Re: [gomp4.1] make libgomp's splay tree implementation key agnostic

[Aldy Hernandez <aldyh@redhat.com>]

On 10/15/2015 12:56 AM, Jakub Jelinek wrote:
> On Sun, Oct 11, 2015 at 12:47:19PM -0700, Aldy Hernandez wrote:
>> I'm investigating balanced binary tree options for the multiple priorities
>> variant of the task scheduler.  In looking at the splay tree adaption in
>> libgomp, I noticed that it requires preexisting typedefs and other
>> definitions before including splay-tree.h.  This makes it impossible to
>> reuse for another key within the library because splay-tree.c must know
>> about the node contents, and other files throughout libgomp all share the
>> aforementioned typedefs (because they all include libgomp.h).
>>
>> I also can't use libiberty's version because there are name conflicts with
>> libgomp's adaptation.
>>
>> I see no reason why the splay tree implementation itself (splay-tree.c)
>> needs to know about the content of the nodes.  With a little rearranging of
>> the data structures and some casts, we can reuse the splay trees at will.
>>
>> With the following patch we achieve the above, with the only penalty of an
>> indirection for a compare callback.
>>
>> Tested with make check-target-libgomp on x86-64 Linux.
>
> What about the following patch instead?
> Untested, other than compile time testing.

I would ideally like to look at sp->root from within header files 
(priority_queue.h) to quickly determine if we have an empty queue, and 
the contents of the splay tree are not available in the header file 
(task.c, or priority_queue.c as you describe).  I'd hate to have to call 
a splay-tree.c function to do so.

I could do pointer magic from the header file (yuck).

I could take sp == NULL to mean empty, but then we need to allocate the 
splay tree which is silly cause it's just one pointer.

Up to you, it's your baby. ;-)

Aldy