Re: [Xen-devel] [PATCH] tests/cpu-policy: Skip building on older versions of GCC

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.05.19 at 16:43, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 24/05/2019 15:19, Jan Beulich wrote:
>>>>> On 24.05.19 at 15:29, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> --- a/tools/tests/cpu-policy/Makefile
>>> +++ b/tools/tests/cpu-policy/Makefile
>>> @@ -1,8 +1,20 @@
>>>  XEN_ROOT = $(CURDIR)/../../..
>>>  include $(XEN_ROOT)/tools/Rules.mk
>>>  
>>> +TARGET-y := test-cpu-policy
>>> +
>>> +# For brevity, these tests make extensive use of designated initialisers, 
>>> but
>>> +# GCCs older than 4.6 can't cope.  Ignore the test in this case.
>> Designated initializers alone are no problem for old gcc. The issue is
>> with ones used for sub-structures/-unions without field name.
>> Perhaps worth slightly extending the comment to this effect?
> 
> " in anonymous unions" ?  I can never remember exactly which bit it
> chokes on, but I think there are two different ones in practice which
> interfere.

" in anonymous unions" is fine with me.

>>> --- a/tools/tests/x86_emulator/Makefile
>>> +++ b/tools/tests/x86_emulator/Makefile
>>> @@ -97,7 +97,7 @@ $(foreach flavor,$(SIMD) $(FMA),$(eval $(call 
>>> simd-check-cc,$(flavor))))
>>>  TARGET-$(shell echo 'asm("{evex} vzeroall");' | $(CC) -x c -c -o /dev/null 
>>> > - || echo y) :=
>>>  
>>>  ifeq ($(TARGET-y),)
>>> -$(warning Test harness not built, use newer compiler than "$(CC)")
>>> +$(warning Test harness not built, use newer compiler than $(CC) $(shell 
>>> $(CC) -dumpversion) and an "{evex}" capable assembler)
>>>  endif
>> I appreciate the idea of providing mode information, but I'm afraid
>> this is going to be clumsy in the other direction now:
>>
>> "Test harness not built, use newer compiler than gcc-4.8 4.8 and ..."
>>
>> Naming the compiler binary, I thought, allows the user to figure
>> out the version easily enough. Therefore, please consider
>> dropping that part again.
> 
> I'm afraid you have a selection bias here.  Your compiler binaries may
> have a version suffix, but the overwhelming majority of people who are
> going to hit that error and need to figure out what to do will be using
> their system-provided binaries, as per the commit message.

Well, I can only judge by what the distro does that I use; I wasn't
aware they do something non-standard. I've already avoided
mentioning my own compiler naming scheme.

> What about:
> 
>   ... than "$(CC)" (version $(shell $(CC) -dumpversion)) and ...
> 
> which should (in your example) render as:
> 
>   ... than "gcc-4.8" (version 4.8) and ...
> 
> ?

Better, so let's go with this.

Jan



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