC3_PREDICT_FALSE(x) (x)
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#define TC3_PREDICT_TRUE(x) (x)
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#endif
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// TC3_HAVE_ATTRIBUTE
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//
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// A function-like feature checking macro that is a wrapper around
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// `__has_attribute`, which is defined by GCC 5+ and Clang and evaluates to a
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// nonzero constant integer if the attribute is supported or 0 if not.
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//
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// It evaluates to zero if `__has_attribute` is not defined by the compiler.
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//
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// GCC: https://gcc.gnu.org/gcc-5/changes.html
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// Clang: https://clang.llvm.org/docs/LanguageExtensions.html
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#ifdef __has_attribute
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#define TC3_HAVE_ATTRIBUTE(x) __has_attribute(x)
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#else
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#define TC3_HAVE_ATTRIBUTE(x) 0
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#endif
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// TC3_ATTRIBUTE_PACKED
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//
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// Prevents the compiler from padding a structure to natural alignment
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#if TC3_HAVE_ATTRIBUTE(packed) || (defined(__GNUC__) && !defined(__clang__))
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#define TC3_ATTRIBUTE_PACKED __attribute__((__packed__))
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#else
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#define TC3_ATTRIBUTE_PACKED
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#endif
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} // namespace libtextclassifier3
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#endif // LIBTEXTCLASSIFIER_UTILS_BASE_MACROS_H_
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