Re: [Tarantool-patches] [PATCH v8 1/4] box/func: factor out c function entry structure

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Sat, Oct 31, 2020 at 01:13:18AM +0100, Vladislav Shpilevoy wrote:
> >>> +			module_delete(module);
> >>> +			return -1;
> >>> +		}
> >>> +	}
> >>> +
> >>> +	mod_sym->addr = module_sym(module, name.sym);
> >>> +	if (mod_sym->addr == NULL)
> >>> +		return -1;
> >>
> >> 2. If the module was loaded first time here, it is not unloaded in case of
> >> an error in this place.
> > 
> > Just like it was before the patch. The patch simply factor outs the old
> > code. It doesn't improve it (because, lets be honest this is a min problem
> > for module management -- we've to check for module symbol not at moment
> > of calling it but rather at the moment when we load a function). That
> > said the issue with module management is known and I think we need to
> > rework modules code more deeply, but not in this series. In the
> > series it remains exactly as it was.
> 
> There is no even a ticket for that. And if you add it, it will go to wishlist,
> I can assure you. The rule is that if you see a bug, the first thing you do is
> ensure there is a ticket on it. This issue is definitely a bug. So you can't rely
> on some refactoring of something sometime in the future. If there is a bug, it
> must not be lost, and must be fixed. Bugs have higher priority than refactoring
> almost always, and there is more chances it will be fixed when filed separately
> from refactoring.
> 
> https://github.com/tarantool/tarantool/issues/5475

I assigned this bug for myself. I see your point, and I rather tend to agree
in general. I'll wix.

> >>
> >> 3. Can't parse the comment. What is the 'C callback'?
> >> And why is this function stored? After you extracted it
> >> from struct func_c, it is not related to _func space, and
> >> is not stored.
> > 
> > It is stored in memory.
> 
> Everything is stored in memory in Tarantool except Vinyl. I
> see the comment is just copy-pasted from the previous place
> in struct func_c, where it meant stored as stored in the
> schema. In spaces.
> 
> > The C callback is the function we
> > call, so we keep a pointer to a module.
> 
> You don't need a module pointer to call a function. It can be 
> called by (), without a module. It is saved here to load it and
> unload. At unload it may delete the module if the function object
> was the last user of the module.

Seems we don't understad each other. This is a symbol we retrieve
from the module and we literally "call" it then. The symbol has
a name and an address, and address used as callable object. I'm
not sure how else I could rephrase it.