Summary

The existing OSS-Fuzz re2_fuzzer exercises single-pattern matching via RE2::FullMatch. RE2::Set — the multi-pattern matching API used for routing, filtering, and URL dispatch — takes a separate code path through set.cc and the DFA multi-pattern accept-state machinery and has no dedicated fuzz coverage.

New harness: re2/fuzzing/re2_set_fuzzer.cc

• Derives number of patterns (1–4) and per-pattern length from fuzz bytes
• Calls RE2::Set::Add() for each pattern then RE2::Set::Compile()
• Calls RE2::Set::Match() on the remaining fuzz bytes as input string

Covers: re2/set.cc Add/Compile/Match, re2/dfa.cc multi-pattern DFA cache and accept-state bitmap, and re2/prog.cc multi-pattern bytecode generation.