Bug: 'break' may not properly close variable in a 'for' loop

roberto-ieru · roberto-ieru · commit 997f11f54322 · 2022-08-24T17:36:47.000-03:00
Function 'leaveblock' was generating "break" label before removing
variables from the closing block. If 'createlabel' created a 'close'
instruction (which it did when matching a goto/break that exited
the scope of an upvalue), that instruction would use the wrong level.
diff --git a/lparser.c b/lparser.c
@@ -674,19 +674,19 @@ static void leaveblock (FuncState *fs) {
   LexState *ls = fs->ls;
   int hasclose = 0;
   int stklevel = reglevel(fs, bl->nactvar);  /* level outside the block */
-  if (bl->isloop)  /* fix pending breaks? */
+  removevars(fs, bl->nactvar);  /* remove block locals */
+  lua_assert(bl->nactvar == fs->nactvar);  /* back to level on entry */
+  if (bl->isloop)  /* has to fix pending breaks? */
     hasclose = createlabel(ls, luaS_newliteral(ls->L, "break"), 0, 0);
-  if (!hasclose && bl->previous && bl->upval)
+  if (!hasclose && bl->previous && bl->upval)  /* still need a 'close'? */
     luaK_codeABC(fs, OP_CLOSE, stklevel, 0, 0);
-  fs->bl = bl->previous;
-  removevars(fs, bl->nactvar);
-  lua_assert(bl->nactvar == fs->nactvar);
   fs->freereg = stklevel;  /* free registers */
   ls->dyd->label.n = bl->firstlabel;  /* remove local labels */
-  if (bl->previous)  /* inner block? */
-    movegotosout(fs, bl);  /* update pending gotos to outer block */
+  fs->bl = bl->previous;  /* current block now is previous one */
+  if (bl->previous)  /* was it a nested block? */
+    movegotosout(fs, bl);  /* update pending gotos to enclosing block */
   else {
-    if (bl->firstgoto < ls->dyd->gt.n)  /* pending gotos in outer block? */
+    if (bl->firstgoto < ls->dyd->gt.n)  /* still pending gotos? */
       undefgoto(ls, &ls->dyd->gt.arr[bl->firstgoto]);  /* error */
   }
 }
diff --git a/testes/locals.lua b/testes/locals.lua
@@ -360,6 +360,26 @@ do
 end
 
 
+do
+  -- bug in 5.4.4: 'break' may generate wrong 'close' instruction when
+  -- leaving a loop block.
+
+  local closed = false
+
+  local o1 = setmetatable({}, {__close=function() closed = true end})
+
+  local function test()
+    for k, v in next, {}, nil, o1 do
+      local function f() return k end   -- create an upvalue
+      break
+    end
+    assert(closed)
+  end
+
+  test()
+end
+
+
 do print("testing errors in __close")
 
   -- original error is in __close
