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Output logs with colors to stderr
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This patch is provided by

http://code.google.com/p/google-glog/issues/detail?id=48

Thanks!
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@shinh
shinh committed Jan 23, 2013
1 parent 51723b9 commit 09f33a5
Showing 1 changed file with 133 additions and 7 deletions.
140 changes: 133 additions & 7 deletions src/logging.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,8 @@ GLOG_DEFINE_bool(logtostderr, BoolFromEnv("GOOGLE_LOGTOSTDERR", false),
"log messages go to stderr instead of logfiles");
GLOG_DEFINE_bool(alsologtostderr, BoolFromEnv("GOOGLE_ALSOLOGTOSTDERR", false),
"log messages go to stderr in addition to logfiles");
GLOG_DEFINE_bool(colorstderr, false,
"color messages logged to stderr (if supported by terminal)");
#ifdef OS_LINUX
GLOG_DEFINE_bool(drop_log_memory, true, "Drop in-memory buffers of log contents. "
"Logs can grow very quickly and they are rarely read before they "
Expand Down Expand Up @@ -199,8 +201,86 @@ static void GetHostName(string* hostname) {
#endif
}

// Returns true iff terminal supports using colors in output.
static bool TerminalSupportsColor() {
bool term_supports_color = false;
#ifdef OS_WINDOWS
// on Windows TERM variable is usually not set, but the console does
// support colors.
term_supports_color = true;
#else
// On non-Windows platforms, we rely on the TERM variable.
const char* const term = getenv("TERM");
if (term != NULL && term[0] != '\0') {
term_supports_color =
!strcmp(term, "xterm") ||
!strcmp(term, "xterm-color") ||
!strcmp(term, "xterm-256color") ||
!strcmp(term, "screen") ||
!strcmp(term, "linux") ||
!strcmp(term, "cygwin");
}
#endif
return term_supports_color;
}

_START_GOOGLE_NAMESPACE_

enum GLogColor {
COLOR_DEFAULT,
COLOR_RED,
COLOR_GREEN,
COLOR_YELLOW
};

static GLogColor SeverityToColor(LogSeverity severity) {
assert(severity >= 0 && severity < NUM_SEVERITIES);
GLogColor color = COLOR_DEFAULT;
switch (severity) {
case GLOG_INFO:
color = COLOR_DEFAULT;
break;
case GLOG_WARNING:
color = COLOR_YELLOW;
break;
case GLOG_ERROR:
case GLOG_FATAL:
color = COLOR_RED;
break;
default:
// should never get here.
assert(false);
}
return color;
}

#ifdef OS_WINDOWS

// Returns the character attribute for the given color.
WORD GetColorAttribute(GLogColor color) {
switch (color) {
case COLOR_RED: return FOREGROUND_RED;
case COLOR_GREEN: return FOREGROUND_GREEN;
case COLOR_YELLOW: return FOREGROUND_RED | FOREGROUND_GREEN;
default: return 0;
}
}

#else

// Returns the ANSI color code for the given color.
const char* GetAnsiColorCode(GLogColor color) {
switch (color) {
case COLOR_RED: return "1";
case COLOR_GREEN: return "2";
case COLOR_YELLOW: return "3";
case COLOR_DEFAULT: return "";
};
return NULL; // stop warning about return type.
}

#endif // OS_WINDOWS

// Safely get max_log_size, overriding to 1 if it somehow gets defined as 0
static int32 MaxLogSize() {
return (FLAGS_max_log_size > 0 ? FLAGS_max_log_size : 1);
Expand Down Expand Up @@ -353,6 +433,9 @@ class LogDestination {
static const int kNetworkBytes = 1400;

static const string& hostname();
static const bool& terminal_supports_color() {
return terminal_supports_color_;
}

static void DeleteLogDestinations();

Expand Down Expand Up @@ -403,6 +486,7 @@ class LogDestination {
static LogSeverity email_logging_severity_;
static string addresses_;
static string hostname_;
static bool terminal_supports_color_;

// arbitrary global logging destinations.
static vector<LogSink*>* sinks_;
Expand All @@ -424,6 +508,7 @@ string LogDestination::hostname_;

vector<LogSink*>* LogDestination::sinks_ = NULL;
Mutex LogDestination::sink_mutex_;
bool LogDestination::terminal_supports_color_ = TerminalSupportsColor();

/* static */
const string& LogDestination::hostname() {
Expand Down Expand Up @@ -544,6 +629,38 @@ inline void LogDestination::SetEmailLogging(LogSeverity min_severity,
LogDestination::addresses_ = addresses;
}

static void ColoredWriteToStderr(const char* message, size_t len, GLogColor color) {
// Avoid using cerr from this module since we may get called during
// exit code, and cerr may be partially or fully destroyed by then.
if ( COLOR_DEFAULT == color ) {
fwrite(message, len, 1, stderr);
return;
}
#ifdef OS_WINDOWS
const HANDLE stderr_handle = GetStdHandle(STD_ERROR_HANDLE);

// Gets the current text color.
CONSOLE_SCREEN_BUFFER_INFO buffer_info;
GetConsoleScreenBufferInfo(stderr_handle, &buffer_info);
const WORD old_color_attrs = buffer_info.wAttributes;

// We need to flush the stream buffers into the console before each
// SetConsoleTextAttribute call lest it affect the text that is already
// printed but has not yet reached the console.
fflush(stderr);
SetConsoleTextAttribute(stderr_handle,
GetColorAttribute(color) | FOREGROUND_INTENSITY);
fwrite(message, len, 1, stderr);
fflush(stderr);
// Restores the text color.
SetConsoleTextAttribute(stderr_handle, old_color_attrs);
#else
fprintf(stderr, "\033[0;3%sm", GetAnsiColorCode(color));
fwrite(message, len, 1, stderr);
fprintf(stderr, "\033[m"); // Resets the terminal to default.
#endif // OS_WINDOWS
}

static void WriteToStderr(const char* message, size_t len) {
// Avoid using cerr from this module since we may get called during
// exit code, and cerr may be partially or fully destroyed by then.
Expand All @@ -553,7 +670,10 @@ static void WriteToStderr(const char* message, size_t len) {
inline void LogDestination::MaybeLogToStderr(LogSeverity severity,
const char* message, size_t len) {
if ((severity >= FLAGS_stderrthreshold) || FLAGS_alsologtostderr) {
WriteToStderr(message, len);
const GLogColor color =
(terminal_supports_color_ && FLAGS_colorstderr) ?
SeverityToColor(severity) : COLOR_DEFAULT;
ColoredWriteToStderr(message, len, color);
#ifdef OS_WINDOWS
// On Windows, also output to the debugger
::OutputDebugStringA(string(message,len).c_str());
Expand Down Expand Up @@ -602,12 +722,15 @@ inline void LogDestination::LogToAllLogfiles(LogSeverity severity,
const char* message,
size_t len) {

if ( FLAGS_logtostderr ) // global flag: never log to file
WriteToStderr(message, len);
else
if ( FLAGS_logtostderr ) { // global flag: never log to file
const GLogColor color =
(terminal_supports_color_ && FLAGS_colorstderr) ?
SeverityToColor(severity) : COLOR_DEFAULT;
ColoredWriteToStderr(message, len, color);
} else {
for (int i = severity; i >= 0; --i)
LogDestination::MaybeLogToLogfile(i, timestamp, message, len);

}
}

inline void LogDestination::LogToSinks(LogSeverity severity,
Expand Down Expand Up @@ -1191,7 +1314,7 @@ void ReprintFatalMessage() {
if (fatal_message[0]) {
const int n = strlen(fatal_message);
if (!FLAGS_logtostderr) {
// Also write to stderr
// Also write to stderr (don't color to avoid terminal checks)
WriteToStderr(fatal_message, n);
}
LogDestination::LogToAllLogfiles(GLOG_ERROR, fatal_time, fatal_message, n);
Expand Down Expand Up @@ -1220,7 +1343,10 @@ void LogMessage::SendToLog() EXCLUSIVE_LOCKS_REQUIRED(log_mutex) {
// file if we haven't parsed the command line flags to get the
// program name.
if (FLAGS_logtostderr || !IsGoogleLoggingInitialized()) {
WriteToStderr(data_->message_text_, data_->num_chars_to_log_);
const GLogColor color =
(LogDestination::terminal_supports_color() && FLAGS_colorstderr) ?
SeverityToColor(data_->severity_) : COLOR_DEFAULT;
ColoredWriteToStderr(data_->message_text_, data_->num_chars_to_log_, color);

// this could be protected by a flag if necessary.
LogDestination::LogToSinks(data_->severity_,
Expand Down

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