Bug fix & run overflow correction much more frequently in tests #2603
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Tests failed because it caught the |
* Fix overflow correction when `windowLog < cycleLog`. Previously, we got the correction wrong in this case, and our chain tables and binary trees would be corrupted. Now, we work as long as `maxDist` is a power of two, by adding `MAX(maxDist, cycleSize)` to our indices. * When `ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLY` is defined to non-zero run overflow correction as frequently as allowed without impacting compression ratio. * Enable `ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLY` in `fuzzer` and `zstreamtest` as well as all the OSS-Fuzz fuzzers. This has a 5-10% speed penalty at most, which seems reasonable.
terrelln
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Switch from `-T0` to the default `-T1` which significantly reduces memory usage for level 19 when there are many cores. This fixes 32-bit issues of running out of address space. Fixes facebook#2603.
Cyan4973
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May 4, 2021
| * code much more frequently. This is very inefficient, and should only be | ||
| * used for tests and fuzzers. | ||
| */ | ||
| #ifndef ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLY |
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Should this macro be documented ?
I presume it's only meant to be used by maintainers.
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I don't think it really deserves documentation in any README.md, since it shouldn't be enabled in anything but tests. It is automatically enabled for fuzzers, which have a standard macro FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION.
If we wanted this to be used more widely, I think we would want to have a general debug flag like DEBUGLOG, except for enabling "expensive" checks.
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windowLog < cycleLog. Previously, wegot the correction wrong in this case, and our chain tables and binary
trees would be corrupted. Now, we work as long as
maxDistis a powerof two, by adding
MAX(maxDist, cycleSize)to our indices.ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLYis defined to non-zerorun overflow correction as frequently as allowed without impacting
compression ratio.
ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLYinfuzzerandzstreamtestas well as all the OSS-Fuzz fuzzers. This has a 5-10%speed penalty at most, which seems reasonable.
This change allows both the OSS-Fuzz fuzzers and
fuzzerandzstreamtestto all catch theZSTD_reduceIndex()bug, as well as the assertion failure.