Joseph Ferano
7ce1d09900
A different primitive from redefining a name. There is no name to install a body into, so the expression is wrapped in a function with nowhere to be called from; the module exports flan_reload_call to say "run this once", and the agent calls it after the install - on the game thread, at a frame boundary, so an expression that reads the program's state sees a point the program agrees is consistent. Nothing is marshalled back because nothing could be. A Flan value carries no header, so no code at run time can say what it is; the compiler knows the type and renders it there, in the thunk. That is the layout decision's bill, and it is why the printer set is the scalars rather than everything. The rendering does not go through stdout. Stdout belongs to the program, it is in the hot path for anything that prints, and a dev-only feature must not put a branch in it - so flan_rt.c is untouched and the value goes to flan_dev_result, read back over the agent's socket. Safe without a handshake because the generation counter is bumped last: the daemon waits for it to move rather than assuming the program has reached a frame boundary. u64 refuses by name, because i64->bytes is signed and anything past 2^63 would come back negative. Everything without a derived printer refuses the same way. A number that is quietly wrong is the failure this whole thing exists to prevent. An evaluation is not a declaration: the thunk is built against the program and never spliced into it, so describe does not fill up with an eval/N for every expression ever typed. The test that matters is the same expression twice. The fixture increments ticks every frame, so two evaluations must disagree - a value computed in the compiler, or read from a copy of the program's state, would not.
299 lines
12 KiB
OCaml
299 lines
12 KiB
OCaml
(** [flan dev]: one long-lived session, the program it belongs to running
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beside it, and a socket an editor talks to.
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This is the piece between an editor and everything else. What it adds over
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[flan reload] is that the session *persists*: a [defvar] added by one
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evaluation is part of the program the next one is checked against, and the
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set of names the running process was built with is the one from the build
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this daemon actually made. A CLI that rebuilds its session from source each
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time cannot have either.
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It owns the build, which is what makes its layout rules mean anything: a
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session's struct layouts and global types describe the memory of a process
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only if it is the session that compiled it. So the daemon launches the
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program rather than attaching to one. *)
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type t = {
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session : Session.t;
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child : int; (* the running program *)
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agent : string; (* where it listens for modules *)
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dir : string; (* modules are built here, one per eval *)
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mutable n : int; (* dlopen caches by path: never reuse one *)
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}
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let await ?(ms = 5000) f =
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let rec go ms =
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if f () then true
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else if ms <= 0 then false
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else begin ignore (Unix.select [] [] [] 0.005); go (ms - 5) end
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in
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go ms
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(* ── Delivery ──────────────────────────────────────────────────────── *)
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(* The agent answers "ok" when it has queued a module, and anything else is a
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refusal with a reason. Reporting that back rather than swallowing it is what
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keeps a failed delivery from looking like a successful evaluation — the
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whole class of bug this socket makes possible. *)
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let deliver t path =
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let s = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
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Fun.protect
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~finally:(fun () -> try Unix.close s with Unix.Unix_error _ -> ())
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(fun () ->
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Unix.connect s (Unix.ADDR_UNIX t.agent);
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let msg = path ^ "\n" in
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ignore (Unix.write_substring s msg 0 (String.length msg));
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let b = Bytes.create 1024 in
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let buf = Buffer.create 64 in
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let rec drain () =
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match Unix.read s b 0 1024 with
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| 0 -> ()
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| n -> Buffer.add_subbytes buf b 0 n; drain ()
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| exception Unix.Unix_error _ -> ()
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in
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drain ();
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String.trim (Buffer.contents buf))
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(* Read back the value of the last expression evaluated, with the counter that
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says whether it is a new one. The thunk runs on the game thread whenever the
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program next reaches a frame boundary, which is not a moment the daemon gets
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to know about, so this waits for the counter to move rather than assuming it
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has. *)
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let result t =
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let s = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
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Fun.protect
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~finally:(fun () -> try Unix.close s with Unix.Unix_error _ -> ())
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(fun () ->
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Unix.connect s (Unix.ADDR_UNIX t.agent);
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ignore (Unix.write_substring s "result\n" 0 7);
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let b = Bytes.create 4096 in
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let buf = Buffer.create 256 in
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let rec drain () =
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match Unix.read s b 0 4096 with
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| 0 -> ()
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| n -> Buffer.add_subbytes buf b 0 n; drain ()
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| exception Unix.Unix_error _ -> ()
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in
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drain ();
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let text = Buffer.contents buf in
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match String.index_opt text '\n' with
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| None -> None
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| Some i ->
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let header = String.sub text 0 i in
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let body = String.sub text (i + 1) (String.length text - i - 1) in
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(match String.split_on_char ' ' header with
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| [ g; _ ] ->
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(match Int64.of_string_opt g with
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| Some g -> Some (g, body)
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| None -> None)
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| _ -> None))
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let alive t =
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match Unix.waitpid [ Unix.WNOHANG ] t.child with
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| 0, _ -> true
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| _ -> false
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| exception Unix.Unix_error _ -> false
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(* ── Ops ───────────────────────────────────────────────────────────── *)
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(* Every reply is a plist with a :status, so an editor can dispatch on one key
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and never has to guess whether a missing field means failure. *)
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let ok fields =
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"(:status \"ok\"" ^ String.concat "" (List.map (fun f -> " " ^ f) fields) ^ ")"
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let error ?loc msg =
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"(:status \"error\" :message " ^ Wire.quote msg
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^ (match loc with None -> "" | Some l -> " :loc " ^ Wire.quote l)
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^ ")"
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let eval t ~code ~origin =
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if not (alive t) then error "the program exited; restart flan dev"
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else
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match Session.eval ~origin t.session code with
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| c when not c.Session.installs ->
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(* Accepted into the session and nothing to send: a declaration the
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program already has, with no body and no new storage. Saying "ok" and
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shipping an empty module would report success for a change that cannot
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have taken effect. *)
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ok
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[ ":names " ^ Wire.strings c.Session.names; ":fns ()";
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":note " ^ Wire.quote "nothing to install" ]
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| c ->
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t.n <- t.n + 1;
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let out = Filename.concat t.dir (Printf.sprintf "m%d.so" t.n) in
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(match Build.shared ~opts:{ Build.default with Build.dev = true }
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~ir:c.Session.ir ~out () with
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| timing ->
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(match deliver t out with
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| "ok" ->
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ok
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[ ":names " ^ Wire.strings c.Session.names;
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":fns " ^ Wire.strings c.Session.fns;
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Printf.sprintf ":ms %.1f"
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(timing.Build.llc_ms +. timing.Build.link_ms) ]
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| reply -> error ("the program refused the module: " ^ reply)
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| exception Unix.Unix_error (e, _, _) ->
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error
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("cannot reach the program on " ^ t.agent ^ ": "
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^ Unix.error_message e))
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| exception Failure m -> error m)
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| exception Loc.Error (l, msg) -> error ~loc:(Loc.to_string l) msg
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(* Redefining a name installs a body; evaluating an expression has no name to
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install into, so the module carries a thunk the agent runs once. The value
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comes back through the runtime rather than through this reply, because the
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frame boundary it runs at is the program's to choose. *)
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let eval_expr t ~code ~origin =
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if not (alive t) then error "the program exited; restart flan dev"
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else
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match Session.eval_expr ~origin t.session code with
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| c ->
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let before = match result t with Some (g, _) -> g | None -> 0L in
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t.n <- t.n + 1;
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let out = Filename.concat t.dir (Printf.sprintf "e%d.so" t.n) in
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(match Build.shared ~opts:{ Build.default with Build.dev = true }
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~ir:c.Session.ir ~out () with
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| _ ->
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(match deliver t out with
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| "ok" ->
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let rec wait ms =
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match result t with
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| Some (g, v) when Int64.compare g before > 0 -> Some v
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| _ when ms <= 0 -> None
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| _ ->
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ignore (Unix.select [] [] [] 0.005);
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if alive t then wait (ms - 5) else None
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in
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(match wait 5000 with
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| Some v -> ok [ ":value " ^ Wire.quote v ]
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| None ->
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error
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"the program did not reach a frame boundary; is it calling \
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(agent/poll)?")
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| reply -> error ("the program refused the module: " ^ reply)
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| exception Unix.Unix_error (e, _, _) ->
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error ("cannot reach the program: " ^ Unix.error_message e))
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| exception Failure m -> error m)
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| exception Loc.Error (l, msg) -> error ~loc:(Loc.to_string l) msg
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let describe t =
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ok
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[ ":fns "
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^ Wire.strings
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(List.map (fun (f : Tast.fn) -> f.Tast.name)
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t.session.Session.program.Tast.fns);
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":globals "
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^ Wire.strings
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(List.map (fun (g : Tast.global) -> g.Tast.gname)
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t.session.Session.program.Tast.globals);
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":alive " ^ (if alive t then "t" else "nil") ]
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let handle t req =
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match Wire.string_field req "op" with
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| Some "eval" ->
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(match Wire.string_field req "code" with
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| Some code ->
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let origin =
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match Wire.string_field req "file" with Some f -> f | None -> "<editor>"
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in
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eval t ~code ~origin
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| None -> error "eval needs :code")
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| Some "eval-expr" ->
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(match Wire.string_field req "code" with
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| Some code ->
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let origin =
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match Wire.string_field req "file" with Some f -> f | None -> "<editor>"
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in
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eval_expr t ~code ~origin
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| None -> error "eval-expr needs :code")
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| Some "describe" -> describe t
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| Some "close" -> ok []
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| Some op -> error ("unknown op: " ^ op)
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| None -> error "no :op"
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(* ── The loop ──────────────────────────────────────────────────────── *)
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(* One connection at a time. An editor is one client, evaluations are
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sequential by nature — each one is checked against the program the last one
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left behind — and a second concurrent evaluation would be racing for the
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same session anyway. *)
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(* Returns whether the client asked to end the session. One editor per daemon,
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so [close] shuts the whole thing down rather than waiting for another
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connection nobody is going to make. *)
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let serve t fd =
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let rec go () =
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match Wire.recv fd with
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| src ->
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let op, reply =
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match Wire.parse src with
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| req -> (Wire.string_field req "op", handle t req)
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| exception Loc.Error (_, m) -> (None, error ("bad request: " ^ m))
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in
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Wire.send fd reply;
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if op = Some "close" then true else go ()
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| exception Wire.Closed -> false
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| exception Unix.Unix_error _ -> false
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in
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go ()
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let start ~file ~sock =
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let t0 = Unix.gettimeofday () in
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let session, l = Session.create ~file in
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let dir =
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Filename.concat (Filename.get_temp_dir_name ())
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(Printf.sprintf "flan-dev-%d" (Unix.getpid ()))
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in
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(try Unix.mkdir dir 0o700 with Unix.Unix_error (Unix.EEXIST, _, _) -> ());
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let exe = Filename.concat dir "program" in
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ignore
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(Build.executable ~opts:{ Build.default with Build.dev = true }
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~csrcs:l.Load.csrcs ~lflags:l.Load.lflags session.Session.host ~out:exe);
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let agent = Filename.concat dir "agent.sock" in
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(* The program's source names some socket path; the daemon is the one that
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knows where it wants to talk to it, so it overrides through the
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environment. Guessing instead would fail silently — everything compiles,
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the module is built, and nothing ever receives it. *)
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Unix.putenv "FLAN_AGENT_SOCKET" agent;
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let child = Unix.create_process exe [| exe |] Unix.stdin Unix.stdout Unix.stderr in
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(* Wait for it to bind before accepting an evaluation. One that arrives first
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would fail for a reason that reads like a compiler bug. *)
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if not (await (fun () -> Sys.file_exists agent)) then begin
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(try Unix.kill child Sys.sigterm with Unix.Unix_error _ -> ());
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failwith
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("the program never listened on " ^ agent
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^ " — does it call (agent/start ...)?")
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end;
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let t = { session; child; agent; dir; n = 0 } in
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(try Unix.unlink sock with Unix.Unix_error _ -> ());
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let ls = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
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Unix.bind ls (Unix.ADDR_UNIX sock);
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Unix.listen ls 4;
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Printf.eprintf "flan dev: %s ready on %s (%.0fms)\n%!" file sock
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((Unix.gettimeofday () -. t0) *. 1000.);
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(* [accept] would block past the program's own exit, so it is waited on with
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a timeout and the child checked each time round: a daemon whose program
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has finished has nothing left to do, and an editor waiting on it would
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wait forever. *)
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let rec accept_loop () =
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if alive t then
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match Unix.select [ ls ] [] [] 0.2 with
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| [], _, _ -> accept_loop ()
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| _ ->
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(match Unix.accept ls with
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| fd, _ ->
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let closed = serve t fd in
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(try Unix.close fd with Unix.Unix_error _ -> ());
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if not closed then accept_loop ()
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| exception Unix.Unix_error (Unix.EINTR, _, _) -> accept_loop ())
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| exception Unix.Unix_error (Unix.EINTR, _, _) -> accept_loop ()
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in
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Fun.protect
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~finally:(fun () ->
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(try Unix.kill child Sys.sigterm with Unix.Unix_error _ -> ());
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(try Unix.close ls with Unix.Unix_error _ -> ());
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(try Unix.unlink sock with Unix.Unix_error _ -> ()))
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accept_loop
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