How to enable HW FPU for RTEMS POSIX API

Joel Sherrill joel.sherrill at
Fri Jun 25 15:45:25 UTC 2010

On 06/25/2010 10:35 AM, Gardner, Michael T wrote:
> We are using the POSIX API with RTEMS 4.10 on a leon3 processor.  We 
> would like to take advantage of the leon3’s floating point hardware, 
> however, in order to get our software to run without generating the 
> “unexpected trap (0x4) fp disabled” error we have to make sure that we 
> compile (and link) everything with the –msoft-float option.   This 
> seems to preclude use of processor’s hardware floating point.
> I have seen references to how to go about setting the RTEMS floating 
> point task attribute but nothing for the POSIX API.  What do we need 
> to do to enable hardware FPU usage with the POSIX API?
The FPU is enabled for all POSIX threads by default.

Are you sure it is not in a Classic API init task or
some other task created via the Classic API rtems_task_create?
> Michael T. Gardner
> Sandia National Labs
> mtgardn at
> 505-844-1299

Joel Sherrill, Ph.D.             Director of Research&  Development
joel.sherrill at        On-Line Applications Research
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