Three things share the name. tests/snapshot.sh is the byte-identity gate across revisions: a refactoring must leave every output unchanged. A setjmp function keeps snapshots, copies of every temporary (filc_amd64:setjmp_snapshots//3filc_amd64.plsetjmp_snapshots/5not documented, setjmp.md). And a variadic callee's argument snapshot is the read-only heap object its extra arguments are copied into at entry.

The last is the one the formal model knows: interp:entry_snapshot/6interp.plentry_snapshot+Blocks, +Args, +Env₀, -Env, +S₀, -Ssemideta variadic callee's entry takes the snapshot of its arguments. Fails when the address space cannot hold the snapshot (alloc_base/6)., Semantics.v's point Snapshot and the hidden name va_snapshot. It is an allocation, so the runtimeruntime Fil-CThe runtime is what Fil-C does around one thread's program, natively libpizlo.so with FUGC: where a new object goes, what free does, and what the collector may change while the program waits at a safepoint. The model does not define it; it states it as one page of axioms, Module Type Runtime (Runtime), each with a native test in tests/c/prog/axiom-*.c. may refuse it (out_of_memory), and freeing it traps at its renew as natively (rocq.md, A freed snapshot traps at its renew).