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SubjectRe: [PATCH] ARM: fix vdsomunge depends on glibc specific byteswap.h
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Am 30.09.2015 um 18:02 schrieb Ard Biesheuvel <ard.biesheuvel@linaro.org>:

> On 30 September 2015 at 17:56, H. Nikolaus Schaller <hns@goldelico.com> wrote:
>> If the host toolchain is not glibc based then the arm kernel build
>> fails with
>>
>> HOSTCC arch/arm/vdso/vdsomunge
>> arch/arm/vdso/vdsomunge.c:48:22: fatal error: byteswap.h: No such file or directory
>>
>> Observed with omap2plus_defconfig and compile on Mac OS X with arm ELF
>> cross-compiler.
>>
>> Reason: byteswap.h is a glibc only header.
>>
>> Changed to detect the host and include the right file as described at:
>>
>> https://bugs.freedesktop.org/show_bug.cgi?id=8882
>>
>> Tested to compile on Mac OS X 10.9.5 host.
>>
>> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
>> ---
>> arch/arm/vdso/vdsomunge.c | 18 ++++++++++++++++++
>> 1 file changed, 18 insertions(+)
>>
>> diff --git a/arch/arm/vdso/vdsomunge.c b/arch/arm/vdso/vdsomunge.c
>> index aedec81..5364cea 100644
>> --- a/arch/arm/vdso/vdsomunge.c
>> +++ b/arch/arm/vdso/vdsomunge.c
>> @@ -45,7 +45,25 @@
>> * it does.
>> */
>>
>> +#if defined(__linux__)
>> #include <byteswap.h>
>> +#elif defined(__OpenBSD__)
>> +#include <sys/endian.h>
>> +#define bswap_16 __swap16
>> +#define bswap_32 __swap32
>> +#define bswap_64 __swap64
>> +#elif defined(__APPLE__)
>> +#include <libkern/OSByteOrder.h>
>> +#define bswap_16 OSSwapInt16
>> +#define bswap_32 OSSwapInt32
>> +#define bswap_64 OSSwapInt64
>> +#else
>> +#include <sys/endian.h>
>> +#define bswap_16 bswap16
>> +#define bswap_32 bswap32
>> +#define bswap_64 bswap64
>> +#endif
>> +
>
> Have you tried this?
>
> #define bswap_16 __builtin_bswap16
> #define bswap_32 __builtin_bswap32
> #define bswap_64 __builtin_bswap64
>
> https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html

OS X host uses llvm and I am not sure if these builtins are
always available.

So it replaces an include file dependency by a compiler
built-in dependency. IMHO my approach is more general
and should cover a broader range of compile hosts.

This is a tool compiled by HOSTCC to be run on the build
host - so I think we can't assume to have a gcc host compiler
(while for the CC cross-compiler we can).

Thanks,
Nikolaus Schaller



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