Improvements

• spdlog can now be compiled as a static or shared lib (thanks @DavidZemon for the help). Using the compiled lib improves greatly compile times when using spdlog and is very recommended.

  $ cd spdlog && mkdir build && cd build
  # Build is static lib (pass -DSPDLOG_BUILD_SHARED=ON for building as shared lib)
  $ cmake .. && make -j
  

• Upgraded to the latest and greatest fmt library version 6.0.0. Thanks @tgpfeiffer (and to @vitaut for fmt!).
• Support for -fno-exceptions (disabled by default). Enabling this will replace all throw() statements in spdlog with std::abort(). To enable, pass -DSPDLOG_NO_EXCEPTIONS=ON to CMake before building spdlog.
• support for building spdlog with meson. Thanks @mensinda
• Backtrace support - store debug/trace messages in a ring buffer to display later on demand. Very useful (thanks @MathijsV for the idea):

spdlog::enable_backtrace(32); // create ring buffer with capacity of 32  messages
// or my_logger->enable_backtrace(32)..
for(int i = 0; i < 100; i++)
{
  spdlog::debug("Backtrace message {}", i); // not logged yet.. 
}
// e.g. if some error happened:
spdlog::dump_backtrace(); // log them now! show the last 32 messages
// or my_logger->dump_backtrace(32)..

• Systemd support. Thanks @WarShoe (#1027)
• Support for cleaning old files in daily_logger.
• Numerous CMake build improvements. Thanks @DavidZemon , @jktjkt , @ksergey , @mnemotic , @cneumann , @dpacbach , @FrancoisChabot , @myd7349 , @matt77hias
• Better support for various Unix BSDs (DragonFly, NetBSD, FreeBSD, OpenBSD). Thanks @jbeich (#1234)
• Provide source location support for systemd sink. Thanks @jbelloncastro (#1122)
• Added fmt::(w)string_view support. Thanks @matt77hias (#1139)
• Add option to force color output without TTY . Thanks @psalz (#1175)
• Add more overloads to spdlog::log and spdlog::logger::log. Thanks @sylveon (@1169)
• Add public API spdlog::initialize_logger for create loggers manually. Thanks @tt4g (#1035)
• Expose should_do_colors_ in ansicolor_sink.h. Thanks Florian Wörter (#1022)
• Add tweak support for user short level names. Thanks @MFornander (#996)
• Add method to filesinks to return filename. Thanks @markniebur (#978)
• rotating_sink: Add option to rotate on open. Thanks @pwm1234 (#958)
• Allow filename/line number at all levels. Add function name %! support. Thanks @possiblyhuman (#956)
• New dups_filter sink -duplicate message removal sink. It will skip a message if previous one is identical and less than "max_skip_duration" old.
• New '%o', '%i', '%u', '%O' format flags - Display elapsed time in mills/micros/nanos/seconds since previous message.
• Some minor pattern formatter performance improvements.

Fixes

• Fix Wundef in os-inl.h. Thanks @AMS21 (#1189)
• Fix use of old style cast in os-inl.h. Thanks @AMS21 (#1164)
• Prevent NEAR and FAR macro definitions from leaking on Windows platforms. Thanks @PeterTh (#1142)
• Fix syslog output. Thanks @mattiasj-axis (#1140)
• Fix msg.time in daily_file_sink. Thanks @s-shin (#1129)
• Fix missing include for null_mutex in rotating_file_sink.h. Thanks @casperevan (#1120)
• Fix warning: redundant move in return statement. Thanks @MarkKoester (#1119)
• Fix use of incomplete type in stdout sinks. Thanks @DanielChabrowski (#1118)
• Fix deprecation warnings in filename_to_str and improve performance of wbuf_to_utf8buf. Thanks @sylveon (#1127)
• Update README.md. Thanks @martinkrammer (#1057)
• Remove extra semicolon. Thanks @Jerry-Ma (#1202)
• Fix unexpected log macro expansion. Thanks @db-panda (#1055)
• Namespace qualify stat functions. Thanks @p-po (#1045)
• Fix typo in Android logger. Thanks @romainthomas (#994)
• Remove unnecessary log function. Thanks @DanielChabrowski (#988)
• Allow custom formatter in sink's ctor. Thanks @DanielChabrowski (#986)
• Fix shadowed parameter. Thanks @ZGCDDoo (#984)
• Update log_msg.h. Thanks @scribam (#969)
• Fix #benchmark link error. Thanks @myd7349 (#962)
• Fix typo in file_helper.h. Thanks @brridder (#955)