warning: output filename collision.

[Wyvern]

Problem

Got lots of warnings like below

warning: output filename collision.
The lib target `cfg_if` in package `cfg-if v1.0.0` has the same output filename as the lib target `cfg_if` in package `cfg-if v1.0.0`.
Colliding filename is: target/debug/deps/libcfg_if-b07c5e93d2d15f7e.rlib
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.

Steps

no warnings:

• stable
• cargo 1.81.0-nightly (a515d46 2024-07-02)

warnings:

• cargo 1.81.0-nightly (154fdac 2024-07-07) start to pop up warnings.

Possible Solution(s)

No response

Notes

Version

nightly-x86_64-apple-darwin

[epage]

Could you provide reproduction steps?

[Wyvern]

I don't know what lead to this warnings, compiling almost all of my rust projects using latest cargo version cargo buildwill pop up some warnings.

For example for one project, the full list of warnings is:

warning: output filename collision.
The lib target `cfg_if` in package `cfg-if v1.0.0` has the same output filename as the lib target `cfg_if` in package `cfg-if v1.0.0`.
Colliding filename is: /debug/deps/libcfg_if-b07c5e93d2d15f7e.rlib
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.
warning: output filename collision.
The lib target `cfg_if` in package `cfg-if v1.0.0` has the same output filename as the lib target `cfg_if` in package `cfg-if v1.0.0`.
Colliding filename is: /debug/deps/libcfg_if-b07c5e93d2d15f7e.rmeta
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.
warning: output filename collision.
The lib target `phf_shared` in package `phf_shared v0.10.0` has the same output filename as the lib target `phf_shared` in package `phf_shared v0.10.0`.
Colliding filename is: /debug/deps/libphf_shared-e4838e974e16f5df.rlib
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.
warning: output filename collision.
The lib target `phf_shared` in package `phf_shared v0.10.0` has the same output filename as the lib target `phf_shared` in package `phf_shared v0.10.0`.
Colliding filename is: /debug/deps/libphf_shared-e4838e974e16f5df.rmeta
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.
warning: output filename collision.
The lib target `siphasher` in package `siphasher v0.3.11` has the same output filename as the lib target `siphasher` in package `siphasher v0.3.11`.
Colliding filename is: /debug/deps/libsiphasher-f5cde03e2e9cf64a.rlib
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.
warning: output filename collision.
The lib target `siphasher` in package `siphasher v0.3.11` has the same output filename as the lib target `siphasher` in package `siphasher v0.3.11`.
Colliding filename is: /debug/deps/libsiphasher-f5cde03e2e9cf64a.rmeta
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.

As you see, every warning duplicate itself; and why only compiling cfg_if, phf_shared, siphasher generate warning but others not.

[epage]

Also, on top of reproduction steps, can you reproduce this on stable Rust? If only testing with nightlies, happen to know what was the last nightly you used without these warnings?

[Wyvern]

Stable Rust is fine.

As noted in the original post,

cargo 1.81.0-nightly (https://github.com/rust-lang/cargo/commit/a515d463427b3912ec0365d106791f88c1c14e1b 2024-07-02) works fine without any warnings

cargo 1.81.0-nightly (https://github.com/rust-lang/cargo/commit/154fdac39ae9629954e19e9986fd2cf2cdd8d964 2024-07-07) start to pop up warnings.

[Wyvern]

After some investigation, found this warning is relate to Cargo's

[unstable]
target-applies-to-host = true
host-config = true

comment them out warning disappears.

[aeubanks]

We're also seeing this after rust-lang/rust#128083, the exact symptoms mentioned in #7859. We also have a similar cargo.config, and not using that config makes the build succeed.

I could reproduce this by setting the CARGO_HOME env var to a directory containing the following config.toml:

[unstable]
target-applies-to-host = true
host-config = true

and running CARGO_HOME="/tmp/asdf" ./x.py build

[weihanglo]

That behavior might come from #13900. I need to dig deeper.

and not using that config makes the build succeed.

@aeubanks Do you mean that you are blocked due to this "bug"? Could you provide a minimal reproducion so I can look into?

[aeubanks]

Yes we are blocked on upgrading Rust due to this. I don't have a more minimal repro than what I described above. I suspect that it will require building the standard library anyway, as opposed to some smaller standalone project.

[aeubanks]

Sorry, to clarify, this is building https://github.com/rust-lang/rust