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| author | Vincent Ambo <mail@tazj.in> | 2022-02-07T19·15+0300 |
|---|---|---|
| committer | tazjin <tazjin@tvl.su> | 2022-02-07T22·25+0000 |
| commit | 5ed7ef8089a6914a81b7592d2b6db93c5d87a1e2 (patch) | |
| tree | d1b86294fd613ed62f131a4ba67bc6e3adf2fc61 /third_party/glog/doc/glog.html | |
| parent | 18c8c41b5c2de5a08530b5185cefef86f6ffaff5 (diff) | |
chore(3p/glog): Unvendor glog r/3784
... and build //third_party/nix with the one from nixpkgs. Change-Id: Iae7f1772a31286f2c22955cdc1fe61ee82d112aa Reviewed-on: https://cl.tvl.fyi/c/depot/+/3016 Tested-by: BuildkiteCI Autosubmit: tazjin <tazjin@tvl.su> Reviewed-by: grfn <grfn@gws.fyi>
Diffstat (limited to 'third_party/glog/doc/glog.html')
| -rw-r--r-- | third_party/glog/doc/glog.html | 631 |
1 files changed, 0 insertions, 631 deletions
diff --git a/third_party/glog/doc/glog.html b/third_party/glog/doc/glog.html deleted file mode 100644 index 699d2ceb80b1..000000000000 --- a/third_party/glog/doc/glog.html +++ /dev/null @@ -1,631 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> - -<html> -<head> -<title>How To Use Google Logging Library (glog)</title> - -<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> -<link href="http://www.google.com/favicon.ico" type="image/x-icon" - rel="shortcut icon"> -<link href="designstyle.css" type="text/css" rel="stylesheet"> -<style type="text/css"> -<!-- - ol.bluelist li { - color: #3366ff; - font-family: sans-serif; - } - ol.bluelist li p { - color: #000; - font-family: "Times Roman", times, serif; - } - ul.blacklist li { - color: #000; - font-family: "Times Roman", times, serif; - } -//--> -</style> -</head> - -<body> - -<h1>How To Use Google Logging Library (glog)</h1> -<small>(as of -<script type=text/javascript> - var lm = new Date(document.lastModified); - document.write(lm.toDateString()); -</script>) -</small> -<br> - -<h2> <A NAME=intro>Introduction</A> </h2> - -<p><b>Google glog</b> is a library that implements application-level -logging. This library provides logging APIs based on C++-style -streams and various helper macros. -You can log a message by simply streaming things to LOG(<a -particular <a href="#severity">severity level</a>>), e.g. - -<pre> - #include <glog/logging.h> - - int main(int argc, char* argv[]) { - // Initialize Google's logging library. - google::InitGoogleLogging(argv[0]); - - // ... - LOG(INFO) << "Found " << num_cookies << " cookies"; - } -</pre> - -<p>Google glog defines a series of macros that simplify many common logging -tasks. You can log messages by severity level, control logging -behavior from the command line, log based on conditionals, abort the -program when expected conditions are not met, introduce your own -verbose logging levels, and more. This document describes the -functionality supported by glog. Please note that this document -doesn't describe all features in this library, but the most useful -ones. If you want to find less common features, please check -header files under <code>src/glog</code> directory. - -<h2> <A NAME=severity>Severity Level</A> </h2> - -<p> -You can specify one of the following severity levels (in -increasing order of severity): <code>INFO</code>, <code>WARNING</code>, -<code>ERROR</code>, and <code>FATAL</code>. -Logging a <code>FATAL</code> message terminates the program (after the -message is logged). -Note that messages of a given severity are logged not only in the -logfile for that severity, but also in all logfiles of lower severity. -E.g., a message of severity <code>FATAL</code> will be logged to the -logfiles of severity <code>FATAL</code>, <code>ERROR</code>, -<code>WARNING</code>, and <code>INFO</code>. - -<p> -The <code>DFATAL</code> severity logs a <code>FATAL</code> error in -debug mode (i.e., there is no <code>NDEBUG</code> macro defined), but -avoids halting the program in production by automatically reducing the -severity to <code>ERROR</code>. - -<p>Unless otherwise specified, glog writes to the filename -"/tmp/<program name>.<hostname>.<user name>.log.<severity level>.<date>.<time>.<pid>" -(e.g., "/tmp/hello_world.example.com.hamaji.log.INFO.20080709-222411.10474"). -By default, glog copies the log messages of severity level -<code>ERROR</code> or <code>FATAL</code> to standard error (stderr) -in addition to log files. - -<h2><A NAME=flags>Setting Flags</A></h2> - -<p>Several flags influence glog's output behavior. -If the <a href="https://github.com/gflags/gflags">Google -gflags library</a> is installed on your machine, the -<code>configure</code> script (see the INSTALL file in the package for -detail of this script) will automatically detect and use it, -allowing you to pass flags on the command line. For example, if you -want to turn the flag <code>--logtostderr</code> on, you can start -your application with the following command line: - -<pre> - ./your_application --logtostderr=1 -</pre> - -If the Google gflags library isn't installed, you set flags via -environment variables, prefixing the flag name with "GLOG_", e.g. - -<pre> - GLOG_logtostderr=1 ./your_application -</pre> - -<!-- TODO(hamaji): Fill the version number -<p>By glog version 0.x.x, you can use GLOG_* environment variables -even if you have gflags. If both an environment variable and a flag -are specified, the value specified by a flag wins. E.g., if GLOG_v=0 -and --v=1, the verbosity will be 1, not 0. ---> - -<p>The following flags are most commonly used: - -<dl> -<dt><code>logtostderr</code> (<code>bool</code>, default=<code>false</code>) -<dd>Log messages to stderr instead of logfiles.<br> -Note: you can set binary flags to <code>true</code> by specifying -<code>1</code>, <code>true</code>, or <code>yes</code> (case -insensitive). -Also, you can set binary flags to <code>false</code> by specifying -<code>0</code>, <code>false</code>, or <code>no</code> (again, case -insensitive). -<dt><code>stderrthreshold</code> (<code>int</code>, default=2, which -is <code>ERROR</code>) -<dd>Copy log messages at or above this level to stderr in -addition to logfiles. The numbers of severity levels -<code>INFO</code>, <code>WARNING</code>, <code>ERROR</code>, and -<code>FATAL</code> are 0, 1, 2, and 3, respectively. -<dt><code>minloglevel</code> (<code>int</code>, default=0, which -is <code>INFO</code>) -<dd>Log messages at or above this level. Again, the numbers of -severity levels <code>INFO</code>, <code>WARNING</code>, -<code>ERROR</code>, and <code>FATAL</code> are 0, 1, 2, and 3, -respectively. -<dt><code>log_dir</code> (<code>string</code>, default="") -<dd>If specified, logfiles are written into this directory instead -of the default logging directory. -<dt><code>v</code> (<code>int</code>, default=0) -<dd>Show all <code>VLOG(m)</code> messages for <code>m</code> less or -equal the value of this flag. Overridable by --vmodule. -See <a href="#verbose">the section about verbose logging</a> for more -detail. -<dt><code>vmodule</code> (<code>string</code>, default="") -<dd>Per-module verbose level. The argument has to contain a -comma-separated list of <module name>=<log level>. -<module name> -is a glob pattern (e.g., <code>gfs*</code> for all modules whose name -starts with "gfs"), matched against the filename base -(that is, name ignoring .cc/.h./-inl.h). -<log level> overrides any value given by --v. -See also <a href="#verbose">the section about verbose logging</a>. -</dl> - -<p>There are some other flags defined in logging.cc. Please grep the -source code for "DEFINE_" to see a complete list of all flags. - -<p>You can also modify flag values in your program by modifying global -variables <code>FLAGS_*</code> . Most settings start working -immediately after you update <code>FLAGS_*</code> . The exceptions are -the flags related to destination files. For example, you might want to -set <code>FLAGS_log_dir</code> before -calling <code>google::InitGoogleLogging</code> . Here is an example: - -<pre> - LOG(INFO) << "file"; - // Most flags work immediately after updating values. - FLAGS_logtostderr = 1; - LOG(INFO) << "stderr"; - FLAGS_logtostderr = 0; - // This won't change the log destination. If you want to set this - // value, you should do this before google::InitGoogleLogging . - FLAGS_log_dir = "/some/log/directory"; - LOG(INFO) << "the same file"; -</pre> - -<h2><A NAME=conditional>Conditional / Occasional Logging</A></h2> - -<p>Sometimes, you may only want to log a message under certain -conditions. You can use the following macros to perform conditional -logging: - -<pre> - LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies"; -</pre> - -The "Got lots of cookies" message is logged only when the variable -<code>num_cookies</code> exceeds 10. - -If a line of code is executed many times, it may be useful to only log -a message at certain intervals. This kind of logging is most useful -for informational messages. - -<pre> - LOG_EVERY_N(INFO, 10) << "Got the " << google::COUNTER << "th cookie"; -</pre> - -<p>The above line outputs a log messages on the 1st, 11th, -21st, ... times it is executed. Note that the special -<code>google::COUNTER</code> value is used to identify which repetition is -happening. - -<p>You can combine conditional and occasional logging with the -following macro. - -<pre> - LOG_IF_EVERY_N(INFO, (size > 1024), 10) << "Got the " << google::COUNTER - << "th big cookie"; -</pre> - -<p>Instead of outputting a message every nth time, you can also limit -the output to the first n occurrences: - -<pre> - LOG_FIRST_N(INFO, 20) << "Got the " << google::COUNTER << "th cookie"; -</pre> - -<p>Outputs log messages for the first 20 times it is executed. Again, -the <code>google::COUNTER</code> identifier indicates which repetition is -happening. - -<h2><A NAME=debug>Debug Mode Support</A></h2> - -<p>Special "debug mode" logging macros only have an effect in debug -mode and are compiled away to nothing for non-debug mode -compiles. Use these macros to avoid slowing down your production -application due to excessive logging. - -<pre> - DLOG(INFO) << "Found cookies"; - - DLOG_IF(INFO, num_cookies > 10) << "Got lots of cookies"; - - DLOG_EVERY_N(INFO, 10) << "Got the " << google::COUNTER << "th cookie"; -</pre> - -<h2><A NAME=check>CHECK Macros</A></h2> - -<p>It is a good practice to check expected conditions in your program -frequently to detect errors as early as possible. The -<code>CHECK</code> macro provides the ability to abort the application -when a condition is not met, similar to the <code>assert</code> macro -defined in the standard C library. - -<p><code>CHECK</code> aborts the application if a condition is not -true. Unlike <code>assert</code>, it is *not* controlled by -<code>NDEBUG</code>, so the check will be executed regardless of -compilation mode. Therefore, <code>fp->Write(x)</code> in the -following example is always executed: - -<pre> - CHECK(fp->Write(x) == 4) << "Write failed!"; -</pre> - -<p>There are various helper macros for -equality/inequality checks - <code>CHECK_EQ</code>, -<code>CHECK_NE</code>, <code>CHECK_LE</code>, <code>CHECK_LT</code>, -<code>CHECK_GE</code>, and <code>CHECK_GT</code>. -They compare two values, and log a -<code>FATAL</code> message including the two values when the result is -not as expected. The values must have <code>operator<<(ostream, -...)</code> defined. - -<p>You may append to the error message like so: - -<pre> - CHECK_NE(1, 2) << ": The world must be ending!"; -</pre> - -<p>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: - -<pre> - CHECK_EQ(string("abc")[1], 'b'); -</pre> - -<p>The compiler reports an error 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. - -<pre> - CHECK_EQ(some_ptr, static_cast<SomeType*>(NULL)); -</pre> - -<p>Better yet, use the CHECK_NOTNULL macro: - -<pre> - CHECK_NOTNULL(some_ptr); - some_ptr->DoSomething(); -</pre> - -<p>Since this macro returns the given pointer, this is very useful in -constructor initializer lists. - -<pre> - struct S { - S(Something* ptr) : ptr_(CHECK_NOTNULL(ptr)) {} - Something* ptr_; - }; -</pre> - -<p>Note that you cannot use this macro as a C++ stream due to this -feature. Please use <code>CHECK_EQ</code> described above to log a -custom message before aborting the application. - -<p>If you are comparing C strings (char *), a handy set of macros -performs case sensitive as well as case insensitive comparisons - -<code>CHECK_STREQ</code>, <code>CHECK_STRNE</code>, -<code>CHECK_STRCASEEQ</code>, and <code>CHECK_STRCASENE</code>. The -CASE versions are case-insensitive. You can safely pass <code>NULL</code> -pointers for this macro. They treat <code>NULL</code> and any -non-<code>NULL</code> string as not equal. Two <code>NULL</code>s are -equal. - -<p>Note that both arguments may be temporary strings which are -destructed at the end of the current "full expression" -(e.g., <code>CHECK_STREQ(Foo().c_str(), Bar().c_str())</code> where -<code>Foo</code> and <code>Bar</code> return C++'s -<code>std::string</code>). - -<p>The <code>CHECK_DOUBLE_EQ</code> macro checks the equality of two -floating point values, accepting a small error margin. -<code>CHECK_NEAR</code> accepts a third floating point argument, which -specifies the acceptable error margin. - -<h2><A NAME=verbose>Verbose Logging</A></h2> - -<p>When you are chasing difficult bugs, thorough log messages are very -useful. However, you may want to ignore too verbose messages in usual -development. For such verbose logging, glog provides the -<code>VLOG</code> macro, which allows you to define your own numeric -logging levels. The <code>--v</code> command line option controls -which verbose messages are logged: - -<pre> - VLOG(1) << "I'm printed when you run the program with --v=1 or higher"; - VLOG(2) << "I'm printed when you run the program with --v=2 or higher"; -</pre> - -<p>With <code>VLOG</code>, the lower the verbose level, the more -likely messages are to be logged. For example, if -<code>--v==1</code>, <code>VLOG(1)</code> will log, but -<code>VLOG(2)</code> will not log. This is opposite of the severity -level, where <code>INFO</code> is 0, and <code>ERROR</code> is 2. -<code>--minloglevel</code> of 1 will log <code>WARNING</code> and -above. Though you can specify any integers for both <code>VLOG</code> -macro and <code>--v</code> flag, the common values for them are small -positive integers. For example, if you write <code>VLOG(0)</code>, -you should specify <code>--v=-1</code> or lower to silence it. This -is less useful since we may not want verbose logs by default in most -cases. The <code>VLOG</code> macros always log at the -<code>INFO</code> log level (when they log at all). - -<p>Verbose logging can be controlled from the command line on a -per-module basis: - -<pre> - --vmodule=mapreduce=2,file=1,gfs*=3 --v=0 -</pre> - -<p>will: - -<ul> - <li>a. Print VLOG(2) and lower messages from mapreduce.{h,cc} - <li>b. Print VLOG(1) and lower messages from file.{h,cc} - <li>c. Print VLOG(3) and lower messages from files prefixed with "gfs" - <li>d. Print VLOG(0) and lower messages from elsewhere -</ul> - -<p>The wildcarding functionality shown by (c) supports both '*' -(matches 0 or more characters) and '?' (matches any single character) -wildcards. Please also check the section about <a -href="#flags">command line flags</a>. - -<p>There's also <code>VLOG_IS_ON(n)</code> "verbose level" condition -macro. This macro returns true when the <code>--v</code> is equal or -greater than <code>n</code>. To be used as - -<pre> - if (VLOG_IS_ON(2)) { - // do some logging preparation and logging - // that can't be accomplished with just VLOG(2) << ...; - } -</pre> - -<p>Verbose level condition macros <code>VLOG_IF</code>, -<code>VLOG_EVERY_N</code> and <code>VLOG_IF_EVERY_N</code> behave -analogous to <code>LOG_IF</code>, <code>LOG_EVERY_N</code>, -<code>LOF_IF_EVERY</code>, but accept a numeric verbosity level as -opposed to a severity level. - -<pre> - VLOG_IF(1, (size > 1024)) - << "I'm printed when size is more than 1024 and when you run the " - "program with --v=1 or more"; - VLOG_EVERY_N(1, 10) - << "I'm printed every 10th occurrence, and when you run the program " - "with --v=1 or more. Present occurence is " << google::COUNTER; - VLOG_IF_EVERY_N(1, (size > 1024), 10) - << "I'm printed on every 10th occurence of case when size is more " - " than 1024, when you run the program with --v=1 or more. "; - "Present occurence is " << google::COUNTER; -</pre> - -<h2> <A name="signal">Failure Signal Handler</A> </h2> - -<p> -The library provides a convenient signal handler that will dump useful -information when the program crashes on certain signals such as SIGSEGV. -The signal handler can be installed by -google::InstallFailureSignalHandler(). The following is an example of output -from the signal handler. - -<pre> -*** Aborted at 1225095260 (unix time) try "date -d @1225095260" if you are using GNU date *** -*** SIGSEGV (@0x0) received by PID 17711 (TID 0x7f893090a6f0) from PID 0; stack trace: *** -PC: @ 0x412eb1 TestWaitingLogSink::send() - @ 0x7f892fb417d0 (unknown) - @ 0x412eb1 TestWaitingLogSink::send() - @ 0x7f89304f7f06 google::LogMessage::SendToLog() - @ 0x7f89304f35af google::LogMessage::Flush() - @ 0x7f89304f3739 google::LogMessage::~LogMessage() - @ 0x408cf4 TestLogSinkWaitTillSent() - @ 0x4115de main - @ 0x7f892f7ef1c4 (unknown) - @ 0x4046f9 (unknown) -</pre> - -<p> -By default, the signal handler writes the failure dump to the standard -error. You can customize the destination by InstallFailureWriter(). - -<h2> <A name="misc">Miscellaneous Notes</A> </h2> - -<h3><A NAME=message>Performance of Messages</A></h3> - -<p>The conditional logging macros provided by glog (e.g., -<code>CHECK</code>, <code>LOG_IF</code>, <code>VLOG</code>, ...) are -carefully implemented and don't execute the right hand side -expressions when the conditions are false. So, the following check -may not sacrifice the performance of your application. - -<pre> - CHECK(obj.ok) << obj.CreatePrettyFormattedStringButVerySlow(); -</pre> - -<h3><A NAME=failure>User-defined Failure Function</A></h3> - -<p><code>FATAL</code> severity level messages or unsatisfied -<code>CHECK</code> condition terminate your program. You can change -the behavior of the termination by -<code>InstallFailureFunction</code>. - -<pre> - void YourFailureFunction() { - // Reports something... - exit(1); - } - - int main(int argc, char* argv[]) { - google::InstallFailureFunction(&YourFailureFunction); - } -</pre> - -<p>By default, glog tries to dump stacktrace and makes the program -exit with status 1. The stacktrace is produced only when you run the -program on an architecture for which glog supports stack tracing (as -of September 2008, glog supports stack tracing for x86 and x86_64). - -<h3><A NAME=raw>Raw Logging</A></h3> - -<p>The header file <code><glog/raw_logging.h></code> can be -used for thread-safe logging, which does not allocate any memory or -acquire any locks. Therefore, the macros defined in this -header file can be used by low-level memory allocation and -synchronization code. -Please check <code>src/glog/raw_logging.h.in</code> for detail. -</p> - -<h3><A NAME=plog>Google Style perror()</A></h3> - -<p><code>PLOG()</code> and <code>PLOG_IF()</code> and -<code>PCHECK()</code> behave exactly like their <code>LOG*</code> and -<code>CHECK</code> equivalents with the addition that they append a -description of the current state of errno to their output lines. -E.g. - -<pre> - PCHECK(write(1, NULL, 2) >= 0) << "Write NULL failed"; -</pre> - -<p>This check fails with the following error message. - -<pre> - F0825 185142 test.cc:22] Check failed: write(1, NULL, 2) >= 0 Write NULL failed: Bad address [14] -</pre> - -<h3><A NAME=syslog>Syslog</A></h3> - -<p><code>SYSLOG</code>, <code>SYSLOG_IF</code>, and -<code>SYSLOG_EVERY_N</code> macros are available. -These log to syslog in addition to the normal logs. Be aware that -logging to syslog can drastically impact performance, especially if -syslog is configured for remote logging! Make sure you understand the -implications of outputting to syslog before you use these macros. In -general, it's wise to use these macros sparingly. - -<h3><A NAME=strip>Strip Logging Messages</A></h3> - -<p>Strings used in log messages can increase the size of your binary -and present a privacy concern. You can therefore instruct glog to -remove all strings which fall below a certain severity level by using -the GOOGLE_STRIP_LOG macro: - -<p>If your application has code like this: - -<pre> - #define GOOGLE_STRIP_LOG 1 // this must go before the #include! - #include <glog/logging.h> -</pre> - -<p>The compiler will remove the log messages whose severities are less -than the specified integer value. Since -<code>VLOG</code> logs at the severity level <code>INFO</code> -(numeric value <code>0</code>), -setting <code>GOOGLE_STRIP_LOG</code> to 1 or greater removes -all log messages associated with <code>VLOG</code>s as well as -<code>INFO</code> log statements. - -<h3><A NAME=strip>Automatically Remove Old Logs</A></h3> - -<p>To enable the log cleaner: - -<pre> -google::EnableLogCleaner(3); // keep your logs for 3 days -</pre> - -And then Google glog will check if there are overdue logs whenever -a flush is performed. In this example, any log file from your project whose -last modified time is greater than 3 days will be unlink()ed. - -<p>This feature can be disabled at any time (if it has been enabled) - -<pre> -google::DisableLogCleaner(); -</pre> - -<h3><A NAME=windows>Notes for Windows users</A></h3> - -<p>Google glog defines a severity level <code>ERROR</code>, which is -also defined in <code>windows.h</code> . You can make glog not define -<code>INFO</code>, <code>WARNING</code>, <code>ERROR</code>, -and <code>FATAL</code> by defining -<code>GLOG_NO_ABBREVIATED_SEVERITIES</code> before -including <code>glog/logging.h</code> . Even with this macro, you can -still use the iostream like logging facilities: - -<pre> - #define GLOG_NO_ABBREVIATED_SEVERITIES - #include <windows.h> - #include <glog/logging.h> - - // ... - - LOG(ERROR) << "This should work"; - LOG_IF(ERROR, x > y) << "This should be also OK"; -</pre> - -<p> -However, you cannot -use <code>INFO</code>, <code>WARNING</code>, <code>ERROR</code>, -and <code>FATAL</code> anymore for functions defined -in <code>glog/logging.h</code> . - -<pre> - #define GLOG_NO_ABBREVIATED_SEVERITIES - #include <windows.h> - #include <glog/logging.h> - - // ... - - // This won't work. - // google::FlushLogFiles(google::ERROR); - - // Use this instead. - google::FlushLogFiles(google::GLOG_ERROR); -</pre> - -<p> -If you don't need <code>ERROR</code> defined -by <code>windows.h</code>, there are a couple of more workarounds -which sometimes don't work: - -<ul> - <li>#define <code>WIN32_LEAN_AND_MEAN</code> or <code>NOGDI</code> - <strong>before</strong> you #include <code>windows.h</code> . - <li>#undef <code>ERROR</code> <strong>after</strong> you #include - <code>windows.h</code> . -</ul> - -<p>See <a href="http://code.google.com/p/google-glog/issues/detail?id=33"> -this issue</a> for more detail. - -<hr> -<address> -Shinichiro Hamaji<br> -Gregor Hohpe<br> -<script type=text/javascript> - var lm = new Date(document.lastModified); - document.write(lm.toDateString()); -</script> -</address> - -</body> -</html> |