similar to GCC's __attribute((used))__. This attribute prevents LLVM from
optimizing away a non-exported symbol, within a compilation unit (object file),
when there are no references to it.
This is better explained with an example:
```
#[used]
static LIVE: i32 = 0;
static REFERENCED: i32 = 0;
static DEAD: i32 = 0;
fn internal() {}
pub fn exported() -> &'static i32 {
&REFERENCED
}
```
Without optimizations, LLVM pretty much preserves all the static variables and
functions within the compilation unit.
```
$ rustc --crate-type=lib --emit=obj symbols.rs && nm -C symbols.o
0000000000000000 t drop::h1be0f8f27a2ba94a
0000000000000000 r symbols::REFERENCED::hb3bdfd46050bc84c
0000000000000000 r symbols::DEAD::hc2ea8f9bd06f380b
0000000000000000 r symbols::LIVE::h0970cf9889edb56e
0000000000000000 T symbols::exported::h6f096c2b1fc292b2
0000000000000000 t symbols::internal::h0ac1aadbc1e3a494
```
With optimizations, LLVM will drop dead code. Here `internal` is dropped because
it's not a exported function/symbol (i.e. not `pub`lic). `DEAD` is dropped for
the same reason. `REFERENCED` is preserved, even though it's not exported,
because it's referenced by the `exported` function. Finally, `LIVE` survives
because of the `#[used]` attribute even though it's not exported or referenced.
```
$ rustc --crate-type=lib -C opt-level=3 --emit=obj symbols.rs && nm -C symbols.o
0000000000000000 r symbols::REFERENCED::hb3bdfd46050bc84c
0000000000000000 r symbols::LIVE::h0970cf9889edb56e
0000000000000000 T symbols::exported::h6f096c2b1fc292b2
```
Note that the linker knows nothing about `#[used]` and will drop `LIVE`
because no other object references to it.
```
$ echo 'fn main() {}' >> symbols.rs
$ rustc symbols.rs && nm -C symbols | grep LIVE
```
At this time, `#[used]` only works on `static` variables.
Fix diagnostic suggestion from:
```rust
help: try parenthesizing the first index
| (1, (2, 3)).((1, (2, 3)).1).1;
```
to the correct:
```rust
help: try parenthesizing the first index
| ((1, (2, 3)).1).1;
```
Properly adjust filenames when multiple emissions
Fixes#40993
Should backport just fine to beta but not sure if we want to do this since this is quite old stable regression.
travis: Update sccache binaries
I've tracked down what I believe is the last spurious sccache failure on #40240
to behavior in mio (carllerche/mio#583), and this commit updates the binaries to
a version which has that fix incorporated.
Do not recommend private fields called as method
```rust
error: no method named `dog_age` found for type `animal::Dog` in the current scope
--> $DIR/private-field.rs:26:23
|
26 | let dog_age = dog.dog_age();
| ^^^^^^^ private field, not a method
```
Fix#27654.
Revert "Implement AsRawFd/IntoRawFd for RawFd"
This reverts commit 2cf686f2cd (#40842)
RawFd is a type alias for c_int, which is itself a type alias for i32.
As a result, adding AsRawFd and IntoRawFd impls for RawFd actually adds
them for i32.
As a result, the reverted commit makes this valid:
```
use std::os::unix::io::AsRawFd;
fn arf<T: AsRawFd>(_: T) {}
fn main() {
arf(32i32)
}
```
Implimenting AsRawFd and IntoRawFd for i32 breaks the promises of both
those traits that their methods return a valid RawFd.
r? @aturon
cc @Mic92 @kamalmarhubi
Fixed typo in doc comments for swap_remove
While reading the Vec docs, I came across the docs for swap_remove. I believe there is a typo in the comment and ```return``` should be ```returns```. This PR fixes this issue.
I also feel that the entire doc comment is a bit of a run-on and could be changed to something along the lines of ```Removes an element from anywhere in the vector and returns it. The vector is mutated and the removed element is replaced by the last element of the vector. ```
Thoughts?
Added links to types in from_utf8 description
References #29375. Link to types mentioned in the documentation for `from_utf8` (`str`, `&[u8`], etc). Paragraphs were reformatted to keep any one line from being excessively long, but are otherwise unchanged.
Added links to from_utf8 methods in Utf8Error
Referencing #29375. Linked the `from_utf8` methods for both `String` and `str` in the description. Also linked the `u8` to its documentation
Add links and some examples to std::sync::mpsc docs
Addresses part of #29377
r? @steveklabnik
I took a stab at adding links to the `std::sync::mpsc` docs, and I also wrote a few examples.
Edit: Whoops, typed in `?r` instead of `r?`.
rustc: Stabilize the `#![windows_subsystem]` attribute
This commit stabilizes the `#![windows_subsystem]` attribute which is a
conservative exposure of the `/SUBSYSTEM` linker flag on Widnows platforms. This
is useful for creating applications as well as console programs.
Closes#37499
This commit shrinks the size of the aforementioned table from
2,102 bytes to 1,197 bytes. This is achieved by an observation that
most u16 entries are common in its upper byte. Specifically:
- SINGLETONS now uses two tables, one for (upper byte, lower count)
and another for a series of lower bytes. For each upper byte given
number of lower bytes are read and compared.
- NORMAL now uses a variable length format for the count of "true"
codepoints and "false" codepoints (one byte with MSB unset, or
two big-endian bytes with the first MSB set).
The code size and relative performance roughly remains same as this
commit tries to optimize for both. The new table and algorithm has
been verified for the equivalence to older ones.
Point at last valid token on failed `expect_one_of`
```rust
error: expected one of `.`, `;`, `?`, `}`, or an operator, found `)`
--> $DIR/token-error-correct-3.rs:29:9
|
25 | foo()
| - expected one of `.`, `;`, `?`, `}`, or an operator after this
...
29 | } else {
| ^ unexpected token
```
Fix#32540.
With `-mcpu=power4`, code might use instructions like `fcfid`, excluding
older CPUs like the PowerPC G4, which apparently some users would like
to use. The generic `-mcpu=powerpc` should stick to pure 32-bit PowerPC
instructions.
Fixesrust-lang/cargo#3852.
I've tracked down what I believe is the last spurious sccache failure on #40240
to behavior in mio (carllerche/mio#583), and this commit updates the binaries to
a version which has that fix incorporated.
* Store capacity_mask instead of capacity
* Move bucket index into RawBucket
* Bucket index is now always within [0..table_capacity)
* Clone RawTable using RawBucket
* Simplify iterators by moving logic into RawBuckets
* Make retain aware of the number of elements
