#!/usr/bin/env python
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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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"""Generates wrapped include files to workaround -Wunused-parameter errors.
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In Chrome repository, "-Wunused-parameter" is disabled, and several header
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files in Chrome repository have actually unused-parameter.
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One of the typical scenarios is; in Chrome, Observer class is often defined
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as follows:
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class Foo {
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public:
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class Observer {
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public:
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virtual void OnSomeEvent(EventArg arg) {}
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virtual void OnAnotherEvent(EventArg arg) {}
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...
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};
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...
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};
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Here, On...Event() methods do nothing by default, and subclasses will override
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only necessary ones.
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In this use case, argument names can also work as documentation, and overrides
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can use these good interface-defined default names as a starting point for
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their implementation.
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On the other hand, in Android, -Wunused-parameter is enabled by default.
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Thus, if such a project includes header files from libchrome, it could cause
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a compile error (by the warning and "-Werror").
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To avoid such a situation, libchrome exports include files wrapped by the
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pragmas as follows.
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wunused-parameter"
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${actual_include_file_content}
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#pragma GCC diagnostic pop
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so, the unused-parameter warning generated by the libchrome include headers
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will be ignored.
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Note that these GCC pragmas are also supported by clang for compatibility. cf)
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https://clang.llvm.org/docs/UsersManual.html#controlling-diagnostics-via-pragmas
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Usage: include_generator.py $(in) $(out)
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"""
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import sys
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def _generate(input_path, output_path):
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"""Generates a include file wrapped by pragmas.
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Reads the file at |input_path| and output the content with wrapping by
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#pragma to ignore unused-parameter warning into the file at |output_path|.
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If the parent directories of |output_path| do not exist, creates them.
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Args:
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input_path: Path to the source file. Expected this is a chrome's header
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file.
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output_path: Path to the output file.
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"""
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with open(input_path, 'r') as f:
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content = f.read()
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with open(output_path, 'w') as f:
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f.writelines([
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'// Generated by %s\n' % sys.argv[0],
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'#pragma GCC diagnostic push\n'
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'#pragma GCC diagnostic ignored "-Wunused-parameter"\n',
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content,
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'#pragma GCC diagnostic pop\n'])
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def main():
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_generate(*sys.argv[1:])
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if __name__ == '__main__':
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main()
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