Re: [Xenomai] Building with hard float: cannot open shared object file libpthread_rt.so.1

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On Tue, Mar 17, 2015 at 09:19:29AM -0700, Steve B wrote:
> Hello all,
> 
> It has come to my attention that when compiling with arm-linux-gnueabi-gcc
> my application is using a libm that seems to be doing soft floating point
> routines when I really want to be using hard float.
> I built a simple test application for now that does just one math operation
> and measures the amount of time taken.
> 
> Switching my compiler to arm-linux-gnueabihf and adding the -mhard-float
> flag, I get this error immediately at runtime:
> error while loading shared libraries: libpthread_rt.so.1: cannot open
> shared object file: No such file or directory
> 
> If I take away the -mhard-float flag, the program runs but the one math
> operation (with a corner case argument that I found to take a long time to
> compute) takes about 3000 microseconds to run.
> If I put the -mhard-float flag back in and take away Xenomai and run as a
> regular Linux application, the same operation takes around 60 microseconds.
> 
> I also tried building the Xenomai on my target system with the
> arm-linux-gnueabihf compiler and the -mhard-float flag at configure time,
> but this didn't fix the problem.
> Has anybody run across this before?

The problem is probably that the libc/libm you are using is not
using hard floats, the loader will refuse to load a program using
hard floats with a soft float library. An intermediate solution may
be to use hardware floating point with soft float ABI, by passing
-mfloat-abi=softfp to gcc.

You do not really get to choose the floating points you can use with
a given toolchain, the possibilities are fixed when the toolchain is
compiled.

-- 
					    Gilles.