Re: No warning issued here?

Re: No warning issued here?

[Doug Semler]

> 
> void f()
> {
>   int i = i;
> }
> 
> /*
> Problem description:
> 
> This compiles without a hitch.
> 
> I would expect a warning to be emitted because of the use of i in the
> righthand side.  Even if this conforms to the C++ standard, this is
> likely to be a programming error, so a warning would be in place.
> 
> 
> 
> 
>   
>  */

(C++ standard basic.scope.pdecl says this is indeterminite value, btw)

You get a warning when compiling with -Wall -O (optimization needed for
reason to ensure the assignment is optimized away...can gcc detect 
uninitialized variables for unoptimized code?)

int i;
int f()
{
   int i = i;
   return i;
}

ruck:~> gcc -O -c crap.c -Wall
crap.c: In function `f':
crap.c:4: warning: `i' might be used uninitialized in this function


---
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Re: No warning issued here?

[Alexandre Oliva]

On Apr 22, 1999, Doug Semler <doug@seaspace.com> wrote:

>> int i = i;

> You get a warning when compiling with -Wall -O (optimization needed for
> reason to ensure the assignment is optimized away...

Yep, this is even documented :-)

`-Wuninitialized'
     An automatic variable is used without first being initialized.

     These warnings are possible only in optimizing compilation,
     because they require data flow information that is computed only
     when optimizing.  If you don't specify `-O', you simply won't get
     these warnings.

-- 
Alexandre Oliva http://www.dcc.unicamp.br/~oliva IC-Unicamp, Brasil
{oliva,Alexandre.Oliva}@dcc.unicamp.br  aoliva@{acm.org,computer.org}
oliva@{gnu.org,kaffe.org,{egcs,sourceware}.cygnus.com,samba.org}
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