[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

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


when building the kernel, so the kernel build system does invoke the
native gcc with the appropriate -I option pointing to

Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering

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