Re: [dpdk-dev] Compiling files with .S with GCC

[Olivier MATZ <olivier.matz@6wind.com>]

On 05/04/2015 04:49 PM, Wiles, Keith wrote:
> 
> 
> On 5/4/15, 1:37 AM, "Olivier MATZ" <olivier.matz@6wind.com> wrote:
> 
>> Hello,
>>
>> On 04/26/2015 06:55 PM, Wiles, Keith wrote:
>>>
>>>
>>> On 4/26/15, 11:53 AM, "Wiles, Keith" <keith.wiles@intel.com> wrote:
>>>
>>>> Hi All,
>>>>
>>>> I noticed in my builds with foo.S file I would get a warning from the
>>>> compiler the foo_s.o.tmp linker file will not be used as the code is
>>>> not
>>>> linked. A strange error and the foo_s.o file would not be created. In
>>>> the
>>>> mk/internal/rte.compile-pre.mk we have the following
>>>>
>>>> # command to assemble a .S file to generate an object
>>>> ifeq ($(USE_HOST),1)
>>>> S_TO_O = $(CPP) $(HOST_CPPFLAGS) $($(@)_CPPFLAGS)
>>>> $(HOST_EXTRA_CPPFLAGS)
>>>> $< $(@).tmp && \
>>>>    $(HOSTAS) $(HOST_ASFLAGS) $($(@)_ASFLAGS) $(HOST_EXTRA_ASFLAGS) -o
>>>> $@
>>>> $(@).tmp
>>>> S_TO_O_STR = $(subst ','\'',$(S_TO_O)) #'# fix syntax highlight
>>>> S_TO_O_DISP =  $(if $(V),"$(S_TO_O_STR)","  HOSTAS $(@)")
>>>> else
>>>> S_TO_O = $(CPP) $(CPPFLAGS) $($(@)_CPPFLAGS) $(EXTRA_CPPFLAGS) $< -o
>>>> $(@).tmp && \
>>>>    $(AS) $(ASFLAGS) $($(@)_ASFLAGS) $(EXTRA_ASFLAGS) -o $@ $(@).tmp
>>>> S_TO_O_STR = $(subst ','\'',$(S_TO_O)) #'# fix syntax highlight
>>>> S_TO_O_DISP =  $(if $(V),"$(S_TO_O_STR)","  AS $(@)")
>>>> endif
>>>>
>>>> I had to change the above Œ.tmp¹ strings to Œ.s¹ to remove this warning
>>>> and get the foo_s.o file created. Using the .s the file name becomes
>>>> foo_s.o.s
>>>
>>> Compiler used on Ubuntu 14.04 'gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2'
>>>
>>>>
>>>> Did not try this with clang or any other compiler, but I expect we can
>>>> safely change the Œ.tmp¹ to Œ.s¹ IMO
>>>>
>>>> Anyone else notice this problem?
>>
>> I tested a similar use-case and I don't reproduce the issue.
>> I don't don't understand why replacing $(@).tmp by $(@).s would
>> solve it.
> 
> In the case I saw the compiler seemed to want the .s to under stand it was
> not some other type of file. Not sure why the error occurred in my
> external build. We can leave it using .tmp if you like, but I feel .s
> would have been the correct name for the file.

Can you send a log of the error you've seen?
Can you reproduce it outside the dpdk framework by trying to assemble
a file called foo.tmp?
This would show that the problem really comes from the extension of
the file.


> 
> If you think it needs to be changed to .s then you can submit a patch or I
> can or just leave it along your option.

Until we really understand the cause of the issue, I don't think this
should be changed. But I'm not opposed to change it if we have a good
justification.


Regards,
Olivier



> 
> Regards,
> ++Keith
>>
>> The file $(@).tmp is used as a temporary file to store the preprocessed
>> version of the $(@).s file. I agree that using the .s extension is not
>> a bad choice (see below), but to me it is not the proper solution to
>> your problem.
>>
>>From https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html
>>
>>  file.s
>>     Assembler code.
>>  file.S
>>  file.sx
>>     Assembler code that must be preprocessed.
>>
>> Regards,
>> Olivier
>