| /** |
| * Copyright 2010 Google Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| #ifndef WEBUTIL_CSS_FALLTHROUGH_INTENDED_H_ |
| #define WEBUTIL_CSS_FALLTHROUGH_INTENDED_H_ |
| |
| // The FALLTHROUGH_INTENDED macro can be used to annotate implicit fall-through |
| // between switch labels: |
| // switch (x) { |
| // case 40: |
| // case 41: |
| // if (truth_is_out_there) { |
| // ++x; |
| // FALLTHROUGH_INTENDED; // Use instead of/along with annotations in |
| // // comments. |
| // } else { |
| // return x; |
| // } |
| // case 42: |
| // ... |
| // |
| // As shown in the example above, the FALLTHROUGH_INTENDED macro should be |
| // followed by a semicolon. It is designed to mimic control-flow statements |
| // like 'break;', so it can be placed in most places where 'break;' can, but |
| // only if there are no statements on the execution path between it and the |
| // next switch label. |
| // |
| // When compiled with clang in C++11 mode, the FALLTHROUGH_INTENDED macro is |
| // expanded to [[clang::fallthrough]] attribute, which is analysed when |
| // performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough'). |
| // See clang documentation on language extensions for details: |
| // http://clang.llvm.org/docs/LanguageExtensions.html#clang__fallthrough |
| // |
| // When used with unsupported compilers, the FALLTHROUGH_INTENDED macro has no |
| // effect on diagnostics. |
| // |
| // In either case this macro has no effect on runtime behavior and performance |
| // of code. |
| #if defined(__clang__) && __cplusplus >= 201103L && defined(__has_warning) |
| #if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough") |
| #define FALLTHROUGH_INTENDED [[clang::fallthrough]] // NOLINT |
| #endif |
| #endif |
| |
| #ifndef FALLTHROUGH_INTENDED |
| #define FALLTHROUGH_INTENDED do { } while (0) |
| #endif |
| |
| #endif // WEBUTIL_CSS_FALLTHROUGH_INTENDED_H_ |