Support 32-bit targets without native 64-bit atomics (ARMv6) #22

zds is running on a 2011 Raspberry Pi 1 Model B (ARMv6, 512 MB) at pi.chadtmiller.com — live and federating with the relay network. Two changes were needed to get there; both are no-ops on 64-bit targets.

1. fix(sync): nowMillis() overflow #

On targets where timespec.sec is 32-bit, ts.sec * 1000 overflows for any current date, so the server trapped at startup. Widening to i64 before the multiply fixes it; on 64-bit targets the math is unchanged.

2. feat(core): PortableAtomic #

ARMv6 has no 64-bit atomic instructions, so std.atomic.Value(u64/i64) fails to compile. PortableAtomic(T) is exactly std.atomic.Value(T) when the target's native atomic width covers T, and otherwise falls back to a spinlock-guarded value (acquire via cmpxchgWeak + Thread.yield). The four 64-bit atomics (store next_seq, DatabaseMutex.acquired_at_ms, eventlog latest_seq, sync crawler_last_notified_ms) switch over.

Verified #

• zig build test passes (zig 0.16.0)
• Native 64-bit ReleaseSafe build unchanged/passing
• -Dtarget=arm-linux-musleabihf -Dcpu=arm1176jzf_s ReleaseSafe build passes
• Running in production on the Pi 1 (~7 MB RSS)

Note: a full 32-bit build also needs two small fixes in zat (comptime struct-size asserts in cbor.zig that hard-code 64-bit pointer sizes, and a std.atomic.Value(u64) byte counter in transport.zig). A follow-up pull to the zat repo with those is ready to send if there's interest.

• Claude