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update from origin 2020-08-01 #17

Merged
merged 111 commits into from
Aug 2, 2020
Merged

update from origin 2020-08-01 #17

merged 111 commits into from
Aug 2, 2020

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richkadel
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Aaron1011 and others added 30 commits July 22, 2020 00:57
As `Rc/Arc::weak_count` returns 0 when having no strong counts, this
could be confusing and it's better to avoid using that completely.

Closes #73840.
Add the rust-docs component to toolchain x86_64-unknown-linux-musl, which allows
people using rustup on their musl-based linux distribution to download the
rust-docs.
This commit is a proof-of-concept for switching the standard library's
backtrace symbolication mechanism on most platforms from libbacktrace to
gimli. The standard library's support for `RUST_BACKTRACE=1` requires
in-process parsing of object files and DWARF debug information to
interpret it and print the filename/line number of stack frames as part
of a backtrace.

Historically this support in the standard library has come from a
library called "libbacktrace". The libbacktrace library seems to have
been extracted from gcc at some point and is written in C. We've had a
lot of issues with libbacktrace over time, unfortunately, though. The
library does not appear to be actively maintained since we've had
patches sit for months-to-years without comments. We have discovered a
good number of soundness issues with the library itself, both when
parsing valid DWARF as well as invalid DWARF. This is enough of an issue
that the libs team has previously decided that we cannot feed untrusted
inputs to libbacktrace. This also doesn't take into account the
portability of libbacktrace which has been difficult to manage and
maintain over time. While possible there are lots of exceptions and it's
the main C dependency of the standard library right now.

For years it's been the desire to switch over to a Rust-based solution
for symbolicating backtraces. It's been assumed that we'll be using the
Gimli family of crates for this purpose, which are targeted at safely
and efficiently parsing DWARF debug information. I've been working
recently to shore up the Gimli support in the `backtrace` crate. As of a
few weeks ago the `backtrace` crate, by default, uses Gimli when loaded
from crates.io. This transition has gone well enough that I figured it
was time to start talking seriously about this change to the standard
library.

This commit is a preview of what's probably the best way to integrate
the `backtrace` crate into the standard library with the Gimli feature
turned on. While today it's used as a crates.io dependency, this commit
switches the `backtrace` crate to a submodule of this repository which
will need to be updated manually. This is not done lightly, but is
thought to be the best solution. The primary reason for this is that the
`backtrace` crate needs to do some pretty nontrivial filesystem
interactions to locate debug information. Working without `std::fs` is
not an option, and while it might be possible to do some sort of
trait-based solution when prototyped it was found to be too unergonomic.
Using a submodule allows the `backtrace` crate to build as a submodule
of the `std` crate itself, enabling it to use `std::fs` and such.

Otherwise this adds new dependencies to the standard library. This step
requires extra attention because this means that these crates are now
going to be included with all Rust programs by default. It's important
to note, however, that we're already shipping libbacktrace with all Rust
programs by default and it has a bunch of C code implementing all of
this internally anyway, so we're basically already switching
already-shipping functionality to Rust from C.

* `object` - this crate is used to parse object file headers and
  contents. Very low-level support is used from this crate and almost
  all of it is disabled. Largely we're just using struct definitions as
  well as convenience methods internally to read bytes and such.

* `addr2line` - this is the main meat of the implementation for
  symbolication. This crate depends on `gimli` for DWARF parsing and
  then provides interfaces needed by the `backtrace` crate to turn an
  address into a filename / line number. This crate is actually pretty
  small (fits in a single file almost!) and mirrors most of what
  `dwarf.c` does for libbacktrace.

* `miniz_oxide` - the libbacktrace crate transparently handles
  compressed debug information which is compressed with zlib. This crate
  is used to decompress compressed debug sections.

* `gimli` - not actually used directly, but a dependency of `addr2line`.

* `adler32`- not used directly either, but a dependency of
  `miniz_oxide`.

The goal of this change is to improve the safety of backtrace
symbolication in the standard library, especially in the face of
possibly malformed DWARF debug information. Even to this day we're still
seeing segfaults in libbacktrace which could possibly become security
vulnerabilities. This change should almost entirely eliminate this
possibility whilc also paving the way forward to adding more features
like split debug information.

Some references for those interested are:

* Original addition of libbacktrace - #12602
* OOM with libbacktrace - #24231
* Backtrace failure due to use of uninitialized value - #28447
* Possibility to feed untrusted data to libbacktrace - #21889
* Soundness fix for libbacktrace - #33729
* Crash in libbacktrace - #39468
* Support for macOS, never merged - ianlancetaylor/libbacktrace#2
* Performance issues with libbacktrace - #29293, #37477
* Update procedure is quite complicated due to how many patches we
  need to carry - #50955
* Libbacktrace doesn't work on MinGW with dynamic libs - #71060
* Segfault in libbacktrace on macOS - #71397

Switching to Rust will not make us immune to all of these issues. The
crashes are expected to go away, but correctness and performance may
still have bugs arise. The gimli and `backtrace` crates, however, are
actively maintained unlike libbacktrace, so this should enable us to at
least efficiently apply fixes as situations come up.
The reason for `Box::leak` not to be a method (`Deref` to an arbitrary `T`
which might have its own, different `leak` method) does not apply.
This commit updates the metadata location logic to ignore errors when
calling `fs::canonicalize`. Canonicalization was added historically so
multiple `-L` paths to the same directory don't print errors about
multiple candidates (since rustc can deduplicate same-named paths), but
canonicalization doesn't work on all filesystems. Cargo, for example,
always uses this sort of fallback where it will opportunitistically try
to canonicalize but fall back to using the input path if it otherwise
doesn't work.

If rustc is run on a filesystem that doesn't support canonicalization
then the effect of this change will be that `-L` paths which logically
point to the same directory will cause errors, but that's a rare enough
occurrence it shouldn't cause much issue in practice. Otherwise rustc
doesn't work at all today on those sorts of filesystem where
canonicalization isn't supported!
Lezzz and others added 28 commits July 31, 2020 22:15
Remove `linked_list_extras` methods.

Removing these in favor of the `Cursor` API in #58533 .
Closes #27794.

r? @Amanieu
Run all tests if have no specified tests

The behaviour was changed in #74905 (comment)
cc @alex if you could check it again, thank you.
…lacrum

1.45.2 release notes

(for master)

cc #74958
Miri: fix ICE when unwinding past topmost stack frame

Fixes rust-lang/miri#1389
fix part of comparison that would always evaluate to "true", probably an oversight

cc  @jumbatm
Fix Const-Generic Cycle ICE #74199

This PR intends to fix the bug in Issue #74199 by following the suggestion provided of ignoring the error that causes the ICE.

This does not fix the underlying cycle detection issue, but fixes the ICE.
Also adds a test to check that it doesn't causes an ICE but returns a valid error for now.

r? @lcnr

Edit: Also it's funny how this PR number is an anagram of the issue number
Among other things, this brings in [the `__main_argc_argv`] patch,
which simplifies the interaction between the compiler and WASI libc's
startup code, which will help work on reactor support.

[the `__main_argc_argv` patch]: llvm/llvm-project@00072c0
Changes:
````
Use the same index location on nightly as beta
relax deprecated diagnostic message check
Don't print to raw stderr in test
Emit the `test` field in cargo metadata
````
Rollup of 6 pull requests

Successful merges:

 - #74644 (Remove `linked_list_extras` methods.)
 - #74968 (Run all tests if have no specified tests)
 - #74982 (1.45.2 release notes)
 - #74984 (Miri: fix ICE when unwinding past topmost stack frame)
 - #74986 (fix part of comparison that would always evaluate to "true", probably an oversight)
 - #74991 (Fix Const-Generic Cycle ICE #74199)

Failed merges:

r? @ghost
…nherited-params, r=oli-obk

mir: add `used_generic_parameters_needs_subst`

Fixes #74636.

This PR adds a `used_generic_parameters_needs_subst` helper function which checks whether a type needs substitution, but only for parameters that the `unused_generic_params` query considers used. This is used in the MIR interpreter to make the check for some pointer casts and for reflection intrinsics more precise.

I've opened this as a draft PR because this might not be the approach we want to fix this issue and we have to decide what to do about the reflection case.

r? @eddyb
cc @lcnr @wesleywiser
…li-obk

[mir] Special treatment for dereferencing a borrow to a static definition

Fix #70584.

As suggested by @oli-obk in this [comment](#70584 (comment)), one can chase the definition of the local variable being de-referenced and check if it is a true static variable. If that is the case, `validate_place` will admit the promotion.

This is my first time to contribute to `rustc`, and I have two questions.
1. A generalization to some extent is applied to decide if the promotion is possible in the static context. In case that there are more projection operations preceding the de-referencing, `validate_place` recursively decent into inner projection operations. I have put thoughts into its correctness but I am not totally sure about it.
2. I have a hard time to find a good place for the test case. This patch has to do with MIR, but this test case would look out of place compared to other tests in `src/test/ui/mir` or `src/test/ui/borrowck` because it does not generate errors while others do. It is tentatively placed in `src/test/ui/statics` for now.

Thank you for any comments and suggestions!
add `slice::array_chunks` to std

Now that #74113 has landed, these methods are suddenly usable. A rebirth of #72334

Tests are directly copied from `chunks_exact` and some additional tests for type inference.

r? @withoutboats as you are both part of t-libs and working on const generics. closes #60735
Rename HAIR to THIR (Typed HIR).

r? @nikomatsakis

Originally suggested by @eddyb
Update the bundled wasi-libc with libstd

This just updates WASI libc, in preparation for WASI reactor support in
a separate change.

r? @alexcrichton
Replace a recursive algorithm with an iterative one and a stack.

fixes #74931
Update the WASI libc build to LLVM 10.

Among other things, this brings in [the `__main_argc_argv`] patch,
which simplifies the interaction between the compiler and WASI libc's
startup code, which will help work on reactor support.

[the `__main_argc_argv` patch]: llvm/llvm-project@00072c0

r? @alexcrichton
submodules: update cargo from 974eb438d to 2d5c2381e

Changes:
````
Use the same index location on nightly as beta
relax deprecated diagnostic message check
Don't print to raw stderr in test
Emit the `test` field in cargo metadata
````

r? @ehuss

Trying to get the fix to the registry-index-hash upstream soonish.
Rollup of 6 pull requests

Successful merges:

 - #74977 (Clean up E0741 error explanation)
 - #74981 (Some fixes for `plugin.md` in unstable-book)
 - #74983 (Replace a recursive algorithm with an iterative one and a stack.)
 - #74995 (Update the WASI libc build to LLVM 10.)
 - #74996 (submodules: update cargo from 974eb438d to 2d5c2381e)
 - #75007 (Clean up E0743 explanation)

Failed merges:

r? @ghost
Move from `log` to `tracing`

The only visible change is that we now get timestamps in our logs:

```
Jul 24 18:41:01.065 TRACE rustc_mir::transform::const_prop: skipping replace of Rvalue::Use(const () because it is already a const
Jul 24 18:41:01.065 TRACE rustc_mir::transform::const_prop: propagated into _2
Jul 24 18:41:01.065 TRACE rustc_mir::transform::const_prop: visit_constant: const ()
```

This PR was explicitly designed to be as low-impact as possible. We can now move to using the name `tracing` insteads of `log` on a crate-by-crate basis and use any of the other tracing features where desirable.

As far as I can tell this will allow tools to seamlessly keep working (since they are using `rustc_driver::init_log...`).

This is the first half of step 1 of the accepted `tracing` MCP (rust-lang/compiler-team#331)
Stabilize Vec::leak as a method

Closes #62195

The signature is changed to a method rather than an associated function:

```diff
-pub fn leak<'a>(vec: Vec<T>) -> &'a mut [T]
+pub fn leak<'a>(self) -> &'a mut [T]
```

The reason for `Box::leak` not to be a method (`Deref` to an arbitrary `T` which might have its own, different `leak` method) does not apply.
@richkadel richkadel merged this pull request into richkadel:master Aug 2, 2020
richkadel added a commit that referenced this pull request Oct 5, 2020
This is a combination of 18 commits.

Commit #2:

Additional examples and some small improvements.

Commit #3:

fixed mir-opt non-mir extensions and spanview title elements

Corrected a fairly recent assumption in runtest.rs that all MIR dump
files end in .mir. (It was appending .mir to the graphviz .dot and
spanview .html file names when generating blessed output files. That
also left outdated files in the baseline alongside the files with the
incorrect names, which I've now removed.)

Updated spanview HTML title elements to match their content, replacing a
hardcoded and incorrect name that was left in accidentally when
originally submitted.

Commit #4:

added more test examples

also improved Makefiles with support for non-zero exit status and to
force validation of tests unless a specific test overrides it with a
specific comment.

Commit #5:

Fixed rare issues after testing on real-world crate

Commit #6:

Addressed PR feedback, and removed temporary -Zexperimental-coverage

-Zinstrument-coverage once again supports the latest capabilities of
LLVM instrprof coverage instrumentation.

Also fixed a bug in spanview.

Commit #7:

Fix closure handling, add tests for closures and inner items

And cleaned up other tests for consistency, and to make it more clear
where spans start/end by breaking up lines.

Commit #8:

renamed "typical" test results "expected"

Now that the `llvm-cov show` tests are improved to normally expect
matching actuals, and to allow individual tests to override that
expectation.

Commit #9:

test coverage of inline generic struct function

Commit #10:

Addressed review feedback

* Removed unnecessary Unreachable filter.
* Replaced a match wildcard with remining variants.
* Added more comments to help clarify the role of successors() in the
CFG traversal

Commit #11:

refactoring based on feedback

* refactored `fn coverage_spans()`.
* changed the way I expand an empty coverage span to improve performance
* fixed a typo that I had accidently left in, in visit.rs

Commit #12:

Optimized use of SourceMap and SourceFile

Commit #13:

Fixed a regression, and synched with upstream

Some generated test file names changed due to some new change upstream.

Commit #14:

Stripping out crate disambiguators from demangled names

These can vary depending on the test platform.

Commit #15:

Ignore llvm-cov show diff on test with generics, expand IO error message

Tests with generics produce llvm-cov show results with demangled names
that can include an unstable "crate disambiguator" (hex value). The
value changes when run in the Rust CI Windows environment. I added a sed
filter to strip them out (in a prior commit), but sed also appears to
fail in the same environment. Until I can figure out a workaround, I'm
just going to ignore this specific test result. I added a FIXME to
follow up later, but it's not that critical.

I also saw an error with Windows GNU, but the IO error did not
specify a path for the directory or file that triggered the error. I
updated the error messages to provide more info for next, time but also
noticed some other tests with similar steps did not fail. Looks
spurious.

Commit #16:

Modify rust-demangler to strip disambiguators by default

Commit #17:

Remove std::process::exit from coverage tests

Due to Issue rust-lang#77553, programs that call std::process::exit() do not
generate coverage results on Windows MSVC.

Commit #18:

fix: test file paths exceeding Windows max path len
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