Fixed bug in tail calls of __call chains

A tail call of a __call chain (a __call metamethod that itself is
also not a function) was being perfomed as a regular call.

lvm.c

@@ -1549,9 +1549,10 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
           luaF_close(L, base, NOCLOSINGMETH);
           lua_assert(base == ci->func + 1);
         }
-        if (!ttisfunction(s2v(ra))) {  /* not a function? */
+        while (!ttisfunction(s2v(ra))) {  /* not a function? */
           luaD_tryfuncTM(L, ra);  /* try '__call' metamethod */
           b++;  /* there is now one extra argument */
+          checkstackp(L, 1, ra);
         }
         if (!ttisLclosure(s2v(ra))) {  /* C function? */
           luaD_call(L, ra, LUA_MULTRET);  /* call it */

testes/calls.lua

@@ -107,7 +107,9 @@ end
 deep(10)
 deep(180)
 
--- testing tail calls
+
+print"testing tail calls"
+
 function deep (n) if n>0 then return deep(n-1) else return 101 end end
 assert(deep(30000) == 101)
 a = {}
@@ -148,6 +150,27 @@ do   -- tail calls x varargs
   assert(X == 10 and Y == 20 and #A == 1 and A[1] == 30)
 end
 
+
+
+do   -- tail calls x chain of __call
+  local n = 10000   -- depth
+
+  local function foo ()
+    if n == 0 then return 1023
+    else n = n - 1; return foo()
+    end
+  end
+
+  -- build a chain of __call metamethods ending in function 'foo'
+  for i = 1, 100 do
+    foo = setmetatable({}, {__call = foo})
+  end
+
+  -- call the first one as a tail call in a new coroutine
+  -- (to ensure stack is not preallocated)
+  assert(coroutine.wrap(function() return foo() end)() == 1023)
+end
+
 print('+')