base/include/android-base/logging.h - android-core - Git at Google

 /*
  * Copyright (C) 2015 The Android Open Source Project
  *
  * 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 ANDROID_BASE_LOGGING_H
 #define ANDROID_BASE_LOGGING_H

 //
 // Google-style C++ logging.
 //

 // This header provides a C++ stream interface to logging.
 //
 // To log:
 //
 //   LOG(INFO) << "Some text; " << some_value;
 //
 // Replace `INFO` with any severity from `enum LogSeverity`.
 //
 // To log the result of a failed function and include the string
 // representation of `errno` at the end:
 //
 //   PLOG(ERROR) << "Write failed";
 //
 // The output will be something like `Write failed: I/O error`.
 // Remember this as 'P' as in perror(3).
 //
 // To output your own types, simply implement operator<< as normal.
 //
 // By default, output goes to logcat on Android and stderr on the host.
 // A process can use `SetLogger` to decide where all logging goes.
 // Implementations are provided for logcat, stderr, and dmesg.
 //
 // By default, the process' name is used as the log tag.
 // Code can choose a specific log tag by defining LOG_TAG
 // before including this header.

 // This header also provides assertions:
 //
 //   CHECK(must_be_true);
 //   CHECK_EQ(a, b) << z_is_interesting_too;

 // NOTE: For Windows, you must include logging.h after windows.h to allow the
 // following code to suppress the evil ERROR macro:
 #ifdef _WIN32
 // windows.h includes wingdi.h which defines an evil macro ERROR.
 #ifdef ERROR
 #undef ERROR
 #endif
 #endif

 #include <functional>
 #include <memory>
 #include <ostream>

 #include "android-base/macros.h"

 // Note: DO NOT USE DIRECTLY. Use LOG_TAG instead.
 #ifdef _LOG_TAG_INTERNAL
 #error "_LOG_TAG_INTERNAL must not be defined"
 #endif
 #ifdef LOG_TAG
 #define _LOG_TAG_INTERNAL LOG_TAG
 #else
 #define _LOG_TAG_INTERNAL nullptr
 #endif

 namespace android {
 namespace base {

 enum LogSeverity {
   VERBOSE,
   DEBUG,
   INFO,
   WARNING,
   ERROR,
   FATAL_WITHOUT_ABORT,
   FATAL,
 };

 enum LogId {
   DEFAULT,
   MAIN,
   SYSTEM,
 };

 using LogFunction = std::function<void(LogId, LogSeverity, const char*, const char*,
                                        unsigned int, const char*)>;
 using AbortFunction = std::function<void(const char*)>;

 void KernelLogger(LogId, LogSeverity, const char*, const char*, unsigned int, const char*);
 void StderrLogger(LogId, LogSeverity, const char*, const char*, unsigned int, const char*);

 void DefaultAborter(const char* abort_message);

 std::string GetDefaultTag();
 void SetDefaultTag(const std::string& tag);

 #ifdef __ANDROID__
 // We expose this even though it is the default because a user that wants to
 // override the default log buffer will have to construct this themselves.
 class LogdLogger {
  public:
   explicit LogdLogger(LogId default_log_id = android::base::MAIN);

   void operator()(LogId, LogSeverity, const char* tag, const char* file,
                   unsigned int line, const char* message);

  private:
   LogId default_log_id_;
 };
 #endif

 // Configure logging based on ANDROID_LOG_TAGS environment variable.
 // We need to parse a string that looks like
 //
 //      *:v jdwp:d dalvikvm:d dalvikvm-gc:i dalvikvmi:i
 //
 // The tag (or '*' for the global level) comes first, followed by a colon and a
 // letter indicating the minimum priority level we're expected to log.  This can
 // be used to reveal or conceal logs with specific tags.
 #ifdef __ANDROID__
 #define INIT_LOGGING_DEFAULT_LOGGER LogdLogger()
 #else
 #define INIT_LOGGING_DEFAULT_LOGGER StderrLogger
 #endif
 void InitLogging(char* argv[],
                  LogFunction&& logger = INIT_LOGGING_DEFAULT_LOGGER,
                  AbortFunction&& aborter = DefaultAborter);
 #undef INIT_LOGGING_DEFAULT_LOGGER

 // Replace the current logger.
 void SetLogger(LogFunction&& logger);

 // Replace the current aborter.
 void SetAborter(AbortFunction&& aborter);

 class ErrnoRestorer {
  public:
   ErrnoRestorer()
       : saved_errno_(errno) {
   }

   ~ErrnoRestorer() {
     errno = saved_errno_;
   }

   // Allow this object to be used as part of && operation.
   operator bool() const {
     return true;
   }

  private:
   const int saved_errno_;

   DISALLOW_COPY_AND_ASSIGN(ErrnoRestorer);
 };

 // A helper macro that produces an expression that accepts both a qualified name and an
 // unqualified name for a LogSeverity, and returns a LogSeverity value.
 // Note: DO NOT USE DIRECTLY. This is an implementation detail.
 #define SEVERITY_LAMBDA(severity) ([&]() {    \
   using ::android::base::VERBOSE;             \
   using ::android::base::DEBUG;               \
   using ::android::base::INFO;                \
   using ::android::base::WARNING;             \
   using ::android::base::ERROR;               \
   using ::android::base::FATAL_WITHOUT_ABORT; \
   using ::android::base::FATAL;               \
   return (severity); }())

 #ifdef __clang_analyzer__
 // Clang's static analyzer does not see the conditional statement inside
 // LogMessage's destructor that will abort on FATAL severity.
 #define ABORT_AFTER_LOG_FATAL for (;; abort())

 struct LogAbortAfterFullExpr {
   ~LogAbortAfterFullExpr() __attribute__((noreturn)) { abort(); }
   explicit operator bool() const { return false; }
 };
 // Provides an expression that evaluates to the truthiness of `x`, automatically
 // aborting if `c` is true.
 #define ABORT_AFTER_LOG_EXPR_IF(c, x) (((c) && ::android::base::LogAbortAfterFullExpr()) || (x))
 // Note to the static analyzer that we always execute FATAL logs in practice.
 #define MUST_LOG_MESSAGE(severity) (SEVERITY_LAMBDA(severity) == ::android::base::FATAL)
 #else
 #define ABORT_AFTER_LOG_FATAL
 #define ABORT_AFTER_LOG_EXPR_IF(c, x) (x)
 #define MUST_LOG_MESSAGE(severity) false
 #endif
 #define ABORT_AFTER_LOG_FATAL_EXPR(x) ABORT_AFTER_LOG_EXPR_IF(true, x)

 // Defines whether the given severity will be logged or silently swallowed.
 #define WOULD_LOG(severity) \
   (UNLIKELY((SEVERITY_LAMBDA(severity)) >= ::android::base::GetMinimumLogSeverity()) || \
    MUST_LOG_MESSAGE(severity))

 // Get an ostream that can be used for logging at the given severity and to the default
 // destination.
 //
 // Notes:
 // 1) This will not check whether the severity is high enough. One should use WOULD_LOG to filter
 //    usage manually.
 // 2) This does not save and restore errno.
 #define LOG_STREAM(severity) LOG_STREAM_TO(DEFAULT, severity)

 // Get an ostream that can be used for logging at the given severity and to the
 // given destination. The same notes as for LOG_STREAM apply.
 #define LOG_STREAM_TO(dest, severity)                                           \
   ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::dest,        \
                               SEVERITY_LAMBDA(severity), _LOG_TAG_INTERNAL, -1) \
       .stream()

 // Logs a message to logcat on Android otherwise to stderr. If the severity is
 // FATAL it also causes an abort. For example:
 //
 //     LOG(FATAL) << "We didn't expect to reach here";
 #define LOG(severity) LOG_TO(DEFAULT, severity)

 // Checks if we want to log something, and sets up appropriate RAII objects if
 // so.
 // Note: DO NOT USE DIRECTLY. This is an implementation detail.
 #define LOGGING_PREAMBLE(severity)                                                         \
   (WOULD_LOG(severity) &&                                                                  \
    ABORT_AFTER_LOG_EXPR_IF((SEVERITY_LAMBDA(severity)) == ::android::base::FATAL, true) && \
    ::android::base::ErrnoRestorer())

 // Logs a message to logcat with the specified log ID on Android otherwise to
 // stderr. If the severity is FATAL it also causes an abort.
 // Use an expression here so we can support the << operator following the macro,
 // like "LOG(DEBUG) << xxx;".
 #define LOG_TO(dest, severity) LOGGING_PREAMBLE(severity) && LOG_STREAM_TO(dest, severity)

 // A variant of LOG that also logs the current errno value. To be used when
 // library calls fail.
 #define PLOG(severity) PLOG_TO(DEFAULT, severity)

 // Behaves like PLOG, but logs to the specified log ID.
 #define PLOG_TO(dest, severity)                                                        \
   LOGGING_PREAMBLE(severity) &&                                                        \
       ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::dest,           \
                                   SEVERITY_LAMBDA(severity), _LOG_TAG_INTERNAL, errno) \
           .stream()

 // Marker that code is yet to be implemented.
 #define UNIMPLEMENTED(level) \
   LOG(level) << __PRETTY_FUNCTION__ << " unimplemented "

 // Check whether condition x holds and LOG(FATAL) if not. The value of the
 // expression x is only evaluated once. Extra logging can be appended using <<
 // after. For example:
 //
 //     CHECK(false == true) results in a log message of
 //       "Check failed: false == true".
 #define CHECK(x)                                                                 \
   LIKELY((x)) || ABORT_AFTER_LOG_FATAL_EXPR(false) ||                            \
       ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT,  \
                                   ::android::base::FATAL, _LOG_TAG_INTERNAL, -1) \
               .stream()                                                          \
           << "Check failed: " #x << " "

 // clang-format off
 // Helper for CHECK_xx(x,y) macros.
 #define CHECK_OP(LHS, RHS, OP)                                                                 \
   for (auto _values = ::android::base::MakeEagerEvaluator(LHS, RHS);                           \
        UNLIKELY(!(_values.lhs OP _values.rhs));                                                \
        /* empty */)                                                                            \
   ABORT_AFTER_LOG_FATAL                                                                        \
   ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT,                    \
                               ::android::base::FATAL, _LOG_TAG_INTERNAL, -1)                   \
           .stream()                                                                            \
       << "Check failed: " << #LHS << " " << #OP << " " << #RHS << " (" #LHS "=" << _values.lhs \
       << ", " #RHS "=" << _values.rhs << ") "
 // clang-format on

 // Check whether a condition holds between x and y, LOG(FATAL) if not. The value
 // of the expressions x and y is evaluated once. Extra logging can be appended
 // using << after. For example:
 //
 //     CHECK_NE(0 == 1, false) results in
 //       "Check failed: false != false (0==1=false, false=false) ".
 #define CHECK_EQ(x, y) CHECK_OP(x, y, == )
 #define CHECK_NE(x, y) CHECK_OP(x, y, != )
 #define CHECK_LE(x, y) CHECK_OP(x, y, <= )
 #define CHECK_LT(x, y) CHECK_OP(x, y, < )
 #define CHECK_GE(x, y) CHECK_OP(x, y, >= )
 #define CHECK_GT(x, y) CHECK_OP(x, y, > )

 // clang-format off
 // Helper for CHECK_STRxx(s1,s2) macros.
 #define CHECK_STROP(s1, s2, sense)                                             \
   while (UNLIKELY((strcmp(s1, s2) == 0) != (sense)))                           \
     ABORT_AFTER_LOG_FATAL                                                      \
     ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT,  \
                                 ::android::base::FATAL, _LOG_TAG_INTERNAL, -1) \
         .stream()                                                              \
         << "Check failed: " << "\"" << (s1) << "\""                            \
         << ((sense) ? " == " : " != ") << "\"" << (s2) << "\""
 // clang-format on

 // Check for string (const char*) equality between s1 and s2, LOG(FATAL) if not.
 #define CHECK_STREQ(s1, s2) CHECK_STROP(s1, s2, true)
 #define CHECK_STRNE(s1, s2) CHECK_STROP(s1, s2, false)

 // Perform the pthread function call(args), LOG(FATAL) on error.
 #define CHECK_PTHREAD_CALL(call, args, what)                           \
   do {                                                                 \
     int rc = call args;                                                \
     if (rc != 0) {                                                     \
       errno = rc;                                                      \
       ABORT_AFTER_LOG_FATAL                                            \
       PLOG(FATAL) << #call << " failed for " << (what);                \
     }                                                                  \
   } while (false)

 // CHECK that can be used in a constexpr function. For example:
 //
 //    constexpr int half(int n) {
 //      return
 //          DCHECK_CONSTEXPR(n >= 0, , 0)
 //          CHECK_CONSTEXPR((n & 1) == 0),
 //              << "Extra debugging output: n = " << n, 0)
 //          n / 2;
 //    }
 #define CHECK_CONSTEXPR(x, out, dummy)                                     \
   (UNLIKELY(!(x)))                                                         \
       ? (LOG(FATAL) << "Check failed: " << #x out, dummy) \
       :

 // DCHECKs are debug variants of CHECKs only enabled in debug builds. Generally
 // CHECK should be used unless profiling identifies a CHECK as being in
 // performance critical code.
 #if defined(NDEBUG) && !defined(__clang_analyzer__)
 static constexpr bool kEnableDChecks = false;
 #else
 static constexpr bool kEnableDChecks = true;
 #endif

 #define DCHECK(x) \
   if (::android::base::kEnableDChecks) CHECK(x)
 #define DCHECK_EQ(x, y) \
   if (::android::base::kEnableDChecks) CHECK_EQ(x, y)
 #define DCHECK_NE(x, y) \
   if (::android::base::kEnableDChecks) CHECK_NE(x, y)
 #define DCHECK_LE(x, y) \
   if (::android::base::kEnableDChecks) CHECK_LE(x, y)
 #define DCHECK_LT(x, y) \
   if (::android::base::kEnableDChecks) CHECK_LT(x, y)
 #define DCHECK_GE(x, y) \
   if (::android::base::kEnableDChecks) CHECK_GE(x, y)
 #define DCHECK_GT(x, y) \
   if (::android::base::kEnableDChecks) CHECK_GT(x, y)
 #define DCHECK_STREQ(s1, s2) \
   if (::android::base::kEnableDChecks) CHECK_STREQ(s1, s2)
 #define DCHECK_STRNE(s1, s2) \
   if (::android::base::kEnableDChecks) CHECK_STRNE(s1, s2)
 #if defined(NDEBUG) && !defined(__clang_analyzer__)
 #define DCHECK_CONSTEXPR(x, out, dummy)
 #else
 #define DCHECK_CONSTEXPR(x, out, dummy) CHECK_CONSTEXPR(x, out, dummy)
 #endif

 // Temporary class created to evaluate the LHS and RHS, used with
 // MakeEagerEvaluator to infer the types of LHS and RHS.
 template <typename LHS, typename RHS>
 struct EagerEvaluator {
   constexpr EagerEvaluator(LHS l, RHS r) : lhs(l), rhs(r) {
   }
   LHS lhs;
   RHS rhs;
 };

 // Helper function for CHECK_xx.
 template <typename LHS, typename RHS>
 constexpr EagerEvaluator<LHS, RHS> MakeEagerEvaluator(LHS lhs, RHS rhs) {
   return EagerEvaluator<LHS, RHS>(lhs, rhs);
 }

 // Explicitly instantiate EagerEvalue for pointers so that char*s aren't treated
 // as strings. To compare strings use CHECK_STREQ and CHECK_STRNE. We rely on
 // signed/unsigned warnings to protect you against combinations not explicitly
 // listed below.
 #define EAGER_PTR_EVALUATOR(T1, T2)               \
   template <>                                     \
   struct EagerEvaluator<T1, T2> {                 \
     EagerEvaluator(T1 l, T2 r)                    \
         : lhs(reinterpret_cast<const void*>(l)),  \
           rhs(reinterpret_cast<const void*>(r)) { \
     }                                             \
     const void* lhs;                              \
     const void* rhs;                              \
   }
 EAGER_PTR_EVALUATOR(const char*, const char*);
 EAGER_PTR_EVALUATOR(const char*, char*);
 EAGER_PTR_EVALUATOR(char*, const char*);
 EAGER_PTR_EVALUATOR(char*, char*);
 EAGER_PTR_EVALUATOR(const unsigned char*, const unsigned char*);
 EAGER_PTR_EVALUATOR(const unsigned char*, unsigned char*);
 EAGER_PTR_EVALUATOR(unsigned char*, const unsigned char*);
 EAGER_PTR_EVALUATOR(unsigned char*, unsigned char*);
 EAGER_PTR_EVALUATOR(const signed char*, const signed char*);
 EAGER_PTR_EVALUATOR(const signed char*, signed char*);
 EAGER_PTR_EVALUATOR(signed char*, const signed char*);
 EAGER_PTR_EVALUATOR(signed char*, signed char*);

 // Data for the log message, not stored in LogMessage to avoid increasing the
 // stack size.
 class LogMessageData;

 // A LogMessage is a temporarily scoped object used by LOG and the unlikely part
 // of a CHECK. The destructor will abort if the severity is FATAL.
 class LogMessage {
  public:
   LogMessage(const char* file, unsigned int line, LogId id, LogSeverity severity, const char* tag,
              int error);

   ~LogMessage();

   // Returns the stream associated with the message, the LogMessage performs
   // output when it goes out of scope.
   std::ostream& stream();

   // The routine that performs the actual logging.
   static void LogLine(const char* file, unsigned int line, LogId id, LogSeverity severity,
                       const char* tag, const char* msg);

  private:
   const std::unique_ptr<LogMessageData> data_;

   // TODO(b/35361699): remove these symbols once all prebuilds stop using it.
   LogMessage(const char* file, unsigned int line, LogId id, LogSeverity severity, int error);
   static void LogLine(const char* file, unsigned int line, LogId id, LogSeverity severity,
                       const char* msg);

   DISALLOW_COPY_AND_ASSIGN(LogMessage);
 };

 // Get the minimum severity level for logging.
 LogSeverity GetMinimumLogSeverity();

 // Set the minimum severity level for logging, returning the old severity.
 LogSeverity SetMinimumLogSeverity(LogSeverity new_severity);

 // Allows to temporarily change the minimum severity level for logging.
 class ScopedLogSeverity {
  public:
   explicit ScopedLogSeverity(LogSeverity level);
   ~ScopedLogSeverity();

  private:
   LogSeverity old_;
 };

 }  // namespace base
 }  // namespace android

 namespace std {

 // Emit a warning of ostream<< with std::string*. The intention was most likely to print *string.
 //
 // Note: for this to work, we need to have this in a namespace.
 // Note: lots of ifdef magic to make this work with Clang (platform) vs GCC (windows tools)
 // Note: using diagnose_if(true) under Clang and nothing under GCC/mingw as there is no common
 //       attribute support.
 // Note: using a pragma because "-Wgcc-compat" (included in "-Weverything") complains about
 //       diagnose_if.
 // Note: to print the pointer, use "<< static_cast<const void*>(string_pointer)" instead.
 // Note: a not-recommended alternative is to let Clang ignore the warning by adding
 //       -Wno-user-defined-warnings to CPPFLAGS.
 #ifdef __clang__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wgcc-compat"
 #define OSTREAM_STRING_POINTER_USAGE_WARNING \
     __attribute__((diagnose_if(true, "Unexpected logging of string pointer", "warning")))
 #else
 #define OSTREAM_STRING_POINTER_USAGE_WARNING /* empty */
 #endif
 inline std::ostream& operator<<(std::ostream& stream, const std::string* string_pointer)
     OSTREAM_STRING_POINTER_USAGE_WARNING {
   return stream << static_cast<const void*>(string_pointer);
 }
 #ifdef __clang__
 #pragma clang diagnostic pop
 #endif
 #undef OSTREAM_STRING_POINTER_USAGE_WARNING

 }  // namespace std

 #endif  // ANDROID_BASE_LOGGING_H
	/*
	* Copyright (C) 2015 The Android Open Source Project
	*
	* 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 ANDROID_BASE_LOGGING_H
	#define ANDROID_BASE_LOGGING_H

	//
	// Google-style C++ logging.
	//

	// This header provides a C++ stream interface to logging.
	//
	// To log:
	//
	// LOG(INFO) << "Some text; " << some_value;
	//
	// Replace `INFO` with any severity from `enum LogSeverity`.
	//
	// To log the result of a failed function and include the string
	// representation of `errno` at the end:
	//
	// PLOG(ERROR) << "Write failed";
	//
	// The output will be something like `Write failed: I/O error`.
	// Remember this as 'P' as in perror(3).
	//
	// To output your own types, simply implement operator<< as normal.
	//
	// By default, output goes to logcat on Android and stderr on the host.
	// A process can use `SetLogger` to decide where all logging goes.
	// Implementations are provided for logcat, stderr, and dmesg.
	//
	// By default, the process' name is used as the log tag.
	// Code can choose a specific log tag by defining LOG_TAG
	// before including this header.

	// This header also provides assertions:
	//
	// CHECK(must_be_true);
	// CHECK_EQ(a, b) << z_is_interesting_too;

	// NOTE: For Windows, you must include logging.h after windows.h to allow the
	// following code to suppress the evil ERROR macro:
	#ifdef _WIN32
	// windows.h includes wingdi.h which defines an evil macro ERROR.
	#ifdef ERROR
	#undef ERROR
	#endif
	#endif

	#include <functional>
	#include <memory>
	#include <ostream>

	#include "android-base/macros.h"

	// Note: DO NOT USE DIRECTLY. Use LOG_TAG instead.
	#ifdef _LOG_TAG_INTERNAL
	#error "_LOG_TAG_INTERNAL must not be defined"
	#endif
	#ifdef LOG_TAG
	#define _LOG_TAG_INTERNAL LOG_TAG
	#else
	#define _LOG_TAG_INTERNAL nullptr
	#endif

	namespace android {
	namespace base {

	enum LogSeverity {
	VERBOSE,
	DEBUG,
	INFO,
	WARNING,
	ERROR,
	FATAL_WITHOUT_ABORT,
	FATAL,
	};

	enum LogId {
	DEFAULT,
	MAIN,
	SYSTEM,
	};

	using LogFunction = std::function<void(LogId, LogSeverity, const char, const char,
	unsigned int, const char*)>;
	using AbortFunction = std::function<void(const char*)>;

	void KernelLogger(LogId, LogSeverity, const char, const char, unsigned int, const char*);
	void StderrLogger(LogId, LogSeverity, const char, const char, unsigned int, const char*);

	void DefaultAborter(const char* abort_message);

	std::string GetDefaultTag();
	void SetDefaultTag(const std::string& tag);

	#ifdef __ANDROID__
	// We expose this even though it is the default because a user that wants to
	// override the default log buffer will have to construct this themselves.
	class LogdLogger {
	public:
	explicit LogdLogger(LogId default_log_id = android::base::MAIN);

	void operator()(LogId, LogSeverity, const char* tag, const char* file,
	unsigned int line, const char* message);

	private:
	LogId default_log_id_;
	};
	#endif

	// Configure logging based on ANDROID_LOG_TAGS environment variable.
	// We need to parse a string that looks like
	//
	// *:v jdwp:d dalvikvm:d dalvikvm-gc:i dalvikvmi:i
	//
	// The tag (or '*' for the global level) comes first, followed by a colon and a
	// letter indicating the minimum priority level we're expected to log. This can
	// be used to reveal or conceal logs with specific tags.
	#ifdef __ANDROID__
	#define INIT_LOGGING_DEFAULT_LOGGER LogdLogger()
	#else
	#define INIT_LOGGING_DEFAULT_LOGGER StderrLogger
	#endif
	void InitLogging(char* argv[],
	LogFunction&& logger = INIT_LOGGING_DEFAULT_LOGGER,
	AbortFunction&& aborter = DefaultAborter);
	#undef INIT_LOGGING_DEFAULT_LOGGER

	// Replace the current logger.
	void SetLogger(LogFunction&& logger);

	// Replace the current aborter.
	void SetAborter(AbortFunction&& aborter);

	class ErrnoRestorer {
	public:
	ErrnoRestorer()
	: saved_errno_(errno) {
	}

	~ErrnoRestorer() {
	errno = saved_errno_;
	}

	// Allow this object to be used as part of && operation.
	operator bool() const {
	return true;
	}

	private:
	const int saved_errno_;

	DISALLOW_COPY_AND_ASSIGN(ErrnoRestorer);
	};

	// A helper macro that produces an expression that accepts both a qualified name and an
	// unqualified name for a LogSeverity, and returns a LogSeverity value.
	// Note: DO NOT USE DIRECTLY. This is an implementation detail.
	#define SEVERITY_LAMBDA(severity) ([&]() { \
	using ::android::base::VERBOSE; \
	using ::android::base::DEBUG; \
	using ::android::base::INFO; \
	using ::android::base::WARNING; \
	using ::android::base::ERROR; \
	using ::android::base::FATAL_WITHOUT_ABORT; \
	using ::android::base::FATAL; \
	return (severity); }())

	#ifdef __clang_analyzer__
	// Clang's static analyzer does not see the conditional statement inside
	// LogMessage's destructor that will abort on FATAL severity.
	#define ABORT_AFTER_LOG_FATAL for (;; abort())

	struct LogAbortAfterFullExpr {
	~LogAbortAfterFullExpr() __attribute__((noreturn)) { abort(); }
	explicit operator bool() const { return false; }
	};
	// Provides an expression that evaluates to the truthiness of `x`, automatically
	// aborting if `c` is true.
	#define ABORT_AFTER_LOG_EXPR_IF(c, x) (((c) && ::android::base::LogAbortAfterFullExpr()) \|\| (x))
	// Note to the static analyzer that we always execute FATAL logs in practice.
	#define MUST_LOG_MESSAGE(severity) (SEVERITY_LAMBDA(severity) == ::android::base::FATAL)
	#else
	#define ABORT_AFTER_LOG_FATAL
	#define ABORT_AFTER_LOG_EXPR_IF(c, x) (x)
	#define MUST_LOG_MESSAGE(severity) false
	#endif
	#define ABORT_AFTER_LOG_FATAL_EXPR(x) ABORT_AFTER_LOG_EXPR_IF(true, x)

	// Defines whether the given severity will be logged or silently swallowed.
	#define WOULD_LOG(severity) \
	(UNLIKELY((SEVERITY_LAMBDA(severity)) >= ::android::base::GetMinimumLogSeverity()) \|\| \
	MUST_LOG_MESSAGE(severity))

	// Get an ostream that can be used for logging at the given severity and to the default
	// destination.
	//
	// Notes:
	// 1) This will not check whether the severity is high enough. One should use WOULD_LOG to filter
	// usage manually.
	// 2) This does not save and restore errno.
	#define LOG_STREAM(severity) LOG_STREAM_TO(DEFAULT, severity)

	// Get an ostream that can be used for logging at the given severity and to the
	// given destination. The same notes as for LOG_STREAM apply.
	#define LOG_STREAM_TO(dest, severity) \
	::android::base::LogMessage(__FILE__, __LINE__, ::android::base::dest, \
	SEVERITY_LAMBDA(severity), _LOG_TAG_INTERNAL, -1) \
	.stream()

	// Logs a message to logcat on Android otherwise to stderr. If the severity is
	// FATAL it also causes an abort. For example:
	//
	// LOG(FATAL) << "We didn't expect to reach here";
	#define LOG(severity) LOG_TO(DEFAULT, severity)

	// Checks if we want to log something, and sets up appropriate RAII objects if
	// so.
	// Note: DO NOT USE DIRECTLY. This is an implementation detail.
	#define LOGGING_PREAMBLE(severity) \
	(WOULD_LOG(severity) && \
	ABORT_AFTER_LOG_EXPR_IF((SEVERITY_LAMBDA(severity)) == ::android::base::FATAL, true) && \
	::android::base::ErrnoRestorer())

	// Logs a message to logcat with the specified log ID on Android otherwise to
	// stderr. If the severity is FATAL it also causes an abort.
	// Use an expression here so we can support the << operator following the macro,
	// like "LOG(DEBUG) << xxx;".
	#define LOG_TO(dest, severity) LOGGING_PREAMBLE(severity) && LOG_STREAM_TO(dest, severity)

	// A variant of LOG that also logs the current errno value. To be used when
	// library calls fail.
	#define PLOG(severity) PLOG_TO(DEFAULT, severity)

	// Behaves like PLOG, but logs to the specified log ID.
	#define PLOG_TO(dest, severity) \
	LOGGING_PREAMBLE(severity) && \
	::android::base::LogMessage(__FILE__, __LINE__, ::android::base::dest, \
	SEVERITY_LAMBDA(severity), _LOG_TAG_INTERNAL, errno) \
	.stream()

	// Marker that code is yet to be implemented.
	#define UNIMPLEMENTED(level) \
	LOG(level) << __PRETTY_FUNCTION__ << " unimplemented "

	// Check whether condition x holds and LOG(FATAL) if not. The value of the
	// expression x is only evaluated once. Extra logging can be appended using <<
	// after. For example:
	//
	// CHECK(false == true) results in a log message of
	// "Check failed: false == true".
	#define CHECK(x) \
	LIKELY((x)) \|\| ABORT_AFTER_LOG_FATAL_EXPR(false) \|\| \
	::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT, \
	::android::base::FATAL, _LOG_TAG_INTERNAL, -1) \
	.stream() \
	<< "Check failed: " #x << " "

	// clang-format off
	// Helper for CHECK_xx(x,y) macros.
	#define CHECK_OP(LHS, RHS, OP) \
	for (auto _values = ::android::base::MakeEagerEvaluator(LHS, RHS); \
	UNLIKELY(!(_values.lhs OP _values.rhs)); \
	/* empty */) \
	ABORT_AFTER_LOG_FATAL \
	::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT, \
	::android::base::FATAL, _LOG_TAG_INTERNAL, -1) \
	.stream() \
	<< "Check failed: " << #LHS << " " << #OP << " " << #RHS << " (" #LHS "=" << _values.lhs \
	<< ", " #RHS "=" << _values.rhs << ") "
	// clang-format on

	// Check whether a condition holds between x and y, LOG(FATAL) if not. The value
	// of the expressions x and y is evaluated once. Extra logging can be appended
	// using << after. For example:
	//
	// CHECK_NE(0 == 1, false) results in
	// "Check failed: false != false (0==1=false, false=false) ".
	#define CHECK_EQ(x, y) CHECK_OP(x, y, == )
	#define CHECK_NE(x, y) CHECK_OP(x, y, != )
	#define CHECK_LE(x, y) CHECK_OP(x, y, <= )
	#define CHECK_LT(x, y) CHECK_OP(x, y, < )
	#define CHECK_GE(x, y) CHECK_OP(x, y, >= )
	#define CHECK_GT(x, y) CHECK_OP(x, y, > )

	// clang-format off
	// Helper for CHECK_STRxx(s1,s2) macros.
	#define CHECK_STROP(s1, s2, sense) \
	while (UNLIKELY((strcmp(s1, s2) == 0) != (sense))) \
	ABORT_AFTER_LOG_FATAL \
	::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT, \
	::android::base::FATAL, _LOG_TAG_INTERNAL, -1) \
	.stream() \
	<< "Check failed: " << "\"" << (s1) << "\"" \
	<< ((sense) ? " == " : " != ") << "\"" << (s2) << "\""
	// clang-format on

	// Check for string (const char*) equality between s1 and s2, LOG(FATAL) if not.
	#define CHECK_STREQ(s1, s2) CHECK_STROP(s1, s2, true)
	#define CHECK_STRNE(s1, s2) CHECK_STROP(s1, s2, false)

	// Perform the pthread function call(args), LOG(FATAL) on error.
	#define CHECK_PTHREAD_CALL(call, args, what) \
	do { \
	int rc = call args; \
	if (rc != 0) { \
	errno = rc; \
	ABORT_AFTER_LOG_FATAL \
	PLOG(FATAL) << #call << " failed for " << (what); \
	} \
	} while (false)

	// CHECK that can be used in a constexpr function. For example:
	//
	// constexpr int half(int n) {
	// return
	// DCHECK_CONSTEXPR(n >= 0, , 0)
	// CHECK_CONSTEXPR((n & 1) == 0),
	// << "Extra debugging output: n = " << n, 0)
	// n / 2;
	// }
	#define CHECK_CONSTEXPR(x, out, dummy) \
	(UNLIKELY(!(x))) \
	? (LOG(FATAL) << "Check failed: " << #x out, dummy) \
	:

	// DCHECKs are debug variants of CHECKs only enabled in debug builds. Generally
	// CHECK should be used unless profiling identifies a CHECK as being in
	// performance critical code.
	#if defined(NDEBUG) && !defined(__clang_analyzer__)
	static constexpr bool kEnableDChecks = false;
	#else
	static constexpr bool kEnableDChecks = true;
	#endif

	#define DCHECK(x) \
	if (::android::base::kEnableDChecks) CHECK(x)
	#define DCHECK_EQ(x, y) \
	if (::android::base::kEnableDChecks) CHECK_EQ(x, y)
	#define DCHECK_NE(x, y) \
	if (::android::base::kEnableDChecks) CHECK_NE(x, y)
	#define DCHECK_LE(x, y) \
	if (::android::base::kEnableDChecks) CHECK_LE(x, y)
	#define DCHECK_LT(x, y) \
	if (::android::base::kEnableDChecks) CHECK_LT(x, y)
	#define DCHECK_GE(x, y) \
	if (::android::base::kEnableDChecks) CHECK_GE(x, y)
	#define DCHECK_GT(x, y) \
	if (::android::base::kEnableDChecks) CHECK_GT(x, y)
	#define DCHECK_STREQ(s1, s2) \
	if (::android::base::kEnableDChecks) CHECK_STREQ(s1, s2)
	#define DCHECK_STRNE(s1, s2) \
	if (::android::base::kEnableDChecks) CHECK_STRNE(s1, s2)
	#if defined(NDEBUG) && !defined(__clang_analyzer__)
	#define DCHECK_CONSTEXPR(x, out, dummy)
	#else
	#define DCHECK_CONSTEXPR(x, out, dummy) CHECK_CONSTEXPR(x, out, dummy)
	#endif

	// Temporary class created to evaluate the LHS and RHS, used with
	// MakeEagerEvaluator to infer the types of LHS and RHS.
	template <typename LHS, typename RHS>
	struct EagerEvaluator {
	constexpr EagerEvaluator(LHS l, RHS r) : lhs(l), rhs(r) {
	}
	LHS lhs;
	RHS rhs;
	};

	// Helper function for CHECK_xx.
	template <typename LHS, typename RHS>
	constexpr EagerEvaluator<LHS, RHS> MakeEagerEvaluator(LHS lhs, RHS rhs) {
	return EagerEvaluator<LHS, RHS>(lhs, rhs);
	}

	// Explicitly instantiate EagerEvalue for pointers so that char*s aren't treated
	// as strings. To compare strings use CHECK_STREQ and CHECK_STRNE. We rely on
	// signed/unsigned warnings to protect you against combinations not explicitly
	// listed below.
	#define EAGER_PTR_EVALUATOR(T1, T2) \
	template <> \
	struct EagerEvaluator<T1, T2> { \
	EagerEvaluator(T1 l, T2 r) \
	: lhs(reinterpret_cast<const void*>(l)), \
	rhs(reinterpret_cast<const void*>(r)) { \
	} \
	const void* lhs; \
	const void* rhs; \
	}
	EAGER_PTR_EVALUATOR(const char, const char);
	EAGER_PTR_EVALUATOR(const char, char);
	EAGER_PTR_EVALUATOR(char, const char);
	EAGER_PTR_EVALUATOR(char, char);
	EAGER_PTR_EVALUATOR(const unsigned char, const unsigned char);
	EAGER_PTR_EVALUATOR(const unsigned char, unsigned char);
	EAGER_PTR_EVALUATOR(unsigned char, const unsigned char);
	EAGER_PTR_EVALUATOR(unsigned char, unsigned char);
	EAGER_PTR_EVALUATOR(const signed char, const signed char);
	EAGER_PTR_EVALUATOR(const signed char, signed char);
	EAGER_PTR_EVALUATOR(signed char, const signed char);
	EAGER_PTR_EVALUATOR(signed char, signed char);

	// Data for the log message, not stored in LogMessage to avoid increasing the
	// stack size.
	class LogMessageData;

	// A LogMessage is a temporarily scoped object used by LOG and the unlikely part
	// of a CHECK. The destructor will abort if the severity is FATAL.
	class LogMessage {
	public:
	LogMessage(const char* file, unsigned int line, LogId id, LogSeverity severity, const char* tag,
	int error);

	~LogMessage();

	// Returns the stream associated with the message, the LogMessage performs
	// output when it goes out of scope.
	std::ostream& stream();

	// The routine that performs the actual logging.
	static void LogLine(const char* file, unsigned int line, LogId id, LogSeverity severity,
	const char* tag, const char* msg);

	private:
	const std::unique_ptr<LogMessageData> data_;

	// TODO(b/35361699): remove these symbols once all prebuilds stop using it.
	LogMessage(const char* file, unsigned int line, LogId id, LogSeverity severity, int error);
	static void LogLine(const char* file, unsigned int line, LogId id, LogSeverity severity,
	const char* msg);

	DISALLOW_COPY_AND_ASSIGN(LogMessage);
	};

	// Get the minimum severity level for logging.
	LogSeverity GetMinimumLogSeverity();

	// Set the minimum severity level for logging, returning the old severity.
	LogSeverity SetMinimumLogSeverity(LogSeverity new_severity);

	// Allows to temporarily change the minimum severity level for logging.
	class ScopedLogSeverity {
	public:
	explicit ScopedLogSeverity(LogSeverity level);
	~ScopedLogSeverity();

	private:
	LogSeverity old_;
	};

	} // namespace base
	} // namespace android

	namespace std {

	// Emit a warning of ostream<< with std::string. The intention was most likely to print string.
	//
	// Note: for this to work, we need to have this in a namespace.
	// Note: lots of ifdef magic to make this work with Clang (platform) vs GCC (windows tools)
	// Note: using diagnose_if(true) under Clang and nothing under GCC/mingw as there is no common
	// attribute support.
	// Note: using a pragma because "-Wgcc-compat" (included in "-Weverything") complains about
	// diagnose_if.
	// Note: to print the pointer, use "<< static_cast<const void*>(string_pointer)" instead.
	// Note: a not-recommended alternative is to let Clang ignore the warning by adding
	// -Wno-user-defined-warnings to CPPFLAGS.
	#ifdef __clang__
	#pragma clang diagnostic push
	#pragma clang diagnostic ignored "-Wgcc-compat"
	#define OSTREAM_STRING_POINTER_USAGE_WARNING \
	__attribute__((diagnose_if(true, "Unexpected logging of string pointer", "warning")))
	#else
	#define OSTREAM_STRING_POINTER_USAGE_WARNING /* empty */
	#endif
	inline std::ostream& operator<<(std::ostream& stream, const std::string* string_pointer)
	OSTREAM_STRING_POINTER_USAGE_WARNING {
	return stream << static_cast<const void*>(string_pointer);
	}
	#ifdef __clang__
	#pragma clang diagnostic pop
	#endif
	#undef OSTREAM_STRING_POINTER_USAGE_WARNING

	} // namespace std

	#endif // ANDROID_BASE_LOGGING_H