Support raw-dylib link kind on ELF
raw-dylib is a link kind that allows rustc to link against a library without having any library files present.
This currently only exists on Windows. rustc will take all the symbols from raw-dylib link blocks and put them in an import library, where they can then be resolved by the linker.
While import libraries don't exist on ELF, it would still be convenient to have this same functionality. Not having the libraries present at build-time can be convenient for several reasons, especially cross-compilation. With raw-dylib, code linking against a library can be cross-compiled without needing to have these libraries available on the build machine. If the libc crate makes use of this, it would allow cross-compilation without having any libc available on the build machine. This is not yet possible with this implementation, at least against libc's like glibc that use symbol versioning. The raw-dylib kind could be extended with support for symbol versioning in the future.
This implementation is very experimental and I have not tested it very well. I have tested it for a toy example and the lz4-sys crate, where it was able to successfully link a binary despite not having a corresponding library at build-time.
I was inspired by Björn's comments in https://internals.rust-lang.org/t/bundle-zig-cc-in-rustup-by-default/22096/27
Tracking issue: #135694
r? bjorn3
try-job: aarch64-apple
try-job: x86_64-msvc-1
try-job: x86_64-msvc-2
try-job: test-various
The run-make test suite contains tests which are the most flexible out of all
the rust-lang/rust test suites. run-make
tests can basically contain arbitrary code, and are supported by the
run_make_support library.
Infrastructure
There are two kinds of run-make tests:
The new rmake.rs version: this allows run-make tests to be written in Rust
(with rmake.rs as the main test file).
The legacy Makefile version: this is what run-make tests were written with
before support for rmake.rs was introduced.
The implementation for collecting and building the rmake.rs recipes (or
Makefiles) are in
src/tools/compiletest/src/runtest.rs,
in run_rmake_v2_test and run_rmake_legacy_test.
Rust-based run-make tests: rmake.rs
The setup for the rmake.rs version is a 3-stage process:
First, we build the run_make_support library in bootstrap as a tool lib.
Then, we compile the rmake.rs "recipe" linking the support library and its
dependencies in, and provide a bunch of env vars. We setup a directory
structure within build/<target>/test/run-make/
<test-name>/
rmake.exe # recipe binary
rmake_out/ # sources from test sources copied over
and copy non-rmake.rs input support files over to rmake_out/. The
support library is made available as an extern prelude.
Finally, we run the recipe binary and set rmake_out/ as the working
directory.
Formatting
Note that files under tests/ are not formatted by ./x fmt,
use rustfmt tests/path/to/file.rs to format a specific file if desired.
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