1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Utilities for program-wide and customizable logging
16 //! #![feature(phase)]
17 //! #[phase(plugin, link)] extern crate log;
20 //! debug!("this is a debug {}", "message");
21 //! error!("this is printed by default");
23 //! if log_enabled!(log::INFO) {
24 //! let x = 3i * 4i; // expensive computation
25 //! info!("the answer was: {}", x);
30 //! Assumes the binary is `main`:
33 //! $ RUST_LOG=error ./main
34 //! ERROR:main: this is printed by default
38 //! $ RUST_LOG=info ./main
39 //! ERROR:main: this is printed by default
40 //! INFO:main: the answer was: 12
44 //! $ RUST_LOG=debug ./main
45 //! DEBUG:main: this is a debug message
46 //! ERROR:main: this is printed by default
47 //! INFO:main: the answer was: 12
50 //! You can also set the log level on a per module basis:
53 //! $ RUST_LOG=main=info ./main
54 //! ERROR:main: this is printed by default
55 //! INFO:main: the answer was: 12
58 //! And enable all logging:
61 //! $ RUST_LOG=main ./main
62 //! DEBUG:main: this is a debug message
63 //! ERROR:main: this is printed by default
64 //! INFO:main: the answer was: 12
70 //! There are five macros that the logging subsystem uses:
72 //! * `log!(level, ...)` - the generic logging macro, takes a level as a u32 and any
73 //! related `format!` arguments
74 //! * `debug!(...)` - a macro hard-wired to the log level of `DEBUG`
75 //! * `info!(...)` - a macro hard-wired to the log level of `INFO`
76 //! * `warn!(...)` - a macro hard-wired to the log level of `WARN`
77 //! * `error!(...)` - a macro hard-wired to the log level of `ERROR`
79 //! All of these macros use the same style of syntax as the `format!` syntax
80 //! extension. Details about the syntax can be found in the documentation of
81 //! `std::fmt` along with the Rust tutorial/manual.
83 //! If you want to check at runtime if a given logging level is enabled (e.g. if the
84 //! information you would want to log is expensive to produce), you can use the
87 //! * `log_enabled!(level)` - returns true if logging of the given level is enabled
89 //! ## Enabling logging
91 //! Log levels are controlled on a per-module basis, and by default all logging is
92 //! disabled except for `error!` (a log level of 1). Logging is controlled via the
93 //! `RUST_LOG` environment variable. The value of this environment variable is a
94 //! comma-separated list of logging directives. A logging directive is of the form:
97 //! path::to::module=log_level
100 //! The path to the module is rooted in the name of the crate it was compiled for,
101 //! so if your program is contained in a file `hello.rs`, for example, to turn on
102 //! logging for this file you would use a value of `RUST_LOG=hello`.
103 //! Furthermore, this path is a prefix-search, so all modules nested in the
104 //! specified module will also have logging enabled.
106 //! The actual `log_level` is optional to specify. If omitted, all logging will be
107 //! enabled. If specified, the it must be either a numeric in the range of 1-255, or
108 //! it must be one of the strings `debug`, `error`, `info`, or `warn`. If a numeric
109 //! is specified, then all logging less than or equal to that numeral is enabled.
110 //! For example, if logging level 3 is active, error, warn, and info logs will be
111 //! printed, but debug will be omitted.
113 //! As the log level for a module is optional, the module to enable logging for is
114 //! also optional. If only a `log_level` is provided, then the global log level for
115 //! all modules is set to this value.
117 //! Some examples of valid values of `RUST_LOG` are:
119 //! * `hello` turns on all logging for the 'hello' module
120 //! * `info` turns on all info logging
121 //! * `hello=debug` turns on debug logging for 'hello'
122 //! * `hello=3` turns on info logging for 'hello'
123 //! * `hello,std::option` turns on hello, and std's option logging
124 //! * `error,hello=warn` turn on global error logging and also warn for hello
126 //! ## Filtering results
128 //! A RUST_LOG directive may include a regex filter. The syntax is to append `/`
129 //! followed by a regex. Each message is checked against the regex, and is only
130 //! logged if it matches. Note that the matching is done after formatting the log
131 //! string but before adding any logging meta-data. There is a single filter for all
136 //! * `hello/foo` turns on all logging for the 'hello' module where the log message
138 //! * `info/f.o` turns on all info logging where the log message includes 'foo',
139 //! 'f1o', 'fao', etc.
140 //! * `hello=debug/foo*foo` turns on debug logging for 'hello' where the log
141 //! message includes 'foofoo' or 'fofoo' or 'fooooooofoo', etc.
142 //! * `error,hello=warn/[0-9] scopes` turn on global error logging and also warn for
143 //! hello. In both cases the log message must include a single digit number
144 //! followed by 'scopes'
146 //! ## Performance and Side Effects
148 //! Each of these macros will expand to code similar to:
151 //! if log_level <= my_module_log_level() {
152 //! ::log::log(log_level, format!(...));
156 //! What this means is that each of these macros are very cheap at runtime if
157 //! they're turned off (just a load and an integer comparison). This also means that
158 //! if logging is disabled, none of the components of the log will be executed.
160 #![crate_name = "log"]
162 #![license = "MIT/ASL2"]
163 #![crate_type = "rlib"]
164 #![crate_type = "dylib"]
165 #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
166 html_favicon_url = "http://www.rust-lang.org/favicon.ico",
167 html_root_url = "http://doc.rust-lang.org/nightly/",
168 html_playground_url = "http://play.rust-lang.org/")]
169 #![feature(macro_rules)]
170 #![deny(missing_docs)]
176 use std::io::LineBufferedWriter;
182 use std::sync::{Once, ONCE_INIT};
184 use directive::LOG_LEVEL_NAMES;
189 /// Maximum logging level of a module that can be specified. Common logging
190 /// levels are found in the DEBUG/INFO/WARN/ERROR constants.
191 pub const MAX_LOG_LEVEL: u32 = 255;
193 /// The default logging level of a crate if no other is specified.
194 const DEFAULT_LOG_LEVEL: u32 = 1;
196 /// An unsafe constant that is the maximum logging level of any module
197 /// specified. This is the first line of defense to determining whether a
198 /// logging statement should be run.
199 static mut LOG_LEVEL: u32 = MAX_LOG_LEVEL;
201 static mut DIRECTIVES: *const Vec<directive::LogDirective> =
202 0 as *const Vec<directive::LogDirective>;
204 /// Optional regex filter.
205 static mut FILTER: *const Regex = 0 as *const _;
208 pub const DEBUG: u32 = 4;
210 pub const INFO: u32 = 3;
212 pub const WARN: u32 = 2;
214 pub const ERROR: u32 = 1;
216 local_data_key!(local_logger: Box<Logger + Send>)
218 /// A trait used to represent an interface to a task-local logger. Each task
219 /// can have its own custom logger which can respond to logging messages
220 /// however it likes.
222 /// Logs a single message described by the `record`.
223 fn log(&mut self, record: &LogRecord);
226 struct DefaultLogger {
227 handle: LineBufferedWriter<io::stdio::StdWriter>,
230 /// Wraps the log level with fmt implementations.
231 #[deriving(PartialEq, PartialOrd)]
232 pub struct LogLevel(pub u32);
234 impl fmt::Show for LogLevel {
235 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
236 let LogLevel(level) = *self;
237 match LOG_LEVEL_NAMES.get(level as uint - 1) {
238 Some(name) => name.fmt(fmt),
239 None => level.fmt(fmt)
244 impl Logger for DefaultLogger {
245 fn log(&mut self, record: &LogRecord) {
246 match writeln!(&mut self.handle,
251 Err(e) => panic!("failed to log: {}", e),
257 impl Drop for DefaultLogger {
259 // FIXME(#12628): is panicking the right thing to do?
260 match self.handle.flush() {
261 Err(e) => panic!("failed to flush a logger: {}", e),
267 /// This function is called directly by the compiler when using the logging
268 /// macros. This function does not take into account whether the log level
269 /// specified is active or not, it will always log something if this method is
272 /// It is not recommended to call this function directly, rather it should be
273 /// invoked through the logging family of macros.
275 pub fn log(level: u32, loc: &'static LogLocation, args: &fmt::Arguments) {
276 // Test the literal string from args against the current filter, if there
278 match unsafe { FILTER.as_ref() } {
279 Some(filter) if !filter.is_match(args.to_string().as_slice()) => return,
283 // Completely remove the local logger from TLS in case anyone attempts to
284 // frob the slot while we're doing the logging. This will destroy any logger
285 // set during logging.
286 let mut logger = local_logger.replace(None).unwrap_or_else(|| {
287 box DefaultLogger { handle: io::stderr() } as Box<Logger + Send>
289 logger.log(&LogRecord {
290 level: LogLevel(level),
293 module_path: loc.module_path,
296 local_logger.replace(Some(logger));
299 /// Getter for the global log level. This is a function so that it can be called
303 pub fn log_level() -> u32 { unsafe { LOG_LEVEL } }
305 /// Replaces the task-local logger with the specified logger, returning the old
307 pub fn set_logger(logger: Box<Logger + Send>) -> Option<Box<Logger + Send>> {
308 local_logger.replace(Some(logger))
311 /// A LogRecord is created by the logging macros, and passed as the only
312 /// argument to Loggers.
314 pub struct LogRecord<'a> {
316 /// The module path of where the LogRecord originated.
317 pub module_path: &'a str,
319 /// The LogLevel of this record.
322 /// The arguments from the log line.
323 pub args: &'a fmt::Arguments<'a>,
325 /// The file of where the LogRecord originated.
328 /// The line number of where the LogRecord originated.
333 pub struct LogLocation {
334 pub module_path: &'static str,
335 pub file: &'static str,
339 /// Tests whether a given module's name is enabled for a particular level of
340 /// logging. This is the second layer of defense about determining whether a
341 /// module's log statement should be emitted or not.
343 pub fn mod_enabled(level: u32, module: &str) -> bool {
344 static INIT: Once = ONCE_INIT;
347 // It's possible for many threads are in this function, only one of them
348 // will perform the global initialization, but all of them will need to check
349 // again to whether they should really be here or not. Hence, despite this
350 // check being expanded manually in the logging macro, this function checks
351 // the log level again.
352 if level > unsafe { LOG_LEVEL } { return false }
354 // This assertion should never get tripped unless we're in an at_exit
355 // handler after logging has been torn down and a logging attempt was made.
356 assert!(unsafe { !DIRECTIVES.is_null() });
358 enabled(level, module, unsafe { (*DIRECTIVES).iter() })
361 fn enabled(level: u32,
363 iter: slice::Items<directive::LogDirective>)
365 // Search for the longest match, the vector is assumed to be pre-sorted.
366 for directive in iter.rev() {
367 match directive.name {
368 Some(ref name) if !module.starts_with(name.as_slice()) => {},
370 return level <= directive.level
374 level <= DEFAULT_LOG_LEVEL
377 /// Initialize logging for the current process.
379 /// This is not threadsafe at all, so initialization is performed through a
380 /// `Once` primitive (and this function is called from that primitive).
382 let (mut directives, filter) = match os::getenv("RUST_LOG") {
383 Some(spec) => directive::parse_logging_spec(spec.as_slice()),
384 None => (Vec::new(), None),
387 // Sort the provided directives by length of their name, this allows a
388 // little more efficient lookup at runtime.
389 directives.sort_by(|a, b| {
390 let alen = a.name.as_ref().map(|a| a.len()).unwrap_or(0);
391 let blen = b.name.as_ref().map(|b| b.len()).unwrap_or(0);
396 let max = directives.iter().max_by(|d| d.level);
397 max.map(|d| d.level).unwrap_or(DEFAULT_LOG_LEVEL)
401 LOG_LEVEL = max_level;
403 assert!(FILTER.is_null());
405 Some(f) => FILTER = mem::transmute(box f),
409 assert!(DIRECTIVES.is_null());
410 DIRECTIVES = mem::transmute(box directives);
412 // Schedule the cleanup for the globals for when the runtime exits.
414 assert!(!DIRECTIVES.is_null());
415 let _directives: Box<Vec<directive::LogDirective>> =
416 mem::transmute(DIRECTIVES);
417 DIRECTIVES = 0 as *const Vec<directive::LogDirective>;
419 if !FILTER.is_null() {
420 let _filter: Box<Regex> = mem::transmute(FILTER);
421 FILTER = 0 as *const _;
430 use directive::LogDirective;
433 fn match_full_path() {
436 name: Some("crate2".to_string()),
440 name: Some("crate1::mod1".to_string()),
444 assert!(enabled(2, "crate1::mod1", dirs.iter()));
445 assert!(!enabled(3, "crate1::mod1", dirs.iter()));
446 assert!(enabled(3, "crate2", dirs.iter()));
447 assert!(!enabled(4, "crate2", dirs.iter()));
453 LogDirective { name: Some("crate2".to_string()), level: 3 },
454 LogDirective { name: Some("crate1::mod1".to_string()), level: 2 }
456 assert!(!enabled(2, "crate3", dirs.iter()));
460 fn match_beginning() {
462 LogDirective { name: Some("crate2".to_string()), level: 3 },
463 LogDirective { name: Some("crate1::mod1".to_string()), level: 2 }
465 assert!(enabled(3, "crate2::mod1", dirs.iter()));
469 fn match_beginning_longest_match() {
471 LogDirective { name: Some("crate2".to_string()), level: 3 },
472 LogDirective { name: Some("crate2::mod".to_string()), level: 4 },
473 LogDirective { name: Some("crate1::mod1".to_string()), level: 2 }
475 assert!(enabled(4, "crate2::mod1", dirs.iter()));
476 assert!(!enabled(4, "crate2", dirs.iter()));
482 LogDirective { name: None, level: 3 },
483 LogDirective { name: Some("crate1::mod1".to_string()), level: 2 }
485 assert!(enabled(2, "crate1::mod1", dirs.iter()));
486 assert!(enabled(3, "crate2::mod2", dirs.iter()));
492 LogDirective { name: None, level: 3 },
493 LogDirective { name: Some("crate1::mod1".to_string()), level: 0 }
495 assert!(!enabled(1, "crate1::mod1", dirs.iter()));
496 assert!(enabled(3, "crate2::mod2", dirs.iter()));