[PATCH 3/8] memtx: pass engine to memory allocation functions

[Vladimir Davydov]

On Tue, May 22, 2018 at 04:47:28PM +0300, Konstantin Osipov wrote:
> * Vladimir Davydov <vdavydov.dev at gmail.com> [18/05/22 15:10]:
> > We need this so that we can force garbage collection when we are short
> > on memory. There are two such functions: one is used for allocating
> > index extents, another for allocating tuples. Index allocating function
> > has an opaque context so we simply reuse it for passing memtx engine to
> > it. To pass memtx engine to tuple allocating function, we add an opaque
> > engine specific pointer to tuple_format (engine_data) and set it to
> > memtx_engine for memtx spaces.
> 
> Please rename engine_data to engine.

OK.

> I would not use an opaque pointer either, reference the engine
> explicitly.

The reason I decided to make it an opaque pointer is that we might want
to reuse it in vinyl to make vy_max_tuple_size, which is currently a
global variable, a part of vy_env. The problem is vy_max_tuple_size is
used in vy_stmt.c, which knows nothing about vy_env, so to avoid cross
dependencies we will probably have to introduce vy_stmt_env to store
this variable and make tuple_format reference not the whole vy_env, but
only vy_stmt_env hence the opaque pointer.