Fixed bug in tail calls of __call chains

roberto-ieru · roberto-ieru · commit 7d526e75a7f4 · 2019-10-28T15:58:07.000-03:00
A tail call of a __call chain (a __call metamethod that itself is
also not a function) was being perfomed as a regular call.
diff --git a/lvm.c b/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 */
diff --git a/testes/calls.lua b/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('+')
 
 

Original file line number	Diff line number	Diff line change
`@@ -1549,9 +1549,10 @@ void luaV_execute (lua_State L, CallInfo ci) {`
`1549`	`1549`	`luaF_close(L, base, NOCLOSINGMETH);`
`1550`	`1550`	`lua_assert(base == ci->func + 1);`
`1551`	`1551`	`}`
`1552`		`- if (!ttisfunction(s2v(ra))) { /* not a function? */`
	`1552`	`+ while (!ttisfunction(s2v(ra))) { /* not a function? */`
`1553`	`1553`	`luaD_tryfuncTM(L, ra); /* try '__call' metamethod */`
`1554`	`1554`	`b++; /* there is now one extra argument */`
	`1555`	`+ checkstackp(L, 1, ra);`
`1555`	`1556`	`}`
`1556`	`1557`	`if (!ttisLclosure(s2v(ra))) { /* C function? */`
`1557`	`1558`	`luaD_call(L, ra, LUA_MULTRET); /* call it */`