Clarify undefined behaviour for binary heap, btree and hashset
Previously, it wasn't clear whether "This could include" was referring
to logic errors, or undefined behaviour. Tweak wording to clarify this
sentence does not relate to UB.
bors [Thu, 21 Oct 2021 08:04:19 +0000 (08:04 +0000)]
Auto merge of #90119 - JohnTitor:rollup-e5t6khz, r=JohnTitor
Rollup of 14 pull requests
Successful merges:
- #86984 (Reject octal zeros in IPv4 addresses)
- #87440 (Remove unnecessary condition in Barrier::wait())
- #88644 (`AbstractConst` private fields)
- #89292 (Stabilize CString::from_vec_with_nul[_unchecked])
- #90010 (Avoid overflow in `VecDeque::with_capacity_in()`.)
- #90029 (Add test for debug logging during incremental compilation)
- #90031 (config: add the option to enable LLVM tests)
- #90048 (Add test for line-number setting)
- #90071 (Remove hir::map::blocks and use FnKind instead)
- #90074 (2229 migrations small cleanup)
- #90077 (Make `From` impls of NonZero integer const.)
- #90097 (Add test for duplicated sidebar entries for reexported macro)
- #90098 (Add test to ensure that the missing_doc_code_examples is not triggered on foreign trait implementations)
- #90099 (Fix MIRI UB in `Vec::swap_remove`)
Yuki Okushi [Thu, 21 Oct 2021 05:11:13 +0000 (14:11 +0900)]
Rollup merge of #90099 - SkiFire13:fix-vec-swap-remove, r=dtolnay
Fix MIRI UB in `Vec::swap_remove`
Fixes #90055
I find it weird that `Vec::swap_remove` read the last element to the stack just to immediately put it back in the `Vec` in place of the one at index `index`. It seems much more natural to me to just read the element at position `index` and then move the last element in its place. I guess this might also slightly improve codegen.
Yuki Okushi [Thu, 21 Oct 2021 05:11:07 +0000 (14:11 +0900)]
Rollup merge of #90031 - durin42:allow-llvm-tests, r=Mark-Simulacrum
config: add the option to enable LLVM tests
I'm working on some LLVM patches in concert with a Rust patch, and it's
helping me quite a bit to have this as an option. It doesn't seem that
hard, so I figured I'd formalize it in x.py and send it upstream.
Yuki Okushi [Thu, 21 Oct 2021 05:11:06 +0000 (14:11 +0900)]
Rollup merge of #90029 - tgnottingham:incr-debug-logging-test, r=Mark-Simulacrum
Add test for debug logging during incremental compilation
Debug logging during incremental compilation had been broken for some
time, until #89343 fixed it (among other things). Add a test so this is
less likely to break without being noticed. This test is nearly a copy
of the `src/test/ui/rustc-rust-log.rs` test, but tests debug logging in
the incremental compliation code paths.
Yuki Okushi [Thu, 21 Oct 2021 05:11:05 +0000 (14:11 +0900)]
Rollup merge of #90010 - rusticstuff:vecdeque_with_capacity_in_overflow, r=m-ou-se
Avoid overflow in `VecDeque::with_capacity_in()`.
The overflow only happens if alloc is compiled with overflow checks enabled and the passed capacity is greater or equal 2^(usize::BITS-1). The overflow shadows the expected "capacity overflow" panic leading to a test failure if overflow checks are enabled for std in the CI.
Unblocks [CI: Enable overflow checks for test (non-dist) builds #89776](https://github.com/rust-lang/rust/pull/89776).
For some reason the overflow is only observable with optimization turned off, but that is a separate issue.
Yuki Okushi [Thu, 21 Oct 2021 05:11:02 +0000 (14:11 +0900)]
Rollup merge of #87440 - twetzel59:fix-barrier-no-op, r=yaahc
Remove unnecessary condition in Barrier::wait()
This is my first pull request for Rust, so feel free to call me out if anything is amiss.
After some examination, I realized that the second condition of the "spurious-wakeup-handler" loop in ``std::sync::Barrier::wait()`` should always evaluate to ``true``, making it redundant in the ``&&`` expression.
Here is the affected function before the fix:
```rust
#[stable(feature = "rust1", since = "1.0.0")]
pub fn wait(&self) -> BarrierWaitResult {
let mut lock = self.lock.lock().unwrap();
let local_gen = lock.generation_id;
lock.count += 1;
if lock.count < self.num_threads {
// We need a while loop to guard against spurious wakeups.
// https://en.wikipedia.org/wiki/Spurious_wakeup
while local_gen == lock.generation_id && lock.count < self.num_threads { // fixme
lock = self.cvar.wait(lock).unwrap();
}
BarrierWaitResult(false)
} else {
lock.count = 0;
lock.generation_id = lock.generation_id.wrapping_add(1);
self.cvar.notify_all();
BarrierWaitResult(true)
}
}
```
At first glance, it seems that the check that ``lock.count < self.num_threads`` would be necessary in order for a thread A to detect when another thread B has caused the barrier to reach its thread count, making thread B the "leader".
However, the control flow implicitly results in an invariant that makes observing ``!(lock.count < self.num_threads)``, i.e. ``lock.count >= self.num_threads`` impossible from thread A.
When thread B, which will be the leader, calls ``.wait()`` on this shared instance of the ``Barrier``, it locks the mutex in the first line and saves the ``MutexGuard`` in the ``lock`` variable. It then increments the value of ``lock.count``. However, it then proceeds to check if ``lock.count < self.num_threads``. Since it is the leader, it is the case that (after the increment of ``lock.count``), the lock count is *equal* to the number of threads. Thus, the second branch is immediately taken and ``lock.count`` is zeroed. Additionally, the generation ID is incremented (with wrap). Then, the condition variable is signalled. But, the other threads are waiting at the line ``lock = self.cvar.wait(lock).unwrap();``, so they cannot resume until thread B's call to ``Barrier::wait()`` returns, which drops the ``MutexGuard`` acquired in the first ``let`` statement and unlocks the mutex.
The order of events is thus:
1. A thread A calls `.wait()`
2. `.wait()` acquires the mutex, increments `lock.count`, and takes the first branch
3. Thread A enters the ``while`` loop since the generation ID has not changed and the count is less than the number of threads for the ``Barrier``
3. Spurious wakeups occur, but both conditions hold, so the thread A waits on the condition variable
4. This process repeats for N - 2 additional times for non-leader threads A'
5. *Meanwhile*, Thread B calls ``Barrier::wait()`` on the same barrier that threads A, A', A'', etc. are waiting on. The thread count reaches the number of threads for the ``Barrier``, so all threads should now proceed, with B being the leader. B acquires the mutex and increments the value ``lock.count`` only to find that it is not less than ``self.num_threads``. Thus, it immediately clamps ``self.num_threads`` back down to 0 and increments the generation. Then, it signals the condvar to tell the A (prime) threads that they may continue.
6. The A, A', A''... threads wake up and attempt to re-acquire the ``lock`` as per the internal operation of a condition variable. When each A has exclusive access to the mutex, it finds that ``lock.generation_id`` no longer matches ``local_generation`` **and the ``&&`` expression short-circuits -- and even if it were to evaluate it, ``self.count`` is definitely less than ``self.num_threads`` because it has been reset to ``0`` by thread B *before* B dropped its ``MutexGuard``**.
Therefore, it my understanding that it would be impossible for the non-leader threads to ever see the second boolean expression evaluate to anything other than ``true``. This PR simply removes that condition.
Any input would be appreciated. Sorry if this is terribly verbose. I'm new to the Rust community and concurrency can be hard to explain in words. Thanks!
Yuki Okushi [Thu, 21 Oct 2021 05:11:01 +0000 (14:11 +0900)]
Rollup merge of #86984 - Smittyvb:ipv4-octal-zero, r=m-ou-se
Reject octal zeros in IPv4 addresses
This fixes #86964 by rejecting octal zeros in IP addresses, such that `192.168.00.00000000` is rejected with a parse error, since having leading zeros in front of another zero indicates it is a zero written in octal notation, which is not allowed in the strict mode specified by RFC 6943 3.1.1. Octal rejection was implemented in #83652, but due to the way it was implemented octal zeros were still allowed.
bors [Thu, 21 Oct 2021 05:04:39 +0000 (05:04 +0000)]
Auto merge of #90072 - ehuss:empty-rmeta-no-warn, r=Mark-Simulacrum
Don't emit a warning for empty rmeta files.
This avoids displaying a warning when attempting to load an empty rmeta file. Warnings were enabled via #89634 which can cause a lot of noise (for example, running `./x.py check`). rustc generates empty rmeta files for things like binaries, which can happen when checking libraries as unittests.
bors [Thu, 21 Oct 2021 01:38:55 +0000 (01:38 +0000)]
Auto merge of #89998 - camelid:box-default, r=jyn514
rustdoc: Box some fields of `GenericParamDefKind` to reduce size
This change shrinks `GenericParamDef` from 120 to 56 bytes. `GenericParamDef` is
used a lot, so the extra indirection should hopefully be worth the size savings.
bors [Wed, 20 Oct 2021 20:35:58 +0000 (20:35 +0000)]
Auto merge of #7838 - nhamovitz:trailing_zs_arr_wo_repr, r=Manishearth
Warn on structs with a trailing zero-sized array but no `repr` attribute
Closes #2868
changelog: Implement ``[`trailing_empty_array`]``, which warns if a struct is defined where the last field is a zero-sized array but there are no `repr` attributes. Zero-sized arrays aren't very useful in Rust itself, so such a struct is likely being created to pass to C code or in some other situation where control over memory layout matters. Either way, a `repr` attribute is needed.
bors [Wed, 20 Oct 2021 17:57:35 +0000 (17:57 +0000)]
Auto merge of #89978 - cjgillot:qarray, r=Mark-Simulacrum
Merge the two depkind vtables
Knowledge of `DepKind`s is managed using two arrays containing flags (is_anon, eval_always, fingerprint_style), and function pointers (forcing and loading code).
This PR aims at merging the two arrays so as to reduce unneeded indirect calls and (hopefully) increase code locality.
r? `@ghost`
bors [Wed, 20 Oct 2021 14:37:48 +0000 (14:37 +0000)]
Auto merge of #90050 - michaelwoerister:fix-vtable-debug-name-crash-90019, r=wesleywiser
Erase late-bound regions before computing vtable debuginfo name.
Fixes #90019.
The `msvc_enum_fallback()` for computing enum type names needs to access the memory layout of niche enums in order to determine the type name. `compute_debuginfo_vtable_name()` did not properly erase regions before computing type names which made memory layout computation ICE when encountering un-erased regions.
bors [Wed, 20 Oct 2021 07:21:01 +0000 (07:21 +0000)]
Auto merge of #89100 - petrochenkov:localbind, r=cjgillot
resolve: Use `NameBinding` for local variables and generic parameters
`NameBinding` is a structure used for representing any name introduction (an item, or import, or even a built-in).
Except that local variables and generic parameters weren't represented as `NameBinding`s, for this reason they requires separate paths in name resolution code in several places.
This PR introduces `NameBinding`s for local variables as well and simplifies all the code working with them leaving only the `NameBinding` paths.
woppopo [Wed, 20 Oct 2021 03:04:58 +0000 (12:04 +0900)]
Make `From` impls of NonZero integer const.
I also changed the feature gate added to `From` impls of Atomic integer to `const_num_from_num` from `const_convert`.
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