[Buildroot] using BR2 variables to find a specific header file

[Mike Zick <minimod@morethan.org>]

On Mon, 13 Oct 2014 19:10:13 +0200
Sylvain Raybaud <sylvain.raybaud@green-communications.fr> wrote:

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> Dear all
> 
> I'm trying to integrate a cmake based package wich is not very
> cross-compiling friendly (MariaDB galera cluster). During normal
> compile this package runs some tests in order to determine if stacks
> grows downward or upward. During cross-compile these tests cannot be
> run therefore the package expects -DSTACK_DIRECTION=+/-1 to be passed
> to cmake. Of course you cannot do it in buildroot.
>

I think that the only processor where the stack grows up is PA-RISC.
Which is not one of the Buildroot supported processors.

So just hard code it (by patching if required) to down.

At least that would be my (non-BR developer) solution.

Mike 
> It seems to be possible to access this information in another way
> since STACK_GROWS_DOWNWARD is defined in some headers. In my case they
> are:
> 
> output/build/host-gcc-final-4.8.3/gcc/config/arm/arm.h
> (option a)
> 
> or
> 
> output/host/usr/lib/gcc/arm-buildroot-linux-uclibcgnueabi/4.8.3/plugin/include/config/arm/arm.h
> (option b)
> 
> or
> 
> output/host/usr/lib/gcc/arm-buildroot-linux-uclibcgnueabi/4.8.3/plugin/include/tm.h
> which in turns includes config/arm/arm.h  but seems more generic
> (option c)
> 
> using these files I could automatically determine the correct value
> for STACK_DIRECTION (either searching them for STACK_GROWS_DOWNWARD or
> calling C preprocessor on an ad-hoc source file that would include
> them).
> 
> The question is: how to determine inside buildroot which file to use?
> 
> I was thinking of using a combination of the following variables to
> determine the position of these headers. I'll list them with the value
> they have in my case. Do you think it's a good idea? Do you think it's
> portable?
> 
> BR2_ARCH="arm"
> BR2_GCC_VERSION=4.8.3
> BR2_GCC_TARGET_MODE=arm
> BR2_TOOLCHAIN=y
> BR2_TOOLCHAIN_BUILDROOT=y
> BR2_TOOLCHAIN_BUILDROOT_VENDOR=buildroot
> BR_TOOLCHAIN_USES_UCLIBC=y
> BR2_TOOLCHAIN_BUILDROOT_UCLIBC=y
> BR2_ARM_EABI=y
> 
> Using these variables it seems I can find the correct file but I'm not
> sure it's the correct way to do things. What do you think? Do you have
> suggestions?
> 
> Cheers,
> 
> - -- 
> Sylvain Raybaud
> www.green-communications.fr
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