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From:	Mirko <phaccount AT nycap DOT rr DOT com>
Subject:	Problem linking cygwin dll with MSVC application
Date:	Mon, 09 Aug 2004 21:22:01 -0400
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Hello,

(this is a repeat post, as I have not seen the first one on the list)

I am trying to link a numerical routine written in Fortran to a data 
analysis application running on MS Windows 2000(IDL from RSI -- see 
www.rsinc.com).  IDL is compiled using MS' visual C compiler.

IDL has provisions to link external routines to it.  In essence, I have 
to generate a dll, and provide IDL with 1) the dll name and 2) entry 
point into the dll (i.e. a symbol for the subroutine that IDL will be 
calling).

I've been using gcc on cygwin with the following command in order for my 
dll to use MS' and not Cygwin's dll:

g77 -share -fPIC -mno-cygwin ...

If I compile and link with Cygwin's dll (don't use the -mno-cygwin 
option), I'll get IDL to crash all the time.  I guess that is because of 
some conflicts between Cygwin's and MS dll's.

Using -mno-cygwin works for some cases and not others (i.e, causes IDL 
to not to crash or crash.  Basically, if I pass the routine a vector of 
values, it will cause IDL to crash and conversely, if I pass it a 
scalar, it will run fine and return to IDL.

(No, this has nothing to do with incompatibility with declared variables 
in the routine.  Instead, if I am passing a vector, I call one interface 
Fortran routine with a Do loop over the individual values in the vector, 
and if I am passing a scalar, I am calling a different interface routine.)

My question is: are there other switches or options that I need to use 
so as not to cause conflicts between Cygwin compiled dll's and MS 
utilitites?

I understand that I may be mis-using Cygwin.  I am thus considering to 
do the compilation and dll creation using MinGW, because, as I 
understand it, that package is meant for program development on the MS 
platform.  However, I am not certain as how to  create a DLL in MinGW 
that is compatible with software compiled with MS' compiler.  I posted a 
such a question on the MinGW list.

Any suggestions or pointers to documentation?

Thanks,

Mirko

-- 
*m*irko*vukovic*-at-*nycap*ital-*r*oad*r*unner-com


-- 
*m*irko*vukovic*-at-nycap-rr-com


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