blob: 0504af61ed34a6e0cd0f7f9c33b7c0677d642840 [file] [log] [blame]
// Copyright 2019 The Dawn Authors
// 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef COMMON_LOG_H_
#define COMMON_LOG_H_
// Dawn targets shouldn't use iostream or printf directly for several reasons:
// - iostream adds static initializers which we want to avoid.
// - printf and iostream don't show up in logcat on Android so printf debugging doesn't work but
// log-message debugging does.
// - log severity helps provide intent compared to a printf.
// Logging should in general be avoided: errors should go through the regular WebGPU error reporting
// mechanism and others form of logging should (TODO: eventually) go through the logging dependency
// injection, so for example they show up in Chromium's about:gpu page. Nonetheless there are some
// cases where logging is necessary and when this file was first introduced we needed to replace all
// uses of iostream so we could see them in Android's logcat.
// Regular logging is done using the [Debug|Info|Warning|Error]Log() function this way:
// InfoLog() << things << that << ostringstream << supports; // No need for a std::endl or "\n"
// It creates a LogMessage object that isn't stored anywhere and gets its destructor called
// immediately which outputs the stored ostringstream in the right place.
// This file also contains DAWN_DEBUG for "printf debugging" which works on Android and
// additionally outputs the file, line and function name. Use it this way:
// // Pepper this throughout code to get a log of the execution
// // Get more information
// DAWN_DEBUG() << texture.GetFormat();
#include <sstream>
namespace dawn {
// Log levels mostly used to signal intent where the log message is produced and used to route
// the message to the correct output.
enum class LogSeverity {
// Essentially an ostringstream that will print itself in its destructor.
class LogMessage {
LogMessage(LogSeverity severity);
LogMessage(LogMessage&& other) = default;
LogMessage& operator=(LogMessage&& other) = default;
template <typename T>
LogMessage& operator<<(T&& value) {
mStream << value;
return *this;
LogMessage(const LogMessage& other) = delete;
LogMessage& operator=(const LogMessage& other) = delete;
LogSeverity mSeverity;
std::ostringstream mStream;
// Short-hands to create a LogMessage with the respective severity.
LogMessage DebugLog();
LogMessage InfoLog();
LogMessage WarningLog();
LogMessage ErrorLog();
// DAWN_DEBUG is a helper macro that creates a DebugLog and outputs file/line/function
// information
LogMessage DebugLog(const char* file, const char* function, int line);
#define DAWN_DEBUG() ::dawn::DebugLog(__FILE__, __func__, __LINE__)
} // namespace dawn
#endif // COMMON_LOG_H_