Soft Float for PC386

Joel Sherrill joel.sherrill at
Mon Feb 12 13:05:32 UTC 2001

Ralf Corsepius wrote:
> Angelo Fraietta wrote:
> >
> > I have noticed during the configure stage of the script, the following is shown (this is from the ts_386 so
> > it should be soft float)
> > running /bin/sh ../../../../../RTEMS4.5.0ss/c/src/make/configure  --host=i386-rt
> > ems --build=i586-pc-linux-gnu --target=i386-rtems --prefix=/opt/rtems --disable-
> > hwapi --enable-multiprocessing --enable-cxx --enable-rdbg --disable-tests --disa
> > ble-networking --enable-posix --disable-itron --with-target-subdir=i386-rtems --
> > libdir=/opt/rtems/i386-rtems/lib --cache-file=.././config.cache --srcdir=../../.
> >
> > does libdir=/opt/rtems/i386-rtems/lib mean that it would be linking with the libraries in that directory
> > instead of the soft-float directory?
> No. libdir is used by autoconf and automake to specify the path to
> the directory where libraries shall be install during "make
> install".
> Currently is not used at all by RTEMS,and therefore should not have
> any influence at all.
> > Shouldn't that be /opt/rtems/i386-rtems/lib/soft-float ??
> No. libdir can vary inside of the build tree and should better not
> be passed manually to the toplevel configure script at all.
> However, there should neither be a need to set it, nor should having
> set it have any effect on building RTEMS. (Warning: Future versions
> of RTEMS probably will be using it.)
> > I copied the files from the soft-float directory to that directory but still had the same fault, i.e.
> > exception 7.
> >  Is there anywhere else I should be looking
> You could try to isolate the location of the offending FPU-call
> (find the caller, eg. by debugging paranoia.exe, disassembly,
> linker-map analysis).

My guess is that incorrectly/accidentally there is an FP instruction.
It could be by linking against the wrong library, incorrect code
generation, or simply a piece of code assuming an FPU.  Given the
fault address, you can do an objdump on the executable and see
what instruction is at that address.  Using the objdump and symbol
table (nm), you can tell what routine the offending instruction is
in.  That plus possible the output of linking with -v should be
enough to figure out where to look.  

> > or am I off the track completely??
> :)
> >
> > angelo wrote:
> >
> > > Is it possible that the wrong libraries are being linked.
> You might want to add -v to the linker invocation in your BSP's
> make-exe (make/custom/<BSP>.cfg) and try to analyse the what it
> reports for linking paranoia.exe.
> Ralf
> --
> Ralf Corsepius
> Forschungsinstitut fuer Anwendungsorientierte Wissensverarbeitung
> (FAW)
> Helmholtzstr. 16, 89081 Ulm, Germany     Tel: +49/731/501-8690
> mailto:corsepiu at           FAX: +49/731/501-999

Joel Sherrill, Ph.D.             Director of Research & Development
joel at                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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