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error code 141 / "unknown C primitive `unix_dup'" when flushing to unopened pipe #5289

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vicuna opened this issue Jun 15, 2011 · 4 comments
Closed

error code 141 / "unknown C primitive `unix_dup'" when flushing to unopened pipe #5289

vicuna opened this issue Jun 15, 2011 · 4 comments
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@vicuna
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vicuna commented Jun 15, 2011

Original bug ID: 5289
Reporter: cvp
Status: closed (set by @xavierleroy on 2013-08-31T10:43:57Z)
Resolution: not a bug
Priority: normal
Severity: crash
Platform: GNU/Linux (x86_64)
OS: Fedora Core (x86_64)
OS Version: 15
Version: 3.12.0
Category: ~DO NOT USE (was: OCaml general)

Bug description

When piping to programs that don't use stdin, the toplevel and the bytecode interpreter straight-up crash, when you would expect that an exception be thrown instead or something.

Steps to reproduce

Toplevel:
$ ocaml

#load "unix.cma" ;;

let p_out = Unix.open_process_out "true" ;;

val p_out : out_channel =

output_string p_out "foo" ;;

  • : unit = ()

flush p_out ;; (* crashes *)

$ echo $?
141
$

(Also crashes in toplevel without dynamic loading, made with:
$ ocamlmktop -custom -cclib -lunix unix.cma -o unix-top
)

Bytecode:
$ cat > fail.ml
let p_out = Unix.open_process_out "true" in
output_string p_out "foo";
flush p_out;
close_out p_out;
Unix.close_process_out p_out ;;
print_endline "executed successfully" ;;
^D
$ ocamlc -custom -cclib -lunix unix.cma fail.ml -o fail
$ ./fail # works
executed successfully
$ ocamlrun fail # doesn't
Fatal error: unknown C primitive `unix_dup'
$

Compiling to native machine code produces no errors (i.e. "executed successfully").

Additional information

$ uname -a
Linux icarus 2.6.38.7-30.fc15.x86_64 #1 SMP Fri May 27 05:15:53 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

$ ocaml -version
The Objective Caml toplevel, version 3.12.0

$ grep '$Id' $(ocamlc -where)/unix.mli
(* $Id: unix.mli 10450 2010-05-21 12:00:49Z doligez $ *)
@vicuna
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vicuna commented Jun 15, 2011

Comment author: cvp

Er... click the "View Advanced" link to see Steps to Reproduce.

@vicuna
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vicuna commented Jun 16, 2011

Comment author: @ygrek

It doesn't crash, but exits on SIGPIPE because true exits before output channel is flushed. Try yes > /dev/null' instead and see. Bytecode compiled works because channel happens to be flushed before trueis launched (race condition).unix_dup` is not found in last example because you shouldn't use ocamlrun to run executables with custom runtime.

@vicuna
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vicuna commented Jun 16, 2011

Comment author: cvp

In that case, shouldn't the interactive toplevel handle a SIGPIPE a little more gracefully? Because all the user sees is a sudden termination without an explanation.

@vicuna
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vicuna commented Aug 3, 2011

Comment author: @damiendoligez

You have your explanation right here:

flush p_out ;; (* crashes *)

$ echo $?
141

The termination code is 128 + 13. The 128 is a flag telling you that the process was killed by a signal, and the 13 is the signal number (SIGPIPE). Maybe the shell should report exit codes more explicitely ?

Should we try to catch all signals? And what do we do when we get one?

@vicuna vicuna closed this as completed Aug 31, 2013
@vicuna vicuna added the bug label Mar 20, 2019
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