-Z linker-flavor
(Please read the commit message first)
This PR is an alternative to rust-lang/rust#36120 (internal lld linker). The
main goal of this PR is to make it *possible* to use LLD as a linker to allow
out of tree experimentation. Now that LLD is going to be shipped with LLVM 4.0,
it should become easier to get a hold of LLD (hopefully, it will be packaged by
Linux distros soon).
Since LLD is a multiarch linker, it has the potential to make cross compilation
easier (less tools need to be installed). Supposedly, LLD is also faster than
the gold linker so LLD may improve build times where link times are significant
(e.g. 100% incremental compilation reuse).
The place where LLD shines is at linking Rust programs that don't depend on
system libraries. For example, here's how you would link a bare metal ARM
Cortex-M program:
```
$ xargo rustc --target thumbv7m-none-eabi -- -Z linker-flavor=ld -C linker=ld.lld -Z print-link-args
"ld.lld" \
"-L" \
"$XARGO_HOME/lib/rustlib/thumbv7m-none-eabi/lib" \
"$PWD/target/thumbv7m-none-eabi/debug/deps/app-de1f86df314ad68c.0.o" \
"-o" \
"$PWD/target/thumbv7m-none-eabi/debug/deps/app-de1f86df314ad68c" \
"--gc-sections" \
"-L" \
"$PWD/target/thumbv7m-none-eabi/debug/deps" \
"-L" \
"$PWD/target/debug/deps" \
"-L" \
"$XARGO_HOME/lib/rustlib/thumbv7m-none-eabi/lib" \
"-Bstatic" \
"-Bdynamic" \
"$XARGO_HOME/lib/rustlib/thumbv7m-none-eabi/lib/libcore-11670d2bd4951fa7.rlib"
$ file target/thumbv7m-none-eabi/debug/app
app: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, not stripped, with debug_info
```
This doesn't require installing the `arm-none-eabi-gcc` toolchain.
Even cooler (but I'm biased) is that you can link Rust programs that use
[`steed`] (`steed` is a `std` re-implementation free of C dependencies for Linux
systems) instead of `std` for a bunch of different architectures without having
to install a single cross toolchain.
[`steed`]: https://github.com/japaric/steed
```
$ xargo rustc --target aarch64-unknown-linux-steed --example hello --release -- -Z print-link-args
"ld.lld" \
"-L" \
"$XARGO_HOME/lib/rustlib/aarch64-unknown-linux-steed/lib" \
"$PWD/target/aarch64-unknown-linux-steed/release/examples/hello-80c130ad884c0f8f.0.o" \
"-o" \
"$PWD/target/aarch64-unknown-linux-steed/release/examples/hello-80c130ad884c0f8f" \
"--gc-sections" \
"-L" \
"$PWD/target/aarch64-unknown-linux-steed/release/deps" \
"-L" \
"$PWD/target/release/deps" \
"-L" \
"$XARGO_HOME/lib/rustlib/aarch64-unknown-linux-steed/lib" \
"-Bstatic" \
"-Bdynamic" \
"/tmp/rustc.lAybk9Ltx93Q/libcompiler_builtins-589aede02de78434.rlib"
$ file target/aarch64-unknown-linux-steed/release/examples/hello
hello: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, not stripped, with debug_info
```
All these targets (architectures) worked with LLD:
- [aarch64-unknown-linux-steed](https://github.com/japaric/steed/blob/lld/docker/aarch64-unknown-linux-steed.json)
- [arm-unknown-linux-steedeabi](https://github.com/japaric/steed/blob/lld/docker/arm-unknown-linux-steedeabi.json)
- [arm-unknown-linux-steedeabihf](https://github.com/japaric/steed/blob/lld/docker/arm-unknown-linux-steedeabihf.json)
- [armv7-unknown-linux-steedeabihf](https://github.com/japaric/steed/blob/lld/docker/armv7-unknown-linux-steedeabihf.json)
- [i686-unknown-linux-steed](https://github.com/japaric/steed/blob/lld/docker/i686-unknown-linux-steed.json)
- [mips-unknown-linux-steed](https://github.com/japaric/steed/blob/lld/docker/mips-unknown-linux-steed.json)
- [mipsel-unknown-linux-steed](https://github.com/japaric/steed/blob/lld/docker/mipsel-unknown-linux-steed.json)
- [powerpc-unknown-linux-steed](https://github.com/japaric/steed/blob/lld/docker/powerpc-unknown-linux-steed.json)
- [powerpc64-unknown-linux-steed](https://github.com/japaric/steed/blob/lld/docker/powerpc64-unknown-linux-steed.json)
- [x86_64-unknown-linux-steed](https://github.com/japaric/steed/blob/lld/docker/x86_64-unknown-linux-steed.json)
---
The case where lld is unergonomic is linking binaries that depend on system
libraries. Like "Hello, world" for `x86_64-unknown-linux-gnu`. Because you have
to pass as linker arguments: the path to the startup objects, the path to the
dynamic linker and the library search paths. And all those are system specific
so they can't be encoded in the target itself.
```
$ cargo \
rustc \
--release \
-- \
-C \
linker=ld.lld \
-Z \
linker-flavor=ld \
-C \
link-args='-dynamic-linker /lib64/ld-linux-x86-64.so.2 -L/usr/lib -L/usr/lib/gcc/x86_64-pc-linux-gnu/6.3.1 /usr/lib/Scrt1.o /usr/lib/crti.o /usr/lib/gcc/x86_64-pc-linux-gnu/6.3.1/crtbeginS.o /usr/lib/gcc/x86_64-pc-linux-gnu/6.3.1/crtendS.o /usr/lib/crtn.o'
```
---
Another case where `-Z linker-flavor` may come in handy is directly calling
Solaris' linker which is also a multiarch linker (or so I have heard). cc
@binarycrusader
cc @alexcrichton
Heads up: [breaking-change] due to changes in the target specification format.
Added doc comments for fmt::Result
Added doc comments for fmt::Result in regards to item 3 in issue #29355. I'm not certain that this is all that's needed but I think it's a good starting point on this item.
Apply clippy's doc_markdown improvements to libcollections
Since my last PR led to linker failure, I'm now taking much smaller steps.
This only fixes some doc_markdown warnings; as they are in comments only,
we shouldn't get any problems building.
Since my last PR led to linker failure, I'm now taking much smaller steps.
This only fixes some doc_markdown warnings; as they are in comments only,
we shouldn't get any problems building.
Previously, rustdoc's LibEmbargoVisitor unconditionally visited the
child modules of an external crate. If a module re-exported its parent
via 'pub use super::*', rustdoc would re-walk the parent, leading to
infinite recursion.
This commit makes LibEmbargoVisitor store already visited modules in an
FxHashSet, ensuring that each module is only walked once.
Fixes#40936
Update ChildStderr docs to be clearer
Before the docs only had a line about where it was found and that it was
a handle to stderr. This commit changes it so that the summary second line is
removed and that it's a bit clearer about what can be done with it. Part of
#29370
Use ty::layout for ABI computation instead of LLVM types.
This is the first step in creating a backend-agnostic library for computing call ABI details from signatures.
I wanted to open the PR *before* attempting to move `cabi_*` from trans to avoid rebase churn in #39999.
**EDIT**: As I suspected, #39999 needs this PR to fully work (see https://github.com/rust-lang/rust/pull/39999#issuecomment-287723379).
The first 3 commits add more APIs to `ty::layout` and replace non-ABI uses of `sizing_type_of`.
These APIs are probably usable by other backends, and miri too (cc @stoklund @solson).
The last commit rewrites `rustc_trans::cabi_*` to use `ty::layout` and new `rustc_trans::abi` APIs.
Also, during the process, a couple trivial bugs were identified and fixed:
* `msp430`, `nvptx`, `nvptx64`: type sizes *in bytes* were compared with `32` and `64`
* `x86` (`fastcall`): `f64` was incorrectly not treated the same way as `f32`
Although not urgent, this PR also uses the more general "homogenous aggregate" logic to fix#32045.
Implement .rfind() for slice iterators Iter and IterMut
Just like the forward case find, implement rfind explicitly for slice iterators Iter and IterMut.
Add safe wrapper for atomic_compilerfence intrinsics
This PR adds a proposed safe wrapper for the `atomic_singlethreadfence_*` intrinsics introduced by [RFC #888](https://github.com/rust-lang/rfcs/pull/888). See #41091 for further discussion.
Just like DragonFlyBSD, using the same symbols as the system allocator will
result in a segmentation fault at runtime due to allocator mismatches.
As such, prefix the jemalloc symbols instead.
borrowck::mir::dataflow: ignore unwind edges of empty drops
This avoids creating drop flags in many unnecessary situations.
Fixes#41110.
r? @nagisa
beta-nominating because regression. However, that is merely a small perf regression and codegen changes are always risky, so we might let this slide for 1.17.
Fixed ICEs with pattern matching in const expression
Fixed 2 ICEs with when pattern matching inside a constant expression.
Both of these ICEs now resolve to an appropriate compiler error.
1. ICE was caused by a compiler bug to implement discriminant const qualify.
I removed this intentionally thrown bug and changed it to a FIXME as the unimplemented expression type is handled as a compiler error elsewhere.
2. ICE was caused during a drop check when checking if a variable lifetime outlives the current scope if there was no parent scope .
I've changed it to stop checking if there is no parent scope for the current scope. It is valid syntax for a const variable to be assigned a match expression with no enclosing scope.
The ICE seemed to mainly be used as a defensive check for bugs elsewhere.
Fixes#38199.
Fixes#31577.
Fixes#29093.
Fixes#40012.
