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Re: [Consult] g++: About "-Wunused-variable" for constant variable initialized by function

On 10/22/2014 09:44 PM, Jonathan Wakely wrote:
> On 22 October 2014 02:46, Chen Gang <> wrote:
>> On 10/15/14 18:07, Chen Gang wrote:
>>> On 10/13/14 21:18, Chen Gang wrote:
>>>> On 10/13/14 18:53, Jason Merrill wrote:
>>>>> On 10/12/2014 10:32 AM, Chen Gang wrote:
>>>>>>    [root@localhost qemu_cc]# cat
>>>>>>    const char n() { return 1; }
>>>>>>    const char c =  n();
>>>>>>    [root@localhost qemu_cc]# /usr/local/bin/g++ -Wall -O0 -c -o test.o
>>>>>>    [root@localhost qemu_cc]# /usr/local/bin/g++ -Wall -O2 -c -o test.o
>>>>>> warning: 'c' defined but not used [-Wunused-variable]
>>>>>>     const char c =  n();
>>>>>>                ^
>>>>> The warning is correct (and new).  Please submit bug reports via the website; see
>> Aftr trying, I can not make a new account for gcc bugzilla.
>>  - Before file a bug, it is mandatory to have an acount.
>>  - I try to register a new account on the website, it said that need
>>    send mail to
>>  - I sent related mail to, but get no response.
>> Need I wait for some days? or could any member help to file this bug to
>> gcc bugzilla?
>> And whether it is OK or not, I shall try to analyze this issue directly,
>> I should try to finish it within 2014-10-31 (although I am really not
>> quite sure about it).
> I thought we'd established this is not a bug.

OK, thanks. I guess your meaning is that this warning is only for
optimization (let user notice to speed up performance and save code size
), not for correctness, so:

 - it is reasonable to report warning when user requires optimization

 - and also, need not report warning when user do not need optimization

If what I guess is correct, at least for me, it sounds reasonable, and
welcome any other members' ideas, suggestions or completions.

Chen Gang

Open share and attitude like air water and life which God blessed

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