Reader: fix fill when implementation writes to reader directly #24677
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rohlem
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Aug 3, 2025
gooncreeper
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`r.end += stream` is the same as `r.end = r.end + stream`, which causes `r.end` to be analyzed before stream is called and that value is added to. However, the implementation is allowed to write directly to `r` (for example, inflate does this to keep a window) and update `r.end` independently, causing the outdated value to be added to.
gooncreeper
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better fix: #24706 |
andrewrk
reviewed
Aug 6, 2025
| .stream = struct { | ||
| fn stream(r: *Reader, _: *Writer, _: Limit) StreamError!usize { | ||
| @memset(r.buffer[r.seek..], 0xff); | ||
| r.end = r.buffer.len; |
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actually this is not a valid use of the API
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@andrewrk Apologies, though what is invalid with it? The vtable doc comment says you can do this and flate.Decompress.streamIndirectInner takes advantage of this.
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r.end += streamis the same asr.end = r.end + stream, which causesr.endto be analyzed before stream is called and that value is added to. However, the implementation is allowed to write directly tor(for example, inflate does this to keep a window) and updater.endindependently, causing the outdated value to be added to.Progress towards #24695 (fixes the first two issues)