From 389116d8abcc96db3cfe2f3cc25789c089fe12d6 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Thu, 9 May 2019 11:13:45 -0300
Subject: Coroutines do not unwind the stack in case of errors

Back to how it was, a coroutine does not unwind its stack in case of
errors (and therefore do not close its to-be-closed variables). This
allows the stack to be examined after the error. The program can
use 'coroutine.kill' to close the variables.

The function created by 'coroutine.wrap', however, closes the
coroutine's variables in case of errors, as it is impossible to examine
the stack any way.
---
 testes/coroutine.lua |  8 ++++++--
 testes/db.lua        | 14 ++++++++++----
 testes/locals.lua    | 35 +++++++++++++++++++++++++++--------
 3 files changed, 43 insertions(+), 14 deletions(-)

(limited to 'testes')

diff --git a/testes/coroutine.lua b/testes/coroutine.lua
index 35ff27fb..9dd501e7 100644
--- a/testes/coroutine.lua
+++ b/testes/coroutine.lua
@@ -346,9 +346,13 @@ do
   local st, res = coroutine.resume(B)
   assert(st == true and res == false)
 
-  A = coroutine.wrap(function() return pcall(A, 1) end)
+  local X = false
+  A = coroutine.wrap(function()
+    local *toclose _ = setmetatable({}, {__close = function () X = true end})
+    return pcall(A, 1)
+  end)
   st, res = A()
-  assert(not st and string.find(res, "non%-suspended"))
+  assert(not st and string.find(res, "non%-suspended") and X == true)
 end
 
 
diff --git a/testes/db.lua b/testes/db.lua
index 95275fb4..3d94f776 100644
--- a/testes/db.lua
+++ b/testes/db.lua
@@ -734,18 +734,24 @@ a, b = coroutine.resume(co, 100)
 assert(a and b == 30)
 
 
--- check traceback of suspended coroutines
+-- check traceback of suspended (or dead with error) coroutines
+
+function f(i)
+  if i == 0 then error(i)
+  else coroutine.yield(); f(i-1)
+  end
+end
 
-function f(i) coroutine.yield(i == 0); f(i - 1) end
 
 co = coroutine.create(function (x) f(x) end)
 a, b = coroutine.resume(co, 3)
 t = {"'coroutine.yield'", "'f'", "in function <"}
-repeat
+while coroutine.status(co) == "suspended" do
   checktraceback(co, t)
   a, b = coroutine.resume(co)
   table.insert(t, 2, "'f'")   -- one more recursive call to 'f'
-until b
+end
+t[1] = "'error'"
 checktraceback(co, t)
 
 
diff --git a/testes/locals.lua b/testes/locals.lua
index de47ae31..814d1b16 100644
--- a/testes/locals.lua
+++ b/testes/locals.lua
@@ -417,12 +417,13 @@ if rawget(_G, "T") then
 end
 
 
--- to-be-closed variables in coroutines
+print "to-be-closed variables in coroutines"
+
 do
-  -- an error in a coroutine closes variables
+  -- an error in a wrapped coroutine closes variables
   local x = false
   local y = false
-  local co = coroutine.create(function ()
+  local co = coroutine.wrap(function ()
     local *toclose xv = func2close(function () x = true end)
     do
       local *toclose yv = func2close(function () y = true end)
@@ -432,14 +433,31 @@ do
     error(23)              -- error does
   end)
 
-  local a, b = coroutine.resume(co)
-  assert(a and b == 100 and not x and not y)
-  a, b = coroutine.resume(co)
-  assert(a and b == 200 and not x and y)
-  a, b = coroutine.resume(co)
+  local b = co()
+  assert(b == 100 and not x and not y)
+  b = co()
+  assert(b == 200 and not x and y)
+  local a, b = pcall(co)
   assert(not a and b == 23 and x and y)
 end
 
+
+do
+  -- error in a wrapped coroutine raising errors when closing a variable
+  local x = false
+  local co = coroutine.wrap(function ()
+    local *toclose xv = func2close(function () error("XXX") end)
+      coroutine.yield(100)
+      error(200)
+  end)
+  assert(co() == 100)
+  local st, msg = pcall(co)
+print(msg)
+  -- should get last error raised
+  assert(not st and string.find(msg, "%w+%.%w+:%d+: XXX"))
+end
+
+
 -- a suspended coroutine should not close its variables when collected
 local co
 co = coroutine.wrap(function()
@@ -449,6 +467,7 @@ co = coroutine.wrap(function()
 end)
 co()                 -- start coroutine
 assert(co == nil)    -- eventually it will be collected
+collectgarbage()
 
 
 -- to-be-closed variables in generic for loops
-- 
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