Re: [PATCH] coverage: update gcov info for newer versions of gcc

[Jan Beulich <jbeulich@xxxxxxxx>]

On 11.09.2023 17:26, Alex Bennée wrote:
> Jan Beulich <jbeulich@xxxxxxxx> writes:
>> On 02.09.2023 17:11, Javi Merino wrote:
>>> --- a/xen/common/coverage/Makefile
>>> +++ b/xen/common/coverage/Makefile
>>> @@ -5,7 +5,9 @@ obj-y += $(call cc-ifversion,-lt,0407, \
>>>             gcc_3_4.o, $(call cc-ifversion,-lt,0409, \
> 
> This isn't even supported, see below:
> 
>>>             gcc_4_7.o, $(call cc-ifversion,-lt,0500, \
>>>             gcc_4_9.o, $(call cc-ifversion,-lt,0700, \
>>> -           gcc_5.o, gcc_7.o))))
>>> +           gcc_5.o, $(call cc-ifversion,-lt,1000, \
>>> +           gcc_7.o,  $(call cc-ifversion,-lt,1200, \
>>> +           gcc_10.o, gcc_12.o))))))
>>
>> This is getting unwieldy, so I think we ought to try to limit the number
>> of different files we have. Already gcc_4_9.c and gcc_7.c specify the
>> same GCOV_COUNTERS and differ only in the version checks (which could be
>> combined). Therefore ...
> 
> You may want to consider your policy on supported GCC versions. I see
> you still support:
> 
>     * C compiler and linker:
>       - For x86:
>         - GCC 4.1.2_20070115 or later
>         - GNU Binutils 2.16.91.0.5 or later
>         or
>         - Clang/LLVM 3.5 or later
>       - For ARM 32-bit:
>         - GCC 4.9 or later
>         - GNU Binutils 2.24 or later
>       - For ARM 64-bit:
>         - GCC 5.1 or later
>         - GNU Binutils 2.24 or later
> 
> While also having some commented out warnings because the base GCC is so old:
> 
>   CFLAGS   += -Wmissing-prototypes
>   # (gcc 4.3x and later)   -Wconversion -Wno-sign-conversion
> 
> For reference QEMU's minimum GCC is 7.4
> 
>   if compiler.get_id() == 'gcc' and 
> compiler.version().version_compare('>=7.4')
> 
> and while our support cycle is based off distro LTS releases I have to
> wonder do you actually need to support users building the
> latest/greatest version of the hypervisor on ancient user-spaces with
> old compilers?
> 
> I think the oldest distro you have in your CI is jessie (still hanging
> on with extended LTS support) and that uses GCC 4.9.
> 
> I see there are various scripts to gather support status into the
> documentation but I couldn't find a general statement on the projects
> overall approach to supported versions of components.

That's the problem - we've been intending to raise the baseline for quite
some time, but figuring at least a rule of thumb by which to go both now
and in the future turns out problematic.

Jan