Sigil (0.16.0)

Generational GC By Default

Sigil now builds with the generational garbage collector by default. The collector is designed for allocation-heavy programs: servers, tools that keep long-lived state around, and interactive apps that create many short-lived values per frame. Those workloads should see less time spent in full-heap collection and smoother latency under steady allocation.

The old mark-sweep collector is still available as an escape hatch:

SIGIL_GC=marksweep sigil build ...

Minor collection is enabled adaptively by default. Sigil watches how effective young-generation collection is and grows the young-generation threshold when a program is keeping most of what it allocates. That means allocation-heavy programs can benefit from minor collection without paying an unnecessary pause tax in workloads where young collections are not helping.

Faster Native Builds And Binaries

Native code generation now uses cross-compilation-unit optimization by default. Sigil writes and reads compact CPS summaries between modules, which lets the native compiler make better decisions when code in one module calls code from another. This helps larger programs most, especially apps split across many modules.

You can opt out while investigating a native-codegen problem:

SIGIL_CPS_NO_CROSS_CU=1 sigil build ...

Several common native call paths were also tightened up. Calls to known native functions, small helper closures, native struct accessors, vector field accessors, imported math helpers, and self-recursive named let loops now emit less general-purpose dispatch code when Sigil can prove a direct path is safe. For users, the expected effect is simpler generated C, smaller hot paths, and better runtime performance in code that leans on small abstractions.

Sigil also reduces metadata allocation for anonymous native closures. This matters most for programs that create many small closures in hot loops or frame updates; the runtime now avoids constructing location metadata that would never be useful to the user.

Smoother Interactive Apps

This release was validated against Cinder Cantata and the local native MCP server fleet. The practical target was not just "does it compile," but whether native Sigil programs can run for a while with stable frame pacing and without the small allocation-driven shivers that were visible in interactive workloads.

The GC and native-codegen defaults in 0.16.0 are the result of that validation. They make the optimized path the normal path, while keeping environment-variable opt-outs available for bisecting regressions.