error on non-rustic ABIs using unsized parameters #148302
Open
+228
−4
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
rustbot
added
S-waiting-on-review
folkertdev
commented
Oct 30, 2025
Comment on lines
+59
to
+60
| extern "C" fn c_polymorphic<T: ?Sized>(_: T) {} | ||
| //~^ ERROR this function definition uses unsized type `[u8]` which is not supported with the chosen ABI |
There was a problem hiding this comment.
The mention of [u8] here is a bit unfortunate, but I think it's the best we can do.
folkertdev
force-pushed
the
non-rustic-unsized
branch
from
b594a4e to
52bfde2
Compare
|
Would have been nice if we could also get rid of the checks for unsized params in the call conv calculation code, but alas this checks runs after the call conv calculation code, so removing those checks would probably cause issues. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
tracking issue: #48055
This came up in #144529 (comment).
The idea is that the layout of an unsized type is unstable (following the rust layout rules), and hence stable ABIs should not use unsized types. On stable, unsized types (or generics with a
?Sizedbound) are not accepted as parameters, so the errors introduced by this PR can only be observed when the unstableunsized_fn_paramsfeature is enabled.r? @bjorn3
cc @RalfJung