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Guard the qasmtools recursive-descent parser against malformed input reachable through the public entry point: catch out-of-range numeric literals, bound expression recursion depth, guard EOF in string lexing, and replace exception-throwing variant access with safe accessors. No behavioral change on valid input (all bundled .qasm samples parse identically). Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01JdMbZBMa3kMKd2QTRoqnff
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Harden the OpenQASM 2.0 parser against malformed input
Summary
Malformed OpenQASM input reachable via
parse_string(hencepystaq.parse_str/staqCLI) can abort or hang the process. This PR closes five such cases; valid input is unchanged.Cases
> INT_MAXabort()std::out_of_rangefromstd::stoifloatrange (1e99999999)abort()std::out_of_rangefromstd::stof(((…)))parse_exp/parse_atomlex_stringloop omits the EOF checkqreg 5[2];)abort()std::bad_variant_accessfromas_string()/as_int()Cases 1, 2 and 5 raise exceptions other than
ParseError(aParseError-only handler still aborts); cases 3 and 4 bypass exception handling entirely.Changes
lexer.hppstd::stoi/std::stofintry/catch (std::out_of_range)→Token::Kind::error; add&& buf_->peek() != EOFto thelex_stringloopparser.hppMAX_EXPR_DEPTH = 1000) on expression recursion; overflow raisesParseErrortoken.hppas_int/as_real/as_stringmade total viastd::get_if, returning a default on mismatch; parsererror_flag still yieldsParseErrorCHANGES.md# Pre-releaseTesting
ParseErroror parse cleanly — no abort or hang..qasmfiles parse identically before and after.