[Buildroot] [PATCH] sh4: fix toolchain creation

[Arnout Vandecappelle <arnout@mind.be>]

 Hi Waldemar,

On 20/03/15 19:22, Waldemar Brodkorb wrote:
> The Linux kernel does force compile with -m4-nofpu, which is only
> available when building a multilib toolchain.
> The interesting part here is, that buildroot use --disable-multilib for
> gcc configure, but enables --with-multilib-list=m4,m4-nofpu in
> the default configuration for Qemu targeting r2d emulation.
> This results in a toolchain, which can be used for the kernel and
> for userland without creating a multilib toolchain with different
> kinds of libgcc version. In the multilib case there would be some
> subdirectories created like !m4 or m4-nofpu. As buildroot uses a
> short version of toolchain creation, a multilib enabled gcc build
> fails when creating libgcc.

 To be honest, I still don't understand what's going on here despite all this
explanation...


> So the best solution is to just keep multilib disabled, but always
> add --with-multilib-list=m4,m4-nofpu when sh4/sh4eb is choosen.

 But this sounds sane.

 However:

> Tested with sh4 minimal toolchain build and qemu defconfig with
> gcc 4.8.x and uClibc.

 If I understand correctly, you applied your patch and tested that
qemu_sh4_r2d_defconfig still works, right? Well, that should come as no surprise
since it just moves the --with-multilib-list option from one place to the other,
so you'll end up with exactly the same toolchain.

 The real question is: does it also work for other SH targets? Does it work on
real hardware? Or rather, is there anything that used to work that breaks now?


 Regards,
 Arnout


> 
> To sum up, compiling gcc with disabled multilib, but with a mulitlib-list
> provides a working toolchain which can create sh4 nofpu code without trying to
> create a libgcc for every variant.
> 
> Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
> ---
>  configs/qemu_sh4_r2d_defconfig     |    4 ----
>  package/gcc/gcc-final/gcc-final.mk |    6 ++++++
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/configs/qemu_sh4_r2d_defconfig b/configs/qemu_sh4_r2d_defconfig
> index 88bf914..586c400 100644
> --- a/configs/qemu_sh4_r2d_defconfig
> +++ b/configs/qemu_sh4_r2d_defconfig
> @@ -10,10 +10,6 @@ BR2_TARGET_GENERIC_GETTY_PORT="ttySC1"
>  BR2_TARGET_ROOTFS_EXT2=y
>  # BR2_TARGET_ROOTFS_TAR is not set
>  
> -# The kernel wants to use the -m4-nofpu option to make sure that it
> -# doesn't use floating point operations.
> -BR2_EXTRA_GCC_CONFIG_OPTIONS="--with-multilib-list=m4,m4-nofpu"
> -
>  # Lock to 3.19 headers to avoid breaking with newer kernels
>  BR2_KERNEL_HEADERS_VERSION=y
>  BR2_DEFAULT_KERNEL_VERSION="3.19"
> diff --git a/package/gcc/gcc-final/gcc-final.mk b/package/gcc/gcc-final/gcc-final.mk
> index c014bc5..607e850 100644
> --- a/package/gcc/gcc-final/gcc-final.mk
> +++ b/package/gcc/gcc-final/gcc-final.mk
> @@ -53,6 +53,12 @@ HOST_GCC_FINAL_CONF_OPTS = \
>  	--enable-poison-system-directories \
>  	--with-build-time-tools=$(HOST_DIR)/usr/$(GNU_TARGET_NAME)/bin
>  
> +# The kernel wants to use the -m4-nofpu option to make sure that it
> +# doesn't use floating point operations.
> +ifeq ($(BR2_sh4)$(BR2_sh4eb),y)
> +HOST_GCC_FINAL_CONF_OPTS += "--with-multilib-list=m4,m4-nofpu"
> +endif
> +
>  # Disable shared libs like libstdc++ if we do static since it confuses linking
>  ifeq ($(BR2_STATIC_LIBS),y)
>  HOST_GCC_FINAL_CONF_OPTS += --disable-shared
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F