Invert event loop

compiler/src/emit/mod.rs

@@ -18,7 +18,7 @@ use std::{
 
 use crate::{
     infer::{
-        HOST, InferResult, Place, TypeCache,
+        HOST, HOST_COMPLETE, InferResult, Place, TypeCache,
         cells::{Cell, Code, LENGTH_FIELD, ObjKind, read_value},
         types::Type,
     },
@@ -94,11 +94,16 @@ pub fn emit(fns: &[RegFn], cache: &TypeCache, atoms: &[Atom]) -> String {
         }
     }
 
-    // The walks that the code calls, from the entry. The host calls the entry
-    // with nothing: its env and `this` are undefined
+    if cache.host_complete != Type::Unknown {
+        let _ = writeln!(statics, "static {} {HOST_COMPLETE_GLOBAL};", e.c_type(e.rep(&cache.host_complete)));
+    }
+
+    // The walks that the code calls, from the host's calls. The host calls the
+    // entry with nothing: its env and `this` are undefined
     let entry = cache.find(fns.len() - 1, HOST, &[], fns);
     let entry_args = vec!["(undefined_t){0}"; cache.walks[entry].req.arg_types.len()].join(", ");
     e.use_walk(entry);
+    let complete = e.host_complete();
 
     let mut fn_protos = String::new();
     let mut bodies = String::new();
@@ -127,7 +132,9 @@ pub fn emit(fns: &[RegFn], cache: &TypeCache, atoms: &[Atom]) -> String {
         e.helper_protos,
         e.helper_defs
     );
-    let _ = writeln!(out, "int main(void) {{\n{init}    {}({entry_args});\n    return 0;\n}}", e.fn_name(entry));
+    // What the host calls (see `lib/rt/jsrt.h`)
+    let _ = writeln!(out, "void jsrt_start(void) {{\n{init}    {}({entry_args});\n}}\n", e.fn_name(entry));
+    let _ = writeln!(out, "void jsrt_complete(int32_t h) {{\n{complete}}}");
     out
 }
 
@@ -287,6 +294,9 @@ fn builtin_name(id: CellNum) -> String {
     format!("b{id}")
 }
 
+/// The global that holds what the host calls when an IO op completes
+const HOST_COMPLETE_GLOBAL: &str = "jsrt_host_complete";
+
 fn proto_global(kind: ProtoOf) -> String {
     format!("proto_{kind:?}").to_lowercase()
 }