Debug overflow checks for arithmetic negation landed in #24500, at which time
the `abs` method on signed integers was changed to using `wrapping_neg` to
ensure that the function never panicked. This implied that `abs` of `INT_MIN`
would return `INT_MIN`, another negative value. When this change was back-ported
to beta, however, in #24708, the `wrapping_neg` function had not yet been
backported, so the implementation was changed in #24785 to `!self + 1`. This
change had the unintended side effect of enabling debug overflow checks for the
`abs` function. Consequently, the current state of affairs is that the beta
branch checks for overflow in debug mode for `abs` and the nightly branch does
not.
This commit alters the behavior of nightly to have `abs` always check for
overflow in debug mode. This change is more consistent with the way the standard
library treats overflow as well, and it is also not a breaking change as it's
what the beta branch currently does (albeit if by accident).
cc #25378
This is a fork of the flt2dec portion of rust-strconv [1] with
a necessary relicensing (the original code was licensed CC0-1.0).
Each module is accompanied with large unit tests, integrated
in this commit as coretest::num::flt2dec. This module is added
in order to replace the existing core::fmt::float method.
The forked revision of rust-strconv is from 2015-04-20, with a commit ID
9adf6d3571c6764a6f240a740c823024f70dc1c7.
[1] https://github.com/lifthrasiir/rust-strconv/
Ensures that the same error type is propagated throughout. Unnecessary leakage
of the internals is prevented through the usage of stability attributes.
Closes#24748
```asm
movzbl %dil, %eax
bsfl %eax, %eax
movl $32, %ecx
cmovnel %eax, %ecx
cmpl $32, %ecx
movl $8, %eax
cmovnel %ecx, %eax
```
which has some unnecessary overhead, having two conditional moves.
To improve the codegen, we can zero extend the 8 bit integer, then set
bit 8 and perform a cttz operation on the extended value. That way
there's no conditional operation involved at all.
This commit removes all the old casting/generic traits from `std::num` that are
no longer in use by the standard library. This additionally removes the old
`strconv` module which has not seen much use in quite a long time. All generic
functionality has been supplanted with traits in the `num` crate and the
`strconv` module is supplanted with the [rust-strconv crate][rust-strconv].
[rust-strconv]: https://github.com/lifthrasiir/rust-strconv
This is a breaking change due to the removal of these deprecated crates, and the
alternative crates are listed above.
[breaking-change]
`wrapping_div`, `wrapping_rem`, `wrapping_neg`,
`wrapping_shl`, `wrapping_shr`.
All marked unstable under `core` feature for now (with expectation of
being marked as stable by 1.0 release).
From [here](http://doc.rust-lang.org/nightly/std/primitive.i8.html):
> `fn rotate_right(self, n: u32) -> i8`
> Shifts the bits to the right by a specified __amount amount__, n, wrapping the truncated bits to the beginning of the resulting integer.
This commit series starts out with more official test harness support for rustdoc tests, and then each commit afterwards adds a test (where appropriate). Each commit should also test and finish independently of all others (they're all pretty separable).
I've uploaded a [copy of the documentation](http://people.mozilla.org/~acrichton/doc/std/) generated after all these commits were applied, and a double check on issues being closed would be greatly appreciated! I'll also browse the docs a bit and make sure nothing regressed too horribly.
These traits are currently all just unstable parts of the facade which are
implementation details for primitives further up the facade. This may make it
more difficult to find what set of methods you get if only linking to libcore,
but for now that's also unstable behavior.
Closes#22025
In addition to being nicer, this also allows you to use `sum` and `product` for
iterators yielding custom types aside from the standard integers.
Due to removing the `AdditiveIterator` and `MultiplicativeIterator` trait, this
is a breaking change.
[breaking-change]
Recent numerics stabilization removed the inherent `min_value` and
`max_value` methods from integer types, assuming that the module-level
constants would suffice. However, that failed to account for the use
case in FFI code when dealing with integer type aliases.
This commit reintroduces the methods as `#[stable]`, since this is
essential functionality for 1.0.
It's unfortunate to freeze these as methods, but when we can provide
inherent associated constants these methods can be deprecated.
r? @sfackler
cc @alexcrichton
Recent numerics stabilization removed the inherent `min_value` and
`max_value` methods from integer types, assuming that the module-level
constants would suffice. However, that failed to account for the use
case in FFI code when dealing with integer type aliases.
This commit reintroduces the methods as `#[stable]`, since this is
essential functionality for 1.0.
It's unfortunate to freeze these as methods, but when we can provide
inherent associated constants these methods can be deprecated.
This commit stabilizes the `std::num` module:
* The `Int` and `Float` traits are deprecated in favor of (1) the
newly-added inherent methods and (2) the generic traits available in
rust-lang/num.
* The `Zero` and `One` traits are reintroduced in `std::num`, which
together with various other traits allow you to recover the most
common forms of generic programming.
* The `FromStrRadix` trait, and associated free function, is deprecated
in favor of inherent implementations.
* A wide range of methods and constants for both integers and floating
point numbers are now `#[stable]`, having been adjusted for integer
guidelines.
* `is_positive` and `is_negative` are renamed to `is_sign_positive` and
`is_sign_negative`, in order to address #22985
* The `Wrapping` type is moved to `std::num` and stabilized;
`WrappingOps` is deprecated in favor of inherent methods on the
integer types, and direct implementation of operations on
`Wrapping<X>` for each concrete integer type `X`.
Closes#22985Closes#21069
[breaking-change]
This permits all coercions to be performed in casts, but adds lints to warn in those cases.
Part of this patch moves cast checking to a later stage of type checking. We acquire obligations to check casts as part of type checking where we previously checked them. Once we have type checked a function or module, then we check any cast obligations which have been acquired. That means we have more type information available to check casts (this was crucial to making coercions work properly in place of some casts), but it means that casts cannot feed input into type inference.
[breaking change]
* Adds two new lints for trivial casts and trivial numeric casts, these are warn by default, but can cause errors if you build with warnings as errors. Previously, trivial numeric casts and casts to trait objects were allowed.
* The unused casts lint has gone.
* Interactions between casting and type inference have changed in subtle ways. Two ways this might manifest are:
- You may need to 'direct' casts more with extra type information, for example, in some cases where `foo as _ as T` succeeded, you may now need to specify the type for `_`
- Casts do not influence inference of integer types. E.g., the following used to type check:
```
let x = 42;
let y = &x as *const u32;
```
Because the cast would inform inference that `x` must have type `u32`. This no longer applies and the compiler will fallback to `i32` for `x` and thus there will be a type error in the cast. The solution is to add more type information:
```
let x: u32 = 42;
let y = &x as *const u32;
```
