1 files changed, 874 insertions, 0 deletions

diff --git a/testes/coroutine.lua b/testes/coroutine.lua
new file mode 100644
index 00000000..c8fc8572
--- /dev/null
+++ b/testes/coroutine.lua
@@ -0,0 +1,874 @@
+-- $Id: coroutine.lua,v 1.42 2016/11/07 13:03:20 roberto Exp $
+-- See Copyright Notice in file all.lua
+
+print "testing coroutines"
+
+local debug = require'debug'
+
+local f
+
+local main, ismain = coroutine.running()
+assert(type(main) == "thread" and ismain)
+assert(not coroutine.resume(main))
+assert(not coroutine.isyieldable())
+assert(not pcall(coroutine.yield))
+
+
+-- trivial errors
+assert(not pcall(coroutine.resume, 0))
+assert(not pcall(coroutine.status, 0))
+
+
+-- tests for multiple yield/resume arguments
+
+local function eqtab (t1, t2)
+  assert(#t1 == #t2)
+  for i = 1, #t1 do
+    local v = t1[i]
+    assert(t2[i] == v)
+  end
+end
+
+_G.x = nil   -- declare x
+function foo (a, ...)
+  local x, y = coroutine.running()
+  assert(x == f and y == false)
+  -- next call should not corrupt coroutine (but must fail,
+  -- as it attempts to resume the running coroutine)
+  assert(coroutine.resume(f) == false)
+  assert(coroutine.status(f) == "running")
+  local arg = {...}
+  assert(coroutine.isyieldable())
+  for i=1,#arg do
+    _G.x = {coroutine.yield(table.unpack(arg[i]))}
+  end
+  return table.unpack(a)
+end
+
+f = coroutine.create(foo)
+assert(type(f) == "thread" and coroutine.status(f) == "suspended")
+assert(string.find(tostring(f), "thread"))
+local s,a,b,c,d
+s,a,b,c,d = coroutine.resume(f, {1,2,3}, {}, {1}, {'a', 'b', 'c'})
+assert(s and a == nil and coroutine.status(f) == "suspended")
+s,a,b,c,d = coroutine.resume(f)
+eqtab(_G.x, {})
+assert(s and a == 1 and b == nil)
+s,a,b,c,d = coroutine.resume(f, 1, 2, 3)
+eqtab(_G.x, {1, 2, 3})
+assert(s and a == 'a' and b == 'b' and c == 'c' and d == nil)
+s,a,b,c,d = coroutine.resume(f, "xuxu")
+eqtab(_G.x, {"xuxu"})
+assert(s and a == 1 and b == 2 and c == 3 and d == nil)
+assert(coroutine.status(f) == "dead")
+s, a = coroutine.resume(f, "xuxu")
+assert(not s and string.find(a, "dead") and coroutine.status(f) == "dead")
+
+
+-- yields in tail calls
+local function foo (i) return coroutine.yield(i) end
+f = coroutine.wrap(function ()
+  for i=1,10 do
+    assert(foo(i) == _G.x)
+  end
+  return 'a'
+end)
+for i=1,10 do _G.x = i; assert(f(i) == i) end
+_G.x = 'xuxu'; assert(f('xuxu') == 'a')
+
+-- recursive
+function pf (n, i)
+  coroutine.yield(n)
+  pf(n*i, i+1)
+end
+
+f = coroutine.wrap(pf)
+local s=1
+for i=1,10 do
+  assert(f(1, 1) == s)
+  s = s*i
+end
+
+-- sieve
+function gen (n)
+  return coroutine.wrap(function ()
+    for i=2,n do coroutine.yield(i) end
+  end)
+end
+
+
+function filter (p, g)
+  return coroutine.wrap(function ()
+    while 1 do
+      local n = g()
+      if n == nil then return end
+      if math.fmod(n, p) ~= 0 then coroutine.yield(n) end
+    end
+  end)
+end
+
+local x = gen(100)
+local a = {}
+while 1 do
+  local n = x()
+  if n == nil then break end
+  table.insert(a, n)
+  x = filter(n, x)
+end
+
+assert(#a == 25 and a[#a] == 97)
+x, a = nil
+
+-- yielding across C boundaries
+
+co = coroutine.wrap(function()
+       assert(not pcall(table.sort,{1,2,3}, coroutine.yield))
+       assert(coroutine.isyieldable())
+       coroutine.yield(20)
+       return 30
+     end)
+
+assert(co() == 20)
+assert(co() == 30)
+
+
+local f = function (s, i) return coroutine.yield(i) end
+
+local f1 = coroutine.wrap(function ()
+             return xpcall(pcall, function (...) return ... end,
+               function ()
+                 local s = 0
+                 for i in f, nil, 1 do pcall(function () s = s + i end) end
+                 error({s})
+               end)
+           end)
+
+f1()
+for i = 1, 10 do assert(f1(i) == i) end
+local r1, r2, v = f1(nil)
+assert(r1 and not r2 and v[1] ==  (10 + 1)*10/2)
+
+
+function f (a, b) a = coroutine.yield(a);  error{a + b} end
+function g(x) return x[1]*2 end
+
+co = coroutine.wrap(function ()
+       coroutine.yield(xpcall(f, g, 10, 20))
+     end)
+
+assert(co() == 10)
+r, msg = co(100)
+assert(not r and msg == 240)
+
+
+-- unyieldable C call
+do
+  local function f (c)
+          assert(not coroutine.isyieldable())
+          return c .. c
+        end
+
+  local co = coroutine.wrap(function (c)
+               assert(coroutine.isyieldable())
+               local s = string.gsub("a", ".", f)
+               return s
+             end)
+  assert(co() == "aa")
+end
+
+
+-- errors in coroutines
+function foo ()
+  assert(debug.getinfo(1).currentline == debug.getinfo(foo).linedefined + 1)
+  assert(debug.getinfo(2).currentline == debug.getinfo(goo).linedefined)
+  coroutine.yield(3)
+  error(foo)
+end
+
+function goo() foo() end
+x = coroutine.wrap(goo)
+assert(x() == 3)
+local a,b = pcall(x)
+assert(not a and b == foo)
+
+x = coroutine.create(goo)
+a,b = coroutine.resume(x)
+assert(a and b == 3)
+a,b = coroutine.resume(x)
+assert(not a and b == foo and coroutine.status(x) == "dead")
+a,b = coroutine.resume(x)
+assert(not a and string.find(b, "dead") and coroutine.status(x) == "dead")
+
+
+-- co-routines x for loop
+function all (a, n, k)
+  if k == 0 then coroutine.yield(a)
+  else
+    for i=1,n do
+      a[k] = i
+      all(a, n, k-1)
+    end
+  end
+end
+
+local a = 0
+for t in coroutine.wrap(function () all({}, 5, 4) end) do
+  a = a+1
+end
+assert(a == 5^4)
+
+
+-- access to locals of collected corroutines
+local C = {}; setmetatable(C, {__mode = "kv"})
+local x = coroutine.wrap (function ()
+            local a = 10
+            local function f () a = a+10; return a end
+            while true do
+              a = a+1
+              coroutine.yield(f)
+            end
+          end)
+
+C[1] = x;
+
+local f = x()
+assert(f() == 21 and x()() == 32 and x() == f)
+x = nil
+collectgarbage()
+assert(C[1] == nil)
+assert(f() == 43 and f() == 53)
+
+
+-- old bug: attempt to resume itself
+
+function co_func (current_co)
+  assert(coroutine.running() == current_co)
+  assert(coroutine.resume(current_co) == false)
+  coroutine.yield(10, 20)
+  assert(coroutine.resume(current_co) == false)
+  coroutine.yield(23)
+  return 10
+end
+
+local co = coroutine.create(co_func)
+local a,b,c = coroutine.resume(co, co)
+assert(a == true and b == 10 and c == 20)
+a,b = coroutine.resume(co, co)
+assert(a == true and b == 23)
+a,b = coroutine.resume(co, co)
+assert(a == true and b == 10)
+assert(coroutine.resume(co, co) == false)
+assert(coroutine.resume(co, co) == false)
+
+
+-- other old bug when attempting to resume itself
+-- (trigger C-code assertions)
+do
+  local A = coroutine.running()
+  local B = coroutine.create(function() return coroutine.resume(A) end)
+  local st, res = coroutine.resume(B)
+  assert(st == true and res == false)
+
+  A = coroutine.wrap(function() return pcall(A, 1) end)
+  st, res = A()
+  assert(not st and string.find(res, "non%-suspended"))
+end
+
+
+-- attempt to resume 'normal' coroutine
+local co1, co2
+co1 = coroutine.create(function () return co2() end)
+co2 = coroutine.wrap(function ()
+        assert(coroutine.status(co1) == 'normal')
+        assert(not coroutine.resume(co1))
+        coroutine.yield(3)
+      end)
+
+a,b = coroutine.resume(co1)
+assert(a and b == 3)
+assert(coroutine.status(co1) == 'dead')
+
+-- infinite recursion of coroutines
+a = function(a) coroutine.wrap(a)(a) end
+assert(not pcall(a, a))
+a = nil
+
+
+-- access to locals of erroneous coroutines
+local x = coroutine.create (function ()
+            local a = 10
+            _G.f = function () a=a+1; return a end
+            error('x')
+          end)
+
+assert(not coroutine.resume(x))
+-- overwrite previous position of local `a'
+assert(not coroutine.resume(x, 1, 1, 1, 1, 1, 1, 1))
+assert(_G.f() == 11)
+assert(_G.f() == 12)
+
+
+if not T then
+  (Message or print)('\n >>> testC not active: skipping yield/hook tests <<<\n')
+else
+  print "testing yields inside hooks"
+
+  local turn
+  
+  function fact (t, x)
+    assert(turn == t)
+    if x == 0 then return 1
+    else return x*fact(t, x-1)
+    end
+  end
+
+  local A, B = 0, 0
+
+  local x = coroutine.create(function ()
+    T.sethook("yield 0", "", 2)
+    A = fact("A", 6)
+  end)
+
+  local y = coroutine.create(function ()
+    T.sethook("yield 0", "", 3)
+    B = fact("B", 7)
+  end)
+
+  while A==0 or B==0 do    -- A ~= 0 when 'x' finishes (similar for 'B','y')
+    if A==0 then turn = "A"; assert(T.resume(x)) end
+    if B==0 then turn = "B"; assert(T.resume(y)) end
+  end
+
+  assert(B // A == 7)    -- fact(7) // fact(6)
+
+  local line = debug.getinfo(1, "l").currentline + 2    -- get line number
+  local function foo ()
+    local x = 10    --<< this line is 'line'
+    x = x + 10
+    _G.XX = x
+  end
+
+  -- testing yields in line hook
+  local co = coroutine.wrap(function ()
+    T.sethook("setglobal X; yield 0", "l", 0); foo(); return 10 end)
+
+  _G.XX = nil;
+  _G.X = nil; co(); assert(_G.X == line)
+  _G.X = nil; co(); assert(_G.X == line + 1)
+  _G.X = nil; co(); assert(_G.X == line + 2 and _G.XX == nil)
+  _G.X = nil; co(); assert(_G.X == line + 3 and _G.XX == 20)
+  assert(co() == 10)
+
+  -- testing yields in count hook
+  co = coroutine.wrap(function ()
+    T.sethook("yield 0", "", 1); foo(); return 10 end)
+
+  _G.XX = nil;
+  local c = 0
+  repeat c = c + 1; local a = co() until a == 10
+  assert(_G.XX == 20 and c >= 5)
+
+  co = coroutine.wrap(function ()
+    T.sethook("yield 0", "", 2); foo(); return 10 end)
+
+  _G.XX = nil;
+  local c = 0
+  repeat c = c + 1; local a = co() until a == 10
+  assert(_G.XX == 20 and c >= 5)
+  _G.X = nil; _G.XX = nil
+
+  do
+    -- testing debug library on a coroutine suspended inside a hook
+    -- (bug in 5.2/5.3)
+    c = coroutine.create(function (a, ...)
+      T.sethook("yield 0", "l")   -- will yield on next two lines
+      assert(a == 10)
+      return ...
+    end)
+
+    assert(coroutine.resume(c, 1, 2, 3))   -- start coroutine
+    local n,v = debug.getlocal(c, 0, 1)    -- check its local
+    assert(n == "a" and v == 1)
+    n,v = debug.getlocal(c, 0, -1)         -- check varargs
+    assert(v == 2)
+    n,v = debug.getlocal(c, 0, -2)
+    assert(v == 3)
+    assert(debug.setlocal(c, 0, 1, 10))     -- test 'setlocal'
+    assert(debug.setlocal(c, 0, -2, 20))
+    local t = debug.getinfo(c, 0)        -- test 'getinfo'
+    assert(t.currentline == t.linedefined + 1)
+    assert(not debug.getinfo(c, 1))      -- no other level
+    assert(coroutine.resume(c))          -- run next line
+    v = {coroutine.resume(c)}         -- finish coroutine
+    assert(v[1] == true and v[2] == 2 and v[3] == 20 and v[4] == nil)
+    assert(not coroutine.resume(c))
+  end
+
+  do
+    -- testing debug library on last function in a suspended coroutine
+    -- (bug in 5.2/5.3)
+    local c = coroutine.create(function () T.testC("yield 1", 10, 20) end)
+    local a, b = coroutine.resume(c)
+    assert(a and b == 20)
+    assert(debug.getinfo(c, 0).linedefined == -1)
+    a, b = debug.getlocal(c, 0, 2)
+    assert(b == 10)
+  end
+
+
+  print "testing coroutine API"
+  
+  -- reusing a thread
+  assert(T.testC([[
+    newthread      # create thread
+    pushvalue 2    # push body
+    pushstring 'a a a'  # push argument
+    xmove 0 3 2   # move values to new thread
+    resume -1, 1    # call it first time
+    pushstatus
+    xmove 3 0 0   # move results back to stack
+    setglobal X    # result
+    setglobal Y    # status
+    pushvalue 2     # push body (to call it again)
+    pushstring 'b b b'
+    xmove 0 3 2
+    resume -1, 1    # call it again
+    pushstatus
+    xmove 3 0 0
+    return 1        # return result
+  ]], function (...) return ... end) == 'b b b')
+
+  assert(X == 'a a a' and Y == 'OK')
+
+
+  -- resuming running coroutine
+  C = coroutine.create(function ()
+        return T.testC([[
+                 pushnum 10;
+                 pushnum 20;
+                 resume -3 2;
+                 pushstatus
+                 gettop;
+                 return 3]], C)
+      end)
+  local a, b, c, d = coroutine.resume(C)
+  assert(a == true and string.find(b, "non%-suspended") and
+         c == "ERRRUN" and d == 4)
+
+  a, b, c, d = T.testC([[
+    rawgeti R 1    # get main thread
+    pushnum 10;
+    pushnum 20;
+    resume -3 2;
+    pushstatus
+    gettop;
+    return 4]])
+  assert(a == coroutine.running() and string.find(b, "non%-suspended") and
+         c == "ERRRUN" and d == 4)
+
+
+  -- using a main thread as a coroutine
+  local state = T.newstate()
+  T.loadlib(state)
+
+  assert(T.doremote(state, [[
+    coroutine = require'coroutine';
+    X = function (x) coroutine.yield(x, 'BB'); return 'CC' end;
+    return 'ok']]))
+
+  t = table.pack(T.testC(state, [[
+    rawgeti R 1     # get main thread
+    pushstring 'XX'
+    getglobal X    # get function for body
+    pushstring AA      # arg
+    resume 1 1      # 'resume' shadows previous stack!
+    gettop
+    setglobal T    # top
+    setglobal B    # second yielded value
+    setglobal A    # fist yielded value
+    rawgeti R 1     # get main thread
+    pushnum 5       # arg (noise)
+    resume 1 1      # after coroutine ends, previous stack is back
+    pushstatus
+    return *
+  ]]))
+  assert(t.n == 4 and t[2] == 'XX' and t[3] == 'CC' and t[4] == 'OK')
+  assert(T.doremote(state, "return T") == '2')
+  assert(T.doremote(state, "return A") == 'AA')
+  assert(T.doremote(state, "return B") == 'BB')
+
+  T.closestate(state)
+
+  print'+'
+
+end
+
+
+-- leaving a pending coroutine open
+_X = coroutine.wrap(function ()
+      local a = 10
+      local x = function () a = a+1 end
+      coroutine.yield()
+    end)
+
+_X()
+
+
+if not _soft then
+  -- bug (stack overflow)
+  local j = 2^9
+  local lim = 1000000    -- (C stack limit; assume 32-bit machine)
+  local t = {lim - 10, lim - 5, lim - 1, lim, lim + 1}
+  for i = 1, #t do
+    local j = t[i]
+    co = coroutine.create(function()
+           local t = {}
+           for i = 1, j do t[i] = i end
+           return table.unpack(t)
+         end)
+    local r, msg = coroutine.resume(co)
+    assert(not r)
+  end
+  co = nil
+end
+
+
+assert(coroutine.running() == main)
+
+print"+"
+
+
+print"testing yields inside metamethods"
+
+local mt = {
+  __eq = function(a,b) coroutine.yield(nil, "eq"); return a.x == b.x end,
+  __lt = function(a,b) coroutine.yield(nil, "lt"); return a.x < b.x end,
+  __le = function(a,b) coroutine.yield(nil, "le"); return a - b <= 0 end,
+  __add = function(a,b) coroutine.yield(nil, "add"); return a.x + b.x end,
+  __sub = function(a,b) coroutine.yield(nil, "sub"); return a.x - b.x end,
+  __mod = function(a,b) coroutine.yield(nil, "mod"); return a.x % b.x end,
+  __unm = function(a,b) coroutine.yield(nil, "unm"); return -a.x end,
+  __bnot = function(a,b) coroutine.yield(nil, "bnot"); return ~a.x end,
+  __shl = function(a,b) coroutine.yield(nil, "shl"); return a.x << b.x end,
+  __shr = function(a,b) coroutine.yield(nil, "shr"); return a.x >> b.x end,
+  __band = function(a,b)
+             a = type(a) == "table" and a.x or a
+             b = type(b) == "table" and b.x or b
+             coroutine.yield(nil, "band")
+             return a & b
+           end,
+  __bor = function(a,b) coroutine.yield(nil, "bor"); return a.x | b.x end,
+  __bxor = function(a,b) coroutine.yield(nil, "bxor"); return a.x ~ b.x end,
+
+  __concat = function(a,b)
+               coroutine.yield(nil, "concat");
+               a = type(a) == "table" and a.x or a
+               b = type(b) == "table" and b.x or b
+               return a .. b
+             end,
+  __index = function (t,k) coroutine.yield(nil, "idx"); return t.k[k] end,
+  __newindex = function (t,k,v) coroutine.yield(nil, "nidx"); t.k[k] = v end,
+}
+
+
+local function new (x)
+  return setmetatable({x = x, k = {}}, mt)
+end
+
+
+local a = new(10)
+local b = new(12)
+local c = new"hello"
+
+local function run (f, t)
+  local i = 1
+  local c = coroutine.wrap(f)
+  while true do
+    local res, stat = c()
+    if res then assert(t[i] == nil); return res, t end
+    assert(stat == t[i])
+    i = i + 1
+  end
+end
+
+
+assert(run(function () if (a>=b) then return '>=' else return '<' end end,
+       {"le", "sub"}) == "<")
+-- '<=' using '<'
+mt.__le = nil
+assert(run(function () if (a<=b) then return '<=' else return '>' end end,
+       {"lt"}) == "<=")
+assert(run(function () if (a==b) then return '==' else return '~=' end end,
+       {"eq"}) == "~=")
+
+assert(run(function () return a & b + a end, {"add", "band"}) == 2)
+
+assert(run(function () return a % b end, {"mod"}) == 10)
+
+assert(run(function () return ~a & b end, {"bnot", "band"}) == ~10 & 12)
+assert(run(function () return a | b end, {"bor"}) == 10 | 12)
+assert(run(function () return a ~ b end, {"bxor"}) == 10 ~ 12)
+assert(run(function () return a << b end, {"shl"}) == 10 << 12)
+assert(run(function () return a >> b end, {"shr"}) == 10 >> 12)
+
+assert(run(function () return a..b end, {"concat"}) == "1012")
+
+assert(run(function() return a .. b .. c .. a end,
+       {"concat", "concat", "concat"}) == "1012hello10")
+
+assert(run(function() return "a" .. "b" .. a .. "c" .. c .. b .. "x" end,
+       {"concat", "concat", "concat"}) == "ab10chello12x")
+
+
+do   -- a few more tests for comparsion operators
+  local mt1 = {
+    __le = function (a,b)
+      coroutine.yield(10)
+      return
+        (type(a) == "table" and a.x or a) <= (type(b) == "table" and b.x or b)
+    end,
+    __lt = function (a,b)
+      coroutine.yield(10)
+      return
+        (type(a) == "table" and a.x or a) < (type(b) == "table" and b.x or b)
+    end,
+  }
+  local mt2 = { __lt = mt1.__lt }   -- no __le
+
+  local function run (f)
+    local co = coroutine.wrap(f)
+    local res
+    repeat
+      res = co()
+    until res ~= 10
+    return res
+  end
+  
+  local function test ()
+    local a1 = setmetatable({x=1}, mt1)
+    local a2 = setmetatable({x=2}, mt2)
+    assert(a1 < a2)
+    assert(a1 <= a2)
+    assert(1 < a2)
+    assert(1 <= a2)
+    assert(2 > a1)
+    assert(2 >= a2)
+    return true
+  end
+  
+  run(test)
+
+end
+
+assert(run(function ()
+             a.BB = print
+             return a.BB
+           end, {"nidx", "idx"}) == print)
+
+-- getuptable & setuptable
+do local _ENV = _ENV
+  f = function () AAA = BBB + 1; return AAA end
+end
+g = new(10); g.k.BBB = 10;
+debug.setupvalue(f, 1, g)
+assert(run(f, {"idx", "nidx", "idx"}) == 11)
+assert(g.k.AAA == 11)
+
+print"+"
+
+print"testing yields inside 'for' iterators"
+
+local f = function (s, i)
+      if i%2 == 0 then coroutine.yield(nil, "for") end
+      if i < s then return i + 1 end
+    end
+
+assert(run(function ()
+             local s = 0
+             for i in f, 4, 0 do s = s + i end
+             return s
+           end, {"for", "for", "for"}) == 10)
+
+
+
+-- tests for coroutine API
+if T==nil then
+  (Message or print)('\n >>> testC not active: skipping coroutine API tests <<<\n')
+  return
+end
+
+print('testing coroutine API')
+
+local function apico (...)
+  local x = {...}
+  return coroutine.wrap(function ()
+    return T.testC(table.unpack(x))
+  end)
+end
+
+local a = {apico(
+[[
+  pushstring errorcode
+  pcallk 1 0 2;
+  invalid command (should not arrive here)
+]],
+[[return *]],
+"stackmark",
+error
+)()}
+assert(#a == 4 and
+       a[3] == "stackmark" and
+       a[4] == "errorcode" and
+       _G.status == "ERRRUN" and
+       _G.ctx == 2)       -- 'ctx' to pcallk
+
+local co = apico(
+  "pushvalue 2; pushnum 10; pcallk 1 2 3; invalid command;",
+  coroutine.yield,
+  "getglobal status; getglobal ctx; pushvalue 2; pushstring a; pcallk 1 0 4; invalid command",
+  "getglobal status; getglobal ctx; return *")
+
+assert(co() == 10)
+assert(co(20, 30) == 'a')
+a = {co()}
+assert(#a == 10 and
+       a[2] == coroutine.yield and
+       a[5] == 20 and a[6] == 30 and
+       a[7] == "YIELD" and a[8] == 3 and
+       a[9] == "YIELD" and a[10] == 4)
+assert(not pcall(co))   -- coroutine is dead now
+
+
+f = T.makeCfunc("pushnum 3; pushnum 5; yield 1;")
+co = coroutine.wrap(function ()
+  assert(f() == 23); assert(f() == 23); return 10
+end)
+assert(co(23,16) == 5)
+assert(co(23,16) == 5)
+assert(co(23,16) == 10)
+
+
+-- testing coroutines with C bodies
+f = T.makeCfunc([[
+        pushnum 102
+        yieldk  1 U2
+        cannot be here!
+]],
+[[      # continuation
+        pushvalue U3   # accessing upvalues inside a continuation
+        pushvalue U4
+        return *
+]], 23, "huu")
+
+x = coroutine.wrap(f)
+assert(x() == 102)
+eqtab({x()}, {23, "huu"})
+
+
+f = T.makeCfunc[[pushstring 'a'; pushnum 102; yield 2; ]]
+
+a, b, c, d = T.testC([[newthread; pushvalue 2; xmove 0 3 1; resume 3 0;
+                       pushstatus; xmove 3 0 0;  resume 3 0; pushstatus;
+                       return 4; ]], f)
+
+assert(a == 'YIELD' and b == 'a' and c == 102 and d == 'OK')
+
+
+-- testing chain of suspendable C calls
+
+local count = 3   -- number of levels
+
+f = T.makeCfunc([[
+  remove 1;             # remove argument
+  pushvalue U3;         # get selection function
+  call 0 1;             # call it  (result is 'f' or 'yield')
+  pushstring hello      # single argument for selected function
+  pushupvalueindex 2;   # index of continuation program
+  callk 1 -1 .;         # call selected function
+  errorerror            # should never arrive here
+]],
+[[
+  # continuation program
+  pushnum 34    # return value
+  return *     # return all results
+]],
+function ()     -- selection function
+  count = count - 1
+  if count == 0 then return coroutine.yield
+  else return f
+  end
+end
+)
+
+co = coroutine.wrap(function () return f(nil) end)
+assert(co() == "hello")   -- argument to 'yield'
+a = {co()}
+-- three '34's (one from each pending C call)
+assert(#a == 3 and a[1] == a[2] and a[2] == a[3] and a[3] == 34)
+
+
+-- testing yields with continuations
+
+co = coroutine.wrap(function (...) return
+       T.testC([[ # initial function
+          yieldk 1 2
+          cannot be here!
+       ]],
+       [[  # 1st continuation
+         yieldk 0 3 
+         cannot be here!
+       ]],
+       [[  # 2nd continuation
+         yieldk 0 4 
+         cannot be here!
+       ]],
+       [[  # 3th continuation
+          pushvalue 6   # function which is last arg. to 'testC' here
+          pushnum 10; pushnum 20;
+          pcall 2 0 0   # call should throw an error and return to next line
+          pop 1         # remove error message
+          pushvalue 6
+          getglobal status; getglobal ctx
+          pcallk 2 2 5  # call should throw an error and jump to continuation
+          cannot be here!
+       ]],
+       [[  # 4th (and last) continuation
+         return *
+       ]],
+       -- function called by 3th continuation
+       function (a,b) x=a; y=b; error("errmsg") end,
+       ...
+)
+end)
+
+local a = {co(3,4,6)}
+assert(a[1] == 6 and a[2] == nil)
+a = {co()}; assert(a[1] == nil and _G.status == "YIELD" and _G.ctx == 2)
+a = {co()}; assert(a[1] == nil and _G.status == "YIELD" and _G.ctx == 3)
+a = {co(7,8)};
+-- original arguments
+assert(type(a[1]) == 'string' and type(a[2]) == 'string' and
+     type(a[3]) == 'string' and type(a[4]) == 'string' and
+     type(a[5]) == 'string' and type(a[6]) == 'function')
+-- arguments left from fist resume
+assert(a[7] == 3 and a[8] == 4)
+-- arguments to last resume
+assert(a[9] == 7 and a[10] == 8)
+-- error message and nothing more
+assert(a[11]:find("errmsg") and #a == 11)
+-- check arguments to pcallk
+assert(x == "YIELD" and y == 4)
+
+assert(not pcall(co))   -- coroutine should be dead
+
+
+-- bug in nCcalls
+local co = coroutine.wrap(function ()
+  local a = {pcall(pcall,pcall,pcall,pcall,pcall,pcall,pcall,error,"hi")}
+  return pcall(assert, table.unpack(a))
+end)
+
+local a = {co()}
+assert(a[10] == "hi")
+
+print'OK'