You would need to use a global because lwgeom_set_handlers belongs to the global context, i.e. it is not part of an object that can have it's own separate state.

Consider this workflow:

A:

1. we decide to use pool_1 to allocate memory; this is SomeInfo pool_1

2. call lwgeom_set_handlers to use allocator pointing to pool_1

3. lwgeom now does a bunch of stuff and want to allocate 12 objects, it will call the allocator set above and 12 objects get allocated form pool_1

B:

1. now we want to use pool_2

2. call lwgeom_set_handlers to use allocator pointing to pool_2

3. lwgeom need to allocate 4 objects and does that with above allocator from pool_2

Implementation:

• Declare a global variable SomeInfo *active_pool = NULL

• Implement an allocator function that uses (active_pool != NULL) to allocate memory

• Call lwgeom_set_handlers passing the above allocator

• Create SomeInfo pool_1 and optinally pool_2

A:

1. assign active_pool = &pool_1;

2. do stuff with lwgeom library that requires allocation

B:

1. create pool_2 in case it was not created above

2. assign active_pool = &pool_2;

3. do stuff with lwgeom library that requires allocation