On Wed, 2017-02-22 at 15:22 +0100, greg@xxxxxxxxx wrote: > On Wed, Feb 22, 2017 at 02:00:53PM +0000, Joakim Tjernlund wrote: > > On Wed, 2017-02-22 at 14:03 +0100, greg@xxxxxxxxx wrote: > > > On Wed, Feb 22, 2017 at 07:50:46AM +0000, Joakim Tjernlund wrote: > > > > On Wed, 2017-02-22 at 08:10 +0100, Greg KH wrote: > > > > > On Tue, Feb 21, 2017 at 04:24:04PM +0100, Joakim Tjernlund wrote: > > > > > > C++ does does not like the extra extern before asmlinkage, remove it. > > > > > > > > > > > > Signed-off-by: Joakim Tjernlund <joakim.tjernlund@xxxxxxxxxxxx> > > > > > > --- > > > > > > include/linux/printk.h | 4 ++-- > > > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > > > > > diff --git a/include/linux/printk.h b/include/linux/printk.h > > > > > > index 3472cc6..be823f5 100644 > > > > > > --- a/include/linux/printk.h > > > > > > +++ b/include/linux/printk.h > > > > > > > > > > > > > > > Why are you building this file with a C++ compiler? > > > > > > > > virtualbox uses C++ and includes various kernel headers and the build > > > > fails, virtualbox guest additions has not build for quite some time now and > > > > this is one of the problems. > > > > > > Virtualbox is a horrid pile of crap. You can quote me on that. We > > > don't care about out-of-tree drivers, the authors should work to get > > > them merged properly if they do care. > > > > Sure, I believe you :) > > > > But in this case it is not the kernel modules that fails, it is their > > guest additions/xf86 video driver. Seem like that these need to include some > > kernel herders there too. > > Seems like their build system is broken, it should not be including non > uapi header files at all. > > > > Kernel code should be C, not C++, and if you do want to use C++, then > > > you are on your own, sorry. > > > > But there are already a lot of C++ adjustments!? Just grepping for __cplusplus shows > > plenty of hits and what is the point of asmlinkage then: > > #ifdef __cplusplus > > #define CPP_ASMLINKAGE extern "C" > > #else > > #define CPP_ASMLINKAGE > > #endif > > > > #ifndef asmlinkage > > #define asmlinkage CPP_ASMLINKAGE > > #endif > > The usages in include/uapi/ make a bit of sense, but not much. > Everything outside of there makes no sense at all (really just some drm > and one scsi file.) They should be removed. > > > I read all of this that C++ code should be able to at least include kernel headers > > without fatal errors. > > For uapi stuff, yes. But that's not what you are doing here. You are > trying to build kernel code with a c++ compiler. That's not going to > work. Right, I looked into guest-addition and it builds a few kernel modules too and include linux/string.h and that pulls in the offending code. Anyhow, the code in printk.h is "wrong" to add an extra extern so that change should not be a big deal as is, C++ or not. > > How is a C++ compiler supposed to parse the following line in device.h > struct class; > (one of my most proud moments...) :)