Hi Eric, On Fri, 30 Aug 2019, Eric Wong wrote: > Johannes Schindelin <Johannes.Schindelin@xxxxxx> wrote: > > > > On Tue, 27 Aug 2019, Derrick Stolee wrote: > > > > > On 8/25/2019 10:43 PM, Eric Wong wrote: > > > > C compilers do type checking to make life easier for us. So > > > > rely on that and update all hashmap_entry_init callers to take > > > > "struct hashmap_entry *" to avoid future bugs while improving > > > > safety and readability. > > > > > > Overall I like this change. I'll need to keep it in mind with my > > > sparse-checkout work that is adding more hashmap types. > > > > > > One _might_ think that this change is relaxing the condition on > > > where the hashmap_entry appears within the super-struct, but > > > the hashmap internals will still use void* and perform a cast > > > to hashmap_entry for hash comparisons. > > > > I thought precisely the same. > > Yes, that's the goal I'm working towards as mentioned in patches > 10 and 11 :) Well, it is not exactly clear to me how memory management would work (I have not read patch 10 or 11 due to lack of time). At the moment, releasing a hashmap means we can simply `free()` the stored pointers. If you drop the requirement to make the `hashmap_entry` field the first field of the enclosing `struct`, that is no longer possible. Of course, you could add an `offsetof` value to the hashmap that says what number we have to subtract from the stored pointer before calling `free()`, but that sounds quite a bit more fragile to me than the current design. > > Maybe we can get a Coccinelle rule that verifies that `struct > > hashmap_entryh` fields are always the first ones? > > At this point, why? Given the goal is to remove that requirement > entirely. With a Coccinelle rule, we could maintain a simple design *and* be certain that no user violates the assumption that the `hashmap_entry` field is the first one in the enclosing `struct`. Ciao, Dscho
