Fix NCountWriteBound #2779
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Fix NCountWriteBound #2779
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Fix looks good ! Does that seem possible to add one test case that triggers this situation (and fails without this PR) ? |
terrelln
reviewed
Sep 21, 2021
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Test case added (fails when fuzzer.c is built with ASAN) |
Cyan4973
approved these changes
Sep 22, 2021
terrelln
approved these changes
Sep 22, 2021
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OSS-Fuzz discovered an error in FSE_writeNCount().
Problem distribution:
Write: 6, 6, 5, 5, 5, 5, 5, 5, 5, 5, 1 bits
Total: 53 bits
But, main loop prior to flush currently writes 8 bytes rather than 7. Why?
BitCount initialized at 4, and first two symbols require an additional bit each, so we actually need 4 + 2 + 53 = 59 bits.
Currently calculated bound = 55 bits ((10+1)*5). So we need to add 4 + 2 to this bound.