RE: linking ocaml in multithreaded shared dll app

["Lionel Fourquaux" <lionel.fourquaux@wanadoo.fr>]

> -----Message d'origine-----
> De : Pierre.Weis@inria.fr [mailto:Pierre.Weis@inria.fr]De la part de
> Charles Neveu
> Envoye : mardi 7 novembre 2000 20:19
> A : caml-list@inria.fr
> Objet : linking ocaml in multithreaded shared dll app
>
>
> I'm trying to link the ocaml library into a Windows NT 4.0,
> MS VC++ 6.0
> application that uses MFC in a shared dll (because another library,
> OpenInventor, has to be linked this way).
> I'm getting an unresolved external symbol error for the symbols
> __pctype, ___mb_cur_max, and __dosmaperr from files like win32.obj,
> read.obj, write.obj, etc. (complete text at bottom).

	That's because you're linking with msvcrt.dll (DLL version of
Microsoft's C runtime). OCaml is linked with libcmt.lib (static
multithreaded
version of the same).


>
> I'm not a MSVC++ expert, but I'm guessing that the libunix library is
> compiled to be linked with a statically-linked MFC library. Is this
> right? Is there anyway to compile it to link to a
> dynamically-linked MFC
> library?

	Not exactly. OCaml doesn't use MFC. The problem is with the C library.
Moreover, you can't build the libunix library for linking with msvcrt.dll,
because it uses the internal function _dosmaperr, which is not exported by
the DLL.


>
> Or is there something else going on?
>
> Charles
>
> Here is the linker output (ignore the first few Maestro errors, I'm
> porting that):
> --------------------Configuration: talkdll - Win32
> Debug--------------------
> Compiling...
> Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 12.00.8168 for
> 80x86
> Copyright (C) Microsoft Corp 1984-1998. All rights reserved.
> cl /MDd /W3 /Gm /GX /ZI /Od /D "WIN32" /D "_DEBUG" /D "_WINDOWS" /D
     ^^^^

	This should be /MT. (See the documentation of the compiler.)


> "_MBCS" /D "_AFXDLL" /Fp"Debug/talkdll.pch" /Yc"stdafx.h" /Fo"Debug/"
> /Fd"Debug/" /FD /GZ /c
>    "E:\neveu\Development\talkdll\StdAfx.cpp"
> StdAfx.cpp
> Note: reusing persistent precompiled header
> Compiling...
> Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 12.00.8168 for
> 80x86
> Copyright (C) Microsoft Corp 1984-1998. All rights reserved.
> cl /MDd /W3 /Gm /GX /ZI /Od /D "WIN32" /D "_DEBUG" /D "_WINDOWS" /D
> "_MBCS" /D "_AFXDLL" /Fp"Debug/talkdll.pch" /Yu"stdafx.h" /Fo"Debug/"
> /Fd"Debug/" /FD /GZ /c
>    "E:\neveu\Development\talkdll\Mbr.cpp"
>    "E:\neveu\Development\talkdll\talkdll.cpp"
>    "E:\neveu\Development\talkdll\talkdllDlg.cpp"
> Skipping... (no relevant changes detected)
> Mbr.cpp
> talkdll.cpp
> talkdllDlg.cpp
> Linking...
> msvcirtd.lib(MSVCIRTD.dll) : error LNK2005: "public: class ostream &
> __thiscall ostream::operator<<(class ostream &
> (__cdecl*)(class ostream
> &))" (??6ostream@@QAEAAV0@P6AAAV0@AAV0@@Z@Z) already defined in
> libmae-nt.lib(Maestro_Types.obj)
> msvcirtd.lib(MSVCIRTD.dll) : error LNK2005: "class ostream & __cdecl
> endl(class ostream &)" (?endl@@YAAAVostream@@AAV1@@Z) already
> defined in
> libmae-nt.lib(Maestro_Types.obj)
> libmae-nt.lib(Maestro_GroupMember.obj) : error LNK2001: unresolved
> external symbol "class ostream_withassign  cerr"
> (?cerr@@3Vostream_withassign@@A)
> libmae-nt.lib(Maestro_GroupMember.obj) : error LNK2001: unresolved
> external symbol "class ostream_withassign  cout"
> (?cout@@3Vostream_withassign@@A)
> libmae-nt.lib(win32.obj) : error LNK2001: unresolved external symbol
> __pctype
> libmae-nt.lib(win32.obj) : error LNK2001: unresolved external symbol
> ___mb_cur_max
> libmae-nt.lib(read.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(write.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(close_on.obj) : error LNK2001: unresolved
> external symbol
> __dosmaperr
> libmae-nt.lib(createprocess.obj) : error LNK2001: unresolved external
> symbol __dosmaperr
> libmae-nt.lib(spawn-nt.obj) : error LNK2001: unresolved
> external symbol
> __dosmaperr
> libmae-nt.lib(dup.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(lseek.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(open.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(close.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(dup2.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(pipe.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(winwait.obj) : error LNK2001: unresolved external symbol
> __dosmaperr
> libmae-nt.lib(envir.obj) : error LNK2001: unresolved external symbol
> __environ
> libmae-nt.lib(execvp.obj) : error LNK2001: unresolved external symbol
> __environ
> Debug/talkdll.exe : fatal error LNK1120: 6 unresolved externals
> Error executing link.exe.
>
> talkdll.exe - 21 error(s), 0 warning(s)
>
> --
> Dr. Charles Frederick Neveu     T: 650 604-2525
> Autonomy and Robotics Group     F: 650 604-4036
> NASA Ames Research Center       E: neveu@artemis.arc.nasa.gov
> Mail Stop 269-4                 W: http://img.arc.nasa.gov/~neveu
> Moffett Field, CA 94035-1000
>


	There are several solutions :
 * if the source is available, build OpenInventor with /MT instead of /MD,
   and use static libs everywhere (including MFC)
 * split your program into several DLLs that uses different versions of
   the C runtime (Be careful with this !)
 * try to build OCaml with /MD, using DOSMAP.C from the CRT source if you
   need libunix.


	And some people from this mailing list will probably suggest better
solutions !


	I hope this will help you.


		Lionel Fourquaux