cc6ec8df95
This commit moves all logging out of the standard library into an external
crate. This crate is the new crate which is responsible for all logging macros
and logging implementation. A few reasons for this change are:
* The crate map has always been a bit of a code smell among rust programs. It
has difficulty being loaded on almost all platforms, and it's used almost
exclusively for logging and only logging. Removing the crate map is one of the
end goals of this movement.
* The compiler has a fair bit of special support for logging. It has the
__log_level() expression as well as generating a global word per module
specifying the log level. This is unfairly favoring the built-in logging
system, and is much better done purely in libraries instead of the compiler
itself.
* Initialization of logging is much easier to do if there is no reliance on a
magical crate map being available to set module log levels.
* If the logging library can be written outside of the standard library, there's
no reason that it shouldn't be. It's likely that we're not going to build the
highest quality logging library of all time, so third-party libraries should
be able to provide just as high-quality logging systems as the default one
provided in the rust distribution.
With a migration such as this, the change does not come for free. There are some
subtle changes in the behavior of liblog vs the previous logging macros:
* The core change of this migration is that there is no longer a physical
log-level per module. This concept is still emulated (it is quite useful), but
there is now only a global log level, not a local one. This global log level
is a reflection of the maximum of all log levels specified. The previously
generated logging code looked like:
if specified_level <= __module_log_level() {
println!(...)
}
The newly generated code looks like:
if specified_level <= ::log::LOG_LEVEL {
if ::log::module_enabled(module_path!()) {
println!(...)
}
}
Notably, the first layer of checking is still intended to be "super fast" in
that it's just a load of a global word and a compare. The second layer of
checking is executed to determine if the current module does indeed have
logging turned on.
This means that if any module has a debug log level turned on, all modules
with debug log levels get a little bit slower (they all do more expensive
dynamic checks to determine if they're turned on or not).
Semantically, this migration brings no change in this respect, but
runtime-wise, this will have a perf impact on some code.
* A `RUST_LOG=::help` directive will no longer print out a list of all modules
that can be logged. This is because the crate map will no longer specify the
log levels of all modules, so the list of modules is not known. Additionally,
warnings can no longer be provided if a malformed logging directive was
supplied.
The new "hello world" for logging looks like:
#[phase(syntax, link)]
extern crate log;
fn main() {
debug!("Hello, world!");
}
231 lines
5.8 KiB
Rust
231 lines
5.8 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! # The Rust standard library
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//!
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//! The Rust standard library is a group of interrelated modules defining
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//! the core language traits, operations on built-in data types,
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//! platform abstractions, the task scheduler, runtime support for language
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//! features and other common functionality.
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//!
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//! `std` includes modules corresponding to each of the integer types,
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//! each of the floating point types, the `bool` type, tuples, characters,
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//! strings (`str`), vectors (`vec`), managed boxes (`managed`), owned
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//! boxes (`owned`), and unsafe pointers and references (`ptr`, `borrowed`).
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//! Additionally, `std` provides pervasive types (`option` and `result`),
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//! task creation and communication primitives (`task`, `comm`), platform
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//! abstractions (`os` and `path`), basic I/O abstractions (`io`), common
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//! traits (`kinds`, `ops`, `cmp`, `num`, `to_str`), and complete bindings
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//! to the C standard library (`libc`).
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//!
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//! # Standard library injection and the Rust prelude
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//!
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//! `std` is imported at the topmost level of every crate by default, as
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//! if the first line of each crate was
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//!
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//! extern crate std;
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//!
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//! This means that the contents of std can be accessed from any context
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//! with the `std::` path prefix, as in `use std::vec`, `use std::task::spawn`,
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//! etc.
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//!
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//! Additionally, `std` contains a `prelude` module that reexports many of the
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//! most common types, traits and functions. The contents of the prelude are
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//! imported into every *module* by default. Implicitly, all modules behave as if
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//! they contained the following prologue:
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//!
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//! use std::prelude::*;
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#[crate_id = "std#0.10-pre"];
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#[comment = "The Rust standard library"];
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#[license = "MIT/ASL2"];
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#[crate_type = "rlib"];
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#[crate_type = "dylib"];
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#[doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
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html_favicon_url = "http://www.rust-lang.org/favicon.ico",
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html_root_url = "http://static.rust-lang.org/doc/master")];
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#[feature(macro_rules, globs, asm, managed_boxes, thread_local, link_args,
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simd, linkage, default_type_params, phase)];
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// NOTE remove the following two attributes after the next snapshot.
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#[allow(unrecognized_lint)];
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#[allow(default_type_param_usage)];
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// Don't link to std. We are std.
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#[no_std];
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#[deny(non_camel_case_types)];
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#[deny(missing_doc)];
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#[allow(unknown_features)];
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#[allow(deprecated_owned_vector)];
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// When testing libstd, bring in libuv as the I/O backend so tests can print
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// things and all of the std::io tests have an I/O interface to run on top
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// of
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#[cfg(test)] extern crate rustuv;
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#[cfg(test)] extern crate native;
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#[cfg(test)] extern crate green;
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#[cfg(test)] #[phase(syntax, link)] extern crate log;
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// Make and rand accessible for benchmarking/testcases
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#[cfg(test)] extern crate rand;
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// Make std testable by not duplicating lang items. See #2912
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#[cfg(test)] extern crate realstd = "std";
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#[cfg(test)] pub use kinds = realstd::kinds;
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#[cfg(test)] pub use ops = realstd::ops;
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#[cfg(test)] pub use cmp = realstd::cmp;
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pub mod macros;
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mod rtdeps;
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/* The Prelude. */
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pub mod prelude;
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/* Primitive types */
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#[path = "num/float_macros.rs"] mod float_macros;
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#[path = "num/int_macros.rs"] mod int_macros;
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#[path = "num/uint_macros.rs"] mod uint_macros;
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#[path = "num/int.rs"] pub mod int;
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#[path = "num/i8.rs"] pub mod i8;
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#[path = "num/i16.rs"] pub mod i16;
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#[path = "num/i32.rs"] pub mod i32;
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#[path = "num/i64.rs"] pub mod i64;
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#[path = "num/uint.rs"] pub mod uint;
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#[path = "num/u8.rs"] pub mod u8;
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#[path = "num/u16.rs"] pub mod u16;
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#[path = "num/u32.rs"] pub mod u32;
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#[path = "num/u64.rs"] pub mod u64;
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#[path = "num/f32.rs"] pub mod f32;
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#[path = "num/f64.rs"] pub mod f64;
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pub mod unit;
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pub mod bool;
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pub mod char;
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pub mod tuple;
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pub mod vec;
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pub mod vec_ng;
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pub mod str;
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pub mod ascii;
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pub mod ptr;
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pub mod owned;
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pub mod managed;
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mod reference;
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pub mod rc;
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pub mod gc;
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/* Core language traits */
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#[cfg(not(test))] pub mod kinds;
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#[cfg(not(test))] pub mod ops;
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#[cfg(not(test))] pub mod cmp;
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/* Common traits */
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pub mod from_str;
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pub mod num;
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pub mod iter;
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pub mod to_str;
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pub mod clone;
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pub mod hash;
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pub mod container;
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pub mod default;
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pub mod any;
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/* Common data structures */
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pub mod option;
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pub mod result;
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pub mod cell;
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/* Tasks and communication */
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pub mod task;
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pub mod comm;
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pub mod local_data;
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pub mod sync;
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/* Runtime and platform support */
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#[unstable]
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pub mod libc;
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pub mod c_str;
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pub mod c_vec;
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pub mod os;
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pub mod io;
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pub mod path;
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pub mod cast;
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pub mod fmt;
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pub mod cleanup;
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pub mod mem;
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/* Unsupported interfaces */
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#[unstable]
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pub mod repr;
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#[unstable]
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pub mod reflect;
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// Private APIs
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#[unstable]
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pub mod unstable;
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#[experimental]
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pub mod intrinsics;
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#[experimental]
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pub mod raw;
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/* For internal use, not exported */
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mod unicode;
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#[path = "num/cmath.rs"]
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mod cmath;
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// FIXME #7809: This shouldn't be pub, and it should be reexported under 'unstable'
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// but name resolution doesn't work without it being pub.
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#[unstable]
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pub mod rt;
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// A curious inner-module that's not exported that contains the binding
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// 'std' so that macro-expanded references to std::error and such
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// can be resolved within libstd.
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#[doc(hidden)]
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mod std {
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pub use clone;
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pub use cmp;
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pub use comm;
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pub use fmt;
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pub use hash;
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pub use io;
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pub use kinds;
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pub use local_data;
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pub use option;
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pub use os;
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pub use rt;
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pub use str;
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pub use to_str;
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pub use unstable;
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}
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