Re: [Tarantool-patches] [PATCH 3/3] lua: expose temporary Lua state for iproto calls

[Alexander Turenko <alexander.turenko@tarantool.org>]

> > +	/*
> > +	 * A code that need a temporary fiber-local Lua state may
> > +	 * save some time and resources for creating a new state
> > +	 * and use this one.
> > +	 */
> > +	bool has_lua_stack = fiber()->storage.lua.stack != NULL;
> > +	if (! has_lua_stack)
> > +		fiber()->storage.lua.stack = L;
> 
> 1. According to recent code style changes, we should omit single
> whitespace after unary operators.

Fixed.

> > +	/*
> > +	 * Since this field is optional we're not obligated to
> > +	 * keep it until the Lua state will be unreferenced in
> > +	 * port_lua_destroy().
> > +	 *
> > +	 * There is no much sense to keep it beyond the Lua call,
> > +	 * so let's zap now.
> > +	 *
> > +	 * But: keep the stack if it was present before the call,
> > +	 * because it would be counter-intuitive if the existing
> > +	 * state pointer would be zapped after this function call.
> 
> 2. It is not just counter-intuitive. It would break Lua-born fibers,
> since they would suddenly loose their stack.

Nope, it'll work.

Once we put the stack into a Lua-born fiber, this field may be safely
zapped. (I looked into this, because I want to create a test case that
would verify whether we keep the existing state here, but failed to find
such scenario.)

> >  		/**
> > -		 * Lua stack and the optional
> > -		 * fiber.storage Lua reference.
> > +		 * Optional Lua state (may be NULL). Useful as a
> > +		 * temporary Lua state to save time and resources
> > +		 * on creating it. Should not be used in other
> > +		 * fibers.
> > +		 *
> > +		 * Optional fiber.storage Lua reference.
> 
> 3. You change the comment anyway, so it would be better to make it
> right and put the member-related comments just above the members.
> One comment for the stack, and separate comment for the ref.

Fixed.