[Buildroot] gmp.h error compiling Linux 5.11 with Buildroot 2021.02 default arm toolchain

Thomas Petazzoni thomas.petazzoni at bootlin.com
Wed Mar 24 14:12:54 UTC 2021


On Wed, 24 Mar 2021 14:47:28 +0100
Michael Opdenacker <michael.opdenacker at bootlin.com> wrote:

> On 3/24/21 10:50 AM, Thomas Petazzoni wrote:
> > Do you have a Buildroot configuration that uses an internal toolchain +
> > a Linux kernel built by Buildroot, that reproduces this? Or does it
> > only happens with an external toolchain and/or when you build the
> > kernel outside of Buildroot?  
> 
> Actually, the compile job succeeds with the "omap2plus" configuration
> when the 5.11 kernel is built by Buildroot. Good guess.
> 
> What doesn't work is building the kernel outside Buildroot with (the
> Buildroot toolchain from output/host/ or the latest ARM 32 GNU toolchain).
> 
> Does this help?

It doesn't help per-se, but it's another useful data point. This whole
gmp.h is due to the gcc plugins that the kernel is building.

The gcc plugin causing issue there is built when
CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK=y in your kernel configuration.
Could you double check you have that enabled both when building the
kernel within Buildroot, and outside of Buildroot ?

To me, it seems like passing
HOSTCXXFLAGS=-I/path/to/buildroot/output/host/include when building
the kernel should get you passed the issue when building the kernel
externally.

And it probably works when Buildroot builds the kernel, because we're
passing:

        HOSTCC="$(HOSTCC) $(HOST_CFLAGS) $(HOST_LDFLAGS)" \

when building the kernel, so the kernel build system does invoke the
native gcc with the appropriate -I option pointing to
$(HOST_DIR)/include.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com


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