Fix Config::load reading one byte past the end of the config - #131
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alexey-milovidov wants to merge 1 commit into
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Fix Config::load reading one byte past the end of the config#131alexey-milovidov wants to merge 1 commit into
alexey-milovidov wants to merge 1 commit into
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`Config::save` writes `confSize = c - c0`, i.e. the total size of the serialized config including the one-byte length prefix. In `Config::load` the end pointer was computed as `c + confSize` after the prefix byte had already been consumed, so it pointed one byte past the real end of the config blob. The `if (c < c1)` guards that read the optional trailing fields then use a boundary that is one byte too far. For a config that does not contain all of the trailing fields (e.g. data produced by a build with fewer fields) this makes `load` read one field past the end of the config. Compute the end as `c0 + confSize` instead.
This was referenced Sep 1, 2026
ayzk
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Bug fixes only: no compressed-format change and no interface signature change. Covers the reviewed content of #131, #133, #134, #135, #137, #138 and #139, plus the findings ported from the fz branch. #132 is only partly covered -- see the PR body for the four exclusions and the measurement behind each. 31 dataset x algorithm x error-bound combinations are byte-identical to master, and every master-produced file still decompresses to the same bytes.
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Problem
Config::savewrites the config size asconfSize = c - c0, i.e. the total size of the serialized config including the one-byte length prefix it reserves at the start.In
Config::load, the end pointer is computed asc + confSizeafter the prefix byte has already been read, so it ends up one byte past the real end of the config blob:The
if (c < c1)guards that read the optional trailing fields then use a boundary that is one byte too far. For a config that does not contain all of the trailing fields, this makesloadread one field past the end of the config.Fix
Compute the end of the config relative to its start:
No format change; this only corrects the in-memory end pointer used by
load.Context
Found while integrating SZ3 as an experimental compression codec in ClickHouse: ClickHouse/ClickHouse#108788