Re: [BUG] Build error for 4.15-rc3 kernel caused by patch "kbuild: Add a cache for generated variables"

[Yang Shi]

On 12/18/17 7:50 AM, Masahiro Yamada wrote:
> 2017-12-18 23:56 GMT+09:00 Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>:
> > 2017-12-17 7:35 GMT+09:00 Yang Shi <yang.s@xxxxxxxxxxxxxxx>:
> > > Hi folks,
> > >
> > > I just upgraded gcc to 6.4 on my centos 7 machine by Arnd's suggestion. But,
> > > I ran into the below compile error with 4.15-rc3 kernel:
> > >
> > > In file included from ./include/uapi/linux/uuid.h:21:0,
> > >                   from ./include/linux/uuid.h:19,
> > >                   from ./include/linux/mod_devicetable.h:12,
> > >                   from scripts/mod/devicetable-offsets.c:2:
> > > ./include/linux/string.h:8:20: fatal error: stdarg.h: No such file or
> > > directory
> > >   #include <stdarg.h>
> > >
> > > I bisected to commit 3298b690b21cdbe6b2ae8076d9147027f396f2b1 ("kbuild: Add
> > > a cache for generated variables"). Once I revert this commit, kernel build
> > > is fine.
> > >
> > > gcc 4.8.5 is fine to build kernel with this commit.
> > >
> > > I'm not quite sure if this is a bug or my gcc install is skewed although it
> > > can build kernel without that commit since that commit might exacerbate the
> > > case.
> > >
> > > Any hint is appreciated
> >
> >
> > Today, I was also hit with the same error
> > when I was compiling linux-next.
> > I am not so sure why this error happens, but
> > "make clean" will probably fix the problem.
> >
> > You need to do "make clean" to blow .cache.mk
> > when you upgrade your compiler.
> > This is nasty, though...
>
>
> I got it.
>
> The following line in the top-level Makefile.
>
> NOSTDINC_FLAGS += -nostdinc -isystem $(call shell-cached,$(CC)
> -print-file-name=include)
>
>
> If the stale result of -print-file-name is stored in the cache file,
> the compiler fails to find <stdarg.h>

Thanks for figuring it out.

"make clean" does help. I'm supposed it is an interim approach, right?

Regards,
Yang

>