1 /* 2 * Copyright (C) 2019 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 SRC_ANDROID_INTERNAL_LAZY_LIBRARY_LOADER_H_ 18 #define SRC_ANDROID_INTERNAL_LAZY_LIBRARY_LOADER_H_ 19 20 #include <stddef.h> 21 #include <stdint.h> 22 23 namespace perfetto { 24 namespace android_internal { 25 26 // Dynamically loads (once) the libperfetto_android_internal.so and looks up the 27 // given symbol name. It never unloads the library once loaded. Doing so is very 28 // bug-prone (see b/137280403). 29 // |name| can be either a symbol name (e.g. DoFoo) or a (partially or fully) 30 // qualified name (e.g., android_internal::DoFoo). In the latter case the 31 // namespace is dropped only the symbol name is retained (in other words this 32 // function assumes all symbols are declared as extern "C"). 33 void* LazyLoadFunction(const char* name); 34 35 // Convenience wrapper to avoid the reinterpret_cast boilerplate. Boils down to: 36 // FunctionType name = reinterpret_cast<FunctionType>(LazyLoadFunction(...)). 37 // Can be used both for member fields and local variables. 38 #define PERFETTO_LAZY_LOAD(FUNCTION, VAR_NAME) \ 39 decltype(&FUNCTION) VAR_NAME = reinterpret_cast<decltype(&FUNCTION)>( \ 40 ::perfetto::android_internal::LazyLoadFunction(#FUNCTION)) 41 42 } // namespace android_internal 43 } // namespace perfetto 44 45 #endif // SRC_ANDROID_INTERNAL_LAZY_LIBRARY_LOADER_H_ 46