[libvirt] [PATCH 1/4] util: alloc: Remove pointless clearing of variable in AUTOPTR_FUNCs

[Erik Skultety]

On Fri, Feb 22, 2019 at 05:04:37PM +0100, Peter Krempa wrote:
> VIR_DEFINE_AUTOPTR_FUNC defines a function which is supposed to free the
> resources for the given VIR_AUTOPTR variable. Given that the cleanup
> function is executed when the stack frame is being destroyed it does not
> make much sense to set the pointer to NULL.

Although correct, the current code is correct too and I really don't see any
benefit behind removing a single line where you reset a variable to NULL, if
anything, this adds more safety regardless of scenario (defensive programming
in general).

Originally, I wanted to argue, that this might introduce an issue in loops if
you pass the temporary variable to a function by reference and then exiting on
failure would free some garbage, but that's irrelevant since Sukrit introduced
a syntax check to ensure, VIR_AUTO variables are always initialized.

>
> Making the inline function contain less code also decreases the
> possibility that for a given type the inlining will be declined by the
> compiler due to increasing code size.

I honestly doubt that re-setting a variable to NULL will have any impact on
this and it's such a trivial operation that the compiler might optimize this
for you in some way.

I think this patch should be dropped from the series and left as is.

Erik