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From: "Dave Korn" <dave DOT korn AT artimi DOT com>
To: <cygwin AT cygwin DOT com>
Subject: RE: Fortran calling c compilation problem
Date: Wed, 2 Aug 2006 15:11:35 +0100
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On 01 August 2006 15:39, Ben Wright wrote:


> g++ -mno-cygwin -Wl,--add-stdcall-alias
> -I/cygdrive/c/Java/jdk1.5.0_07/include
> -I/cygdrive/c/Java/jdk1.5.0_07/include/win32 -shared -o Samplers.dll <a
> whole bunch of source files here> -lstdc++ -lg2c
> 
> /cygdrive/c/DOCUME~1/ben/LOCALS~1/Temp/ccWWbiIF.o:gengam.f(.text+0x5):
> undefined reference to `_dgamdv_'
> (plus others of similar form)
> 
> The linker can't seem to find references of the form _dgamdv_. Functions
> are defined in the c portion as gdamdv_(<whatever>), and are called from
> Fortran as DGAMDV(). This works fine under Linux.

  Not quite sure why you would expect a function called _dgamdv_ to match one
which is called gdamdv_XXXXXX.  They appear to have very different names, and
one has a suffix where the other doesn't.  Is there some kind of typo in this
para?
 
> What's baffling is that if I compile just the c portion and inspect the
> output with nm then the supposedly undefined references are in there.
> 
> 10004148 T _dgamdv_

  However, this suggests that the real problem is just that the source files
are in the wrong (meaning non-dependency) order on the compiler command line,
and hence on the linker command line.

> Is there some quirk of cygwin when calling c from within fortran I need
> to set a flag for when compiling? I'd ordinarily chalk it up to my weak
> knowledge of c- but it compiles without complaint under Linux.

  This works fine on Linux where a shared lib can contain undefined references
that are linked up at runtime, but it doesn't work on 'doze where a dll has to
be fully resolved.  To fix it, you could just reorder the source files into
dependency order on the command-line, so that any file that refers to an
undefined symbol comes *before* the file that supplies that symbol, or you
could separate compiling and linking into two separate stages, and use the
--start-group and --end-group options to wrap all the object files on the
linker command line.

    cheers,
      DaveK
-- 
Can't think of a witty .sigline today....


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