Recompilation regression on cdylib on toolchain mixing #15209
Description
Problem
Hi,
On a library crate
Cargo.toml
[package]
name = "crate_name"
version = "0.1.0"
edition = "2021"
[lib]
crate-type = ["lib", "cdylib"]
lib.rs
/// ```rust
/// crate_name::a();
/// ```
pub fn a() {}
Makefile
stable:
cargo +1.84.1 test
nightly:
cargo +nightly-2024-12-15 test
broken:
cargo clean
make stable
make nightly
make stable
make broken fails on the 2nd call of the stable test doctest compilation with error[E0514]: found crate `crate_name` compiled by an incompatible version of rustc
Using +nightly-2024-12-14 instead of +nightly-2024-12-15 fixes the issue (cargo diff 20a4432...769f622)
As of nightly-2025-02-19, this error still appears.
Does not fail with either crate-type = ["lib"] or crate-type = ["cdylib"]
This looks like a cargo regression on compilation artifacts reuse.
I'm not sure what guarantees cargo make when mixing toolchains without cleaning.
When also using rlib, there is also error (didn't first appear with nightly-2024-12-15, already present in nightly-2024-12-14):
thread 'main' panicked at src/cargo/core/compiler/fingerprint/mod.rs:1160:13:
assertion failed: mtimes.insert(output.clone(), mtime).is_none()
With crate-type = ["lib", "rlib"], make broken fails on the 2nd call of the stable test compilation
With crate-type = ["lib", "cdylib", "rlib"], make broken fails on the 1st call of the nightly test compilation
With crate-type = ["cdylib", "rlib"], we get the error[E0514] seen before
With crate-type = ["rlib"], no fail
I can open a separate issue if needed for this different error
Steps
No response
Possible Solution(s)
Running cargo clean between compilation when changing toolchain
Notes
No response
Version
$ cargo +nightly-2024-12-15 --version
cargo 1.85.0-nightly (769f622e1 2024-12-14)
And later versions