improve the TryFrom implementations
This removes the need for a 128 bit storage by making use of the fact that there can be either no over/underflow, either one or both, and each time the target type suffices to hold the limit for comparison. This also means that the implementation will work in targets without 128bit support (unless it's for 128bit types, of course).
The downside is that the code looks a bit more complex.
This removes the need for a 128 bit storage by making use of the fact that
there can be either no over/underflow, either one or both, and each time
the target type suffices to hold the limit for comparison.
The downside is that the code looks a bit more complex.
This test code included in this commit is from @oyvindln 's PR. They also
greatly helped fixing a number of errors I made along the way. Thanks a lot!
Add generic example of std::ops::Sub in doc comments
This PR adds an example of using generics with std::ops::Sub and is a follow up of PR #41612 and is related to issue #29365. I also wanted to add examples to Mul and Div, but I think these two traits are already loaded with examples.
std: Cut down #[inline] annotations where not necessary
This PR cuts down on a large number of `#[inline(always)]` and `#[inline]`
annotations in libcore for various core functions. The `#[inline(always)]`
annotation is almost never needed and is detrimental to debug build times as it
forces LLVM to perform inlining when it otherwise wouldn't need to in debug
builds. Additionally `#[inline]` is an unnecessary annoation on almost all
generic functions because the function will already be monomorphized into other
codegen units and otherwise rarely needs the extra "help" from us to tell LLVM
to inline something.
Overall this PR cut the compile time of a [microbenchmark][1] by 30% from 1s to
0.7s.
[1]: https://gist.github.com/alexcrichton/a7d70319a45aa60cf36a6a7bf540dd3a
This PR cuts down on a large number of `#[inline(always)]` and `#[inline]`
annotations in libcore for various core functions. The `#[inline(always)]`
annotation is almost never needed and is detrimental to debug build times as it
forces LLVM to perform inlining when it otherwise wouldn't need to in debug
builds. Additionally `#[inline]` is an unnecessary annoation on almost all
generic functions because the function will already be monomorphized into other
codegen units and otherwise rarely needs the extra "help" from us to tell LLVM
to inline something.
Overall this PR cut the compile time of a [microbenchmark][1] by 30% from 1s to
0.7s.
[1]: https://gist.github.com/alexcrichton/a7d70319a45aa60cf36a6a7bf540dd3a
Workaround "Quasi-quoting is inefficient" warning in incremental rustbuild introduced in #43252.
After #43252 is merged, building stage0 libcore with `-i` (`--incremental`) flag will cause 17 "Quasi-quoting might make incremental compilation very inefficient: NtExpr(..)" warnings, as in #40946.
```
warning: Quasi-quoting might make incremental compilation very inefficient: NtExpr(..)
--> src/libcore/default.rs:133:21
|
133 | #[doc = $doc]
| ^^^^
...
139 | default_impl! { (), (), "Returns the default value of `()`" }
| ------------------------------------------------------------- in this macro invocation
(× 17)
```
True fix for #40946 will take at least 12 weeks from now to make into the next stage0, so it is quicker to workaround it in libcore instead.
cc @vbrandl @jseyfried
Update docs on Error struct. #29355
This adds a pretty contrived example of the usage of fmt::Error. I am
very open to suggestions for a better one.
I have also highlighted the fmt::Error vs std::error::Error.
r? @steveklabnik
After #43252 is merged, building stage0 libcore with -i (--incremental)
flag will cause 17 "Quasi-quoting might make incremental compilation very
inefficient: NtExpr(..)" warnings, as in #40946.
Fixing the warning in #40946 will take 12 weeks from now to make into the
next stage0, so it is quicker to workaround it in libcore instead.
Document default values for primitive types
All primitive types implement the `Default` trait but the documentation just says `Returns the "default value" for a type.` and doesn't give a hint about the actual default value. I think it would be good to document the default values in a proper way.
I changed the `default_impl` macro to accept a doc string as a third parameter and use this string to overwrite the documentation of `default()` for each primitive type.
The generated documentation now looks like this:
Disable big-endian simd in swap_nonoverlapping_bytes
This is a workaround for #42778, which was git-bisected to #40454's
optimizations to `mem::swap`, later moved to `ptr` in #42819. Natively
compiled rustc couldn't even compile stage1 libcore on powerpc64 and
s390x, but they work fine without this `repr(simd)`. Since powerpc64le
works OK, it seems probably related to being big-endian.
The underlying problem is not yet known, but this at least makes those
architectures functional again in the meantime.
cc @arielb1
This adds a pretty contrived example of the usage of fmt::Error. I am
very open to suggestions for a better one.
I have also highlighted the fmt::Error vs std::error::Error.
r? @steveklabnik
Implement Eq/Hash/Debug etc. for unsized tuples.
As I mentioned in [the comment in #18469](https://github.com/rust-lang/rust/issues/18469#issuecomment-306767422), the implementations of `PartialEq`, `Eq`, `PartialOrd`, `Ord`, `Debug`, `Hash` can be generalized to unsized tuples.
This is consistent with the `derive` behavior for unsized structs.
```rust
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
struct MyTuple<X, Y, Z: ?Sized>(X, Y, Z);
fn f(x: &MyTuple<i32, i32, [i32]>) {
x == x;
x < x;
println!("{:?}", x);
}
```
Questions:
- Need an RFC?
- Need a feature gate? I don't think it does because the unsized tuple coercion #42527 is feature-gated.
- I changed `builder.field($name);` into `builder.field(&$name);` in the `Debug` implementation to pass compilation. This won't affect the behavior because `Debug for &'a T` is a mere redirection to `Debug for T`. However, I don't know if it affects code size / performance.
This is a workaround for #42778, which was git-bisected to #40454's
optimizations to `mem::swap`, later moved to `ptr` in #42819. Natively
compiled rustc couldn't even compile stage1 libcore on powerpc64 and
s390x, but they work fine without this `repr(simd)`. Since powerpc64le
works OK, it seems probably related to being big-endian.
The underlying problem is not yet known, but this at least makes those
architectures functional again in the meantime.
cc @arielb1
Update docs for Debug* structs. #29355
This adds docs for the Debug* structs as well as examples from the
Formatter::debug_* methods, so that a user knows how to construct them.
I added these examples as the builders module is not public and hence
the debug_*_new() functions are not available to a user.
r? @steveklabnik
Delete deprecated & unstable range-specific `step_by`
Using the new one is annoying while this one exists, since the inherent method hides the one on iterator.
Tracking issue: #27741
Replacement: #41439
Deprecation: #42310 for 1.19
Fixes#41477
Alex Crichton
