Arm Multilib Question

[Sebastian Huber]

On 11/10/2019 15:46, Joel Sherrill wrote:
> Hi
> 
> I'm trying to find the right multilib for the ARM Deos BSP. They compile 
> their native
> ARINC 653 applications with these:
> 
> arm-eabi-gcc   -MP -MMD -nostdinc -gdwarf-2 -fno-exceptions 
> -mabi=aapcs-linux -march=armv7-a -mfloat-abi=hard -mfpu=vfpv3-d16 
> -mthumb -mthumb-interwork   -O0  -fno-threadsafe-statics 
>   -fno-use-cxa-atexit -fno-rtti

I am not sure if -mabi=aapcs-linux is a nop or dangerous. Why do they 
use this option.

The -mthumb-interwork is superfluous.

The -fno-exceptions and -fno-rtti make more sense if you build libstdc++ 
also with it.

> 
> Neither arm-eabi nor arm-rtems will link this. arm-eabi picks a variant 
> for crtn0.o but doesn't seem to find a libm even though one is there in 
> the same multilib path and ends up with the math function undefined. 
> arm-rtems is just missing the multlib info as best I can tell.
> 
> /data/home/joel/test-gcc/install-master/bin/../lib/gcc/arm-rtems5/10.0.0/../../../../arm-rtems5/bin/ld: 
> error: /tmp/cc8zsaRc.o uses VFP register arguments, armtest does not
> /data/home/joel/test-gcc/install-master/bin/../lib/gcc/arm-rtems5/10.0.0/../../../../arm-rtems5/bin/ld: 
> failed to merge target specific data of file /tmp/cc8zsaRc.o
> 
> I have attached my simple example. Do we have a multlib that should be 
> matching this or does one need to be added?
> 
> Assistance definitely appreciated.

GCC 8, 9 and 10 are not supported by the ARM BSPs right now.

You can try this with GCC 10:

-mthumb -march=armv7-a+simd -mfloat-abi=hard

Why do they use -mfpu=vfpv3-d16? This seems to be quite a non-standard 
ARMv7-A chip.

-- 
Sebastian Huber, embedded brains GmbH

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