Re: [PATCH 1/3] Add luaT_iscallable with support of cdata metatype

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

Updated Totktonada/gh-3276-on-board-merger and
Totktonada/gh-3276-on-board-merger-1.10.

On Wed, Dec 26, 2018 at 09:35:56PM +0300, Vladimir Davydov wrote:
> On Sun, Dec 16, 2018 at 11:17:24PM +0300, Alexander Turenko wrote:
> > Needed for #3276.
> > ---
> >  extra/exports                    |  1 +
> >  src/lua/utils.c                  | 43 ++++++++++++++++
> >  src/lua/utils.h                  | 10 ++++
> >  test/app-tap/module_api.c        | 10 ++++
> >  test/app-tap/module_api.test.lua | 85 +++++++++++++++++++++++++++++++-
> >  5 files changed, 147 insertions(+), 2 deletions(-)
> > 
> > diff --git a/extra/exports b/extra/exports
> > index 5f69e0730..52f0b2378 100644
> > --- a/extra/exports
> > +++ b/extra/exports
> > @@ -134,6 +134,7 @@ luaT_call
> >  luaT_cpcall
> >  luaT_state
> >  luaT_tolstring
> > +luaT_iscallable
> 
> Do we really need to export it?

No, we don't obligated to export it. I'll remove it and rewrite the test
case (at least I'll try) if you sure we shouldn't. But I think it is
better to leave it as the public function.

I think luajit's support of cdata (in C/Lua APIs) could be better and we
can invest some effort to make it better for users of our C API and ffi.
Also filed #3915.

> 
> >  box_txn
> >  box_txn_begin
> >  box_txn_commit
> > diff --git a/src/lua/utils.c b/src/lua/utils.c
> > index 978fe61f1..7a6069fbb 100644
> > --- a/src/lua/utils.c
> > +++ b/src/lua/utils.c
> > @@ -920,6 +920,49 @@ luaT_tolstring(lua_State *L, int idx, size_t *len)
> >  	return lua_tolstring(L, -1, len);
> >  }
> >  
> > +/* Based on ffi_meta___call() from luajit/src/lib_ffi.c. */
> > +static int
> > +luaT_cdata_iscallable(lua_State *L, int idx)
> 
> I think this function should have prefix luaL_ rather than luaT_.
> Other than that, this particular patch looks OK to me.
> 

Fixed.

> > +{
> > +	/* Calculate absolute value in the stack. */
> > +	if (idx < 0)
> > +		idx = lua_gettop(L) + idx + 1;
> > +
> > +	/* Get cdata from the stack. */
> > +	assert(lua_type(L, idx) == LUA_TCDATA);
> > +	GCcdata *cd = cdataV(L->base + idx - 1);
> > +
> > +	CTState *cts = ctype_cts(L);
> > +	CTypeID id = cd->ctypeid;
> > +	CType *ct = ctype_raw(cts, id);
> > +	if (ctype_isptr(ct->info))
> > +		id = ctype_cid(ct->info);
> > +
> > +	/* Get ctype metamethod. */
> > +	cTValue *tv = lj_ctype_meta(cts, id, MM_call);
> > +
> > +	return tv != NULL;
> > +}