Crash under sparc/rtems-4.11 when compiling with FPU

Athanasios.Tsiodras at Athanasios.Tsiodras at
Mon Feb 8 08:50:14 UTC 2016

Hi Sebastian.

1. Regarding separate, FPU-based BSPs

Using separate BSP targets would clear up the issue... but note that the 
documentation refers to the so called "deferred floating point context 
switch" as a feature, not a bug...  That is, whether a task/thread has 
support for FPU-state-saving during context switches or not, is left up to 
the creation flags of the thread itself - so that  FPU-state-saving work 
is only done when context switching from an FPU-enabled thread to another 
FPU-enabled one (and not when switching to non-FPU threads).

2. Regarding compiling BSP with "-mhard-float"

I am guessing that you are suggesting I patch 
"leon3/make/custom/leon3.cfg" and switch -msoft-float to -mhard-float 
there (I didn't see anything FPU-related in the "configure" options). I'll 
try this and report back. 

European Space Agency (via HE Space)
Thanassis Tsiodras
Real-time Embedded Software Engineer 
System, Software and Technology Department

Keplerlaan 1, PO Box 299
NL-2200 AG Noordwijk, The Netherlands
Athanasios.Tsiodras at |
T +31 71 565 5332

From:   "Sebastian Huber" <sebastian.huber at>
To:     "RTEMS List" <users at>
Cc:     software at
Date:   07/02/2016 07:40
Subject:        Re: Crash under sparc/rtems-4.11 when compiling with FPU
Sent by:        "users" <users-bounces at>

Hello Athanasios,

it was always a miracle to me how you are supposed to use the leon2/leon3 
BSPs with a FPU. If you want to use the FPU, then the BSP must be built 
with the -mhard-float option, otherwise the FPU support is not enabled in 
the operating system support. In addition the application configuration 
must be compiled with exactly the same compiler flags as the BSP, 
otherwise it will generate a corrupt configuration.

I think we need leon2fp and leon3fp BSPs, which use -mhard-float.

Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at
PGP     : Public key available on request.

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