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

["Yang Shi" <yang.s@alibaba-inc.com>]

On 12/18/17 7:50 AM, Masahiro Yamada wrote:
> 2017-12-18 23:56 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
>> 2017-12-17 7:35 GMT+09:00 Yang Shi <yang.s@alibaba-inc.com>:
>>> 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

> 
>