intializing the variables and compling with optimization

[Robert William Fuller]

Maybe you should add a default: case.  That may eliminate the warning.

J M Sharath Bharadwaj bharadwaj wrote:
> hi Andrew,
> 
> I was talking about warning option called -Wuninitialized
> Here in the below code, compiler gives warning like " might be used
> uninitialized in this function" for x ,
> {
>   int x;
>   switch (y)
>    {
>     case 1: x = 1;
>       break;
>     case 2: x = 4;
>       break;
>     case 3: x = 5;
>    }
>   foo (x);
> }
> 
> If the value code{y} is always 1, 2 or 3, then code{x} is
> always initialized, but GCC doesn't know this. So it emits a warning.
> 
> My question was, if I am going to initialize the variable x to some
> value. is that going to help for the compiler to perform better
> optimization, without giving ant warnings
> 
> Sharath.
> 
> 
> 
> On Fri, Jul 11, 2008 at 7:19 PM, Andrew Haley <aph@redhat.com> wrote:
>> J M Sharath Bharadwaj bharadwaj wrote:
>>> hi All,
>>>
>>> Is GCC going to perform a better optimization, if I am going to
>>> initialize the variable explicitly. I am asking this because I was
>>> reading the GCC online doc for warning options like as in
>>> http://www.cs.cmu.edu/cgi-bin/info2www?(gcc.info)Warning%20Options
>> This is a strange question.
>>
>> If you read an uninitialized variable your program contains undefined
>> behaviour, and optimization is going to be the least of your problems.
>> If you don't read from an uninitialized variable it doesn't matter.
>>
>> Andrew.
>>
>