Create `_imp__` symbols also when doing ThinLTO
When generating a rlib crate on Windows we create `dllimport` / `_imp__` symbols for each global. This effectively makes the rlib contain an import library for itself and allows them to both be dynamically and statically linked. However when doing ThinLTO we do not generate these and thus we end up with missing symbols. Microsoft's `link` can fix these up (and emits warnings), but `lld` seems to currently be unable to.
This PR also does this generation for ThinLTO avoiding those issues with `lld` and also avoids the warnings on `link`.
This is an workaround for https://github.com/rust-lang/rust/issues/81408.
cc `@lqd`
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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