Hello Arnaldo,
>>>> Em Wed, Sep 12, 2018 at 07:02:32PM +0200, Alexander Sverdlin escreveu:
>>>>> CC .../tools/objtool/builtin-check.o
>>>>> ...
>>>>> In file included from
>>>>> .../tools/arch/x86/include/uapi/asm/bitsperlong.h:11:0,
>>>>> from .../tools/include/asm-generic/bitops/__ffs.h:6,
>>>>> from .../tools/include/asm-generic/bitops.h:16,
>>>>> from .../tools/include/linux/bitops.h:35,
>>>>> from .../tools/include/linux/hashtable.h:13,
>>>>> from elf.h:24,
>>>>> from check.h:22,
>>>>> from builtin-check.c:30:
>>>>> .../tools/include/asm-generic/bitsperlong.h:8:0: error: "BITS_PER_LONG"
>>>>> redefined [-Werror]
>>>>> #define BITS_PER_LONG (__CHAR_BIT__ * __SIZEOF_LONG__)
[...]
finally I more or less know what happens here. In the actual Linux we have two
files defining the
same define:
>> # 1 ".../tools/include/linux/bitops.h" 1
#ifndef BITS_PER_LONG
# define BITS_PER_LONG __WORDSIZE
#endif
>> # 6 ".../tools/include/asm-generic/bitsperlong.h" 2
#ifdef __SIZEOF_LONG__
#define BITS_PER_LONG (__CHAR_BIT__ * __SIZEOF_LONG__)
#else
#define BITS_PER_LONG __WORDSIZE
#endif
So the two defines only work together if bitsperlong.h is included first.
In objtool both files are included and for most people bitsperlong.h is indeed
included first.
> I'll try and get one for building a x86_64 tools/perf,
> tools/lib/{api,bpf,traceevent} to see if I manage to reproduce the
> problem you're reporting.
One way to reproduce the reverted include order is to take a HOST compiler
built against old Linux headers, namely 2.6.30 and older.
This is because of the changes in asm/types.h.
It would be possible to put a guard into bitsperlong.h (#ifndef BITS_PER_LONG),
but it just doesn't look correct to me that we have two files defining the same
thing once quite simple, in the second case even more tricky.
--
Best regards,
Alexander Sverdlin.
