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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!");
}
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Most of these are unnecessary because we're only looking at static strings. This
also moves to Vec in a few places instead of ~[T].
This didn't end up getting much of a code size win (update_log_settings is the
third largest function in the executables I'm looking at), but this seems like a
generally nice improvement regardless.
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Fallout from the previous commits
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This will allow capturing of common things like logging messages, stdout prints
(using stdio println), and failure messages (printed to stderr). Any new prints
added to libstd should be funneled through these task handles to allow capture
as well.
Additionally, this commit redirects logging back through a `Logger` trait so the
log level can be usefully consumed by an arbitrary logger.
This commit also introduces methods to set the task-local stdout handles:
* std::io::stdio::set_stdout
* std::io::stdio::set_stderr
* std::io::logging::set_logger
These methods all return the previous logger just in case it needs to be used
for inspection.
I plan on using this infrastructure for extra::test soon, but we don't quite
have the primitives that I'd like to use for it, so it doesn't migrate
extra::test at this time.
Closes #6369
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Fixes #8949.
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These two attributes are no longer useful now that Rust has decided to leave
segmented stacks behind. It is assumed that the rust task's stack is always
large enough to make an FFI call (due to the stack being very large).
There's always the case of stack overflow, however, to consider. This does not
change the behavior of stack overflow in Rust. This is still normally triggered
by the __morestack function and aborts the whole process.
C stack overflow will continue to corrupt the stack, however (as it did before
this commit as well). The future improvement of a guard page at the end of every
rust stack is still unimplemented and is intended to be the mechanism through
which we attempt to detect C stack overflow.
Closes #8822
Closes #10155
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Almost all languages provide some form of buffering of the stdout stream, and
this commit adds this feature for rust. A handle to stdout is lazily initialized
in the Task structure as a buffered owned Writer trait object. The buffer
behavior depends on where stdout is directed to. Like C, this line-buffers the
stream when the output goes to a terminal (flushes on newlines), and also like C
this uses a fixed-size buffer when output is not directed at a terminal.
We may decide the fixed-size buffering is overkill, but it certainly does reduce
write syscall counts when piping output elsewhere. This is a *huge* benefit to
any code using logging macros or the printing macros. Formatting emits calls to
`write` very frequently, and to have each of them backed by a write syscall was
very expensive.
In a local benchmark of printing 10000 lines of "what" to stdout, I got the
following timings:
when | terminal | redirected
----------------------------------
before | 0.575s | 0.525s
after | 0.197s | 0.013s
C | 0.019s | 0.004s
I can also confirm that we're buffering the output appropriately in both
situtations. We're still far slower than C, but I believe much of that has to do
with the "homing" that all tasks due, we're still performing an order of
magnitude more write syscalls than C does.
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When uv's TTY I/O is used for the stdio streams, the file descriptors are put
into a non-blocking mode. This means that other concurrent writes to the same
stream can fail with EAGAIN or EWOULDBLOCK. By all I/O to event-loop I/O, we
avoid this error.
There is one location which cannot move, which is the runtime's dumb_println
function. This was implemented to handle the EAGAIN and EWOULDBLOCK errors and
simply retry again and again.
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This makes some headway on #3309, see commits for details.
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Relaxe lifetime of CrateMap as well.
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This adds a large doc-block to the top of the std::logging module explaining how
to use it. This is mostly just making sure that all the information in the
manual's section about logging is also here (in case someone decides to look
into this module first).
This also removes the old console_{on,off} methods. As far as I can tell, the
functions were only used by the compiler, and there's no reason for them to be
used because they're all turned off by default anyway (maybe they were turned on
by default at some point...)
I believe that this is the final nail in the coffin and closes #5021
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Closes #9467
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This lifts various restrictions on the runtime, for example the character limit
when logging a message. Right now the old debug!-style macros still involve
allocating (because they use fmt! syntax), but the new debug2! macros don't
involve allocating at all (unless the formatter for a type requires allocation.
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A SendStr is a string that can hold either a ~str or a &'static str.
This can be useful as an optimization when an allocation is sometimes needed but the common case is statically known.
Possible use cases include Maps with both static and owned keys, or propagating error messages across task boundaries.
SendStr implements most basic traits in a way that hides the fact that it is an enum; in particular things like order and equality are only determined by the content of the wrapped strings.
Replaced std::rt:logging::SendableString with SendStr
Added tests for using an SendStr as key in Hash- and Treemaps
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Remove these in favor of the two traits themselves and the wrapper
function std::from_str::from_str.
Add the function std::num::from_str_radix in the corresponding role for
the FromStrRadix trait.
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Conflicts:
src/libstd/rt/logging.rs
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.with_c_str() is a replacement for the old .as_c_str(), to avoid
unnecessary boilerplate.
Replace all usages of .to_c_str().with_ref() with .with_c_str().
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remove-str-trailing-nulls
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The truncation needs to be done in the console logger in order
to catch all the logging output, and because truncation only matters
when outputting to the console.
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