D159 - Stack alignment is measured, never forced

Status: decided Date: 2026-08-20

The trampoline records the stack pointer as the guest's call left it, and every run reports how many calls arrived on a conforming stack, including when all did. It never realigns the stack.

Why: a misaligned stack does nothing until some callee spills a vector register, then faults far from the cause. Measuring names the violator; forcing alignment makes the crash vanish while the guest keeps running misaligned internally. A line that appears only on failure cannot be told from a line nobody wired up.

Rejected:

• and rsp, -16 in the trampoline: hides the fault permanently.
• Reporting only violations: silence is ambiguous.