Re: [libvirt RFC PATCH 0/5] eliminating VIR_FREE in the *Clear() functions

On Fri, Feb 12, 2021 at 12:54:02AM -0500, Laine Stump wrote: > I've looked at a few of these, and one thing I've found is that very > often we have a function called somethingSomethingClear(), and: > > 1) The only places it is ever called will immediately free the memory > of the object as soon as they clear it. > > and very possibly > > 2) It doesn't actually *clear* everything. Some items are cleared via VIR_FREE(), but then some of the other pointers call > > bobLoblawFree(def->bobloblaw) > > and then don't actually set def->bobloblaw to NULL - so the functions > aren't actually "Clearing", they're "Freeing and then clearing a few > things, but not everything". > One thing I am wondering is whether this is really only used where it makes sense. As far as I understand, and please correct me if I am way off, the purpose of the Clear functions is to: a) provide a way to remove everything from a structure that the current function cannot recreate (there is a pointer to it somewhere else which would not be updated) and b) provide a way to reset a structure so that it can be filled again without needless reallocation. I think (b) is obviously pointless, especially lately, so the only reasonable usage would be for the scenario (a). However, I think I remember this also being used in places where it would be perfectly fine to free the variable and recreate it. Maybe it could ease up the decision, at least by eliminating some of the code, if my hunch is correct. In my quick search I only found virDomainVideoDefClear to be used in this manner and I am not convinced that it is worth having this extra function with extra