source_location.h

/*
 * Copyright 2025 Google LLC
 *
 * 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 ACTIONENGINE_UTIL_SOURCE_LOCATION_H_
#define ACTIONENGINE_UTIL_SOURCE_LOCATION_H_
 
#include <cstdint>
 
namespace act::util {
 
// Class representing a specific location in the source code of a program.
// source_location is copyable.
class source_location {
 public:
  // Avoid this constructor; it populates the object with dummy values.
  constexpr source_location() : line_(0), file_name_(nullptr) {}
 
  // Wrapper to invoke the private constructor below. This should only be
  // used by the ACTIONENGINE_LOC macro, hence the name.
  static constexpr source_location DoNotInvokeDirectly(std::uint_least32_t line,
                                                       const char* file_name) {
    return source_location(line, file_name);
  }
 
  // The line number of the captured source location.
  [[nodiscard]] constexpr std::uint_least32_t line() const { return line_; }
 
  // The file name of the captured source location.
  [[nodiscard]] constexpr const char* file_name() const { return file_name_; }
 
  // column() and function_name() are omitted because we don't have a
  // way to support them.
 
 private:
  // Do not invoke this constructor directly. Instead, use the
  // ACTIONENGINE_LOC macro below.
  //
  // file_name must outlive all copies of the source_location
  // object, so in practice it should be a string literal.
  constexpr source_location(std::uint_least32_t line, const char* file_name)
      : line_(line), file_name_(file_name) {}
 
  std::uint_least32_t line_;
  const char* file_name_;
};
 
}  // namespace act::util
 
// If a function takes a source_location parameter, pass this as the argument.
#define ACTIONENGINE_LOC \
  act::util::source_location::DoNotInvokeDirectly(__LINE__, __FILE__)
 
#endif  // ACTIONENGINE_UTIL_SOURCE_LOCATION_H_