[Buildroot] [PATCHv3 08/14] configs: use new EABIhf option for beaglebone_defconfig

Thomas Petazzoni thomas.petazzoni at free-electrons.com
Tue Jul 16 13:47:04 UTC 2013

Dear Peter Korsgaard,

On Tue, 16 Jul 2013 15:39:19 +0200, Peter Korsgaard wrote:

>  Thomas> Yes, I tried beaglebone_defconfig, which uses an internal toolchain...
>  Thomas> which would not exhibit this problem.
> Ok, good. Then I'll commit it.
>  Thomas> Unfortunately, I'm not sure how to fix this particular problem. It's
>  Thomas> gcc that is too stupid to understand that -msoft-float appearing in the
>  Thomas> command line after -mfloat-abi=hard should take precedence over
>  Thomas> -mfloat-abi=hard. I believe we already had this case in the past, maybe
>  Thomas> not specifically with those options, but with other options.
>  Thomas> One solution I see to this is not very nice:
>  Thomas> 	if (gcc command line contains -msoft-float) {
>  Thomas> 		do not pass -mfloat-abi and -mfpu arguments
>  Thomas> 	}
> You mean in the toolchain wrapper? Yddrk.

Yes, I meant in the toolchain wrapper. I'm pretty sure we had a similar
discussion not long ago about an incompatibility between options
hard-coded into the wrapper and additional options passed to the

>  Thomas> The other solution is to simply not pass -mfloat-abi=hard, assuming the
>  Thomas> toolchain would by default generate such binaries, which should be the
>  Thomas> case because EABI and EABIhf are not compatible. However, we should
>  Thomas> still pass -mfloat-abi=soft/softfp as needed.
> That could work, but also doesn't sound really nice. Presumably gcc
> doesn't complain about -mfloat-abi=softfp -mfloat-abi=soft as those are
> compatible.

$ arm-linux-gnueabihf-gcc -mfloat-abi=hard -msoft-float -c toto.c
arm-linux-gnueabihf-gcc: erreur: -mfloat-abi=soft and -mfloat-abi=hard may not be used together
$ arm-linux-gnueabihf-gcc -mfloat-abi=soft -msoft-float -c toto.c
$ arm-linux-gnueabihf-gcc -mfloat-abi=softfp -msoft-float -c toto.c
$ arm-linux-gnueabihf-gcc -mfloat-abi=softfp -mfloat-abi=soft -msoft-float -c toto.c

So I'm not sure how to handle that.

>  Thomas> That makes me think that I should maybe add a check that ensures that
>  Thomas> the ABI selection (EABI/EABIhf) matches the one provided by the
>  Thomas> external toolchain (which is useful when custom external toolchains are
>  Thomas> used).
> That would be a nice addition, yes.

Indeed, I'll try to cook a patch for this.


Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.

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