blob: 5353b59bd933b09d2309712cc59fbc8282f68d22 [file] [log] [blame]
// Copyright 2006 Google Inc. All Rights Reserved.
// Author: brettw (Brett Wilson)
#ifndef BASE_LOGGING_H__
#define BASE_LOGGING_H__
#include <string>
#include <cstring>
#include <strstream>
#include <tchar.h>
#include "base/basictypes.h"
#include "base/scoped_ptr.h"
// Optional message capabilities
// -----------------------------
// Assertion failed messages and fatal errors are displayed in a dialog box
// before the application exits. However, running this UI creates a message
// loop, which causes application messages to be processed and potentially
// dispatched to existing application windows. Since the application is in a
// bad state when this assertion dialog is displayed, these messages may not
// get processed and hang the dialog, or the application might go crazy.
// Therefore, it can be beneficial to display the error dialog in a separate
// process from the main application. When the logging system needs to display
// a fatal error dialog box, it will look for a program called
// "DebugMessage.exe" in the same directory as the application executable. It
// will run this application with the message as the command line, and will
// not include the name of the application as is traditional for easier
// parsing.
// The code for DebugMessage.exe is only one line. In WinMain, do:
// MessageBox(NULL, GetCommandLineW(), L"Fatal Error", 0);
// If DebugMessage.exe is not found, the logging code will use a normal
// MessageBox, potentially causing the problems discussed above.
// Instructions
// ------------
// Make a bunch of macros for logging. The way to log things is to stream
// things to LOG(<a particular severity level>). E.g.,
// LOG(INFO) << "Found " << num_cookies << " cookies";
// You can also do conditional logging:
// LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";
// The above will cause log messages to be output on the 1st, 11th, 21st, ...
// times it is executed. Note that the special COUNTER value is used to
// identify which repetition is happening.
// There are also "debug mode" logging macros like the ones above:
// DLOG(INFO) << "Found cookies";
// DLOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";
// All "debug mode" logging is compiled away to nothing for non-debug mode
// compiles. LOG_IF and development flags also work well together
// because the code can be compiled away sometimes.
// We also have
// LOG_ASSERT(assertion);
// DLOG_ASSERT(assertion);
// which is syntactic sugar for {,D}LOG_IF(FATAL, assert fails) << assertion;
// We also override the standard 'assert' to use 'DLOG_ASSERT'.
// The supported severity levels for macros that allow you to specify one
// are (in increasing order of severity) INFO, WARNING, ERROR, and FATAL.
// There is also the special severity of DFATAL, which logs FATAL in
// debug mode, ERROR in normal mode.
// Very important: logging a message at the FATAL severity level causes
// the program to terminate (after the message is logged).
namespace logging {
// Where to record logging output? A flat file and/or system debug log via
// OutputDebugString. Defaults to LOG_ONLY_TO_FILE.
enum LoggingDestination { LOG_ONLY_TO_FILE,
// Indicates that the log file should be locked when being written to.
// Often, there is no locking, which is fine for a single threaded program.
// If logging is being done from multiple threads or there can be more than
// one process doing the logging, the file should be locked during writes to
// make each log outut atomic. Other writers will block.
// All processes writing to the log file must have their locking set for it to
// work properly. Defaults to DONT_LOCK_LOG_FILE.
enum LogLockingState { LOCK_LOG_FILE, DONT_LOCK_LOG_FILE };
// On startup, should we delete or append to an existing log file (if any)?
// Defaults to APPEND_TO_OLD_LOG_FILE.
// Sets the log file name and other global logging state. Calling this function
// is recommended, and is normally done at the beginning of application init.
// If you don't call it, all the flags will be initialized to their default
// values, and there is a race condition that may leak a critical section
// object if two threads try to do the first log at the same time.
// See the definition of the enums above for descriptions and default values.
// The default log file is initialized to "debug.log" in the application
// directory. You probably don't want this, especially since the program
// directory may not be writable on an enduser's system.
void InitLogging(const TCHAR* log_file, LoggingDestination logging_dest,
LogLockingState lock_log, OldFileDeletionState delete_old);
// Sets the log level. Anything at or above this level will be written to the
// log file/displayed to the user (if applicable). Anything below this level
// will be silently ignored. The log level defaults to 0 (everything is logged)
// if this function is not called.
void SetMinLogLevel(int level);
// Sets the log filter prefix. Any log message below LOG_ERROR severity that
// doesn't start with this prefix with be silently ignored. The filter defaults
// to NULL (everything is logged) if this function is not called. Messages
// with severity of LOG_ERROR or higher will not be filtered.
void SetLogFilterPrefix(char* filter);
// Sets the common items you want to be prepended to each log message.
// process and thread IDs default to off, the timestamp defaults to on.
// If this function is not called, logging defaults to writing the timestamp
// only.
void SetLogItems(bool enable_process_id, bool enable_thread_id,
bool enable_timestamp, bool enable_tickcount);
// Sets the Log Assert Handler that will be used to notify of check failures.
// The default handler shows a dialog box, however clients can use this
// function to override with their own handling (e.g. a silent one for Unit
// Tests)
typedef void (*LogAssertHandlerFunction)(const std::string& str);
void SetLogAssertHandler(LogAssertHandlerFunction handler);
typedef int LogSeverity;
const LogSeverity LOG_INFO = 0;
const LogSeverity LOG_WARNING = 1;
const LogSeverity LOG_ERROR = 2;
const LogSeverity LOG_FATAL = 3;
const LogSeverity LOG_NUM_SEVERITIES = 4;
// LOG_DFATAL_LEVEL is LOG_FATAL in debug mode, ERROR in normal mode
#ifdef NDEBUG
// A few definitions of macros that don't generate much code. These are used
// by LOG() and LOG_IF, etc. Since these are used all over our code, it's
// better to have compact code for these operations.
logging::LogMessage(__FILE__, __LINE__)
logging::LogMessage(__FILE__, __LINE__, logging::LOG_WARNING)
logging::LogMessage(__FILE__, __LINE__, logging::LOG_ERROR)
logging::LogMessage(__FILE__, __LINE__, logging::LOG_FATAL)
logging::LogMessage(__FILE__, __LINE__, logging::LOG_DFATAL_LEVEL)
// wingdi.h defines ERROR to be 0. When we call LOG(ERROR), it gets
// substituted with 0, and it expands to COMPACT_GOOGLE_LOG_0. To allow us
// to keep using this syntax, we define this macro to do the same thing
// as COMPACT_GOOGLE_LOG_ERROR, and also define ERROR the same way that
// the Windows SDK does for consistency.
#define ERROR 0
logging::LogMessage(__FILE__, __LINE__, logging::LOG_ERROR)
// We use the preprocessor's merging operator, "##", so that, e.g.,
// LOG(INFO) becomes the token COMPACT_GOOGLE_LOG_INFO. There's some funny
// subtle difference between ostream member streaming functions (e.g.,
// ostream::operator<<(int) and ostream non-member streaming functions
// (e.g., ::operator<<(ostream&, string&): it turns out that it's
// impossible to stream something like a string directly to an unnamed
// ostream. We employ a neat hack by calling the stream() member
// function of LogMessage which seems to avoid the problem.
#define LOG(severity) COMPACT_GOOGLE_LOG_ ##
#define SYSLOG(severity) LOG(severity)
#define LOG_IF(severity, condition) \
!(condition) ? (void) 0 : logging::LogMessageVoidify() & LOG(severity)
#define SYSLOG_IF(severity, condition) LOG_IF(severity, condition)
#define LOG_ASSERT(condition) \
LOG_IF(FATAL, !(condition)) << "Assert failed: " #condition ". "
#define SYSLOG_ASSERT(condition) \
SYSLOG_IF(FATAL, !(condition)) << "Assert failed: " #condition ". "
// A container for a string pointer which can be evaluated to a bool -
// true iff the pointer is NULL.
struct CheckOpString {
CheckOpString(std::string* str) : str_(str) { }
// No destructor: if str_ is non-NULL, we're about to LOG(FATAL),
// so there's no point in cleaning up str_.
operator bool() const { return str_ != NULL; }
std::string* str_;
// Build the error message string. This is separate from the "Impl"
// function template because it is not performance critical and so can
// be out of line, while the "Impl" code should be inline.
template<class t1, class t2>
std::string* MakeCheckOpString(const t1& v1, const t2& v2, const char* names) {
std::ostrstream ss;
ss << names << " (" << v1 << " vs. " << v2 << ")";
return new std::string(ss.str(), ss.pcount());
extern std::string* MakeCheckOpStringIntInt(int v1, int v2, const char* names);
template<int, int>
std::string* MakeCheckOpString(const int& v1, const int& v2, const char* names) {
return MakeCheckOpStringIntInt(v1, v2, names);
// Plus some debug-logging macros that get compiled to nothing for production
// DEBUG_MODE is for uses like
// if (DEBUG_MODE) foo.CheckThatFoo();
// instead of
// #ifndef NDEBUG
// foo.CheckThatFoo();
// #endif
#ifndef NDEBUG
#define DLOG(severity) LOG(severity)
#define DLOG_IF(severity, condition) LOG_IF(severity, condition)
#define DLOG_ASSERT(condition) LOG_ASSERT(condition)
// debug-only checking. not executed in NDEBUG mode.
enum { DEBUG_MODE = 1 };
#define DCHECK(condition) \
LOG_IF(FATAL, !(condition)) << "Check failed: " #condition ". "
// Helper functions for DCHECK_OP macro.
// The (int, int) specialization works around the issue that the compiler
// will not instantiate the template version of the function on values of
// unnamed enum type - see comment below.
#define DEFINE_DCHECK_OP_IMPL(name, op) \
template <class t1, class t2> \
inline std::string* Check##name##Impl(const t1& v1, const t2& v2, \
const char* names) { \
if (v1 op v2) return NULL; \
else return MakeCheckOpString(v1, v2, names); \
} \
inline std::string* Check##name##Impl(int v1, int v2, const char* names) { \
if (v1 op v2) return NULL; \
else return MakeCheckOpString(v1, v2, names); \
// Helper macro for binary operators.
// Don't use this macro directly in your code, use CHECK_EQ et al below.
#define DCHECK_OP(name, op, val1, val2) \
while (logging::CheckOpString _result = \
logging::Check##name##Impl((val1), (val2), #val1 " " #op " " #val2)) \
logging::LogMessage(__FILE__, __LINE__, _result).stream()
// Equality/Inequality checks - compare two values, and log a LOG_FATAL message
// including the two values when the result is not as expected. The values
// must have operator<<(ostream, ...) defined.
// You may append to the error message like so:
// CHECK_NE(1, 2) << ": The world must be ending!";
// We are very careful to ensure that each argument is evaluated exactly
// once, and that anything which is legal to pass as a function argument is
// legal here. In particular, the arguments may be temporary expressions
// which will end up being destroyed at the end of the apparent statement,
// for example:
// CHECK_EQ(string("abc")[1], 'b');
// WARNING: These don't compile correctly if one of the arguments is a pointer
// and the other is NULL. To work around this, simply static_cast NULL to the
// type of the desired pointer.
#define DCHECK_EQ(val1, val2) DCHECK_OP(EQ, ==, val1, val2)
#define DCHECK_NE(val1, val2) DCHECK_OP(NE, !=, val1, val2)
#define DCHECK_LE(val1, val2) DCHECK_OP(LE, <=, val1, val2)
#define DCHECK_LT(val1, val2) DCHECK_OP(LT, < , val1, val2)
#define DCHECK_GE(val1, val2) DCHECK_OP(GE, >=, val1, val2)
#define DCHECK_GT(val1, val2) DCHECK_OP(GT, > , val1, val2)
// Helper functions for string comparisons.
// To avoid bloat, the definitions are in
#define DECLARE_DCHECK_STROP_IMPL(func, expected) \
std::string* Check##func##expected##Impl(const char* s1, \
const char* s2, \
const char* names);
// Helper macro for string comparisons.
// Don't use this macro directly in your code, use CHECK_STREQ et al below.
#define DCHECK_STROP(func, op, expected, s1, s2) \
while (CheckOpString _result = \
logging::Check##func##expected##Impl((s1), (s2), \
#s1 " " #op " " #s2)) \
LOG(FATAL) << *_result.str_
// String (char*) equality/inequality checks.
// CASE versions are case-insensitive.
// Note that "s1" and "s2" may be temporary strings which are destroyed
// by the compiler at the end of the current "full expression"
// (e.g. DCHECK_STREQ(Foo().c_str(), Bar().c_str())).
#define DCHECK_STREQ(s1, s2) DCHECK_STROP(strcmp, ==, true, s1, s2)
#define DCHECK_STRNE(s1, s2) DCHECK_STROP(strcmp, !=, false, s1, s2)
#define DCHECK_STRCASEEQ(s1, s2) DCHECK_STROP(_stricmp, ==, true, s1, s2)
#define DCHECK_STRCASENE(s1, s2) DCHECK_STROP(_stricmp, !=, false, s1, s2)
#define DCHECK_INDEX(I,A) DCHECK(I < (sizeof(A)/sizeof(A[0])))
#define DCHECK_BOUND(B,A) DCHECK(B <= (sizeof(A)/sizeof(A[0])))
#else // NDEBUG
#define DLOG(severity) \
true ? (void) 0 : logging::LogMessageVoidify() & LOG(severity)
#define DLOG_IF(severity, condition) \
true ? (void) 0 : logging::LogMessageVoidify() & LOG(severity)
#define DLOG_ASSERT(condition) \
true ? (void) 0 : LOG_ASSERT(condition)
enum { DEBUG_MODE = 0 };
// This macro can be followed by a sequence of stream parameters in
// non-debug mode. The DCHECK and friends macros use this so that
// the expanded expression DCHECK(foo) << "asdf" is still syntactically
// valid, even though the expression will get optimized away.
logging::LogMessage(__FILE__, __LINE__).stream()
#define DCHECK(condition) \
#define DCHECK_EQ(val1, val2) \
#define DCHECK_NE(val1, val2) \
#define DCHECK_LE(val1, val2) \
#define DCHECK_LT(val1, val2) \
#define DCHECK_GE(val1, val2) \
#define DCHECK_GT(val1, val2) \
#define DCHECK_STREQ(str1, str2) \
#define DCHECK_STRCASEEQ(str1, str2) \
#define DCHECK_STRNE(str1, str2) \
#define DCHECK_STRCASENE(str1, str2) \
#endif // NDEBUG
#define NOTREACHED() DCHECK(false)
// Redefine the standard assert to use our nice log files
#undef assert
#define assert(x) DLOG_ASSERT(x)
// This class more or less represents a particular log message. You
// create an instance of LogMessage and then stream stuff to it.
// When you finish streaming to it, ~LogMessage is called and the
// full message gets streamed to the appropriate destination.
// You shouldn't actually use LogMessage's constructor to log things,
// though. You should use the LOG() macro (and variants thereof)
// above.
class LogMessage {
LogMessage(const char* file, int line, LogSeverity severity, int ctr);
// Two special constructors that generate reduced amounts of code at
// LOG call sites for common cases.
// Used for LOG(INFO): Implied are:
// severity = LOG_INFO, ctr = 0
// Using this constructor instead of the more complex constructor above
// saves a couple of bytes per call site.
LogMessage(const char* file, int line);
// Used for LOG(severity) where severity != INFO. Implied
// are: ctr = 0
// Using this constructor instead of the more complex constructor above
// saves a couple of bytes per call site.
LogMessage(const char* file, int line, LogSeverity severity);
// A special constructor used for check failures.
// Implied severity = LOG_FATAL
LogMessage(const char* file, int line, const CheckOpString& result);
std::ostream& stream() { return stream_; }
void Init(const char* file, int line);
LogSeverity severity_;
std::ostrstream stream_;
int message_start_; // offset of the start of the message (past prefix info).
// A non-macro interface to the log facility; (useful
// when the logging level is not a compile-time constant).
inline void LogAtLevel(int const log_level, std::string const &msg) {
LogMessage(__FILE__, __LINE__, log_level).stream() << msg;
// This class is used to explicitly ignore values in the conditional
// logging macros. This avoids compiler warnings like "value computed
// is not used" and "statement has no effect".
class LogMessageVoidify {
LogMessageVoidify() { }
// This has to be an operator with a precedence lower than << but
// higher than ?:
void operator&(std::ostream&) { }
// Closes the log file explicitly if open.
// NOTE: Since the log file is opened as necessary by the action of logging
// statements, there's no guarantee that it will stay closed
// after this call.
void CloseLogFile();
} // namespace Logging
// These functions are provided as a convenience for logging, which is where we
// use streams (it is against Google style to use streams in other places). It
// is designed to allow you to emit non-ASCII Unicode strings to the log file,
// which is normally ASCII. It is relatively slow, so try not to use it for
// common cases. Non-ASCII characters will be converted to UTF-8 by these operators.
std::ostream& operator<<(std::ostream& out, const wchar_t* wstr);
inline std::ostream& operator<<(std::ostream& out, const std::wstring& wstr) {
return out << wstr.c_str();
#endif // BASE_LOGGING_H__