on Windows reading stdin from a pipe command throws"broken pipe" exception

[bdodrem]

On Windows, the following code :

     open Eio.Std
     open Eio.Buf_read  

     let _ = Eio_main.run (fun env ->  Seq.iter (traceln "%s" ) @@ lines @@ of_flow env#stdin ~max_size:1024  )

when run in a terminal (bash console) with the command :
echo 1 | dune exec ./test.exe

Throws the exception :

+1
Fatal error: exception Eio.Io Net Connection_reset Unix_error (Broken pipe, "stub_cstruct_read", "")

(I'm currently using ocaml 5.2.1 and eio 1.2 on MINGW64 )

[talex5]

I did a search on the Internet, and it turns out I reported the same bug in Lwt back in 2013. D'oh!

[bdodrem]

The issue seemed to be solved when I replaced Unix_cstruct.read with Unix.read_bigarray in the function read_cstruct (lib_eio_windows/low_level.ml).

diff --git a/lib_eio_windows/low_level.ml b/lib_eio_windows/low_level.ml
index 85f25cd..962210d 100755
--- a/lib_eio_windows/low_level.ml
+++ b/lib_eio_windows/low_level.ml
@@ -42,9 +42,9 @@ let read fd buf start len =
   Fd.use_exn "read" fd @@ fun fd ->
   do_nonblocking Read (fun fd -> Unix.read fd buf start len) fd

-let read_cstruct fd buf =
+let read_cstruct fd (buf:Cstruct.t) =
   Fd.use_exn "read_cstruct" fd @@ fun fd ->
-  do_nonblocking Read (fun fd -> Unix_cstruct.read fd buf) fd
+  do_nonblocking Read (fun fd -> Unix.read_bigarray fd buf.buffer buf.off buf.len) fd

 let write fd buf start len =
   Fd.use_exn "write" fd @@ fun fd ->

Hopefully this will solve the bug

[talex5]

This fix looks right to me.

@patricoferris how about removing eio_windows_cstruct_stubs.c and using the Unix functions instead?

[bdodrem]

Hi,

Here below is a patch to:

• fix blocking issue on Windows, reading from stdin blocks the whole domain. #793.
• fix broken pipe exception while reading stdin on Windows reading stdin from a pipe command throws"broken pipe" exception  #792.
• replace eio_windows_cstruct_stubs.c by Unix functions.

diff --git a/lib_eio_windows/dune b/lib_eio_windows/dune
index 8791342..0fa2546 100644
--- a/lib_eio_windows/dune
+++ b/lib_eio_windows/dune
@@ -6,7 +6,7 @@
  (foreign_stubs
   (language c)
   (include_dirs ../lib_eio/unix/include)
-  (names eio_windows_stubs eio_windows_cstruct_stubs))
+  (names eio_windows_stubs ))
  (c_library_flags :standard -lbcrypt -lntdll)
  (libraries eio eio.unix eio.utils fmt))

diff --git a/lib_eio_windows/low_level.ml b/lib_eio_windows/low_level.ml
index 85f25cd..54ba0e6 100755
--- a/lib_eio_windows/low_level.ml
+++ b/lib_eio_windows/low_level.ml
@@ -39,17 +39,25 @@ let rec do_nonblocking ty fn fd =
     do_nonblocking ty fn fd

 let read fd buf start len =
+  await_readable fd;
   Fd.use_exn "read" fd @@ fun fd ->
   do_nonblocking Read (fun fd -> Unix.read fd buf start len) fd

-let read_cstruct fd buf =
+let read_cstruct fd (buf:Cstruct.t) =
+  await_readable fd;
   Fd.use_exn "read_cstruct" fd @@ fun fd ->
-  do_nonblocking Read (fun fd -> Unix_cstruct.read fd buf) fd
+  do_nonblocking Read (fun fd -> Unix.read_bigarray fd buf.buffer buf.off buf.len) fd

 let write fd buf start len =
+  await_writable fd;
   Fd.use_exn "write" fd @@ fun fd ->
   do_nonblocking Write (fun fd -> Unix.write fd buf start len) fd

+let write_cstruct fd (buf:Cstruct.t) =
+  await_writable fd;
+  Fd.use_exn "write_cstruct" fd @@ fun fd ->
+  do_nonblocking Write (fun fd -> Unix.write_bigarray fd buf.buffer buf.off buf.len) fd
+
 let sleep_until time =
   Sched.enter @@ fun t k ->
   Sched.await_timeout t k time
@@ -148,8 +156,11 @@ let readv fd bufs =
   do_nonblocking Read (fun fd -> eio_readv fd bufs) fd

 let writev fd bufs =
-  Fd.use_exn "writev" fd @@ fun fd ->
-  do_nonblocking Write (fun fd -> Unix_cstruct.writev fd bufs) fd
+  let rec loop buf = if Cstruct.length buf > 0 then begin
+    let n = write_cstruct fd buf in
+    loop @@ Cstruct.shift buf n
+  end in
+  List.iter loop bufs

 let preadv ~file_offset fd bufs =
   Fd.use_exn "preadv" fd @@ fun fd ->
diff --git a/lib_eio_windows/low_level.mli b/lib_eio_windows/low_level.mli
index e2ec400..782a175 100755
--- a/lib_eio_windows/low_level.mli
+++ b/lib_eio_windows/low_level.mli
@@ -22,6 +22,7 @@ val sleep_until : Mtime.t -> unit
 val read : fd -> bytes -> int -> int -> int
 val read_cstruct : fd -> Cstruct.t -> int
 val write : fd -> bytes -> int -> int -> int
+val write_cstruct : fd -> Cstruct.t -> int

 val socket : sw:Switch.t -> Unix.socket_domain -> Unix.socket_type -> int -> fd
 val connect : fd -> Unix.sockaddr -> unit

Do I need to create a pull request ?

[talex5]

Do I need to create a pull request ?

That would be easier, yes. Though I can do it if that's a problem for you.