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Rollup of 8 pull requests #41100

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wants to merge 33 commits into from
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Rollup of 8 pull requests #41100

wants to merge 33 commits into from

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dotdash and others added 30 commits March 29, 2017 20:43
We currently only emit a single call to the lifetime start intrinsic
for the personality slot alloca. This happens because we create that
call at the time that we create the alloca, instead of creating it each
time we start using it. Because LLVM usually removes the alloca before
the lifetime intrinsics are even considered, this didn't cause any
problems yet, but we should fix this anyway.
This initial commit provides implementations for HIR, MIR, and
everything that also needs to be supported for those two.
For some reason 'command' and 'subcommand' were intermixed to mean the same thing.  Lets just call it the one thing that it is.
…m in the same order to ease comparing the sections of code in order. I chose the order that appears in the help text, because that is most likely to have been ordered with specific reasoning.
Exception handling on MSVC targets doesn't use personality slots.
- Don't print 'unknown subcommand' at the top of the help message.  The help message now clearly instructs the user to provide a subcommand.
- Clarify the usage line.  Subcommand is required.  Don't echo invalid input back out in the usage line (what the...???).  args renamed to paths, because that's what all the args are referred to elsewhere.
- List the available subcommands immediately following the usage line.  It's the one required argument, after all.
- Slightly improve the extra documentation for the build, test, and doc commands.
- Don't print 'Available invocations:' at all.  It occurred immediately before 'Available paths:'.
- Clearly state that running with '-h -v' will produce a list of available paths.
…ction and then not using it until over 100 lines later is just mean.
- No more manual args manipulation -- getopts used for everything.
  As a result, options can be in any position, now, even before the
  subcommand.
- The additional options for test, bench, and dist now appear in the
  help output.
- No more single-letter variable bindings used internally for large
  scopes.
- Don't output the time measurement when just invoking 'x.py'
- Logic is now much more linear.  We build strings up, and then print
  them.
…y bit of manual arg-parsing. Fixed tidy stuff too.
…variable with the same value in two contexts where it was used differently. That's why you don't use "m" as a variable for hundreds of lines in an outer function, and re-use it in closures several times in the same function. Sheesh.
…ang#40860.

The broken condition can be replicated with:

``shell
export MYARCH=x86_64-apple-darwin && mkdir -p build/$MYARCH/subdir &&
touch build/$MYARCH/subdir/file && ln -s build/$MYARCH/subdir/file
build/$MYARCH/subdir/symlink
``

`src/bootstrap/clean.rs` has a custom implementation of removing a tree
`fn rm_rf` that used `std::path::Path::{is_file, is_dir, exists}` while
recursively deleting directories and files.  Unfortunately, `Path`'s
implementation of `is_file()` and `is_dir()` and `exists()` always
unconditionally follow symlinks, which is the exact opposite of standard
implementations of deleting file trees.

It appears that this custom implementation is being used to workaround a
behavior in Windows where the files often get marked as read-only, which
prevents us from simply using something nice and simple like
`std::fs::remove_dir_all`, which properly deletes links instead of
following them.

So it looks like the fix is to use `.symlink_metadata()` to figure out
whether tree items are files/symlinks/directories.  The one corner case
this won't cover is if there is a broken symlink in the "root"
`build/$MYARCH` directory, because those initial entries are run through
`Path::canonicalize()`, which panics with broken symlinks.  So lets just
never use symlinks in that one directory. :-)
This change moves:

1. `libcoretest` into `libcore/tests`
2. `libcollectionstest` into `libcollections/tests`

This is a follow-up to rust-lang#39561.
…0 build' and detect pathological cases like './x.py --option-that-takes-argument clean build'
similar to GCC's __attribute((used))__. This attribute prevents LLVM from
optimizing away a non-exported symbol, within a compilation unit (object file),
when there are no references to it.

This is better explained with an example:

```
#[used]
static LIVE: i32 = 0;

static REFERENCED: i32 = 0;

static DEAD: i32 = 0;

fn internal() {}

pub fn exported() -> &'static i32 {
    &REFERENCED
}
```

Without optimizations, LLVM pretty much preserves all the static variables and
functions within the compilation unit.

```
$ rustc --crate-type=lib --emit=obj symbols.rs && nm -C symbols.o
0000000000000000 t drop::h1be0f8f27a2ba94a
0000000000000000 r symbols::REFERENCED::hb3bdfd46050bc84c
0000000000000000 r symbols::DEAD::hc2ea8f9bd06f380b
0000000000000000 r symbols::LIVE::h0970cf9889edb56e
0000000000000000 T symbols::exported::h6f096c2b1fc292b2
0000000000000000 t symbols::internal::h0ac1aadbc1e3a494
```

With optimizations, LLVM will drop dead code. Here `internal` is dropped because
it's not a exported function/symbol (i.e. not `pub`lic). `DEAD` is dropped for
the same reason. `REFERENCED` is preserved, even though it's not exported,
because it's referenced by the `exported` function. Finally, `LIVE` survives
because of the `#[used]` attribute even though it's not exported or referenced.

```
$ rustc --crate-type=lib -C opt-level=3 --emit=obj symbols.rs && nm -C symbols.o
0000000000000000 r symbols::REFERENCED::hb3bdfd46050bc84c
0000000000000000 r symbols::LIVE::h0970cf9889edb56e
0000000000000000 T symbols::exported::h6f096c2b1fc292b2
```

Note that the linker knows nothing about `#[used]` and will drop `LIVE`
because no other object references to it.

```
$ echo 'fn main() {}' >> symbols.rs
$ rustc symbols.rs && nm -C symbols | grep LIVE
```

At this time, `#[used]` only works on `static` variables.
to match the type signature of the llvm.used variable
it's not related to this feature
[RFC] #[used] attribute

(For an explanation of what this feature does, read the commit message)

I'd like to propose landing this as an experimental feature (experimental as in:
no clear stabilization path -- like `asm!`, `#[linkage]`) as it's low
maintenance (I think) and relevant to the "Usage in resource-constrained
environments" exploration area.

The main use case I see is running code before `main`. This could be used, for
instance, to cheaply initialize an allocator before `main` where the alternative
is to use `lazy_static` to initialize the allocator on its first use which it's
more expensive (atomics) and doesn't work on ARM Cortex-M0 microcontrollers (no
`AtomicUsize` on that platform)

Here's a `std` example of that:

``` rust

unsafe extern "C" fn before_main_1() {
    println!("Hello");
}

unsafe extern "C" fn before_main_2() {
    println!("World");
}

static INIT_ARRAY: [unsafe extern "C" fn(); 2] = [before_main_1, before_main_2];

fn main() {
    println!("Goodbye");
}
```

```
$ rustc -C lto -C opt-level=3 before_main.rs
$ ./before_main
Hello
World
Goodbye
```

In general, this pattern could be used to let *dependencies* run code before
`main` (which sounds like it could go very wrong in some cases). There are
probably other use cases; I hope that the people I have cc-ed can comment on
those.

Note that I'm personally unsure if the above pattern is something we want to
promote / allow and that's why I'm proposing this feature as experimental. If
this leads to more footguns than benefits then we can just axe the feature.

cc @nikomatsakis ^ I know you have some thoughts on having a process for
experimental features though I'm fine with writing an RFC before landing this.

- `dead_code` lint will have to be updated to special case `#[used]` symbols.

- Should we extend `#[used]` to work on non-generic functions?

cc rust-lang/rfcs#1002
cc rust-lang/rfcs#1459
cc @dpc @JinShil
Introduce HashStable trait and base ICH implementations on it.

This PR introduces the `HashStable` trait which marks that a type can be hashed in a way that is stable across multiple compilation sessions. The PR also moves HIR incr. comp. hashing over to implementations of this trait instead of doing this via a HIR visitor. It also provides many `HashStable` implementations that are not used yet (e.g. for MIR types) but soon will be used when we directly hash crate metadata for incr. comp.

I've only done superficial performance measurements but it looks like the new implementation is a bit faster than the current one (due, I suppose, to some bugs I fixed and some unnecessary inefficiencies I removed). Here is the time in seconds for the `compute_incremental_hashes_map` pass for various crates:

|                 |  OLD  |  NEW  |
|:---------------:|:-----:|:-----:|
| libcore         | 0.507 | 0.409 |
| libsyntax       | 0.320 | 0.260 |
| librustc        | 0.730 | 0.611 |
| librustc_driver | 0.024 | 0.015 |

Some notes regarding the implementation:
* Most `HashStable` implementations are provided via the `impl_hash_stable_for!` macro (as suggested by @nikomatsakis). This works out quite well. A custom_derive would have been better but Macros 1.1 are not available in the compiler.
* The trait implementation take care to exhaustively destructure everything they hash so that fields added in the future don't fall through the cracks. This is a bit verbose but I think it's well worth the trouble since we've had quite a few issues with missing fields or visitor callbacks in this area in the past. Most of it is behind the macro anyway.

cc @rust-lang/compiler
r? @nikomatsakis
Emit proper lifetime start intrinsics for personality slots

We currently only emit a single call to the lifetime start intrinsic
for the personality slot alloca. This happens because we create that
call at the time that we create the alloca, instead of creating it each
time we start using it. Because LLVM usually removes the alloca before
the lifetime intrinsics are even considered, this didn't cause any
problems yet, but we should fix this anyway.
…hton

Overhaul Bootstrap (x.py) Command-Line-Parsing & Help Output

While working on rust-lang#40417, I got frustrated with the behavior of x.py and the bootstrap binary it wraps, so I decided to do something about it.  This PR should improve documentation, make the command-line-parsing more flexible, and clean up some of the internals.  No command that worked before should stop working.  At least that's the theory. :-)

This should resolve at least rust-lang#40920 and rust-lang#38373.

Changes:

- No more manual args manipulation -- getopts used everywhere except the one place it's not possible.  As a result, options can be in any position, now, even before the subcommand.
- The additional options for test, bench, and dist now appear in the help output.
- No more single-letter variable bindings used internally for large scopes.
- Don't output the time measurement when just invoking `x.py` or explicitly passing `-h` or `--help`
- Logic is now much more linear.  We build strings up, and then print them.
- Refer to subcommands as subcommands everywhere (some places we were saying "command")
- Other minor stuff.

@alexcrichton This is my first PR. Do I need to do something specific to request reviewers or anything?
frewsxcv added 3 commits April 5, 2017 23:22
Handle symlinks in src/bootstrap/clean.rs (mostly) -- resolves rust-lang#40860.

In response to rust-lang#40860

The broken condition can be replicated with:

```shell
export MYARCH=x86_64-apple-darwin && mkdir -p build/$MYARCH/subdir &&
touch build/$MYARCH/subdir/file && ln -s build/$MYARCH/subdir/file
build/$MYARCH/subdir/symlink
```

`src/bootstrap/clean.rs` has a custom implementation of removing a tree
`fn rm_rf` that used `std::path::Path::{is_file, is_dir, exists}` while
recursively deleting directories and files.  Unfortunately, `Path`'s
implementation of `is_file()` and `is_dir()` and `exists()` always
unconditionally follow symlinks, which is the exact opposite of standard
implementations of deleting file trees.

It appears that this custom implementation is being used to workaround a
behavior in Windows where the files often get marked as read-only, which
prevents us from simply using something nice and simple like
`std::fs::remove_dir_all`, which properly deletes links instead of
following them.

So it looks like the fix is to use `.symlink_metadata()` to figure out
whether tree items are files/symlinks/directories.  The one corner case
this won't cover is if there is a broken symlink in the "root"
`build/$MYARCH` directory, because those initial entries are run through
`Path::canonicalize()`, which panics with broken symlinks.  So lets just
never use symlinks in that one directory. :-)
Move libXtest into libX/tests

This change moves:

1. `libcoretest` into `libcore/tests`
2. `libcollectionstest` into `libcollections/tests`

This is a follow-up to rust-lang#39561.

r? @alexcrichton
…rochenkov

macros: fix bug parsing `#[derive]` invocations

Fixes rust-lang#40962 (introduced in rust-lang#40346).
r? @nrc
@rust-highfive
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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nikomatsakis (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

@frewsxcv frewsxcv closed this Apr 6, 2017
@frewsxcv frewsxcv deleted the rollup branch April 6, 2017 03:24
@Centril Centril added the rollup A PR which is a rollup label Oct 24, 2019
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9 participants