-Wunused-but-set-variable warnings

[Michael Pyne]

On Monday, July 04, 2011 12:02:47 Dawit A wrote:
> The following files all contain set but unused variables:
> 
> kdelibs/kdecore/util/kshareddatacache.cpp:751:14: warning: variable
> ‘freedPagesRequired’ set but not used [-Wunused-but-set-variable]

Thanks for the heads-up on this one!

> Unlike the -Wunused-parameter fixing this warning messages requires
> context because the variable may be set and unused due to a mistake
> that can potentially be causing a bug.

In this case it was not, but as you point out that was only due to other 
things going on afterwards.

> As such can kdelibs cmake file
> be changed to error out, -Werror=unused-but-set-variable, for such
> warnings ?

I really kind of abhor -Werror in all of its incarnations. It's like holding a 
whole village hostage until one man gives themselves up to the posse. In this 
case it would affect /anyone/ trying to simply build KDE (even if they have 
more advanced compilers with more warnings generated than the developer who 
would need to make the fix).

Being unable even to build kdelibs, kde-workspace, etc. would make it very 
difficult for other developers to properly build and *test* the code that they 
are working on elsewhere. So while we should certainly apply social pressure 
to compile without warnings and ensure bug-free code, don't overdo it! The 
likely thing to come from such a decision is that the warnings are "fixed" by 
hastily-applied patches that either do not fix the problem, or possibly even 
introduce new ones.

I almost broke KSharedDataCache in a way I wouldn't have been able to easily 
test until I took a bit more time to think about what the code was actually 
doing now, and needed to be doing.

Regards,
 - Michael Pyne
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