Re: [Qemu-devel] [PATCH v3 2/4] configure: factor out supported flag check

[Stefan Hajnoczi]

On Mon, Mar 23, 2015 at 2:44 PM, John Snow <address@hidden> wrote:
> On 03/23/2015 09:03 AM, Stefan Hajnoczi wrote:
>>
>> On Thu, Mar 19, 2015 at 03:01:35PM -0400, John Snow wrote:
>>>
>>> +cc_has_warning_flag() {
>>> +    if [ "$2" != "--keep-tmpc" ]; then
>>> +        write_c_skeleton;
>>> +    fi
>>> +
>>>       # Use the positive sense of the flag when testing for -Wno-wombat
>>>       # support (gcc will happily accept the -Wno- form of unknown
>>>       # warning options).
>>> -    optflag="$(echo $flag | sed -e 's/^-Wno-/-W/')"
>>> -    if compile_prog "-Werror $optflag" "" ; then
>>> -       QEMU_CFLAGS="$QEMU_CFLAGS $flag"
>>> +    optflag="$(echo $1 | sed -e 's/^-Wno-/-W/')"
>>> +    compile_prog "-Werror $optflag" ""
>>> +}
>>> +
>>> +write_c_skeleton;
>>> +for flag in $gcc_flags; do
>>> +    if cc_has_warning_flag $flag --keep-tmpc; then
>>
>>
>> The only caller that uses --keep-tmpc wants TMPC to be the skeleton
>> program anyway.  The option can be dropped and the write_c_skeleton in
>> cc_has_warning_flag can be unconditional.
>>
>> Stefan
>>
>
> I just figured there was no use in rewriting the same skeleton file
> unconditionally in a loop.
>
> The helper is used later where we do want to regenerate the skeleton.
>
> If you still want me to just make it unconditional, I can, but I don't see
> the point.

Dropping it makes the code cleaner and simpler.  The option is not
needed for functionality or correctness.

IMO it's premature optimization.

Stefan