This patch adds a `-Z linker-flavor` flag to rustc which can be used to invoke
the linker using a different interface.
For example, by default rustc assumes that all the Linux targets will be linked
using GCC. This makes it impossible to use LLD as a linker using just `-C
linker=ld.lld` because that will invoke LLD with invalid command line
arguments. (e.g. rustc will pass -Wl,--gc-sections to LLD but LLD doesn't
understand that; --gc-sections would be the right argument)
With this patch one can pass `-Z linker-flavor=ld` to rustc to invoke the linker
using a LD-like interface. This way, `rustc -C linker=ld.lld -Z
linker-flavor=ld` will invoke LLD with the right arguments.
`-Z linker-flavor` accepts 4 different arguments: `em` (emcc), `ld`,
`gcc`, `msvc` (link.exe). `em`, `gnu` and `msvc` cover all the existing linker
interfaces. `ld` is a new flavor for interfacing GNU's ld and LLD.
This patch also changes target specifications. `linker-flavor` is now a
mandatory field that specifies the *default* linker flavor that the target will
use. This change also makes the linker interface *explicit*; before, it used to
be derived from other fields like linker-is-gnu, is-like-msvc,
is-like-emscripten, etc.
Another change to target specifications is that the fields `pre-link-args`,
`post-link-args` and `late-link-args` now expect a map from flavor to linker
arguments.
``` diff
- "pre-link-args": ["-Wl,--as-needed", "-Wl,-z,-noexecstack"],
+ "pre-link-args": {
+ "gcc": ["-Wl,--as-needed", "-Wl,-z,-noexecstack"],
+ "ld": ["--as-needed", "-z,-noexecstack"],
+ },
```
[breaking-change] for users of custom targets specifications
#[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");
}
#[link_section = ".init_arary"]
#[used]
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
rustdoc: Use pulldown-cmark for Markdown HTML rendering
Instead of rendering all of the HTML in rustdoc this relies on
pulldown-cmark's `push_html` to do most of the work. A few iterator
adapters are used to make rustdoc specific modifications to the output.
This also fixes MarkdownHtml and link titles in plain_summary_line.
https://ollie27.github.io/rust_doc_test/ is the docs built with this change and #41111.
Part of #40912.
cc @GuillaumeGomez
r? @steveklabnik
don't try to blame tuple fields for immutability
Tuple fields don't have an `&T` in their declaration that can be changed
to `&mut T` - skip them..
Fixes#41104.
r? @nikomatsakis
Instead of rendering all of the HTML in rustdoc this relies on
pulldown-cmark's `push_html` to do most of the work. A few iterator
adapters are used to make rustdoc specific modifications to the output.
This also fixes MarkdownHtml and link titles in plain_summary_line.
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.
Make 'overlapping_inherent_impls' lint a hard error
This is ought to be implemented in PR #40728. Unfortunately, when I rebased the PR to resolve merge conflict, the "hard error" code disappeared. This PR complements the initial PR.
Now the following rust code gives the following error:
```rust
struct Foo;
impl Foo {
fn id() {}
}
impl Foo {
fn id() {}
}
fn main() {}
```
```
error[E0592]: duplicate definitions with name `id`
--> /home/topecongiro/test.rs:4:5
|
4 | fn id() {}
| ^^^^^^^^^^ duplicate definitions for `id`
...
8 | fn id() {}
| ---------- other definition for `id`
error: aborting due to previous error
```
Properly adjust filenames when multiple emissions
Fixes#40993
Should backport just fine to beta but not sure if we want to do this since this is quite old stable regression.
Do not recommend private fields called as method
```rust
error: no method named `dog_age` found for type `animal::Dog` in the current scope
--> $DIR/private-field.rs:26:23
|
26 | let dog_age = dog.dog_age();
| ^^^^^^^ private field, not a method
```
Fix#27654.
rustc: Stabilize the `#![windows_subsystem]` attribute
This commit stabilizes the `#![windows_subsystem]` attribute which is a
conservative exposure of the `/SUBSYSTEM` linker flag on Widnows platforms. This
is useful for creating applications as well as console programs.
Closes#37499
This commit stabilizes the `#![windows_subsystem]` attribute which is a
conservative exposure of the `/SUBSYSTEM` linker flag on Widnows platforms. This
is useful for creating applications as well as console programs.
Closes#37499
