Ocamlnet and EINPROGRESS

Ocamlnet and EINPROGRESS

[Yitzhak Mandelbaum]

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Hi,

I'm using the Http_client.Convenience module to get web pages.  
Unfortunately, if I link the Unix module into my program, then  
suddenly I get the Unix_error exception with code EINPROGRESS (38).   
I noticed this issue raised on the list last August, but it does not  
seem to have been resolved. Does anyone know how to solve this?

Thanks,
Yitzhak Mandelbaum

--------------------------------------------------
Yitzhak Mandelbaum
AT&T Labs - Research

http://www.research.att.com/~yitzhak



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Re: [Caml-list] Ocamlnet and EINPROGRESS

[Eric Cooper]

On Wed, Apr 02, 2008 at 09:06:56PM -0400, Yitzhak Mandelbaum wrote:
> I'm using the Http_client.Convenience module to get web pages.
> Unfortunately, if I link the Unix module into my program, then suddenly
> I get the Unix_error exception with code EINPROGRESS (38).

I don't see this with a trivial program that just does http_get:
    open Http_client.Convenience
    let () = print_string (http_get Sys.argv.(1))

The EINPROGRESS is from a connect() call on a socket that's been set
non-blocking.  Running the above program under strace shows that this
occurs, but it's handled within http_get.

Can you post a minimal example that shows the exception escaping?

-- 
Eric Cooper             e c c @ c m u . e d u

Re: [Caml-list] Ocamlnet and EINPROGRESS

[Yitzhak Mandelbaum]

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Sure, here's one:

let mystring = Http_client.Convenience.http_get "http://www.cnn.com"

But, whether or not it raises the exception depends what I link it  
with, which is the essential problem.

Yitzhak

On Apr 2, 2008, at 9:52 PM, Eric Cooper wrote:

> On Wed, Apr 02, 2008 at 09:06:56PM -0400, Yitzhak Mandelbaum wrote:
>> I'm using the Http_client.Convenience module to get web pages.
>> Unfortunately, if I link the Unix module into my program, then  
>> suddenly
>> I get the Unix_error exception with code EINPROGRESS (38).
>
> I don't see this with a trivial program that just does http_get:
>     open Http_client.Convenience
>     let () = print_string (http_get Sys.argv.(1))
>
> The EINPROGRESS is from a connect() call on a socket that's been set
> non-blocking.  Running the above program under strace shows that this
> occurs, but it's handled within http_get.
>
> Can you post a minimal example that shows the exception escaping?
>
> -- 
> Eric Cooper             e c c @ c m u . e d u
>
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> Archives: http://caml.inria.fr
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--------------------------------------------------
Yitzhak Mandelbaum
AT&T Labs - Research

http://www.research.att.com/~yitzhak



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Re: [Caml-list] Ocamlnet and EINPROGRESS

[Eric Cooper]

On Wed, Apr 02, 2008 at 10:08:55PM -0400, Yitzhak Mandelbaum wrote:
>    Sure, here's one:
> 
>    let mystring = Http_client.Convenience.http_get "http://www.cnn.com"
> 
>    But, whether or not it raises the exception depends what I link it
>    with, which is the essential problem.

On my (Debian) system, I can't build that program without linking in
the Unix module, since it's referenced by almost all of the ocamlnet
modules.   So I don't understand the problem you're seeing.

-- 
Eric Cooper             e c c @ c m u . e d u

Re: [Caml-list] Ocamlnet and EINPROGRESS

[Yitzhak Mandelbaum]

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Its a little more complicated than that. The problem arises when  
linking with 1) a library that links with Unix and 2) a file that  
depends on Unix. I've found a minimal example that fails on my system  
(OS X). It involves 4 files: Makefile, mintime.ml, unixprog.ml,  
minprog.ml (names chosen arbitrarily):

########################
Makefile:
########################

all: minprog

timelib.cma: mintime.ml
	ocamlfind ocamlc -package unix -linkpkg \
	-o $@ -a mintime.ml

minprog: timelib.cma  unixprog.ml
	ocamlfind ocamlc $(INCLUDES) -thread -o $@ \
	-package netclient -linkpkg $^ minprog.ml


########################
mintime.ml:
#######################

let now () = Unix.time ()

########################
unixprog.ml:
#######################

let foo x =
   let in_channel, out_channel = Unix.open_process "cat" in
   let read_fd = Unix.descr_of_in_channel in_channel in
   let write_fd = Unix.descr_of_out_channel out_channel in
   ()

########################
minprog.ml:
#######################

let mystring = Http_client.Convenience.http_get "http://www.cnn.com"


Then,

make minprog
./minprog

results in

Fatal error: exception Unix.Unix_error(38, "connect", "")

Yitzhak

On Apr 2, 2008, at 10:30 PM, Eric Cooper wrote:

> On Wed, Apr 02, 2008 at 10:08:55PM -0400, Yitzhak Mandelbaum wrote:
>>    Sure, here's one:
>>
>>    let mystring = Http_client.Convenience.http_get "http:// 
>> www.cnn.com"
>>
>>    But, whether or not it raises the exception depends what I link it
>>    with, which is the essential problem.
>
> On my (Debian) system, I can't build that program without linking in
> the Unix module, since it's referenced by almost all of the ocamlnet
> modules.   So I don't understand the problem you're seeing.
>
> -- 
> Eric Cooper             e c c @ c m u . e d u
>
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> Archives: http://caml.inria.fr
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs

--------------------------------------------------
Yitzhak Mandelbaum
AT&T Labs - Research

http://www.research.att.com/~yitzhak



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Re: [Caml-list] Ocamlnet and EINPROGRESS

[Stéphane Glondu]

Yitzhak Mandelbaum a écrit :
> timelib.cma: mintime.ml ocamlfind ocamlc -package unix -linkpkg \ -o $@
> -a mintime.ml
> minprog: timelib.cma  unixprog.ml  ocamlfind ocamlc $(INCLUDES) -thread
> -o $@ \ -package netclient -linkpkg $^ minprog.ml

With these rules, you link the Unix module twice. Try without -linkpkg
in the first rule. More generally, avoid using -linkpkg when making .cma
unless you know what you are doing (use it only in the final stage of
linking).

Cheers,

-- 
Stéphane

Re: [Caml-list] Ocamlnet and EINPROGRESS

[Dario Teixeira]

> With these rules, you link the Unix module twice. Try without -linkpkg
> in the first rule. More generally, avoid using -linkpkg when making .cma
> unless you know what you are doing (use it only in the final stage of
> linking).

Indeed.  And on that note I would like to report a similar problem
with the "ocamlfind+ocamlbuild" plugin that was discussed on this
list some weeks ago, and available on the Ocamlbuild wiki:
http://brion.inria.fr/gallium/index.php/Using_ocamlfind_with_ocamlbuild

This is the offending code:

(* When one link an OCaml library/binary/package, one should use -linkpkg.
*)
flag ["ocaml"; "link"] & A"-linkpkg";


As Stéphane mentioned, -linkpkg should normally not be used on libraries.
(I have personally run into problems because of this).  The solution I
am using is to apply -linkpkg only when linking programmes:

(* When linking Ocaml programmes (and programmes only!), we use -linkpkg.
*)
flag ["ocaml"; "link"; "program"] & A"-linkpkg";


Regards,
Dario Teixeira





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