Hello, 

I've change the toplevel of Ocaml to replace the standard input and output by named pipes on Windows. 

To achieve this, I've change the toploop.ml (https://github.com/ocaml/ocaml/blob/trunk/toplevel/toploop.ml) to include the named pipes 
of Ocamlnet (http://projects.camlcity.org/projects/dl/ocamlnet-4.1.2/doc/html-main/Netsys_win32.html#1_Supportfornamedpipes). 

After that, I tried to understand how I could compile this custom toplevel. 
I want to compile the toplevel to have a .exe, so I could avoid using Cygwin to launch the application. 

I've run the makefile of the git repository of Ocaml and tried to follow the sequence of compilation for the toplevel. 
I use ocamlopt to have a native aplication and ocamlfind to link toploop.ml with the library ocamlnet 
(via the package netsys where the win32 named pipe are defined) and unix for catching exceptions. 

I use Opam : 1.3.0~dev, Ocaml : 4.03.0 and Cygwin on Windows 7. 

So I write a Makefile (see the attachement) and when I launch it, I get this : 
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ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c genprintval.mli 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c genprintval.ml 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c toploop.mli 
ocamlfind ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c toploop.ml -linkpkg -package netsys -package unix 
File "C:\OCaml64\home\Zar\toplevel_custom\_none_", line 1: 
Warning 58: no cmx file was found in path for module Netsys_win32, and its interface was not compiled with -opaque 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c trace.mli 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c trace.ml 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c topdirs.mli 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c topdirs.ml 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c topmain.mli 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c topmain.ml 
ocamlopt -g -I +compiler-libs -a -o tmp_ocamltoplevel.cmxa genprintval.cmx toploop.cmx trace.cmx topdirs.cmx topmain.cmx 
ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -c topstart.ml 
ocamlfind ocamlopt -g -I +compiler-libs ocamlcommon.cmxa ocamlbytecomp.cmxa ocamlcommon.a ocamlbytecomp.a -linkall -o toplevel_custom.exe tmp_ocamltoplevel.cmxa topstart.cmx tmp_ocamltoplevel.a -linkpkg -package netsys -package unix 
** Cannot resolve symbols for tmp_ocamltoplevel.a(topdirs.o): 
caml_get_current_environment 
File "caml_startup", line 1: 
Error: Error during linking 
______________________________________________________________________ 

But I don't know how to resolve this error. 
I find that "caml_get_current_environment" is defined in meta.c (and used in topdirs.ml) 
(https://github.com/ocaml/ocaml/search?utf8=%E2%9C%93&q=caml_get_current_environment+&type=) 
But I think that meta.c is in the ocamlbytecomp.cmxa library, so I don't know why the linker don't find the symbols. 

Someone know how to resolve this problem ? 

Thank you in advance !