Fix Once perf regression
Because `call_once` is generic, but `is_completed` is not, we need
`#[inline]` annotation to allow LLVM to inline `is_completed` into
`call_once` in downstream crates.
cc https://github.com/rust-lang/rust/pull/53027/files#r221418859
Because `call_once` is generic, but `is_completed` is not, we need
`#[inline]` annotation to allow LLVM to inline `is_completed` into
`call_once` in downstream crates.
Most of these will eventually be filled, but right now travis-ci enjoys
complaining about the fact that there's links that lead nowhere, so
they're gone. Hopefully someone remembers to re-add them later.
This commit is an initial start at implementing the standard library for
wasm32-unknown-unknown with the experimental `atomics` feature enabled. None of
these changes will be visible to users of the wasm32-unknown-unknown target
because they all require recompiling the standard library. The hope with this is
that we can get this support into the standard library and start iterating on it
in-tree to enable experimentation.
Currently there's a few components in this PR:
* Atomic fences are disabled on wasm as there's no corresponding atomic op and
it's not clear yet what the convention should be, but this will change in the
future!
* Implementations of `Mutex`, `Condvar`, and `RwLock` were all added based on
the atomic intrinsics that wasm has.
* The `ReentrantMutex` and thread-local-storage implementations panic currently
as there's no great way to get a handle on the current thread's "id" yet.
Right now the wasm32 target with atomics is unfortunately pretty unusable,
requiring a lot of manual things here and there to actually get it operational.
This will likely continue to evolve as the story for atomics and wasm unfolds,
but we also need more LLVM support for some operations like custom `global`
directives for this to work best.
Switch wasm math symbols to their original names
The names `Math_*` were given to help undefined symbol messages indicate how to
implement them, but these are all implemented in compiler-rt now so there's no
need to rename them! This change should make it so wasm binaries by default, no
matter the math symbols used, will not have unresolved symbols.
Fix `thread` `park`/`unpark` synchronization
Previously the code below would not be guaranteed to exit when the
second unpark took the `return, // already unparked` path because there
was no write to synchronize with a read in `park`.
EDIT: doesn't actually require third thread
```
use std::sync::atomic::{AtomicBool, Ordering};
use std:🧵:{current, spawn, park};
static FLAG: AtomicBool = AtomicBool::new(false);
fn main() {
let thread_0 = current();
spawn(move || {
thread_0.unpark();
FLAG.store(true, Ordering::Relaxed);
thread_0.unpark();
});
while !FLAG.load(Ordering::Relaxed) {
park();
}
}
```
I have some other ideas on how to improve the performance of `park` and `unpark` using fences, avoiding any atomic RMW when the state is already `NOTIFIED`, and also how to avoid calling `notify_one` without the mutex locked. But I need to write some micro benchmarks first, so I'll submit those changes at a later date if they prove to be faster.
Fixes https://github.com/rust-lang/rust/issues/53366 I hope.
This commit also splits out linky-line-thingies into two lines, which
judging from the source code for tidy, should be enough to make it shut
up and accept me for who I am, dammit.
Update to a new pinning API.
~~Blocked on #53843 because of method resolution problems with new pin type.~~
@r? @cramertj
cc @RalfJung @pythonesque anyone interested in #49150
OsStr: Document that it's not NUL terminated
I somehow got confused into thinking this was the case, but
it's definitely not. Let's help the common case of people who
have an `OsStr` and need to call e.g. Unix APIs.
Add doc for impl From for Addr
As part of issue #51430 (cc @skade).
The impl is very simple, let me know if we need to go into any details.
Additionally, I added `#[inline]` for the conversion method, let me know if it is un-necessary or might break something.
I somehow got confused into thinking this was the case, but
it's definitely not. Let's help the common case of people who
have an `OsStr` and need to call e.g. Unix APIs.
Improve output if no_lookup_host_duplicates test fails
If the test fails, output the offending addresses and a helpful error message.
Also slightly improve legibility of the preceding line that puts the addresses
into a HashMap.
fix some uses of pointer intrinsics with invalid pointers
[Found by miri](https://github.com/solson/miri/pull/446):
* `Vec::into_iter` calls `ptr::read` (and the underlying `copy_nonoverlapping`) with an unaligned pointer to a ZST. [According to LLVM devs](https://bugs.llvm.org/show_bug.cgi?id=38583), this is UB because it contradicts the metadata we are attaching to that pointer.
* `HashMap` creation calls `ptr:.write_bytes` on a NULL pointer with a count of 0. This is likely not currently UB *currently*, but it violates the rules we are setting in https://github.com/rust-lang/rust/pull/53783, and we might want to exploit those rules later (e.g. with more `nonnull` attributes for LLVM).
Probably what `HashMap` really should do is use `NonNull::dangling()` instead of 0 for the empty case, but that would require a more careful analysis of the code.
It seems like ideally, we should do a review of usage of such intrinsics all over libstd to ensure that they use valid pointers even when the size is 0. Is it worth opening an issue for that?
The names `Math_*` were given to help undefined symbol messages indicate how to
implement them, but these are all implemented in compiler-rt now so there's no
need to rename them! This change should make it so wasm binaries by default, no
matter the math symbols used, will not have unresolved symbols.
If the test fails, output the offending addresses and a helpful error message.
Also slightly improve legibility of the preceding line that puts the addresses
into a HashMap.
re-mark the never docs as unstable
Fixes https://github.com/rust-lang/rust/issues/54198
This stability attribute was removed in https://github.com/rust-lang/rust/pull/47630, but not replaced with a `#[stable]` attribute, and when https://github.com/rust-lang/rust/pull/50121 reverted that stabilization, it didn't set the docs back to unstable. I'm concerned as to why it was allowed to not have the stability attribute at all, but at least this can put it back.
I'm nominating this for beta backport because it's a really small change, and right now our docs are in an awkward position where the `!` type is technically unstable to use, but the docs don't say so the same way any other library feature would. (And this is also the case *on stable* now, but i'm not suggesting a stable backport for a docs fix.)
