22 days ago
- Fil-C supports memory-safe context switching via longjmp/setjmp and ucontext APIs, preventing stack corruption.
- setjmp/longjmp are used for exception handling, while ucontext APIs (getcontext, setcontext, makecontext, swapcontext) implement coroutines/fibers.
- Fil-C makes setjmp/longjmp safe by storing jmp_buf as an opaque zjmp_buf, restricting direct calls, and validating stack frame ancestry.
- ucontext safety is achieved using opaque zfiber_context objects, a strict state machine, thread affinity, and GC integration with grey fiber tracking.
- The implementation ensures no misuse leads to dangling stack execution; unsafe operations cause panics or compile-time errors.
- GC integration handles fiber stacks during marking via grey fiber lists to prevent race conditions in on-the-fly garbage collection.
- Fil-C's ucontext support is available in glibc builds (from source after version 0.680), with setjmp/longjmp being more mature.
- Examples demonstrate how volatile variables and compiler optimizations affect setjmp behavior, emphasizing Fil-C's compliance with C semantics.