pit: Add fuel economy

1 files changed, 2 insertions, 0 deletions

diff --git a/pit/src/runtime/eval.c b/pit/src/runtime/eval.c
index eba9715..a2ed166 100644
--- a/pit/src/runtime/eval.c
+++ b/pit/src/runtime/eval.c
@@ -155,6 +155,8 @@ bool pit_vm_run_one(pit_runtime *rt) {
     if (rt->callstack->next < 1 || rt->error != PIT_NIL) return false;
     pit_callstack_entry *ent = pit_vec_get(pit_callstack_entry)(rt->callstack, rt->callstack->next - 1);
     if (ent == NULL) { pit_error(rt, "malformed call stack"); return false; }
+    if (rt->fuel == 0) { pit_error(rt, "out of fuel"); return false; }
+    rt->fuel -= 1;
     pit_value ins = pit_value_cons_car(rt, ent->code);
     if (ins == PIT_NIL) { pit_error(rt, "malformed vm instruction: %v %v", ins); return false; }
     ent->code = pit_value_cons_cdr(rt, ent->code);