Fix c_void_returns lint warning

[jchlanda]

Description

Nightly added a lint warning on c_void returns this patch removes the return type to implicitly return ().

See a sample failing job here: https://github.com/rust-lang/libc/actions/runs/28580626120/job/84739740809?pr=5065#step:9:2195

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[jchlanda]

cc: @folkertdev

[folkertdev]

there is one more at

--- a/src/teeos/mod.rs
+++ b/src/teeos/mod.rs
@@ -49,7 +49,7 @@ pub type clockid_t = c_int;
 
 pub type suseconds_t = c_long;
 
-pub type once_fn = extern "C" fn() -> c_void;
+pub type once_fn = extern "C" fn();
 
 pub type pthread_once_t = c_int;

[folkertdev]

also this is technically a breaking change? but the old signature was incorrect so idk.

[tgross35]

also this is technically a breaking change? but the old signature was incorrect so idk.

Technically yes, but the relevant platforms are all T3 and the return type is kind of useless so this will be fine.

[jchlanda]

there is one more at

--- a/src/teeos/mod.rs
+++ b/src/teeos/mod.rs
@@ -49,7 +49,7 @@ pub type clockid_t = c_int;
 
 pub type suseconds_t = c_long;
 
-pub type once_fn = extern "C" fn() -> c_void;
+pub type once_fn = extern "C" fn();
 
 pub type pthread_once_t = c_int;

I wasn't sure about that one, as opposed to the other places, this is a function pointer type. The compiler doesn't seem to be complaining about it: https://rust.godbolt.org/z/3xTezqxrY
And the jobs are all 🟢

[tgross35]

I assume the lint just doesn't catch function pointer types (yet), it would be good to make that change here as well

[folkertdev]

It's odd, based on the tests the lint should fire

https://github.com/rust-lang/rust/blob/c397dae808f70caebab1fc4e11b3edf7e59f58c7/tests/ui/lint/c-void-returns.rs#L20

So maybe that file does not get run in CI? Anyhow, further evidence that we should make the change there too.

[jchlanda]

Done now, thank you.

[tgross35]

Thanks!

View changes since this review