Missing mpc.h in half(?) of the toolchains

[andy-shev]

Neither aarch64 nor powerpc64 (and I believe all flavours of them) are properly compiled / build, can't be used:

/opt/aarch64--glibc--stable-2024.02-1/bin/../lib/gcc/aarch64-buildroot-linux-gnu/12.3.0/plugin/include/builtins.h:23:10: fatal error: mpc.h: No such file or directory
  23 | #include <mpc.h>
     |          ^~~~~~~

I'm wondering how it have been tested, if tested at all...

FWIW, arm7 works good on the same kernel source tree.

[andy-shev]

FWIW, installing libmpc-dev (or analogue, depending on the distribution) "fixes" the issue, but it doesn't seem the right fix as host library headers is not what cross-compilation should use.

[tpetazzoni]

mpc.h is not missing at all:

$ find . -name 'mpc.h'
./include/mpc.h

The problem when you build a gcc plugin is that CROSS-gcc -print-file-name=plugin will return the path to plugins, and Makefiles building plugins usually do -I$(CROSS-gcc -print-file-name=plugin)/include. But the mpc.h and gmp.h are in a different location (they have no reason to be in this directory). So what you need to do is make sure that this other location gets used when building your plugin. In the kernel, it can be done using KBUILD_HOSTCXXFLAGS=-I/path/to/toolchain/include/

I don't really see a way to make this "automagic". Do you have any idea?