[Buildroot] Analysis of build results for 2016-08-05

[Ben Boeckel <mathstuf@gmail.com>]

On Sun, Aug 07, 2016 at 17:48:46 +0200, Samuel Martin wrote:
> It seems to be another error due to "-isystem
> $(STAGING_DIR)/usr/include" passed to g++ [1].
> 
> AFAICS, this is done by CMake when generating the flags.make files.
> Note that removing it from the CXX_INCLUDES variables in all generated
> flags.make prevent from triggering this error.
> 
> It is not clear to me whether it is a gcc-6.x bug or a CMake one.
> According to fedora developers, this is not a gcc-6 bug [2].
> Ben, do you have any idea?

It might be that CMake is having trouble determining the paths that the
compiler uses by default? It should exclude any such directories from
the -I setup (though -isystem may change this behavior). CMake builds up
this variable:

    https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_IMPLICIT_INCLUDE_DIRECTORIES.html

based on the platform. It prefixes these with the value of CMAKE_SYSROOT
to create the list of implicit directories it ignores when building up
-I lines. Is CMAKE_SYSROOT not set properly?

> Ben, I have not opened any ticket yet, nor checked if a similar one is
> already opened. Do you need more details?

Building with VERBOSE=1 would help since it would show the actual
command lines being used. It may also help to move over to the
cmake-developers list to reach more CMake developers:

    https://cmake.org/mailman/listinfo/cmake-developers

--Ben