flan/lib/dev.ml
Joseph Ferano a8f08eda6d A struct's fields, answered out of the build, keyed by the name that is an identity
(:op "layout" :type T) needs no running program: the daemon owns the build, so
Tast.structs is already in the session it compiled the process from. The open
question was what T is, and it needs no new machinery — Load qualifies every
declaration at import, so two packages' Missing are a/Missing and b/Missing and
the name is the type id. Emit already writes that same qualified name into
flan_error, so the string break reports as :condition resolves as :type by
construction, which is the round trip the test makes.

A bare name is refused with the candidates rather than resolved to a unique
suffix: resolving it would put back the ambiguity the rule exists to remove.
2026-09-12 10:39:16 +07:00

1136 lines
48 KiB
OCaml

(** [flan dev]: one long-lived session, the program it belongs to running
beside it, and a socket an editor talks to.
This is the piece between an editor and everything else. What it adds over
[flan reload] is that the session *persists*: a [defvar] added by one
evaluation is part of the program the next one is checked against, and the
set of names the running process was built with is the one from the build
this daemon actually made. A CLI that rebuilds its session from source each
time cannot have either.
It owns the build, which is what makes its layout rules mean anything: a
session's struct layouts and global types describe the memory of a process
only if it is the session that compiled it. So the daemon launches the
program rather than attaching to one. *)
(* Where a function's body was last built. The daemon owns the build, so it is
the only thing that can answer "which module defines this name now" — but
see [basis] below for what that answer honestly is. *)
type origin = {
ogen : int; (* reload generation; 0 is the host's *)
oso : string; (* the object the body was linked into *)
oll : string; (* the IR it was built from *)
oloc : string; (* where the source it came from was written *)
}
type t = {
session : Session.t;
child : int; (* the running program *)
agent : string; (* where it listens for modules *)
dir : string; (* modules are built here, one per eval *)
stdout : Unix.file_descr; (* the program's output, on its way to here *)
out : Buffer.t; (* ...buffered until an editor asks for it *)
mutable n : int; (* dlopen caches by path: never reuse one *)
(* Bookkeeping for disassembly, and the reason it can exist at all: the
daemon compiled every module it sent, so the .ll and the .so are on its
own disk. What it does not have is a way back into the process's cells. *)
mutable gen : int; (* accepted deliveries, in order *)
owners : (string, origin) Hashtbl.t; (* fn name -> the last module sent *)
host_ll : string; (* the IR the running program was built from *)
}
(* The program's stdout is a pipe into this process, so that an editor can see
it. That makes draining it a *liveness* requirement and not a nicety: a pipe
nobody reads fills at 64K and the next write blocks the program forever. So
it is read from the accept loop's select, not only when someone asks. *)
let capacity = 256 * 1024
let drain t =
let b = Bytes.create 8192 in
let rec go () =
match Unix.select [ t.stdout ] [] [] 0. with
| [], _, _ -> ()
| _ ->
(match Unix.read t.stdout b 0 8192 with
| 0 -> ()
| n ->
Buffer.add_subbytes t.out b 0 n;
(* Bounded: a program that prints every frame must not grow this
process without limit. The newest text is the useful end. *)
if Buffer.length t.out > capacity then begin
let keep = Buffer.sub t.out (Buffer.length t.out - capacity) capacity in
Buffer.clear t.out;
Buffer.add_string t.out keep
end;
go ()
| exception Unix.Unix_error (Unix.EAGAIN, _, _) -> ()
| exception Unix.Unix_error (Unix.EWOULDBLOCK, _, _) -> ()
| exception Unix.Unix_error _ -> ())
in
go ()
let take t =
drain t;
let s = Buffer.contents t.out in
Buffer.clear t.out;
s
let await ?(ms = 5000) f =
let rec go ms =
if f () then true
else if ms <= 0 then false
else begin ignore (Unix.select [] [] [] 0.005); go (ms - 5) end
in
go ms
(* ── Delivery ──────────────────────────────────────────────────────── *)
(* The agent answers "ok" when it has queued a module, and anything else is a
refusal with a reason. Reporting that back rather than swallowing it is what
keeps a failed delivery from looking like a successful evaluation — the
whole class of bug this socket makes possible. *)
let deliver t path =
let s = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
Fun.protect
~finally:(fun () -> try Unix.close s with Unix.Unix_error _ -> ())
(fun () ->
Unix.connect s (Unix.ADDR_UNIX t.agent);
let msg = path ^ "\n" in
ignore (Unix.write_substring s msg 0 (String.length msg));
let b = Bytes.create 1024 in
let buf = Buffer.create 64 in
let rec drain () =
match Unix.read s b 0 1024 with
| 0 -> ()
| n -> Buffer.add_subbytes buf b 0 n; drain ()
| exception Unix.Unix_error _ -> ()
in
drain ();
String.trim (Buffer.contents buf))
(* Read back the value of the last expression evaluated, with the counter that
says whether it is a new one. The thunk runs on the game thread whenever the
program next reaches a frame boundary, which is not a moment the daemon gets
to know about, so this waits for the counter to move rather than assuming it
has. *)
let result t =
let s = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
Fun.protect
~finally:(fun () -> try Unix.close s with Unix.Unix_error _ -> ())
(fun () ->
Unix.connect s (Unix.ADDR_UNIX t.agent);
ignore (Unix.write_substring s "result\n" 0 7);
let b = Bytes.create 4096 in
let buf = Buffer.create 256 in
let rec drain () =
match Unix.read s b 0 4096 with
| 0 -> ()
| n -> Buffer.add_subbytes buf b 0 n; drain ()
| exception Unix.Unix_error _ -> ()
in
drain ();
let text = Buffer.contents buf in
match String.index_opt text '\n' with
| None -> None
| Some i ->
let header = String.sub text 0 i in
let body = String.sub text (i + 1) (String.length text - i - 1) in
(match String.split_on_char ' ' header with
| [ g; _ ] ->
(match Int64.of_string_opt g with
| Some g -> Some (g, body)
| None -> None)
| _ -> None))
(* ── The break state ───────────────────────────────────────────────── *)
(* Everything above is about changing a *running* program. This is the other
half: an unhandled [error] does not kill a dev build, it stops the game
thread on the frame that erred and waits. The agent's socket is where that
shows, and the daemon is the only thing holding that socket — so an editor
asks here or not at all.
One line out, one line back, exactly like [result]: the agent is not a
protocol and must not become one. *)
let ask t verb =
let s = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
Fun.protect
~finally:(fun () -> try Unix.close s with Unix.Unix_error _ -> ())
(fun () ->
Unix.connect s (Unix.ADDR_UNIX t.agent);
let msg = verb ^ "\n" in
ignore (Unix.write_substring s msg 0 (String.length msg));
let b = Bytes.create 4096 in
let buf = Buffer.create 128 in
let rec drain () =
match Unix.read s b 0 4096 with
| 0 -> ()
| n -> Buffer.add_subbytes buf b 0 n; drain ()
| exception Unix.Unix_error _ -> ()
in
drain ();
Buffer.contents buf)
type state =
| Running
| Stopped of string (* the condition's class name *)
| Unreachable of string (* no answer: exited, or never listened *)
(* [status] is answered whether or not the program is stopped — "running" is an
answer, not a refusal. Everything else the break loop offers is refused
while running, and rightly: there is no restart stack to walk. But the
question an editor asks *without already knowing* is this one, so it had to
have an answer in both states or there would be nothing to poll. *)
let state t =
match ask t "status" with
| "" -> Unreachable "the program is not answering on its socket"
| text ->
let line = String.trim (List.hd (String.split_on_char '\n' text)) in
if line = "running" then Running
else if String.length line > 8 && String.sub line 0 8 = "stopped " then
Stopped (String.sub line 8 (String.length line - 8))
else Unreachable ("the program answered " ^ line)
| exception Unix.Unix_error (e, _, _) -> Unreachable (Unix.error_message e)
(* Innermost first, terminated by a line that is a single dot — the agent's
framing, not this one's. A refusal comes back as a line starting "err ", and
is passed on rather than turned into an empty list: no restarts and cannot
say are different answers.
Each line is [I ± NAME]: the index it is taken by, whether it can be taken,
and the name. The index is the identity — two frames may offer [retry] and
a name cannot say which — and it is the program's number, not this end's
position in a list, so it is carried rather than recomputed. *)
let restarts t =
match ask t "restarts" with
| text ->
let lines = String.split_on_char '\n' text in
if List.exists (fun l -> String.length l >= 3 && String.sub l 0 3 = "err") lines
then Error (String.trim text)
else begin
let parse line =
match String.index_opt line ' ' with
| None -> None
| Some i ->
(match int_of_string_opt (String.sub line 0 i) with
| None -> None
| Some idx ->
let rest = String.sub line (i + 1) (String.length line - i - 1) in
if String.length rest < 2 then None
else
Some
( idx,
rest.[0] = '+',
String.sub rest 2 (String.length rest - 2) ))
in
Ok
(List.filter_map parse
(List.filter
(fun l -> l <> "" && l <> ".")
(List.map String.trim lines)))
end
| exception Unix.Unix_error (e, _, _) -> Error (Unix.error_message e)
let alive t =
match Unix.waitpid [ Unix.WNOHANG ] t.child with
| 0, _ -> true
| _ -> false
| exception Unix.Unix_error _ -> false
(* ── What a body was built from ─────────────────────────────────────── *)
let write_file path text =
let oc = open_out_bin path in
Fun.protect ~finally:(fun () -> close_out oc) (fun () -> output_string oc text)
let read_file path =
let ic = open_in_bin path in
Fun.protect
~finally:(fun () -> close_in ic)
(fun () -> really_input_string ic (in_channel_length ic))
let find_fn t name =
List.find_opt
(fun (f : Tast.fn) ->
String.equal f.Tast.name name && f.Tast.fparent = None)
t.session.Session.program.Tast.fns
let fn_loc t name =
match find_fn t name with
| Some f -> Loc.to_string f.Tast.floc
| None -> ""
(* Where the *running process* has this function written, which is not where
the session has it. [Session.eval] replaces the checked program as soon as a
form checks — before the build, before delivery — so a body that checked and
then failed to build leaves the session holding a location in a buffer whose
code never landed. [host] is the program the process was launched from and
nothing mutates it, so it is the only honest answer for a name no module has
been accepted for. *)
let host_loc t name =
match
List.find_opt
(fun (f : Tast.fn) ->
String.equal f.Tast.name name && f.Tast.fparent = None)
t.session.Session.host.Tast.fns
with
| Some f -> Loc.to_string f.Tast.floc
| None -> ""
(* ── Ops ───────────────────────────────────────────────────────────── *)
(* Every reply is a plist with a :status, so an editor can dispatch on one key
and never has to guess whether a missing field means failure. *)
let ok fields =
"(:status \"ok\"" ^ String.concat "" (List.map (fun f -> " " ^ f) fields) ^ ")"
(* Anything the program printed since the last reply rides along with this one.
An editor that had to ask separately would miss the output an evaluation
itself caused, which is the output anyone actually wants to see. *)
let with_output t reply =
match take t with
| "" -> reply
| text ->
let i = String.length reply - 1 in
String.sub reply 0 i ^ " :output " ^ Wire.quote text ^ ")"
(* The break state rides along with every reply, exactly as the program's own
output does, and for the same reason: a program can stop at any moment and
nothing in a request/response protocol will mention it unless every response
does. An editor that had to *ask* would find out about a stop only when it
happened to wonder — and the most common moment for a program to stop is the
instant after an evaluation, which is a reply it is already reading.
It is the annotation, not the ops, that decides these two fields, so that
there is one place in the daemon that says whether the program is stopped
and the break ops cannot disagree with the poll. *)
let with_break t reply =
let fields =
match state t with
| Stopped c -> " :stopped t :condition " ^ Wire.quote c
| Running -> " :stopped nil"
(* Unreachable is not "running": the honest shape of "it exited" is
[:alive nil] from [describe], and claiming a state we could not read
would be the [ok]-means-probably failure in miniature. *)
| Unreachable _ -> " :stopped nil"
in
String.sub reply 0 (String.length reply - 1) ^ fields ^ ")"
let error ?loc msg =
"(:status \"error\" :message " ^ Wire.quote msg
^ (match loc with None -> "" | Some l -> " :loc " ^ Wire.quote l)
^ ")"
let eval t ~code ~origin =
if not (alive t) then error "the program exited; restart flan dev"
else
match Session.eval ~origin t.session code with
| c when not c.Session.installs ->
(* Accepted into the session and nothing to send: a declaration the
program already has, with no body and no new storage. Saying "ok" and
shipping an empty module would report success for a change that cannot
have taken effect. *)
ok
[ ":names " ^ Wire.strings c.Session.names; ":fns ()";
":note " ^ Wire.quote "nothing to install" ]
| c ->
t.n <- t.n + 1;
let out = Filename.concat t.dir (Printf.sprintf "m%d.so" t.n) in
(* [Build.shared] deletes its own .ll unless asked to keep it, and what it
keeps is in a working directory named after this process rather than
after the module. Writing our own copy beside the .so is what makes
[disassemble] able to show the IR of a body installed ten reloads ago:
nothing else on this machine still has that text. *)
let ll = Filename.concat t.dir (Printf.sprintf "m%d.ll" t.n) in
write_file ll c.Session.ir;
(match Build.shared
~opts:{ Build.default with Build.dev = true;
Build.debug = t.session.Session.debug }
~ir:c.Session.ir ~out () with
| timing ->
(match deliver t out with
| "ok" ->
t.gen <- t.gen + 1;
List.iter
(fun n ->
Hashtbl.replace t.owners n
{ ogen = t.gen; oso = out; oll = ll; oloc = fn_loc t n })
c.Session.fns;
ok
[ ":names " ^ Wire.strings c.Session.names;
":fns " ^ Wire.strings c.Session.fns;
Printf.sprintf ":ms %.1f"
(timing.Build.llc_ms +. timing.Build.link_ms) ]
| reply -> error ("the program refused the module: " ^ reply)
| exception Unix.Unix_error (e, _, _) ->
error
("cannot reach the program on " ^ t.agent ^ ": "
^ Unix.error_message e))
| exception Failure m -> error m)
| exception Loc.Error (l, msg) -> error ~loc:(Loc.to_string l) msg
(* Redefining a name installs a body; evaluating an expression has no name to
install into, so the module carries a thunk the agent runs once. The value
comes back through the runtime rather than through this reply, because the
frame boundary it runs at is the program's to choose. *)
let eval_expr t ~code ~origin =
if not (alive t) then error "the program exited; restart flan dev"
else
match Session.eval_expr ~origin t.session code with
| c ->
let before = match result t with Some (g, _) -> g | None -> 0L in
t.n <- t.n + 1;
let out = Filename.concat t.dir (Printf.sprintf "e%d.so" t.n) in
(match Build.shared
~opts:{ Build.default with Build.dev = true;
Build.debug = t.session.Session.debug }
~ir:c.Session.ir ~out () with
| _ ->
(match deliver t out with
| "ok" ->
let rec wait ms =
match result t with
| Some (g, v) when Int64.compare g before > 0 -> Some v
| _ when ms <= 0 -> None
| _ ->
ignore (Unix.select [] [] [] 0.005);
if alive t then wait (ms - 5) else None
in
(match wait 5000 with
| Some v -> ok [ ":value " ^ Wire.quote v ]
| None ->
error
"the program did not reach a frame boundary; is it calling \
(agent/poll)?")
| reply -> error ("the program refused the module: " ^ reply)
| exception Unix.Unix_error (e, _, _) ->
error ("cannot reach the program: " ^ Unix.error_message e))
| exception Failure m -> error m)
| exception Loc.Error (l, msg) -> error ~loc:(Loc.to_string l) msg
let describe t =
ok
[ ":fns "
^ Wire.strings
(List.map (fun (f : Tast.fn) -> f.Tast.name)
t.session.Session.program.Tast.fns);
":globals "
^ Wire.strings
(List.map (fun (g : Tast.global) -> g.Tast.gname)
t.session.Session.program.Tast.globals);
":alive " ^ (if alive t then "t" else "nil") ]
(* [describe] answers what exists; this answers what each one *is*. Its own op
rather than more fields on [describe], because [describe] is polled — an
editor uses it to drain the program's output — and this is asked once on
connect and again after each install. Putting signatures on the poll would
pay for them every time anyone looked at the output buffer.
One entry per name: (name kind signature loc). Four strings, so the editor
reads it with [read] and nothing here needs a new wire type. [loc] is empty
where there is none to give — only [Tast.fn] carries one — and an editor
that finds it empty must say so rather than guess a file.
Parameter *names* are not in the Tast, so a signature shows types only. *)
let signature_of_fn (f : Tast.fn) =
Printf.sprintf "%s [%s] %s" f.Tast.name
(String.concat " " (List.map Types.to_string f.Tast.params))
(Types.to_string f.Tast.ret)
let entry ~name ~kind ~sign ~loc =
Wire.list [ Wire.quote name; Wire.quote kind; Wire.quote sign; Wire.quote loc ]
let defs t =
let p = t.session.Session.program in
let fns =
List.filter_map
(fun (f : Tast.fn) ->
match f.Tast.fparent with
(* A handler-bind clause the checker lifted out. Nobody wrote this
name, so completing it is noise and jumping to it is meaningless. *)
| Some _ -> None
| None ->
Some
(entry ~name:f.Tast.name ~kind:"fn" ~sign:(signature_of_fn f)
~loc:(Loc.to_string f.Tast.floc)))
p.Tast.fns
in
let globals =
List.map
(fun (g : Tast.global) ->
entry ~name:g.Tast.gname
~kind:(if g.Tast.gconst then "const" else "var")
~sign:
(Printf.sprintf "%s %s" g.Tast.gname (Types.to_string g.Tast.gty))
~loc:"")
p.Tast.globals
in
let externs =
List.map
(fun (e : Tast.extern) ->
entry ~name:e.Tast.ename ~kind:"extern"
~sign:
(Printf.sprintf "%s [%s] %s" e.Tast.ename
(String.concat " " (List.map Types.to_string e.Tast.eparams))
(Types.to_string e.Tast.eret))
~loc:"")
p.Tast.externs
in
ok [ ":defs " ^ Wire.list (fns @ globals @ externs) ]
(* [(:op "layout" :type T)] — a struct's fields and their types.
The daemon can answer this with no running program at all: [Tast.structs] is
what it built the process from, and a layout is a fact about the build. That
is why it is the one thing the conditions buffer can fill in while the
condition's *values* stay refused.
**The type is a name, and the name is the qualified one.** [Load] qualifies
every declaration as it imports it — [Defstruct (qualify alias n, ...)] — so
the names in [Tast.structs] are a flat namespace in which two packages each
declaring [Missing] are [a/Missing] and [b/Missing] and no collision is
possible. That makes the name a type identity rather than a class name, with
no id table to keep in step, and it is the same string on both ends of the
wire already: [Emit.struct_name_of] puts [Types.Named n] into [flan_error],
the agent holds it in [condition_name], and [break] answers it as
[:condition]. Handing that string straight back as [:type] therefore
resolves, by construction.
A bare name is **refused, not resolved**, even when only one struct's last
segment matches: resolving it is exactly the ambiguity that made this op
need a rule, and a rule with an exception cannot be relied on by a client.
The refusal lists the qualified names it could have meant, so a person who
typed [Missing] is one copy-paste from the answer and a client can offer
them as completions.
Field types are spelled by [Types.to_string], which is what [defs] spells a
signature with — so [(Option T)], [[T]], [[n T]] and [(Ptr T)] read here
exactly as they read in a signature and in the source. A field that is
itself a struct shows its qualified name, which is a [:type] this op
accepts: nesting is another request rather than a second walk, and nothing
here can recurse forever. [Render] is the other walk over a type and is not
reused, because it walks a *value* and emits code that prints it; this emits
text about the type and never touches the program. *)
let layout t ~ty =
let structs = t.session.Session.program.Tast.structs in
match
List.find_opt (fun (s : Tast.structure) -> String.equal s.Tast.sname ty)
structs
with
| Some s ->
ok
[ ":type " ^ Wire.quote s.Tast.sname;
":fields "
^ Wire.list
(List.map
(fun (f : Tast.field) ->
Wire.list
[ Wire.quote f.Tast.fname;
Wire.quote (Types.to_string f.Tast.fty) ])
s.Tast.fields) ]
| None ->
(* An enum is a type the checker knows and this op cannot describe: its
members are erased to i32 before [Tast.program] exists, which is the
same fact that makes a defenum unreloadable. Saying which kind it is
beats "no such type" for a name that plainly exists. *)
if Hashtbl.mem t.session.Session.env.Check.enums ty then
error (ty ^ " is an enum, not a struct; its members are erased to i32")
else
let suffix = "/" ^ ty in
let candidates =
List.filter_map
(fun (s : Tast.structure) ->
let n = s.Tast.sname in
let k = String.length n - String.length suffix in
if k >= 0 && String.equal (String.sub n k (String.length suffix)) suffix
then Some n else None)
structs
in
(match candidates with
| [] -> error ("no struct is named " ^ ty)
| cs ->
(* Resolved on the client's side, deliberately: two packages can each
declare [Missing], and picking one of them here would answer a
layout for a type the asker did not mean. *)
"(:status \"error\" :message "
^ Wire.quote
(ty ^ " is not a qualified name; a package qualifies its \
declarations, so say which one")
^ " :candidates " ^ Wire.strings cs ^ ")")
(* What is on offer where the program stopped. [:stopped] and [:condition] are
not here: the annotation puts them on this reply as it puts them on every
other, so an editor reads the same two keys whatever it asked. What this op
adds is the restart names, which cost a second round trip to the program and
are wanted only when someone is about to choose one. *)
let break t =
if not (alive t) then error "the program exited; restart flan dev"
else
match state t with
| Running -> ok []
| Unreachable m -> error ("cannot ask the program whether it stopped: " ^ m)
| Stopped _ ->
(match restarts t with
| Ok rs ->
(* [:restarts] stays a list of names, positional and innermost first,
with duplicates kept — the position *is* the index, which is what
[restart-at] takes. [:unreachable] names the positions that are on
the list and cannot be chosen: a restart below the evaluation the
break is inside has nowhere for a transfer to land. They are shown
rather than filtered, because a client that quietly dropped them
would leave someone asking where their restart went. *)
ok
[ ":restarts " ^ Wire.strings (List.map (fun (_, _, n) -> n) rs);
":unreachable "
^ Wire.ints
(List.filter_map
(fun (i, ok, _) -> if ok then None else Some i)
rs) ]
| Error m -> error ("the program refused to list its restarts: " ^ m))
(* A choice is validated by the *program*, on its listener thread, against a
stack the stopped game thread is holding still — not here. The daemon has no
copy of that stack and anything it checked would be a guess that was true a
moment ago.
"ok" therefore means accepted, and says so: the resume happens when the
stopped thread next comes round its loop, which is microseconds away and
still not now. An editor that read [ok] as "running again" would poll once,
find it stopped, and re-open the prompt it had just answered. *)
let choose_at t ~index ~name =
if not (alive t) then error "the program exited; restart flan dev"
else if
match name with
| Some n -> String.exists (fun c -> Char.code c < 32 || Char.code c = 127) n
| None -> false
then error "a restart name cannot contain a control character"
else
let verb =
"restart-at " ^ string_of_int index
^ match name with Some n -> " " ^ n | None -> ""
in
match ask t verb with
| reply when String.trim reply = "ok" ->
ok
[ ":index " ^ string_of_int index;
":note "
^ Wire.quote
"accepted; the program resumes at its next pass of the break loop"
]
| reply -> error (String.trim reply)
| exception Unix.Unix_error (e, _, _) ->
error ("cannot reach the program: " ^ Unix.error_message e)
let choose t ~name =
if not (alive t) then error "the program exited; restart flan dev"
else if String.exists (fun c -> Char.code c < 32 || Char.code c = 127) name then
(* The agent's contract is one line per request. A name carrying a newline
would be a second request smuggled into the first, and the guarantee is
this end's to keep: [completing-read] cannot produce one, but the daemon
is what holds the socket and an editor is not the only thing that can
speak to it. *)
error "a restart name cannot contain a control character"
else
match ask t ("restart " ^ name) with
| reply when String.trim reply = "ok" ->
ok
[ ":restart " ^ Wire.quote name;
":note "
^ Wire.quote "accepted; the program resumes at its next pass of the break loop" ]
| reply -> error (String.trim reply)
| exception Unix.Unix_error (e, _, _) ->
error ("cannot reach the program: " ^ Unix.error_message e)
(* The other way out. The program exits 134 where it stopped, which ends this
daemon too — it owns the program's lifetime and has nothing left to serve.
Refused while running, by the program, for the same reason a restart is. *)
let abort t =
if not (alive t) then error "the program exited; restart flan dev"
else
match ask t "abort" with
| reply when String.trim reply = "ok" ->
ok [ ":note " ^ Wire.quote "the program is exiting; flan dev ends with it" ]
| reply -> error (String.trim reply)
| exception Unix.Unix_error (e, _, _) ->
error ("cannot reach the program: " ^ Unix.error_message e)
(* ── Disassembly ───────────────────────────────────────────────────── *)
(* [flan emit --dev] can print the IR of a whole source file, which is a
different question from the one an editor asks: not "what would this compile
to" but "what is the code the running program is calling for this name".
Only the daemon can answer that, because it built every module it sent and
still has the .ll and the .so on disk.
What it cannot do is read a cell back. The agent's socket takes a module
path, [result], [status], [restarts], [restart] and [abort] — there is no
verb that reports an address, [flan_dev_cell] lives in the program's address
space, and an expression evaluated through [eval-expr] renders a pointer as
[<ptr>] on purpose. So the answer is the last module *delivered* for the
name, and the reply says exactly that rather than implying more; see
[basis]. The one case that is certain is the case where nothing has been
delivered at all, and it says that too.
SBCL's presentation is worth two things here and not a third. Offsets from
the function's own start rather than file addresses, because an address into
a .so means nothing to a reader; and labels for branch targets inside the
function, which is most of the difference between readable and not. The
third is source interleaving, which SBCL can do because it has the mapping
and this build has no line tables — so it is refused by name in the reply
instead of being faked by printing the listing with no source in it. *)
let objdump = try Sys.getenv "FLAN_OBJDUMP" with Not_found -> "objdump"
let run_capture cmd =
let ic = Unix.open_process_in (cmd ^ " 2>&1") in
let b = Buffer.create 4096 in
let chunk = Bytes.create 4096 in
let rec go () =
match input ic chunk 0 4096 with
| 0 -> ()
| n -> Buffer.add_subbytes b chunk 0 n; go ()
| exception End_of_file -> ()
in
go ();
let code = match Unix.close_process_in ic with Unix.WEXITED c -> c | _ -> -1 in
(code, Buffer.contents b)
let contains hay needle =
let n = String.length needle and h = String.length hay in
let rec go i = i + n <= h && (String.sub hay i n = needle || go (i + 1)) in
n = 0 || go 0
(* The IR of one function out of a module's text. [Emit] writes a define's
closing brace at column 0 and nowhere else, so the end is unambiguous
without parsing LLVM. One .ll can carry several bodies — [C-c C-k] sends a
buffer's worth as one module — which is why this slices rather than
returning the file. *)
let ir_of ~ir name =
let sym = Emit.fname name in
let rec take = function
| [] -> []
| "}" :: _ -> [ "}" ]
| l :: rest -> l :: take rest
in
let rec find = function
| [] -> None
| l :: rest ->
if String.length l > 7 && String.sub l 0 7 = "define " && contains l (sym ^ "(")
then Some (String.concat "\n" (take (l :: rest)))
else find rest
in
find (String.split_on_char '\n' ir)
(* objdump's own output, rebased and labelled. A line is
[" 250:<tab>bytes<tab>mnemonic"], with a continuation line carrying only
bytes when an instruction's encoding does not fit the column. *)
type insn = { off : int; bytes : string; text : string }
let parse_listing ~sym text =
let head = "<" ^ sym ^ ">:" in
let lines = String.split_on_char '\n' text in
let rec drop = function
| [] -> []
| l :: rest -> if contains l head then rest else drop rest
in
(* objdump prints a blank line after the last instruction of a symbol and
then whatever follows it in the section. Stopping at that line is what
keeps a one-function listing from running into the next function. *)
let rec upto = function
| [] -> []
| l :: rest -> if String.trim l = "" then [] else l :: upto rest
in
let body = upto (drop lines) in
let base = ref None in
let out = ref [] in
List.iter
(fun l ->
match String.split_on_char '\t' l with
| addr :: bytes :: rest ->
let a = String.trim addr in
let a =
if String.length a > 0 && a.[String.length a - 1] = ':' then
String.sub a 0 (String.length a - 1)
else a
in
(match int_of_string_opt ("0x" ^ a) with
| None -> ()
| Some n ->
if !base = None then base := Some n;
let b = match !base with Some b -> b | None -> n in
out :=
{ off = n - b; bytes = String.trim bytes;
text = String.trim (String.concat "\t" rest) }
:: !out)
| _ -> ())
body;
(List.rev !out, !base <> None)
(* A branch inside the function shows as [<flan.step+0x79>] or, for the entry,
[<flan.step>]. Those become [L0]..[Ln] in address order, as SBCL labels
them; anything else objdump annotated — a cell, a plt entry, another
function — is left exactly as it wrote it. *)
let target_of ~sym text =
if not (contains text ("<" ^ sym)) then None
else
match String.index_opt text '<' with
| None -> None
| Some i ->
let rest = String.sub text i (String.length text - i) in
if String.length rest < 3 || rest.[String.length rest - 1] <> '>' then None
else
let inner = String.sub rest 1 (String.length rest - 2) in
if String.equal inner sym then Some 0
else
let p = String.length sym in
if String.length inner > p + 1 && String.sub inner 0 (p + 1) = sym ^ "+"
then
int_of_string_opt (String.sub inner (p + 1) (String.length inner - p - 1))
else None
let render_listing ~sym insns =
let targets =
List.sort_uniq compare
(List.filter_map (fun i -> target_of ~sym i.text) insns)
in
let label n =
let rec idx k = function
| [] -> None
| x :: r -> if x = n then Some (Printf.sprintf "L%d" k) else idx (k + 1) r
in
idx 0 targets
in
let b = Buffer.create 4096 in
List.iter
(fun i ->
(match label i.off with
| Some lb -> Buffer.add_string b (lb ^ ":\n")
| None -> ());
let text =
match target_of ~sym i.text with
| Some n ->
(match label n with
| Some lb ->
(* [jmp 1d9 <flan.step+0x89>] becomes [jmp L1]. The bare number
objdump prints is the address the branch encodes *in the
file*, which is the one number on the line that means nothing
once the listing is rebased — so it goes with the symbol it
duplicates. *)
let j = String.index i.text '<' in
let head = String.sub i.text 0 j in
let k = ref (String.length head) in
while !k > 0 && head.[!k - 1] = ' ' do decr k done;
while !k > 0
&& (match head.[!k - 1] with
| '0' .. '9' | 'a' .. 'f' | 'A' .. 'F' -> true
| _ -> false)
do decr k done;
String.sub head 0 !k ^ lb
| None -> i.text)
| None -> i.text
in
if text = "" then
Buffer.add_string b (Printf.sprintf " %04x %s\n" i.off i.bytes)
else
Buffer.add_string b
(Printf.sprintf " %04x %-22s %s\n" i.off i.bytes text))
insns;
Buffer.contents b
let asm_of ~obj name =
let sym = "flan." ^ name in
let code, text =
run_capture
(String.concat " "
[ Filename.quote objdump; "-d";
"--disassemble=" ^ Filename.quote sym; Filename.quote obj ])
in
if code <> 0 then
Error
(Printf.sprintf "%s failed on %s (exit %d): %s" objdump obj code
(String.trim text))
else
match parse_listing ~sym text with
| _, false -> Error (Printf.sprintf "%s found no symbol %s in %s" objdump sym obj)
| insns, true -> Ok (render_listing ~sym insns)
(* Where a name's body was last built, and how much of that is a claim about
the running process rather than about this daemon's disk. *)
let basis t name =
match Hashtbl.find_opt t.owners name with
| None ->
( { ogen = 0; oso = Filename.concat t.dir "program"; oll = t.host_ll;
oloc = host_loc t name },
"the host executable — nothing defining this name has been delivered in \
this session, so the program's cell still holds this body" )
| Some o ->
let m = Filename.basename o.oso in
( o,
match state t with
| Stopped c ->
(* Not "so it is not installed yet". The commonest way to stop is to
install a body and have it error, so a stopped program is more
likely to be running this code than not — the daemon simply cannot
read the cell back to find out, and saying otherwise would be the
[ok]-means-probably failure in the one field that exists to prevent
it. What is certain is only the second half. *)
Printf.sprintf
"%s — the last module delivered for this name, accepted for install; \
the program is stopped on %s and the daemon cannot read the cell \
back to say whether it installed this before stopping. Nothing \
further installs until it resumes"
m c
| Running ->
Printf.sprintf
"%s — the last module delivered for this name, accepted for install; \
the program installs it at its next frame boundary and the daemon \
cannot read the cell back to confirm that it has"
m
| Unreachable r ->
Printf.sprintf
"%s — the last module delivered for this name; the program is not \
answering (%s), so whether it installed cannot be said"
m r )
let kind_of t name =
let p = t.session.Session.program in
if List.exists (fun (g : Tast.global) -> String.equal g.Tast.gname name)
p.Tast.globals
then Some "a global"
else if
List.exists (fun (e : Tast.extern) -> String.equal e.Tast.ename name)
p.Tast.externs
then Some "an extern"
else None
let disassemble t ~name ~form =
if form <> "ir" && form <> "asm" then
error
(Printf.sprintf
"unknown form %S: disassemble takes :form \"ir\" or :form \"asm\"" form)
else
match find_fn t name with
| None ->
(match kind_of t name with
| Some k ->
error
(Printf.sprintf
"%s is %s, not a function: there is no generated code to show for it"
name k)
| None -> error (Printf.sprintf "no function named %s in this session" name))
| Some f ->
let o, why = basis t name in
let common =
[ ":name " ^ Wire.quote name; ":form " ^ Wire.quote form;
":generation " ^ string_of_int o.ogen;
":signature " ^ Wire.quote (signature_of_fn f);
(* [o.oloc], not the session's: the session moves on as soon as a
form checks, and this has to name the source the code being shown
was built from. *)
":loc " ^ Wire.quote o.oloc;
":basis " ^ Wire.quote why ]
in
if form = "ir" then
match read_file o.oll with
| text ->
(match ir_of ~ir:text name with
| Some body ->
ok (common @ [ ":object " ^ Wire.quote o.oll; ":text " ^ Wire.quote body ])
| None ->
error (Printf.sprintf "no define for %s in %s" (Emit.fname name) o.oll))
| exception Sys_error m ->
error ("the IR this body was built from is gone: " ^ m)
else if not (Sys.file_exists o.oso) then
error ("the object this body was linked into is gone: " ^ o.oso)
else
match asm_of ~obj:o.oso name with
| Ok text ->
ok
(common
@ [ ":object " ^ Wire.quote o.oso;
":note "
^ Wire.quote
"source interleaving needs line tables this build does not \
emit";
":text " ^ Wire.quote text ])
| Error m -> error m
let handle t req =
match Wire.string_field req "op" with
| Some "eval" ->
(match Wire.string_field req "code" with
| Some code ->
let origin =
match Wire.string_field req "file" with Some f -> f | None -> "<editor>"
in
eval t ~code ~origin
| None -> error "eval needs :code")
| Some "eval-expr" ->
(match Wire.string_field req "code" with
| Some code ->
let origin =
match Wire.string_field req "file" with Some f -> f | None -> "<editor>"
in
eval_expr t ~code ~origin
| None -> error "eval-expr needs :code")
| Some "describe" -> describe t
| Some "defs" -> defs t
| Some "break" -> break t
| Some "layout" ->
(match Wire.string_field req "type" with
| Some ty -> layout t ~ty
| None -> error "layout needs :type")
| Some "restart" ->
(match Wire.string_field req "name" with
| Some name -> choose t ~name
| None -> error "restart needs :name")
(* By index, which is the one that can name a shadowed restart. [:name] is
optional and is not the lookup: it is checked against the name the program
has at that index and refused if they have drifted apart, so a client that
listed and then chose cannot take a different restart than the one it
showed. *)
| Some "restart-at" ->
(match Wire.int_field req "index" with
| Some index -> choose_at t ~index ~name:(Wire.string_field req "name")
| None -> error "restart-at needs :index")
| Some "abort" -> abort t
| Some "disassemble" ->
(match Wire.string_field req "name" with
| Some name ->
let form =
match Wire.string_field req "form" with Some f -> f | None -> "asm"
in
disassemble t ~name ~form
| None -> error "disassemble needs :name")
| Some "close" -> ok []
| Some op -> error ("unknown op: " ^ op)
| None -> error "no :op"
(* ── The loop ──────────────────────────────────────────────────────── *)
(* One connection at a time. An editor is one client, evaluations are
sequential by nature — each one is checked against the program the last one
left behind — and a second concurrent evaluation would be racing for the
same session anyway. *)
(* Returns whether the client asked to end the session. One editor per daemon,
so [close] shuts the whole thing down rather than waiting for another
connection nobody is going to make. *)
let serve t fd =
let rec go () =
match Wire.recv fd with
| src ->
let op, reply =
match Wire.parse src with
| req -> (Wire.string_field req "op", handle t req)
| exception Loc.Error (_, m) -> (None, error ("bad request: " ^ m))
in
Wire.send fd (with_output t (with_break t reply));
if op = Some "close" then true else go ()
| exception Wire.Closed -> false
| exception Unix.Unix_error _ -> false
in
go ()
(* [debug] is off by default, which keeps [flan dev] exactly what it was: a
-O2 host and -O2 modules. It is opt-in rather than always-on because a debug
build is an -O0 build — [llvm.dbg.declare] describes an alloca and mem2reg
deletes it — and silently making every reloaded body -O0 would change the
frame time of the one function you are iterating on, in the loop whose whole
point is watching that number. *)
let start ?(debug = false) ~file ~sock () =
let t0 = Unix.gettimeofday () in
(* Absolute, because every location this daemon ever reports is derived from
it and an editor is not in this process's working directory. [flan dev
src/game.flan] run from a project root would otherwise send back
"src/game.flan:12:7", which the editor can only resolve by guessing which
directory it was relative to. *)
let file = try Unix.realpath file with Unix.Unix_error _ -> file in
let session, l = Session.create ~debug ~file () in
let dir =
Filename.concat (Filename.get_temp_dir_name ())
(Printf.sprintf "flan-dev-%d" (Unix.getpid ()))
in
(try Unix.mkdir dir 0o700 with Unix.Unix_error (Unix.EEXIST, _, _) -> ());
let exe = Filename.concat dir "program" in
(* [keep] so the host's own IR survives the build. It is the text [llc] was
actually given, not a second emission of it, which is the difference
between showing what the process was built from and showing what it
probably was. [Build.executable] leaves it in its own working directory
under the module's basename; it is moved here so that nothing else in this
process can reuse the name. *)
(* The host and the modules are one decision. DWARF in a redefinition is
only half a debuggable dev loop: lldb re-resolves a *name* breakpoint
against each module as it loads either way, but a breakpoint set on a line
in the .flan buffer needs a line table on both sides — the host's to fire
before the first C-c C-c, the module's to follow the reload. *)
ignore
(Build.executable
~opts:{ Build.default with Build.dev = true; Build.keep = true;
Build.debug }
~csrcs:l.Load.csrcs ~lflags:l.Load.lflags session.Session.host ~out:exe);
let host_ll = Filename.concat dir "host.ll" in
(try
Sys.rename (Filename.concat (Build.workdir ()) (Filename.basename exe ^ ".ll"))
host_ll
with Sys_error _ -> ());
let agent = Filename.concat dir "agent.sock" in
(* The program's source names some socket path; the daemon is the one that
knows where it wants to talk to it, so it overrides through the
environment. Guessing instead would fail silently — everything compiles,
the module is built, and nothing ever receives it. *)
Unix.putenv "FLAN_AGENT_SOCKET" agent;
(* Through a pipe, so the program's own output can reach an editor instead of
only the terminal the daemon was started in. *)
let rd, wr = Unix.pipe ~cloexec:false () in
let child = Unix.create_process exe [| exe |] Unix.stdin wr Unix.stderr in
Unix.close wr;
Unix.set_nonblock rd;
(* Wait for it to bind before accepting an evaluation. One that arrives first
would fail for a reason that reads like a compiler bug. *)
if not (await (fun () -> Sys.file_exists agent)) then begin
(try Unix.kill child Sys.sigterm with Unix.Unix_error _ -> ());
failwith
("the program never listened on " ^ agent
^ " — does it call (agent/start ...)?")
end;
let t =
{ session; child; agent; dir; stdout = rd; out = Buffer.create 4096; n = 0;
gen = 0; owners = Hashtbl.create 32; host_ll }
in
(try Unix.unlink sock with Unix.Unix_error _ -> ());
let ls = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0 in
Unix.bind ls (Unix.ADDR_UNIX sock);
Unix.listen ls 4;
Printf.eprintf "flan dev: %s ready on %s (%.0fms)\n%!" file sock
((Unix.gettimeofday () -. t0) *. 1000.);
(* [accept] would block past the program's own exit, so it is waited on with
a timeout and the child checked each time round: a daemon whose program
has finished has nothing left to do, and an editor waiting on it would
wait forever. *)
let rec accept_loop () =
if alive t then
(* The program's pipe is in the same select as the listening socket: it
has to be drained whether or not an editor is asking for anything. *)
match Unix.select [ ls; t.stdout ] [] [] 0.2 with
| [], _, _ -> accept_loop ()
| ready, _, _ when not (List.mem ls ready) -> drain t; accept_loop ()
| _ ->
(match Unix.accept ls with
| fd, _ ->
let closed = serve t fd in
(try Unix.close fd with Unix.Unix_error _ -> ());
if not closed then accept_loop ()
| exception Unix.Unix_error (Unix.EINTR, _, _) -> accept_loop ())
| exception Unix.Unix_error (Unix.EINTR, _, _) -> accept_loop ()
in
Fun.protect
~finally:(fun () ->
(try Unix.kill child Sys.sigterm with Unix.Unix_error _ -> ());
(try Unix.close ls with Unix.Unix_error _ -> ());
(try Unix.close rd with Unix.Unix_error _ -> ());
(try Unix.unlink sock with Unix.Unix_error _ -> ()))
accept_loop