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Use rust-lld instead of avr-gcc as the linker

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This fixes the [build error] caused by the `avr-gcc` (used as linker)
not being available in the Rust CI. This is a viable solution, which
shows the wrong/right behavior and, since no functions from `libgcc` are
called, does not produce errors. This was discussed [here]. Another
small problem is, that `lld` doesn't link the correct startup-code by
default. This is not a problem for this test (since it does not actually
use anything the startup code is needed for (no variables, no stack, no
interrupts)), but this causes the `main`-function to be removed by the
default flag `--gc-sections`. Therefore the `rmake`-driver also adds the
linker flag `--entry=main` to mark the `main`-function as the entry
point and thus preventing it from getting removed. The code would work
on a real AVR device.

[build error]: https://github.com/rust-lang/rust/pull/131755#issuecomment-2415127952
[here]: https://github.com/rust-lang/rust/pull/131755#issuecomment-2416469675
This commit is contained in:
Julian Frimmel 2024-10-15 23:07:00 +02:00
parent bb8db13892
commit a35ed2f9eb
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1 changed files with 9 additions and 0 deletions
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9
tests/run-make/avr-rjmp-offset/rmake.rs
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@ -1,4 +1,5 @@
//@ needs-llvm-components: avr
//@ needs-rust-lld
//! Regression test for #129301/llvm-project#106722 within `rustc`.
//!
//! Some LLVM-versions had wrong offsets in the local labels, causing the first
@ -17,6 +18,13 @@ fn main() {
.opt_level("s")
.panic("abort")
.target("avr-unknown-gnu-atmega328")
// normally one links with `avr-gcc`, but this is not available in CI,
// hence this test diverges from the default behavior to enable linking
// at all, which is necessary for the test (to resolve the labels). To
// not depend on a special linker script, the main-function is marked as
// the entry function, causing the linker to not remove it.
.linker("rust-lld")
.link_arg("--entry=main")
.output("compiled")
.run();
@ -35,6 +43,7 @@ fn main() {
// fore the relative jump has an impact on the label offset. Old versions
// of the Rust compiler did produce a label `rjmp .-4` (misses the first
// instruction in the loop).
assert!(disassembly.contains("<main>"), "no main function in output");
disassembly
.trim()
.lines()