C++: Avoid using nullValue predicate (rc/1.19)#575
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The `nullValue` predicate performs a slow custom data-flow analysis to find possible null values. It's so slow that it timed out after 1200s on Wireshark. In `UnsafeCreateProcessCall.ql`, the values found with `nullValue` were used as sources in another data-flow analysis. By using the `NullValue` class as sink instead of `nullValue`, we avoid the slow-down of doing data flow twice. The `NullValue` class is essentially the base case of `nullValue`. Confusing names, yes.
geoffw0
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Nov 30, 2018
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LGTM. Improvement for me is 921s -> 741s, with the latter probably representing a lot of stuff that would be cached. bbSuccessorEntryReachesDefOrUse is no longer an expensive predicate. I couldn't find any real-world results to verify correctness, but the (fairly thorough) tests pass.
cklin
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May 23, 2022
Remove `CODEQL_REDUCE_FILES_FOLDERS_RELATIONS`
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The
nullValuepredicate performs a slow custom data-flow analysis to find possible null values. It's so slow that it timed out after 1200s on Wireshark.In
UnsafeCreateProcessCall.ql, the values found withnullValuewere used as sources in another data-flow analysis. By using theNullValueclass as sink instead ofnullValue, we avoid the slow-down of doing data flow twice. TheNullValueclass is essentially the base case ofnullValue. Confusing names, yes.I'll open the same PR for
ql:masterwhen this is merged.