The posix_spawnattr_init & posix_spawn_file_actions_init might fail,
but their return code is not checked.
Check for non-zero return code and destroy only succesfully initialized
objects.
The cvt function compares the argument with -1 and when equal returns a new
io::Error constructed from errno. It is used together posix_spawn_* functions.
This is incorrect. Those functions do not set errno. Instead they return
non-zero error code directly.
Check for non-zero return code and use it to construct a new io::Error.
(docs): make mutex error comment consistent with codebase
Although exceptionally minor, I found this stands out from other error reporting language used in doc comments. With the existence of the `failure` crate, I suppose this could be slightly ambiguous. In any case, this change brings the particular comment into a consistent state with other mentions of returning errors.
Support static linking with glibc and target-feature=+crt-static
With this change, it's possible to build on a linux-gnu target and pass
RUSTFLAGS='-C target-feature=+crt-static' or the equivalent via a
`.cargo/config.toml` file, and get a statically linked executable.
Update to libc 0.2.78, which adds support for static linking with glibc.
Add `crt_static_respected` to the `linux_base` target spec.
Update `android_base` and `linux_musl_base` accordingly. Avoid enabling
crt_static_respected on Android platforms, since that hasn't been
tested.
Closes https://github.com/rust-lang/rust/issues/65447.
Minor `hash_map` doc adjustments + item attribute orderings
This PR is really a couple visual changes glued together:
1. Some of the doc comments for items in `std::collections::hash_map` referenced the names of types without escaping their formatting (e.g. using "VacantEntry" instead of "`VacantEntry`") - the ones I could find were changed to the latter
2. The vast majority of pre-item attributes seem to place doc comments as the first attribute (instead of things like `#[feature(...)]`), so the few that had the other order were changed.
3. Also ordering related: the general trend seems to be that `#[feature]` attributes follow `#[inline]`, so I swapped the two lines in places where that ordering was reversed. This is primarily a change based on stylistic continuity and aesthetics - I'm not sure how important that actually is / should be.
I figured this would be pretty uncontroversial, but some of these might have been intentional for reasons I don't know about - if so, I'd be happy to remove the relevant changes. Of these, the final set of changes is probably the most unnecessary, so it also might be better to leave those out (in favor of reducing code churn).
Unbox mutexes and condvars on some platforms
Both mutexes and condition variables contained a Box containing the actual os-specific object. This was done because moving these objects may cause undefined behaviour on some platforms.
However, this is not needed on Windows[1], Wasm[2], cloudabi[2], and 'unsupported'[3], were the box was only needlessly making them less efficient.
This change gets rid of the box on those platforms.
On those platforms, `Condvar` can no longer verify it is only used with one `Mutex`, as mutexes no longer have a stable address. This was addressed and considered acceptable in #76932.
[1]\: https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-initializesrwlock
[2]\: These are just a single atomic integer together with futex wait/wake calls/instructions.
[3]\: The `unsupported` platform doesn't support multiple threads at all.
Only use LOCAL_{STDOUT,STDERR} when set_{print/panic} is used.
The thread local `LOCAL_STDOUT` and `LOCAL_STDERR` are only used by the `test` crate to capture output from tests when running them in the same process in differen threads. However, every program will check these variables on every print, even outside of testing.
This involves allocating a thread local key, and registering a thread local destructor. This can be somewhat expensive.
This change keeps a global flag (`LOCAL_STREAMS`) which will be set to `true` when either of these local streams is used. (So, effectively only in test and benchmark runs.) When this flag is off, these thread locals are not even looked at and therefore will not be initialized on the first output on every thread, which also means no thread local destructors will be registered.
---
Together with https://github.com/rust-lang/rust/pull/77154, this should make output a little bit more efficient.
Fix Debug implementations of some of the HashMap and BTreeMap iterator types
HashMap's `ValuesMut`, BTreeMaps `ValuesMut`, IntoValues and `IntoKeys` structs were printing both keys and values on their Debug implementations. But they are iterators over either keys or values. Irrelevant values should not be visible. With this PR, they only show relevant fields.
This fixes#75297.
[Here's an example code.](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=0c79356ed860e347a0c1a205616f93b7) This prints this on nightly:
```
ValuesMut { inner: IterMut { range: [(1, "hello"), (2, "goodbye")], length: 2 } }
IntoKeys { inner: [(1, "hello"), (2, "goodbye")] }
IntoValues { inner: [(1, "hello"), (2, "goodbye")] }
[(2, "goodbye"), (1, "hello")]
```
After the patch this example prints these instead:
```
["hello", "goodbye"]
["hello", "goodbye"]
[1, 2]
["hello", "goodbye"]
```
I didn't add test cases for them, since I couldn't see any tests for Debug implementations anywhere. But please let me know if I should add it to a specific place.
r? @dtolnay
Use posix_spawn on musl targets
The posix_spawn had been available in a form suitable for use in a
Command implementation since musl 0.9.12. Use it in a preference to a
fork when possible, to benefit from CLONE_VM|CLONE_VFORK used there.
Previously `Command::spawn` would fall back to the non-posix_spawn based
implementation if the `PATH` environment variable was possibly changed.
On systems with a modern (g)libc `posix_spawn()` can be significantly
faster. If program is a path itself the `PATH` environment variable is
not used for the lookup and it should be safe to use the
`posix_spawnp()` method. [1]
We found this, because we have a cli application that effectively runs a
lot of subprocesses. It would sometimes noticeably hang while printing
output. Profiling showed that the process was spending the majority of
time in the kernel's `copy_page_range` function while spawning
subprocesses. During this time the process is completely blocked from
running, explaining why users were reporting the cli app hanging.
Through this we discovered that `std::process::Command` has a fast and
slow path for process execution. The fast path is backed by
`posix_spawnp()` and the slow path by fork/exec syscalls being called
explicitly. Using fork for process creation is supposed to be fast, but
it slows down as your process uses more memory. It's not because the
kernel copies the actual memory from the parent, but it does need to
copy the references to it (see `copy_page_range` above!). We ended up
using the slow path, because the command spawn implementation in falls
back to the slow path if it suspects the PATH environment variable was
changed.
Here is a smallish program demonstrating the slowdown before this code
change:
```
use std::process::Command;
use std::time::Instant;
fn main() {
let mut args = std::env::args().skip(1);
if let Some(size) = args.next() {
// Allocate some memory
let _xs: Vec<_> = std::iter::repeat(0)
.take(size.parse().expect("valid number"))
.collect();
let mut command = Command::new("/bin/sh");
command
.arg("-c")
.arg("echo hello");
if args.next().is_some() {
println!("Overriding PATH");
command.env("PATH", std::env::var("PATH").expect("PATH env var"));
}
let now = Instant::now();
let child = command
.spawn()
.expect("failed to execute process");
println!("Spawn took: {:?}", now.elapsed());
let output = child.wait_with_output().expect("failed to wait on process");
println!("Output: {:?}", output);
} else {
eprintln!("Usage: prog [size]");
std::process::exit(1);
}
()
}
```
Running it and passing different amounts of elements to use to allocate
memory shows that the time taken for `spawn()` can differ quite
significantly. In latter case the `posix_spawnp()` implementation is 30x
faster:
```
$ cargo run --release 10000000
...
Spawn took: 324.275µs
hello
$ cargo run --release 10000000 changepath
...
Overriding PATH
Spawn took: 2.346809ms
hello
$ cargo run --release 100000000
...
Spawn took: 387.842µs
hello
$ cargo run --release 100000000 changepath
...
Overriding PATH
Spawn took: 13.434677ms
hello
```
[1]: 5f72f9800b/posix/execvpe.c (L81)
Add accessors to Command.
This adds some accessor methods to `Command` to provide a way to access the values set when building the `Command`. An example where this can be useful is to display the command to be executed. This is roughly based on the [`ProcessBuilder`](13b73cdaf7/src/cargo/util/process_builder.rs (L105-L134)) in Cargo.
Possible concerns about the API:
- Values with NULs on Unix will be returned as `"<string-with-nul>"`. I don't think it is practical to avoid this, since otherwise a whole separate copy of all the values would need to be kept in `Command`.
- Does not handle `arg0` on Unix. This can be awkward to support in `get_args` and is rarely used. I figure if someone really wants it, it can be added to `CommandExt` as a separate method.
- Does not offer a way to detect `env_clear`. I'm uncertain if it would be useful for anyone.
- Does not offer a way to get an environment variable by name (`get_env`). I figure this can be added later if anyone really wants it. I think the motivation for this is weak, though. Also, the API could be a little awkward (return a `Option<Option<&OsStr>>`?).
- `get_envs` could skip "cleared" entries and just return `&OsStr` values instead of `Option<&OsStr>`. I'm on the fence here. My use case is to display a shell command, and I only intend it to be roughly equivalent to the actual execution, and I probably won't display `None` entries. I erred on the side of providing extra information, but I suspect many situations will just filter out the `None`s.
- Could implement more iterator stuff (like `DoubleEndedIterator`).
I have not implemented new std items before, so I'm uncertain if the existing issue should be reused, or if a new tracking issue is needed.
cc #44434
Fix is_absolute on WASI
WASI does not match `cfg(unix)`, but its paths are Unix-like (`/some/path`) and don't have Windows-like prefixes.
Without this change, `is_absolute` for any paths, including `/some/path`, was returning `false`on a WASI target, which is obviously not true and undesirable.
Split sys_common::Mutex in StaticMutex and MovableMutex.
The (unsafe) `Mutex` from `sys_common` had a rather complicated interface. You were supposed to call `init()` manually, unless you could guarantee it was neither moved nor used reentrantly.
Calling `destroy()` was also optional, although it was unclear if 1) resources might be leaked or not, and 2) if `destroy()` should only be called when `init()` was called.
This allowed for a number of interesting (confusing?) different ways to use this `Mutex`, all captured in a single type.
In practice, this type was only ever used in two ways:
1. As a static variable. In this case, neither `init()` nor `destroy()` are called. The variable is never moved, and it is never used reentrantly. It is only ever locked using the `LockGuard`, never with `raw_lock`.
2. As a `Box`ed variable. In this case, both `init()` and `destroy()` are called, it will be moved and possibly used reentrantly.
No other combinations are used anywhere in `std`.
This change simplifies things by splitting this `Mutex` type into two types matching the two use cases: `StaticMutex` and `MovableMutex`.
The interface of both new types is now both safer and simpler. The first one does not call nor expose `init`/`destroy`, and the second one calls those automatically in its `new()` and `Drop` functions. Also, the locking functions of `MovableMutex` are no longer unsafe.
---
This will also make it easier to conditionally box mutexes later, by moving that decision into sys/sys_common. Some of the mutex implementations (at least those of Wasm and 'sys/unsupported') are safe to move, so wouldn't need a box. ~~(But that's blocked on #76932 for now.)~~ (See #77380.)
Improve std::sys::windows::compat
Improves the compat_fn macro in sys::windows, which is used for conditionally loading APIs that might not be available.
- The module (dll) name can now be any string, not just an ident. (Not all Windows api modules are valid Rust identifiers. E.g. `WaitOnAddress` comes from `API-MS-Win-Core-Synch-l1-2-0.dll`.)
- Adds `FuncName::is_available()` for checking if a function is really available without having to do a duplicate lookup.
- Add comment explaining the lack of locking.
- Use `$_:block` to simplify the macro_rules.
- Apply `allow(unused_variables)` only to the fallback instead of everything.
---
The second point (`is_available()`) simplifies code that needs to pick an implementation depening on what is available, like `sys/windows/mutex.rs`. Before this change, it'd do its own lookup and keep its own `AtomicUsize` to track the result. Now it can just use `c::AcquireSRWLockExclusive::is_available()` directly.
This will also be useful when park/unpark/CondVar/etc. get improved implementations (e.g. from parking_lot or something else), as the best APIs for those are not available before Windows 8.
Make RawFd implement the RawFd traits
This PR makes `RawFd` implement `AsRawFd`, `IntoRawFd` and `FromRawFd`, so it can be passed to interfaces that use one of those traits as a bound.
- Module name can now be any string, not just an ident.
(Not all Windows api modules are valid Rust identifiers.)
- Adds c::FuncName::is_available() for checking if a function is really
available without having to do a duplicate lookup.
- Add comment explaining the lack of locking.
- Use `$_:block` to simplify the macro_rules.
- Apply allow(unused_variables) only to the fallback instead of
everything.
Use futex-based thread::park/unpark on Linux.
This moves the parking/unparking logic out of `thread/mod.rs` into a module named `thread_parker` in `sys_common`. The current implementation is moved to `sys_common/thread_parker/generic.rs` and the new implementation using futexes is added in `sys_common/thread_parker/futex.rs`.
The posix_spawn had been available in a form suitable for use in a
Command implementation since musl 0.9.12. Use it in a preference to a
fork when possible, to benefit from CLONE_VM|CLONE_VFORK used there.
Use `rtassert!` instead of `assert!` from the child process after fork() in std::sys::unix::process::Command::spawn()
As discussed in #73894, `assert!` panics on failure, which is not signal-safe, and `rtassert!` is a suitable replacement.
Fixes#73894.
r? @Amanieu @cuviper @joshtriplett
library: Forward compiler-builtins "mem" feature
This fixes https://github.com/rust-lang/wg-cargo-std-aware/issues/53
Now users will be able to do:
```
cargo build -Zbuild-std=core -Zbuild-std-features=compiler-builtins-mem
```
and correctly get the Rust implemenations for `memcpy` and friends.
Signed-off-by: Joe Richey <joerichey@google.com>
WASI does not match `cfg(unix)`, but its paths are Unix-like (`/some/path`) and don't have Windows-like prefixes.
Without this change, `is_absolute` for paths like `/some/path` was returning `false`on a WASI target, which is obviously not true and undesirable.
Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]`
`rustc_allow_const_fn_ptr` was a hack to work around the lack of an escape hatch for the "min `const fn`" checks in const-stable functions. Now that we have co-opted `allow_internal_unstable` for this purpose, we no longer need a bespoke attribute.
Now this functionality is gated under `const_fn_fn_ptr_basics` (how concise!), and `#[allow_internal_unstable(const_fn_fn_ptr_basics)]` replaces `#[rustc_allow_const_fn_ptr]`. `const_fn_fn_ptr_basics` allows function pointer types to appear in the arguments and locals of a `const fn` as well as function pointer casts to be performed inside a `const fn`. Both of these were allowed in constants and statics already. Notably, this does **not** allow users to invoke function pointers in a const context. Presumably, we will use a nicer name for that (`const_fn_ptr`?).
r? @oli-obk
UI to unit test for those using Cell/RefCell/UnsafeCell
Helps with #76268.
I'm working on all files using `Cell` and moving them to unit tests when possible.
r? @matklad
Add missing definitions required by the sparc-unknown-linux-gnu target
This PR adds a few missing definitions required by sparc-unknown-linux-target which were discovered during build tests.
This fixes https://github.com/rust-lang/wg-cargo-std-aware/issues/53
Now users will be able to do:
```
cargo build -Zbuild-std=core -Zbuild-std-features=compiler-builtins-mem
```
and correctly get the Rust implemenations for `memcpy` and friends.
Signed-off-by: Joe Richey <joerichey@google.com>
The syscalls returning a new file descriptors generally use
lowest-numbered file descriptor not currently opened, without any
exceptions for those corresponding to the standard streams.
Previously when any of standard streams has been closed before starting
the application, operations on std::io::{stderr,stdin,stdout} objects
were likely to operate on other logically unrelated file resources
opened afterwards.
Avoid the issue by reopening the standard streams when they are closed.
The thread local LOCAL_STDOUT and LOCAL_STDERR are only used by the test
crate to capture output from tests when running them in the same process
in differen threads. However, every program will check these variables
on every print, even outside of testing.
This involves allocating a thread local key, and registering a thread
local destructor. This can be somewhat expensive.
This change keeps a global flag (LOCAL_STREAMS) which will be set to
true when either of these local streams is used. (So, effectively only
in test and benchmark runs.) When this flag is off, these thread locals
are not even looked at and therefore will not be initialized on the
first output on every thread, which also means no thread local
destructors will be registered.
The (unsafe) Mutex from sys_common had a rather complicated interface.
You were supposed to call init() manually, unless you could guarantee it
was neither moved nor used reentrantly.
Calling `destroy()` was also optional, although it was unclear if 1)
resources might be leaked or not, and 2) if destroy() should only be
called when `init()` was called.
This allowed for a number of interesting (confusing?) different ways to
use this Mutex, all captured in a single type.
In practice, this type was only ever used in two ways:
1. As a static variable. In this case, neither init() nor destroy() are
called. The variable is never moved, and it is never used
reentrantly. It is only ever locked using the LockGuard, never with
raw_lock.
2. As a Boxed variable. In this case, both init() and destroy() are
called, it will be moved and possibly used reentrantly.
No other combinations are used anywhere in `std`.
This change simplifies things by splitting this Mutex type into
two types matching the two use cases: StaticMutex and MovableMutex.
The interface of both new types is now both safer and simpler. The first
one does not call nor expose init/destroy, and the second one calls
those automatically in its new() and Drop functions. Also, the locking
functions of MovableMutex are no longer unsafe.
Remove std::io::lazy::Lazy in favour of SyncOnceCell
The (internal) std::io::lazy::Lazy was used to lazily initialize the stdout and stdin buffers (and mutexes). It uses atexit() to register a destructor to flush the streams on exit, and mark the streams as 'closed'. Using the stream afterwards would result in a panic.
Stdout uses a LineWriter which contains a BufWriter that will flush the buffer on drop. This one is important to be executed during shutdown, to make sure no buffered output is lost. It also forbids access to stdout afterwards, since the buffer is already flushed and gone.
Stdin uses a BufReader, which does not implement Drop. It simply forgets any previously read data that was not read from the buffer yet. This means that in the case of stdin, the atexit() function's only effect is making stdin inaccessible to the program, such that later accesses result in a panic. This is uncessary, as it'd have been safe to access stdin during shutdown of the program.
---
This change removes the entire io::lazy module in favour of SyncOnceCell. SyncOnceCell's fast path is much faster (a single atomic operation) than locking a sys_common::Mutex on every access like Lazy did.
However, SyncOnceCell does not use atexit() to drop the contained object during shutdown.
As noted above, this is not a problem for stdin. It simply means stdin is now usable during shutdown.
The atexit() call for stdout is moved to the stdio module. Unlike the now-removed Lazy struct, SyncOnceCell does not have a 'gone and unusable' state that panics. Instead of adding this again, this simply replaces the buffer with one with zero capacity. This effectively flushes the old buffer *and* makes any writes afterwards pass through directly without touching a buffer, making print!() available during shutdown without panicking.
---
In addition, because the contents of the SyncOnceCell are no longer dropped, we can now use `&'static` instead of `Arc` in `Stdout` and `Stdin`. This also saves two levels of indirection in `stdin()` and `stdout()`, since Lazy effectively stored a `Box<Arc<T>>`, and SyncOnceCell stores the `T` directly.
