Daniel Lemire a7249f86ed replace checked re-parse with O(1) simdjson-style overflow check ... The previous commit detects multi-wrap u64 overflow at the max_digits boundary by re-parsing the digits through a checked multiply-add loop (O(max_digits)). Replace that with the constant-time check used in simdjson: the leading digit plus a single threshold comparison. For a max_digits-length value, min_safe_u64(base) == base^(max_digits-1) is the smallest such value and also the width of each leading-digit band [d*ms, (d+1)*ms). Since that width is < 2^64, the only band that can straddle 2^64 is d == dmax (the largest leading digit that still fits), and there it straddles at most once, so a single threshold dmax*ms separates wrapped from non-wrapped values. A leading digit above dmax always overflows; below dmax always fits. dmax and the threshold derive from the existing min_safe_u64 table, so no new tables are needed and dmax*ms cannot itself overflow. Add a programmatic, self-verifying test for parse_int_string overflow detection covering bases 2..36, complementing the hand-picked strings added earlier. Every generated input is cross-checked against an independent trusted oracle (a plain 64-bit checked multiply-add); on success the parsed value is also compared exactly and full consumption of the input is asserted. Per base it exercises: - an exact-boundary sweep of the 64 values straddling 2^64 (UINT64_MAX-31 .. 2^64+31), built by walking the digit string; - UINT64_MAX, 2^64 and the all-max-digit value, each also with leading zeros; - random max_digits-length values across every leading digit, with the heaviest sampling on the lead == dmax band that straddles 2^64, and full coverage of lead > dmax (the multi-wrap region the naive min_safe check accepted by mistake); - max_digits-1 (never overflows) and max_digits+1 (always overflows). A small signed (int64_t) section checks the exact INT64_MIN/INT64_MAX limits round-trip and that INT64_MAX+1 / INT64_MIN-1 are rejected in every base.		2026-06-13 21:34:34 -04:00
..
fast_float	replace checked re-parse with O(1) simdjson-style overflow check	2026-06-13 21:34:34 -04:00