[fix] Encoding.compatible?: check when swapping args - #9345
Merged
headius merged 1 commit intoMar 31, 2026
Merged
Conversation
Copy link
Copy Markdown
Member
Sorry, something went wrong.
When the first argument is not a String (e.g. Regexp) and the second is, areCompatible check swaps objects so that String is first. However, JRuby also swapped encoding values, which is wrong — CRuby's enc_compatible_latter (encoding.c) only swaps the object/isstr/idx references but keeps enc1/enc2 derived from the original idx values before the swap, so they retain the original argument order. This caused Encoding.compatible?(regexp_eucjp, string_utf8) to return EUC-JP instead of UTF-8 when the string was ASCII-only.
headius
approved these changes
Mar 31, 2026
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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
When the first argument is not a String (e.g. Regexp) and the second is, areCompatible check swaps objects so that String is first.
However, JRuby also swapped encoding values, which is wrong — CRuby's enc_compatible_latter (encoding.c) only swaps the object/isstr/idx references but keeps enc1/enc2 derived from the original idx values before the swap, so they retain the original argument order.
This caused Encoding.compatible?(regexp_eucjp, string_utf8) to return EUC-JP instead of UTF-8 when the string was ASCII-only.