Fix #349: overflow-safe scalar_number arithmetic - #402
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int64 arithmetic in scalar_number wrapped silently (UB): pow(10,30) folded to 5076944270305263616 (10^30 mod 2^64), rat_add/rat_sub cross products were signed-overflow UB at ~2^40 magnitudes (UBSan-confirmed), rat_div could construct an invariant-violating 1/0 rational, and normalize_rational/negation hit UB at INT64_MIN. All int64 paths are now overflow-checked (builtin overflow intrinsics on GCC/Clang, manual range checks on MSVC) and demote to double when the exact value does not fit — value stays correct, exactness is lost only at the extremes. rat_div routes zero denominators to +-inf double like the int/int path, and INT64_MIN operands demote instead of negating. pow needs no change: it composes operator*, so the checked multiply fixes the wraparound. Exact behavior in range is unchanged and lock-in tested (1/3 + 1/6 stays the exact rational 1/2). Signed-off-by: petlenz <peterlenz89.pl@gmail.com>
to_rational promotes int64 operands without normalization, so scalar_number(INT64_MIN) * scalar_number(1,2) reached std::abs(INT64_MIN) in rat_mul's gcd cross-cancel (UBSan-confirmed abort) - the exact class #349 eliminates elsewhere. rat_mul (and rat_div through it) now demotes to double when any component is INT64_MIN, matching the existing normalize_rational guard. Regression test covers mul both ways and div. Signed-off-by: petlenz <peterlenz89.pl@gmail.com>
pow's repeated-squaring negated the exponent with -n before the uint64 cast - signed-negation UB for INT64_MIN (round-2 review; UBSan abort on pow(1/2, INT64_MIN)). |n| is now computed as 0u - unsigned(n). Also repairs conflict markers committed during the stack rebase. Signed-off-by: petlenz <peterlenz89.pl@gmail.com>
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Summary
Fixes #349. Stacked on #401.
pow(10,30)→5076944270305263616(mod 2⁶⁴, silent)1e30(double demotion)rat_addat ~2⁴⁰ magnitudes → signed-overflow UB (UBSan abort)1/2 ÷ 0→ stored1/0rational (invariant violation)+infdouble, matching the int/int pathnormalize_rational/negation at INT64_MIN → UBDesign
__builtin_*_overflowon GCC/Clang, manual range checks on MSVC (which is in the CI matrix and lacks both the builtins and__int128).1/3 + 1/6stays the exact rational1/2).powneeded no change: it composesoperator*, so the checked multiply fixes the wraparound for free.rat_less) with the same demotion philosophy; this completes the arithmetic side. The follow-up idea of keeping exactness via__int128where available is left out deliberately (MSVC portability, and no physics workload needs exact >2⁶³ rationals).Tests
4 lock-ins: pow wraparound, rational-add UB repro (value ≈ 2.0), div-by-zero → +inf double, exactness preservation. Full suite: 2437/2437 pass. gcc-14
-Werrorcompile of the TU clean. The UBSan CI leg (once #356's-fno-sanitize-recoverlands) becomes the standing regression net for this class.