Re: Where did the warning go?

["Eivind LM" <eivliste at online dot no>]

On Tue, 24 Feb 2009 15:13:55 +0100, Tom St Denis  
<tstdenis@ellipticsemi.com> wrote:

> Eivind LM wrote:
> > It does of course depend on each case whether a warning is easy to  
> > avoid or not, and also if it warns about a real problem or not. But in  
> > any case, a warning can help me write code that more surely will do  
> > what I intend. For example the following code is not doing what I  
> > intended:
> >
> >   #include <stdio.h>
> >   void print(int a) { printf("%d\n", a); };
> >   int main() { print(2.5); return 0; };
> >
> > I think the problem in the code is both easy to avoid and serious, but  
> > I get no warning with -Wall and -Wextra (g++ 4.3).
> That's because it's not undefined behaviour.  "default" warnings should  
> be for things that are not guaranteed to have a known meaning or  
> behaviour.

I think the warning should be part of -Wall, but I understand if you don't  
agree. Anyway this is not my point. I trust someone has good reasons for  
the selection of warnings included in -Wall.

My points are: "-Wall" should be renamed, and a new flag should be added  
that would enable absolutely all warnings.

> e.g.
>
> int a;
> if (a == 4) { ... }
>
> Is undefined behaviour since a is unitialized.

Compiling this example with -Wall and -Wextra gives me no warning with g++  
(Debian 4.3.2-1.1) 4.3.2. Installed by apt-get today from Debian  
repositories.

> float a;
> a = 0;
> if (a == 4) { ... }
>
> Is fine, but I should also point out "4" is an integral type that is  
> converted to float for the purpose of the expression "a == 4" .  So by  
> your logic, it should also generate a warning.

Yes, I would like a warning if I compare a float to an int.

I would probably not compare two floats on equality anyway, but if I  
really had to, then I would write "4" as 4.0f.

Compiling the second example with -Wall and -Wextra gives me no warning  
with the same compiler as above.

> -Wall should really just enable every warning that has something to do  
> with behaviour that is not predictable.

Fine, but the name should be changed.

> -Weverything would be an appropriate name for every warning.

Agree! :)

Eivind