That is, return everything in the return argument. On the SysV ABI, that means everything gets returned in registers, in both 32- and 64-bit platforms (unlike QtPrivate::ParsedNumber). There's a minor but perceptible performance improvement in parsing strings and byte arrays. Before: Parsed string "42" "1234" "-1548860221" Clock (ns) 16.673 18.878 25.517 CPU cycles 46.548 52.704 71.243 Instructions 201 233 331 After: Parsed string "42" "1234" "-1548860221" Clock (ns) 15.577 17.998 24.198 CPU cycles 43.491 49.942 67.552 Instructions 179 211 308 On my Core i7-1165G7 @ 2.80 GHz, the 22-23 instruction gain per iteration results in half the expected clock gain in runtime (22 / 2.8 GHz = 7.8 ns) because of a slightly lower instruction per cycle rate. That's acceptable because we need less speculative execution. Pick-to: 6.4 Task-number: QTBUG-107788 Change-Id: I07ec23f3cb174fb197c3fffd17220fd64d473cc0 Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>