Experimental Physics and
Industrial Control System

Jianxun Yan <[email protected]> · Mon, 28 Nov 2016 13:40:21 -0500

Thank you, Ben.
The linker flags for RTEMS is something like this

c/src/lib/libbsp/arm/altera-cyclone-v/make/custom/altcycv.inc:CPU_CFLAGS

= -march=armv7-a -mthumb -mfpu=neon -mfloat-abi=hard -mtune=cortex-a9

And for EPICS is

src/tools/O.RTEMS-altcycv_devkit/epics-base-RTEMS-altcycv_devkit.pc:Cflags:

-I${includedir_osi} -I${includedir_osd} -I${includedir_comp}

-march=armv7-a -mthumb -mfpu=neon -mfloat-abi=hard -mtune=cortex-a9

-DUNIX -DMY_DO_BOOTP=NULL

Both RTEMS & EPICS use -mfloat-abi=hard.

The reason causes the error maybe EPICS base is not compatible with

RTEMS 4.11 yet, just like what Andrew Johnson said.

Thanks,
Jay

On 11/28/2016 12:19 PM, Benjamin Franksen wrote:

On 28.11.2016 18:06, Michael Davidsaver wrote:

On 11/28/2016 11:54 AM, Benjamin Franksen wrote:

On 28.11.2016 15:49, Jianxun Yan wrote:

...

Not sure but

   ".../librtemscpu.a uses VFP register arguments, libComTestHarness does
not"

sounds a lot like a mismatch of compiler or linker flags between the BSP
and EPICS.

Also my first guess for what "VFP" means would be "virtual floating
point" i.e. use FP emulation instead of a 'real' FP unit.

VFP = Vector Floating Point aka. hard float.

https://www.arm.com/products/processors/technologies/vector-floating-point.php

The linker is catching an otherwise hard to detect condition where
different object files are compiled with different function calling
conventions (ABI).  In this case whether function arguments are pass in
VFP registers.

The relevant GCC option is '-mfloat-abi=soft|softfp|hard'.  I would
guess that different values were given when building the RTEMS libraries
vs. EPICS Base.

https://gcc.gnu.org/onlinedocs/gcc-4.9.3/gcc/ARM-Options.html#ARM-Options

Thanks for correcting my half-baked guesses. At least I was right that
it has to do with a compiler flag mismatch... ;-)

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System