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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef LIBTEXTCLASSIFIER_UTIL_BASE_MACROS_H_
     18 #define LIBTEXTCLASSIFIER_UTIL_BASE_MACROS_H_
     19 
     20 #include "util/base/config.h"
     21 
     22 namespace libtextclassifier {
     23 
     24 #if LANG_CXX11
     25 #define TC_DISALLOW_COPY_AND_ASSIGN(TypeName) \
     26   TypeName(const TypeName &) = delete;        \
     27   TypeName &operator=(const TypeName &) = delete
     28 #else  // C++98 case follows
     29 
     30 // Note that these C++98 implementations cannot completely disallow copying,
     31 // as members and friends can still accidentally make elided copies without
     32 // triggering a linker error.
     33 #define TC_DISALLOW_COPY_AND_ASSIGN(TypeName) \
     34   TypeName(const TypeName &);                 \
     35   TypeName &operator=(const TypeName &)
     36 #endif  // LANG_CXX11
     37 
     38 // The TC_FALLTHROUGH_INTENDED macro can be used to annotate implicit
     39 // fall-through between switch labels:
     40 //
     41 //  switch (x) {
     42 //    case 40:
     43 //    case 41:
     44 //      if (truth_is_out_there) {
     45 //        ++x;
     46 //        TC_FALLTHROUGH_INTENDED;  // Use instead of/along with annotations in
     47 //                                  // comments.
     48 //      } else {
     49 //        return x;
     50 //      }
     51 //    case 42:
     52 //      ...
     53 //
     54 //  As shown in the example above, the TC_FALLTHROUGH_INTENDED macro should be
     55 //  followed by a semicolon. It is designed to mimic control-flow statements
     56 //  like 'break;', so it can be placed in most places where 'break;' can, but
     57 //  only if there are no statements on the execution path between it and the
     58 //  next switch label.
     59 //
     60 //  When compiled with clang in C++11 mode, the TC_FALLTHROUGH_INTENDED macro is
     61 //  expanded to [[clang::fallthrough]] attribute, which is analysed when
     62 //  performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough').
     63 //  See clang documentation on language extensions for details:
     64 //  http://clang.llvm.org/docs/AttributeReference.html#fallthrough-clang-fallthrough
     65 //
     66 //  When used with unsupported compilers, the TC_FALLTHROUGH_INTENDED macro has
     67 //  no effect on diagnostics.
     68 //
     69 //  In either case this macro has no effect on runtime behavior and performance
     70 //  of code.
     71 #if defined(__clang__) && defined(LANG_CXX11) && defined(__has_warning)
     72 #if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
     73 #define TC_FALLTHROUGH_INTENDED [[clang::fallthrough]]  // NOLINT
     74 #endif
     75 #endif
     76 
     77 #ifndef TC_FALLTHROUGH_INTENDED
     78 #define TC_FALLTHROUGH_INTENDED do { } while (0)
     79 #endif
     80 
     81 }  // namespace libtextclassifier
     82 
     83 #endif  // LIBTEXTCLASSIFIER_UTIL_BASE_MACROS_H_
     84