Re: [Xen-devel] [PATCH for-4.7] xen/build: Fix build with Clang

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 07/04/16 20:21, Jan Beulich wrote:
>>>> On 07.04.16 at 21:16, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 07/04/16 20:12, Jan Beulich wrote:
>>>>>> On 07.04.16 at 20:46, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>> --- a/xen/Rules.mk
>>>> +++ b/xen/Rules.mk
>>>> @@ -50,9 +50,15 @@ ALL_OBJS-$(CONFIG_X86)   += $(BASEDIR)/crypto/built_in.o
>>>>  CFLAGS += -nostdinc -fno-builtin -fno-common
>>>>  CFLAGS += -Werror -Wredundant-decls -Wno-pointer-arith
>>>>  CFLAGS += -pipe -g -D__XEN__ -include $(BASEDIR)/include/xen/config.h
>>>> -CFLAGS += -Wa,--strip-local-absolute
>>>>  CFLAGS += '-D__OBJECT_FILE__="$@"'
>>>>  
>>>> +ifneq ($(clang),y)
>>>> +# Clang doesn't understand this command line argument, and doesn't appear 
>>>> to
>>>> +# have an suitable alternative.  The resulting compiled binary does 
>>>> function,
>>>> +# but has an excessively large symbol table.
>>>> +CFLAGS += -Wa,--strip-local-absolute
>>>> +endif
>>> Well, that's the brute force undo-it-altogether-for-clang approach
>>> that I think Doug had also considered. You may have seen the
>>> discussion (on irc iirc) - I'd really like to see the option still getting
>>> passed to gas (for all the .S files) even when using clang. Would
>>> that really be hard to arrange for?
>> That won't fix the fact that all the .c files which include
>> cpufeatureset.h also gets the absolute symbols, to allow the
>> alternatives() blocks to compile.
> That's understood.
>
>> It will complicate the clang build quite a bit, and won't make much of a
>> dent on the symbol table bloat.
> While this I'm unclear about: Istr Doug mentioning that simply
> adding the option in suitable for to AFLAGS would do.

In which case I clearly missed that bit on IRC.

I am happy to defer to Doug's solution if it actually resolves the
underlying issue.

~Andrew

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