Add functions to safely transmute float to int
The safe subset of Rust tries to be as powerful as possible. While it is very powerful already, its currently impossible to safely transmute integers to floats. While crates exist that provide a safe interface, most prominently the `iee754` crate (which also inspired naming of the added functions), they themselves only use the unsafe `mem::transmute` function to accomplish this task.
Also, including an entire crate for just two lines of unsafe code seems quite wasteful.
That's why this PR adds functions to safely transmute integers to floats and vice versa, currently gated by the newly added `float_bits_conv` feature.
The functions added are no niche case. Not just `ieee754` [currently implements](https://github.com/huonw/ieee754/blob/master/src/lib.rs#L441) float to int transmutation via unsafe code but also the [very popular `byteorder` crate](https://github.com/BurntSushi/byteorder/blob/1.0.0/src/lib.rs#L258). This functionality of byteorder is in turn used by higher level crates. I only give two examples out of many: [chor](a7363ea9aa/src/ser.rs (L227)) and [bincode](f06a4cfcb5/src/serde/reader.rs (L218)).
One alternative would be to manually use functions like pow or multiplication by 1 to get a similar result, but they only work in the int -> float direction, and are not bit exact, and much slower (also, most likely the optimizer will never optimize it to a transmute because the conversion is not bit exact while the transmute is).
Tracking issue: #40470
We no longer need to track the tasks in these cases since these
particular tasks have no outputs (except, potentially, errors...) and
they always execute.
[on-demand] Turn monomorphic_const_eval into a proper query, not just a cache.
The error definitions and reporting logic, alongside with `eval_length` were moved to `librustc`.
Both local and cross-crate constant evaluation is on-demand now, but the latter is only used for `enum` discriminants, to replace the manual insertion into the cache which was done when decoding variants.
r? @nikomatsakis
Rename compiler_barrier to compiler_fence
This addresses concerns raised following the merge of #41092. Specifically:
> The naming of these seems surprising: the multithreaded functions (and both the single and multithreaded intrinsics themselves) are fences, but this is a barrier. It's not incorrect, but the latter is both inconsistent with the existing functions and slightly confusing with another type in std (e.g., `Barrier`).
`compiler_fence` carries the same semantic implication that this is a compiler-only operation, while being more in line with the fence/barrier concepts already in use in `std`.
Currently the Cargo binary has jumped from 14M to 34M on the beta channel, which
appears to be due to the fact that we're compiling tools with debug information
inside them. This additionally means that the `rls` binary is 62M right now!
This wasn't an intentional change, so be sure to disable debuginfo when
compiling tools as it's just intended for the standard library and compile for
now.
Part of #29368.
* Added a new summary paragraph about std::path's parsing facilities
* Slightly exanded `Component`'s docs
* removed the now redundant section on component types from the module docs
* moved the section on path normalization during parsing to the docs on
`Path::components`
* Clarified difference between `Prefix` and `PrefixComponent` in their
respecive summary sentences
Hoedown big comeback!
```bash
> cargo +local test
Compiling libc v0.2.20
Compiling sysinfo v0.3.4 (file:///Users/imperio/rust/sysinfo)
Finished dev [unoptimized + debuginfo] target(s) in 3.2 secs
Running target/debug/deps/disk_list-dbd70897f1f7e080
running 1 test
test test_disks ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured
Running target/debug/deps/sysinfo-8ad11103abdf5941
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured
Doc-tests sysinfo
WARNING: src/sysinfo.rs - (line 45) test will be run in the next rustdoc version. If it's not supposed to, please update your documentation and make it compliant to common mark specifications.
WARNING: src/sysinfo.rs - (line 48) test will be run in the next rustdoc version. If it's not supposed to, please update your documentation and make it compliant to common mark specifications.
running 1 test
test src/sysinfo.rs - (line 14) ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured
```
r? @rust-lang/docs
:vis matcher for macro_rules
Resurrection of @DanielKeep's implementation posted with [RFC 1575](https://github.com/rust-lang/rfcs/pull/1575).
@jseyfried was of the opinion that this doesn't need an RFC.
Needed before merge:
- [x] sign-off from @DanielKeep since I stole his code
- [x] feature gate
- [x] docs
Add a comment for disabling errexit, try to debug appveyor cache
Comments added as requested.
Also, lets add some cache debugging to appveyor. I *think* this is how to ignore errors in cmd.exe (and I did try it on my own machine), but I'm not 100% sure how appveyor runs them. In the worst case it'll fail but I guess that isn't the end of the world since the build has already failed by this point.
r? @TimNN
Specialize Vec::from_elem to use calloc
Fixes#38723. This specializes the implementation for `u8` only, but it could be extended to other zeroable types if desired.
I haven't tested this extensively, but I did verify that it gives the expected performance boost for large `vec![0; n]` allocations with both alloc_system and jemalloc, on Linux. (I have not tested or even built the Windows code.)
[rustbuild] Side-step HashMap iteration to preserve command-line step order.
The new `HashMap` was introduced by #41227 and it accidentally randomized step order.
r? @alexcrichton
Part of #29368.
* added missing links
* updated method summaries to use 3rd person style
* added missing periods in `Component`'s variant summaries
* use standard iterator boilerplate in `Components`' and `Iter`'s docs
* added example to `Iter::as_path`, adapted from `Components::as_path`'s
example
* consolidated examples for `Path::file_name`
* some other small fixes
