Re: [Xen-devel] [PATCH 02/34] xen: clang: Disable built-in assembler

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Tim,

On 03/26/2014 01:16 PM, Tim Deegan wrote:
> At 11:53 +0000 on 26 Mar (1395831232), Jan Beulich wrote:
>>>>> On 25.03.14 at 17:55, <julien.grall@xxxxxxxxxx> wrote:
>>> --- a/xen/Rules.mk
>>> +++ b/xen/Rules.mk
>>> @@ -74,6 +74,7 @@ AFLAGS-y                += -D__ASSEMBLY__ -include 
>>> $(BASEDIR)/include/xen/config
>>>  
>>>  # Clang's built-in assembler can't handle .code16/.code32/.code64 yet
>>>  AFLAGS-$(clang)         += -no-integrated-as
>>> +CFLAGS-$(clang)         += -no-integrated-as
>>
>> Iirc Tim had found and worked around other built-in assembler issues
>> in the past, so if this is to be done unconditionally I wonder whether
>> we shouldn't then drop those workarounds.
> 
> I would prefer, wherever possible, to make things work with the clang
> assembler rather than rely on the binutils one forever.

The clang integrated assembler is too powerful for some part of Xen :).
Every inline assembly code is parsing by the assembler to check the syntax.

This will result to failure to generate asm-offsets.c because of the ->
in the code (see arch/arm/arm32/asm-offsets.c: DEFINE/BLANK macros).
Indeed, the -> is not a valid assembler syntax.

> BTW, I haven't looked at any of this series in detail yet but I'm
> planning to go through it all tomorrow.

There still have few issues to build the tools and Xen x86_64 with clang
3.5.

I also would like to see if we can re-enable some warnings (see
Config.mk) with newer version of clang.

Regards,

-- 
Julien Grall

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