Untested return values.

[Frits van Bommel]

Hasan Aljudy wrote:
> Frits van Bommel wrote:
>> Lionello Lunesu wrote:
>>> What would happen if DMD would issue a compiler warning for untested 
>>> return values?
>>>
>>> bool somefunc() { ... }
>>>
>>> void main() {
>>>   somefunc();//warning: untested return value
>>>   auto b = somefunc();//OK
>>> }
>>>
>>> Especially useful for C or OS functions returning error values or 
>>> handles.
>>>
>>> L.
>>>
>>> PS. might even be worth a compiler error.
>>
>> I regularly use functions I don't need the return values of, so I 
>> wouldn't like this change.
>>
>> On the other hand, Walter might stop using printf() all over Phobos... :P
>> Nah, not worth it. Besides, the fact that functions like printf() have 
>> a return value is probably enough reason for Walter not to make such a 
>> change.
> 
> LOL, really?
> What does printf return? (what about writef?)

from http://www.cplusplus.com/ref/cstdio/printf.html (at bottom):
-----------
  *Return Value.*
   On success, the total number of characters printed is returned.
   On error, a negative number is returned.
-----------

I suppose it could be used if want to align the next output to a 
specific column without fixing all the fields to specific lengths.
Though the %n specifier could also be used for that[1].


[1] If you don't know what it does, don't worry. It's another obscure 
fact of printf(): %n accepts an int* that's filled with the number of 
characters printed so far. I believe it's main use is in format string 
exploits :P.