rust: Add a `-C default-linker-libraries` option
This commit adds a new codegen option for the compiler which disables
rustc's passing of `-nodefaultlibs` by default on relevant platforms.
Sometimes Rust is linked with C code which fails to link with
`-nodefaultlibs` and is unnecessarily onerous to get linking correctly
with `-nodefaultlibs`.
An example of this is that when you compile C code with sanitizers and
then pass `-fsanitize=address` to the linker, it's incompatible with
`-nodefaultlibs` also being passed to the linker.
In these situations it's easiest to turn off Rust's default passing of
`-nodefaultlibs`, which was more ideological to start with than
anything! Preserving the default is somewhat important but having this
be opt-in shouldn't cause any breakage.
Closes#54237
Fix Once perf regression
Because `call_once` is generic, but `is_completed` is not, we need
`#[inline]` annotation to allow LLVM to inline `is_completed` into
`call_once` in downstream crates.
cc https://github.com/rust-lang/rust/pull/53027/files#r221418859
Don't lint non-extern-prelude extern crate's in Rust 2018.
Fixes#54381 by silencing the lint telling users to remove `extern crate` when `use` doesn't work.
r? @alexcrichton cc @petrochenkov @nikomatsakis @Centril
Add a per-tree error cache to the obligation forest
This implements part of what @nikomatsakis mentioned in https://github.com/rust-lang/rust/pull/30533#issuecomment-170705871:
> 1. If you find that a new obligation is a duplicate of one already in the tree, the proper processing is:
> * if that other location is your parent, you should abort with a cycle error (or accept it, if coinductive)
> * if that other location is not an ancestor, you can safely ignore the new obligation
In particular it implements the "if that other location is your parent accept it, if coinductive" part. This fixes#40827.
I have to say that I'm not 100% confident that this is rock solid. This is my first pull request 🎉, and I didn't know anything about the trait resolver before this. In particular I'm not totally sure that comparing predicates is enough (for instance, do we need to compare `param_env` as well?). Also, I'm not sure what @nikomatsakis mentions [here](https://github.com/rust-lang/rust/issues/30977#issue-127091096), but it might be something that affects this PR:
> In particular, I am wary of getting things wrong around inference variables! We can always add things to the set in their current state, and if unifications occur then the obligation is just kind of out-of-date, but I want to be sure we don't accidentally fail to notice that something is our ancestor. I decided this was subtle enough to merit its own PR.
Anyway, go ahead and review 🙂.
Ref #30977.
# Performance
We are now copying vectors around, so I decided to do some benchmarking. A simple benchmark shows that this does not seem to affect performance in a measurable way:
I ran `cargo clean && cargo build` 20 times on actix-web (84b27db) and these are the results:
```text
rustc master:
Mean Std.Dev. Min Median Max
real 66.637 2.996 57.220 67.714 69.314
user 307.293 14.741 258.093 312.209 320.702
sys 12.524 0.653 10.499 12.726 13.193
rustc fix-bug-overflow-send:
Mean Std.Dev. Min Median Max
real 66.297 4.310 53.532 67.516 70.348
user 306.812 22.371 236.917 314.748 326.229
sys 12.757 0.952 9.671 13.125 13.544
```
I will do a more comprehensive benchmark (compiling rustc stage1) and post the results.
r? @nikomatsakis, @nnethercote
PS: It is better to review this commit-by-commit.
Enable NLL compare mode for more tests
Most of these tests were disabled due to NLL bugs that have since been fixed. A few needed updating for NLL.
r? @nikomatsakis
don't elide lifetimes in paths in librustc/
In light of the "Apply to rustc" checkbox on #44524 and @nikomatsakis's [recent comment about regularly wanting visual indication of elided lifetimes in types](https://github.com/rust-lang/rust/issues/44524#issuecomment-414663773), I was curious to see what it would look like if we turned the `elided_lifetimes_in_path` lint on in at least one crate in the codebase (I chose librustc). Given that I couldn't figure out how to get `cargo fix` work with the build system, this arguably wasn't a very efficient use of my time, but once I started, the conjunction of moral law and the sunk cost fallacy forced me to continue.
This is mostly applying the `<'_>` suggestions issued by the lint, but there were a few places where I named the lifetimes (_e.g._, `<'a, 'gcx, 'tcx>` on `TyCtxt`) in order to match style with surrounding code.
r? @nikomatsakis
Do not put noalias annotations by default
This will be re-enabled sooner or later depending on results of further
investigation.
Fixes#54462
Beta backport is: #54640
r? @nikomatsakis
This seemed like a good way to kick the tires on the
elided-lifetimes-in-paths lint (#52069)—seems to work! This was also
pretty tedious—it sure would be nice if `cargo fix` worked on this
codebase (#53896)!
A few cleanups and minor improvements to typeck
This PR complements https://github.com/rust-lang/rust/pull/54533, which was limited to `check`.
- change a few `push` loops to `extend`s
- prefer `to_owned` to `to_string` for string literals
- prefer `if let` to `match` where only one branch matters
- a few other minor improvements
- whitespace fixes
Currently we ship sanitizer libraries as they're built, but these names
unfortunately conflict with the names of the sanitizer libraries
installed on the system. If a crate, for example, links in C code that
wants to use the system sanitizer and the Rust code doesn't use
sanitizers at all, then using `cargo` may accidentally pull in the
Rust-installed sanitizer library due to a conflict in names.
This change is intended to be entirely transparent for Rust users of
sanitizers, it should only hopefully improve our story with other users!
Closes#54134
This commit adds a new codegen option for the compiler which disables
rustc's passing of `-nodefaultlibs` by default on relevant platforms.
Sometimes Rust is linked with C code which fails to link with
`-nodefaultlibs` and is unnecessarily onerous to get linking correctly
with `-nodefaultlibs`.
An example of this is that when you compile C code with sanitizers and
then pass `-fsanitize=address` to the linker, it's incompatible with
`-nodefaultlibs` also being passed to the linker.
In these situations it's easiest to turn off Rust's default passing of
`-nodefaultlibs`, which was more ideological to start with than
anything! Preserving the default is somewhat important but having this
be opt-in shouldn't cause any breakage.
Closes#54237
use closure def-id in returns, but base def-id in locals
The refactorings to handle `let x: impl Trait` wound up breaking `impl Trait` in closure return types. I think there are some deeper problems with the code in question, but this a least should make @eddyb's example work.
Fixes#54593
r? @eddyb
