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X-Authentication-Warning: slinky.cs.nyu.edu: pechtcha owned process doing -bs
Date: Wed, 5 May 2004 14:19:39 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: Ted Yu <ted_yu AT yahoo DOT com>
cc: cygwin AT cygwin DOT com
Subject: RE: DLL generation under Cygwin
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Message-ID: <Pine.GSO.4.56.0405051410380.15563@slinky.cs.nyu.edu>
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On Wed, 5 May 2004, Ted Yu wrote:

> Hi, Igor:
> > So does MSVCRT.dll, which is what MinGW uses for its
> > runtime.
>
> I am not familiar with MinGW. What is it ?

<http://mingw.org/>.  This is what you invoke when you give the
-mno-cygwin flag to gcc.  Incidentally, once you eliminate Cygwin from the
equation, any further questions or problem reports about "gcc -mno-cygwin"
should go to the mingw-users list.

> > Why are you linking in libc.a explicitly?  The appropriate version
> > should be automatically linked in by the compiler.
>
> If I omit libc.a, I get this:
> ld: warning: cannot find entry symbol fftEntry AT 12; defaulting to 10001000
> djbfft2d.o(.text+0x3c0):djbfft2d.cpp: undefined reference to `_alloca'
> djbfft2d.o(.text+0x44c):djbfft2d.cpp: undefined reference to `malloc'
> djbfft2d.o(.text+0x7a7):djbfft2d.cpp: undefined reference to `free'

That's because you use "ld" instead of "gcc".  "gcc" (with appropriate
flags, i.e., "-mno-cygwin") should do the right thing.  You can also use
"gcc -shared" instead of dlltool, IIRC.

> > What's LIBS set to?  What's DLLNAME set to?  What's AS set to?
>
> LIBS is empty. DLLNAME is djbfft.dll. AS is as.
>
> > and using $(CC) to link instead of $(LD) (you can pass flags to ld via
> > the -Wl,... options, IIRC).
>
> Any difference in doing so ? I got the above Makefile from Cygwin FAQ.

See above.  "gcc" does invoke "ld" under the covers, but it's very hard to
reconstruct the actual command line manually, so why not just use "gcc"?

> Does gcc accept -e option ?
> Thanks

If you mean "ld"'s option to set the start address, then "gcc" itself
doesn't, but you can pass it to "ld" via -Wl,-e...
	Igor
-- 
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