Properly detect overflow in Instance ± Duration.
Fix#44216.
Fix#42622
The computation `Instant::now() + Duration::from_secs(u64::max_value())` now panics. The call `receiver.recv_timeout(Duration::from_secs(u64::max_value()))`, which involves such time addition, will also panic.
The reason #44216 arises is because of an unchecked cast from `u64` to `i64`, making the duration equivalent to -1 second.
Note that the current implementation is over-conservative, since e.g. (-2⁶²) + (2⁶³) is perfectly fine for an `i64`, yet this is rejected because (2⁶³) overflows the `i64`.
Refactoring: move net specific file descriptor methods
Move the implementations of net specific file descriptor methods from
io to net. This makes it easier to exclude net at all if it is not needed
for a target.
Move the implementations of net specific file descriptior implementations
to net. This makes it easier to exclude net at all if not needed for a
target.
Make backtraces work on Redox, copying Unix implementation
The `backtrace/` directory here is the same as the Unix one, except for adding an implementation of `get_executable_filename`.
Expose all OS-specific modules in libstd doc.
1. Uses the special `--cfg dox` configuration passed by rustbuild when running `rustdoc`. Changes the `#[cfg(platform)]` into `#[cfg(any(dox, platform))]` so that platform-specific API are visible to rustdoc.
2. Since platform-specific implementations often won't compile correctly on other platforms, `rustdoc` is changed to apply `everybody_loops` to the functions during documentation and doc-test harness.
3. Since platform-specific code are documented on all platforms now, it could confuse users who found a useful API but is non-portable. Also, their examples will be doc-tested, so must be excluded when not testing on the native platform. An undocumented attribute `#[doc(cfg(...))]` is introduced to serve the above purposed.
Fixes#24658 (Does _not_ fully implement #1998).
Fixed mutable vars being marked used when they weren't
#### NB : bootstrapping is slow on my machine, even with `keep-stage` - fixes for occurances in the current codebase are <s>in the pipeline</s> done. This PR is being put up for review of the fix of the issue.
Fixes#43526, Fixes#30280, Fixes#25049
### Issue
Whenever the compiler detected a mutable deref being used mutably, it marked an associated value as being used mutably as well. In the case of derefencing local variables which were mutable references, this incorrectly marked the reference itself being used mutably, instead of its contents - with the consequence of making the following code emit no warnings
```
fn do_thing<T>(mut arg : &mut T) {
... // don't touch arg - just deref it to access the T
}
```
### Fix
Make dereferences not be counted as a mutable use, but only when they're on borrows on local variables.
#### Why not on things other than local variables?
* Whenever you capture a variable in a closure, it gets turned into a hidden reference - when you use it in the closure, it gets dereferenced. If the closure uses the variable mutably, that is actually a mutable use of the thing being dereffed to, so it has to be counted.
* If you deref a mutable `Box` to access the contents mutably, you are using the `Box` mutably - so it has to be counted.
This commit adds a disabled builder which will run all tests for the standard
library for aarch64 in a QEMU instance. Once we get enough capacity to run this
on Travis this can be used to boost our platform coverage of AArch64
