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Merged
matz merged 1 commit into from
Aug 17, 2026
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doc: say what a build converting case by ASCII stops refusing #7231

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8 changes: 6 additions & 2 deletions doc/guides/mrbconf.md
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Expand Up @@ -225,8 +225,8 @@ end
pairs with one other. Without this macro it folds ASCII letters, and a
pattern holding a character that needs one of the Unicode foldings raises
`RegexpError` rather than answering as if the character had no case.
- `MRB_USE_ASCII_CASE` narrows the case half back to ASCII, leaving the
indexing.
- `MRB_USE_ASCII_CASE` narrows the case half back to ASCII, taking the refusal
with it and leaving the indexing.
- If it isn't defined, they only support the US-ASCII encoding.

`MRB_USE_ASCII_CASE`
Expand All @@ -237,6 +237,10 @@ end
- Drops the Unicode case table the build would otherwise carry. That is what
the option is for: a target counting its bytes buys the UTF-8 indexing of
`MRB_UTF8_STRING` without the table beside it.
- Bytes that spell no character are handed back as they stand rather than
refused with `ArgumentError`. That refusal belongs to the walk over
characters, which is the walk this narrows away: what converts instead reads
bytes, and reading bytes asks nothing about what they spell.
- The regexp `i` flag reads that table too, so it narrows with the rest: it
folds ASCII letters, and a pattern holding a character that needs one of the
Unicode foldings raises `RegexpError` rather than answering as if the
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4 changes: 3 additions & 1 deletion doc/limitations.md
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Expand Up @@ -281,7 +281,9 @@ mruby does not have an `Encoding` class. Strings are treated as
byte sequences by default. UTF-8 aware string operations can be
enabled with the `MRB_UTF8_STRING` compile flag, which is also what
makes case conversion follow Unicode rather than ASCII; `MRB_USE_ASCII_CASE`
narrows that half back without giving up the indexing.
narrows that half back without giving up the indexing. A Unicode conversion
refuses bytes that spell no character with `ArgumentError`; one narrowed to
ASCII reads no characters and hands those bytes back untouched.

## Integer Precision Varies by Boxing Mode

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