D748 - Formatted output renders floating-point and starred conversions

Status: decided Date: 2026-10-06

The formatted-output family renders %f %F %e %E %g %G and takes a * width or precision from the arguments, as ISO C 7.21.6.1 says. A floating-point argument is read where the System V psABI puts it: in the next of the eight vector registers the trampoline already spills (D268), which the thunk now publishes for the length of a call beside the stack area, or in a va_list's floating-point save area by fp_offset; past either, from the same stack cursor the integers use, since overflow arguments of both classes share one area in order. The +, space and # flags are honoured rather than read and dropped. %a is still refused, as its own conversion.

This narrows D183: a format is still complete or empty, and floating point is no longer a cause.

Why: D183 refused floating point because the value never reached the renderer. Since D268 it does, for every call, and a va_list always carried it. STKT00001 refused 73 writes a run on %f alone, and CRFT00001 45 on %*, each an empty string where the game printed a number.

Rejected:

• Rendering through the host's printf: the host library's rounding and spelling of infinities are not the guest's to inherit unexamined, and it would put a C call in the renderer.
• Leaving the flags ignored: a dropped + is a partial rendering, which D183 forbids.