die_if_null.h (2864B)
1 // Copyright 2022 The Abseil Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // ----------------------------------------------------------------------------- 16 // File: log/die_if_null.h 17 // ----------------------------------------------------------------------------- 18 // 19 // This header declares macro `ABSL_DIE_IF_NULL`. 20 21 #ifndef ABSL_LOG_DIE_IF_NULL_H_ 22 #define ABSL_LOG_DIE_IF_NULL_H_ 23 24 #include <stdint.h> 25 26 #include <utility> 27 28 #include "absl/base/attributes.h" 29 #include "absl/base/config.h" 30 #include "absl/base/optimization.h" 31 32 // ABSL_DIE_IF_NULL() 33 // 34 // `ABSL_DIE_IF_NULL` behaves as `CHECK_NE` against `nullptr` but *also* 35 // "returns" its argument. It is useful in initializers where statements (like 36 // `CHECK_NE`) can't be used. Outside initializers, prefer `CHECK` or 37 // `CHECK_NE`. `ABSL_DIE_IF_NULL` works for both raw pointers and (compatible) 38 // smart pointers including `std::unique_ptr` and `std::shared_ptr`; more 39 // generally, it works for any type that can be compared to nullptr_t. For 40 // types that aren't raw pointers, `ABSL_DIE_IF_NULL` returns a reference to 41 // its argument, preserving the value category. Example: 42 // 43 // Foo() : bar_(ABSL_DIE_IF_NULL(MethodReturningUniquePtr())) {} 44 // 45 // Use `CHECK(ptr)` or `CHECK(ptr != nullptr)` if the returned pointer is 46 // unused. 47 #define ABSL_DIE_IF_NULL(val) \ 48 ::absl::log_internal::DieIfNull(__FILE__, __LINE__, #val, (val)) 49 50 namespace absl { 51 ABSL_NAMESPACE_BEGIN 52 namespace log_internal { 53 54 // Crashes the process after logging `exprtext` annotated at the `file` and 55 // `line` location. Called when `ABSL_DIE_IF_NULL` fails. Calling this function 56 // generates less code than its implementation would if inlined, for a slight 57 // code size reduction each time `ABSL_DIE_IF_NULL` is called. 58 [[noreturn]] ABSL_ATTRIBUTE_NOINLINE void DieBecauseNull( 59 const char* file, int line, const char* exprtext); 60 61 // Helper for `ABSL_DIE_IF_NULL`. 62 template <typename T> 63 [[nodiscard]] T DieIfNull(const char* file, int line, const char* exprtext, 64 T&& t) { 65 if (ABSL_PREDICT_FALSE(t == nullptr)) { 66 // Call a non-inline helper function for a small code size improvement. 67 DieBecauseNull(file, line, exprtext); 68 } 69 return std::forward<T>(t); 70 } 71 72 } // namespace log_internal 73 ABSL_NAMESPACE_END 74 } // namespace absl 75 76 #endif // ABSL_LOG_DIE_IF_NULL_H_