codeql/2026-07-17-cpp-regex-non-backtracking-engine.md at copilot/add-cpp-regular-expression-parser

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copilot-swe-agent[bot] e0cc6795dc Add isBacktrackingEngine gate excluding awk/grep/egrep from C++ ReDoS queries

2026-07-17 12:06:30 +00:00

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The C++ ReDoS queries (cpp/redos and cpp/polynomial-redos) now treat regexes constructed with the std::regex_constants::awk, grep, or egrep grammar flags as non-backtracking, and exclude them from analysis. These POSIX tool-style grammars correspond to traditionally linear-time (DFA-based) matching semantics, so super-linear-backtracking ReDoS does not apply. The basic (BRE) and extended (ERE) grammars remain backtracking-eligible. Grammar selection and ReDoS-eligibility are exposed as independent axes via the new isBacktrackingEngine predicate in semmle.code.cpp.regex.RegexFlowConfigs.