On 09/18/2013 02:57 PM, Kenneth Graunke wrote:
On 09/15/2013 12:10 AM, Francisco Jerez wrote:
This patch introduces a pair of helper functions providing a common
implementation of the "new" and "delete" operators for all C++ classes
that are allocated by ralloc via placement new. The 'ralloc_new'
helper function takes care of setting up an ralloc destructor callback
that will call the appropriate destructor before the memory allocated
to an object is released.
Until now objects needed to call 'ralloc_set_destructor' explicitly
with a pointer to a static method which in turn called the actual
destructor in order to get something that should be transparent to
them. After this patch they'll only need to call 'ralloc_new' from
the new operator and 'ralloc_delete' from the delete operator, turning
all overloads of new and delete into one-liners.
I really like the idea of reducing the boilerplate. I'd been meaning to
do that for a while, but was thinking of creating a "rallocable" base
class (which would then introduce multiple inheritance). I never got
around to trying it.
I can't say I'm crazy about this approach, though:
There's still a fair bit of boilerplate; every class still needs to do:
static void* operator new(size_t size, void *ctx)
{
return ralloc_new<whatever>(size, ctx);
}
static void operator delete(void *p)
{
ralloc_delete(p);
}
I'd like to go all the way and condense that to a single line.
This is also the first usage of templates in core Mesa, which I know
will annoy a lot of people. While I would be in favor of using
templates to introduce type safety into things like exec_list or
hash_table, I don't think they provide a very compelling advantage in
this case.
I've sent out a new series which accomplishes the same thing, but
doesn't use templates, and reduces the boilerplate even a bit more.
Comments welcome.
I vote for Ken's method. It reduces the boilerplate from 7 lines
(using Francisco's method) to a single line.
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