Implement extensible syscall interface for wasm
Currently it's possible to run tests with the native wasm target, but it's not possible to tell whether they pass or to capture the output, because libstd throws away stdout, stderr and the exit code. While advanced libstd features should probably require more specific targets (eg. wasm-unknown-web) I think even the unknown target should at least support basic I/O.
Any solution is constrained by these factors:
- It must not be javascript specific
- There must not be too strong coupling between libstd and the host environment (because it's an "unknown" target)
- WebAssembly does not allow "optional" imports - all imports *must* be resolved.
- WebAssembly does not support calling the host environment through any channel *other* than imports.
The best solution I could find to these constraints was to give libstd a single required import, and implement a syscall-style interface through that import. Each syscall is designed such that a no-op implementation gives the most reasonable fallback behaviour. This means that the following import table would be perfectly valid:
```javascript
imports.env = { rust_wasm_syscall: function(index, data) {} }
```
Currently I have implemented these system calls:
- Read from stdin
- Write to stdout/stderr
- Set the exit code
- Get command line arguments
- Get environment variable
- Set environment variable
- Get time
It need not be extended beyond this set if being able to run tests for this target is the only goal.
edit:
As part of this PR I had to make a further change. Previously, the rust entry point would be automatically called when the webassembly module was instantiated. This was problematic because from the javascript side it was impossible to call exported functions, access program memory or get a reference to the instance.
To solve this, ~I changed the default behaviour to not automatically call the entry point, and added a crate-level attribute to regain the old behaviour. (`#![wasm_auto_run]`)~ I disabled this behaviour when building tests.
- filter error on the evaluated value of `Self`
- filter error on the evaluated value of the type arguments
- add argument to include custom note in diagnostic
- allow the parser to parse `Self` when processing attributes
- add custom message to binops
Sometimes the parser attempts to synthesize spans from within a macro
context with the span for the captured argument, leading to non-sensical
spans with very bad output. Given that an incorrect span is worse than
a partially incomplete span, when detecting this situation return only
one of the spans without mergin them.
The current `f32|f64.to_degrees` implementation uses a division to calculate 180/π, which causes a loss of precision. Using a constant is still not perfect (implementing a maximally-precise algorithm would come with a high performance cost), but improves precision with a minimal change.
remove intercrate ambiguity hints
The scheme was causing overflows during coherence checking (e.g. #47139). This is sort of a temporary fix; the proper fix I think involves reworking trait selection in deeper ways.
cc @sgrif -- this *should* fix diesel
cc @qnighy -- I'd like to discuss you with alternative techniques for achieving the same end. =) Actually, it might be good to put some energy into refactoring traits first.
r? @eddyb
Previously, unused variables would get a note that the warning could be
silenced by prefixing the variable with an underscore, but that doesn't
work for field shorthand patterns, which the liveness analysis didn't
know about.
The "to avoid this warning" verbiage seemed unnecessary.
Resolves#47390.
Add approximate suggestions for rustfix
This adds `span_approximate_suggestion()` that lets you emit a
suggestion marked as "non-machine applicable" in the JSON output. UI
users see no difference. This is for when rustc and clippy wish to
emit suggestions which will make sense to the reader (e.g. they may
have placeholders like `<type>`) but are not source-applicable, so that
rustfix/etc can ignore these.
fixes#39254
The glossaries in the draft rustc-guide book and librustc/README.md
state that `NodeId` is being gradually phased out in favor of `HirId`;
as such, the present author claims that we ought to have a typedef for
efficient `HirId` maps and sets in the module for such, even if no use
for them has been made as yet (compatibility constraints preventing the
use of it in the author's present unit of work): it is important to
create the psychological "affordance" (in James J. Gibson's sense) that
`HirId`s are a thing that compiler developers can work with.
Clearing out the infcx's region constraints after processing each type
ends up interacting badly with normalizing associated types. This commit
keeps all region constraints intact until the end of
TypeLivenessGenerator.add_drop_live_constraint, ensuring that normalized
types are able to re-use existing inference variables.
Fixes#47589
Currently ', " and \ are escaped as \', \" and \\ respectively. This
leads to confusing messages such as `error: unknown start of token: \\`
when encountering a single backslash.
Fix by emitting printable ASCII characters directly. This will still
escape \r, \n, \t and Unicode characters.
Fixes#47902
Previously, the `guard::init()` and `guard::current()` functions were
returning a `usize` address representing the top of the stack guard,
respectively for the main thread and for spawned threads. The `SIGSEGV`
handler on `unix` targets checked if a fault was within one page below
that address, if so reporting it as a stack overflow.
Now `unix` targets report a `Range<usize>` representing the guard
memory, so it can cover arbitrary guard sizes. Non-`unix` targets which
always return `None` for guards now do so with `Option<!>`, so they
don't pay any overhead.
For `linux-gnu` in particular, the previous guard upper-bound was
`stackaddr + guardsize`, as the protected memory was *inside* the stack.
This was a glibc bug, and starting from 2.27 they are moving the guard
*past* the end of the stack. However, there's no simple way for us to
know where the guard page actually lies, so now we declare it as the
whole range of `stackaddr ± guardsize`, and any fault therein will be
called a stack overflow. This fixes#47863.
rustc: Move location of `codegen-backends` dir
Right now this directory is located under:
```
$sysroot/lib/rustlib/$target/lib/codegen-backends
```
but after seeing what we do in a few other places it seems that a more
appropriate location would be:
```
$sysroot/lib/rustlib/$target/codegen-backends
```
so this commit moves it!
Avoid underflow in render_source_line
While testing rust-lang/rust#47655 I was able to make the compiler panic when it's compiled with debug assertions:
```shell
> rustc /dev/null --crate-type proc-macro
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.25.0-dev running on x86_64-apple-darwin
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'attempt to subtract with overflow', librustc_errors/emitter.rs:287:49
```
Without debug assertions the following warning is emitted:
```shell
> rustc /dev/null --crate-type proc-macro
warning: unused variable: `registrar`
--> /dev/null:0:1
|
|
= note: #[warn(unused_variables)] on by default
= note: to avoid this warning, consider using `_registrar` instead
```
The panic is due to the unused variable warning being spanned to `/dev/null:0:1`. When `render_source_line` subtracts 1 from the line number to look up the source line it panics due to underflow. Without debug assertions this would wrap and cause us to return a blank string instead.
Fix by explicitly testing for 0 and exiting early. I'm unsure how to automatically test this now that rust-lang/rust#46655 has been approved.
Right now this directory is located under:
$sysroot/lib/rustlib/$target/lib/codegen-backends
but after seeing what we do in a few other places it seems that a more
appropriate location would be:
$sysroot/lib/rustlib/$target/codegen-backends
so this commit moves it!
