Mail Archives: cygwin/2004/11/04/05:39:23
Igor,
Thanks a lot for the clarification
Cheers,
Rene
> On Wed, 3 Nov 2004, Rene Nyffenegger wrote:
>
> > Hello
> >
> > I am trying to create a shared object and use it in a program under
> > cygwin with gcc. I seem to miss a point. If some kind soul could help
> > me on that, I'd be very grateful.
> >
> > Here's the code for the shared object (calc_mean.c):
> >
> > #include "calc_mean.h"
> > double mean(double a, double b) {
> > return (a+b) / 2;
> > }
> >
> > Here's its header file (calc_mean.h):
> >
> > double mean(double, double);
> >
> >
> > So, I compile that to a .so like so:
> >
> > $ gcc -shared -o libmean.so calc_mean.c
> >
> > Then, there's main.c that wants to use the shared object:
> >
> > #include <stdio.h>
> > #include "calc_mean.h"
> >
> > int main(int argc, char* argv[]) {
> > double v1, v2, m;
> > v1 = 5.2;
> > v2 = 7.9;
> >
> > m = mean(v1, v2);
> >
> > printf("The mean of %3.2f and %3.2f is %3.2f\n", v1, v2, m);
> > return 0;
> > }
> >
> > I try to compile main.c like so:
> >
> > $ gcc main.c -o main -L. -lmean
> >
> > However, the following error is returned:
> > /usr/lib/gcc-lib/i686-pc-cygwin/3.3.3/../../../../i686-pc-cygwin/bin/ld:
> > cannot find -lmean
> > collect2: ld returned 1 exit status
> >
> > Obviously, I do something wrong here, but I have no idea what that could
> > be.
>
> As Chris recommended, use the ".dll" extension for your shared libs,
> or you can also build an import lib using
>
> $ gcc -shared -o libmean.so -Wl,--out-implib,libmean.dll.a calc_mean.c
>
> and your link step should work.
> Igor
> --
> http://cs.nyu.edu/~pechtcha/
> |\ _,,,---,,_ pechtcha AT cs DOT nyu DOT edu
> ZZZzz /,`.-'`' -. ;-;;,_ igor AT watson DOT ibm DOT com
> |,4- ) )-,_. ,\ ( `'-' Igor Pechtchanski, Ph.D.
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>
> "The Sun will pass between the Earth and the Moon tonight for a total
> Lunar eclipse..." -- WCBS Radio Newsbrief, Oct 27 2004, 12:01 pm EDT
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