Merge pull request #176 from v-for-vandal/lua_eq

Add default __eq implementation for Lua

Examples/test-suite/common.mk

@@ -210,6 +210,7 @@ CPP_TEST_CASES += \
 	enum_template \
 	enum_thorough \
 	enum_var \
+	equality \
 	evil_diamond \
 	evil_diamond_ns \
 	evil_diamond_prop \

Examples/test-suite/equality.i

@@ -0,0 +1,67 @@
+/* File : equality.i */
+/*
+ Specific test for operator== overload. Partially overlaps with
+ operator_overload.i
+*/
+
+%module equality
+
+%inline %{
+
+/* Point has no equality operator */
+typedef struct Point
+{
+  double x;
+  double y;
+} Point;
+
+static const Point s_zeroPoint = { 0.0, 0.0 };
+/* stack version */
+Point MakePoint(double x, double y) 
+  { Point new_point = {x, y}; return new_point; }
+
+const Point* GetZeroPointPtr() { return &s_zeroPoint; }
+Point GetZeroPointCopy() { return s_zeroPoint; }
+
+/* EqualOpDefined has correct equality operator */
+class EqualOpDefined {
+public:
+  EqualOpDefined():
+    x(5) {}
+  EqualOpDefined(int val):
+    x(val) {}
+
+  int x;
+};
+
+/* EqualOpWrong has logically incorrect equality operator */
+class EqualOpWrong {
+public:
+  inline static const EqualOpWrong* GetStaticObject();
+};
+ 
+static const EqualOpWrong s_wrongEqOp;
+
+const EqualOpWrong* EqualOpWrong::GetStaticObject()
+  { return &s_wrongEqOp; }
+
+
+inline bool operator==( const EqualOpDefined& first, const EqualOpDefined& second )
+  { return first.x == second.x; }
+
+inline bool operator==( const EqualOpWrong& first, const EqualOpWrong& second )
+  { return false; }
+
+%}
+
+/* 
+  in order to wrapper this correctly
+  we need to extend the class
+  to make the friends & non members part of the class
+*/
+%extend EqualOpDefined {
+	bool operator==(const EqualOpDefined& b){return (*$self) == b;}
+}
+%extend EqualOpWrong {
+	bool operator==(const EqualOpWrong& b){return (*$self) == b;}
+}

Examples/test-suite/lua/cpp_basic_runme.lua

@@ -86,3 +86,14 @@ f4_name = tostring(f4)
 assert( f2_name == "Foo" )
 assert( f3_name == "Foo" )
 assert( f4_name == "FooSubSub" )
+
+-- Test __eq implementation supplied by default
+
+-- eq_f1 and eq_f2 must be different userdata with same Foo* pointer. If eq_f1 and eq_f2 are the same userdata (e.g.)
+-- > eq_f1 = smth
+-- > eq_f2 = eq_f1
+-- then default Lua equality comparison kicks in and considers them equal. Access to global_fptr is actually a
+-- function call (internally) and it returns new userdata each time.
+eq_f1 = cb.Bar.global_fptr
+eq_f2 = cb.Bar.global_fptr
+assert( eq_f1 == eq_f2 )

Examples/test-suite/lua/equality_runme.lua

@@ -0,0 +1,47 @@
+require("import")	-- the import fn
+import("equality")	-- import code
+eq=equality    -- renaming import
+
+-- catch "undefined" global variables
+local env = _ENV -- Lua 5.2
+if not env then env = getfenv () end -- Lua 5.1
+setmetatable(env, {__index=function (t,i) error("undefined global variable `"..i.."'",2) end})
+
+-- === No equality operator ===
+
+-- logically same data without equality operator are not equal
+p1 = eq.MakePoint(10,9);
+p2 = eq.MakePoint(10,9);
+
+assert( p1 ~= p2 );
+
+-- different wrappers for same Point* are equal
+p3 = eq.GetZeroPointPtr()
+p4 = eq.GetZeroPointPtr()
+
+assert( p3 == p4 )
+
+
+-- === Logically correct equality operator ===
+
+ed1 = eq.EqualOpDefined(10)
+ed2 = eq.EqualOpDefined(10)
+ed3 = eq.EqualOpDefined(15)
+
+assert( ed1 == ed2 )
+assert( ed1 ~= ed3 )
+
+
+-- === Logically incorrect equality operator ===
+
+ew1 = eq.EqualOpWrong()
+ew2 = eq.EqualOpWrong()
+
+assert( ew1 ~= ew2 );
+
+ew3 = eq.EqualOpWrong.GetStaticObject()
+ew4 = eq.EqualOpWrong.GetStaticObject()
+
+-- Even though these are pointers to same object, operator== overload should
+-- state that they are not equal
+assert( ew3 ~= ew4 )

Lib/lua/luarun.swg

@@ -1037,6 +1037,23 @@ SWIGINTERN int  SWIG_Lua_class_disown(lua_State *L)
   return 0;
 }
 
+/* lua callable function to compare userdata's value
+the issue is that two userdata may point to the same thing
+but to lua, they are different objects */
+SWIGRUNTIME int SWIG_Lua_class_equal(lua_State *L)
+{
+  int result;
+  swig_lua_userdata *usr1,*usr2;
+  if (!lua_isuserdata(L,1) || !lua_isuserdata(L,2))  /* just in case */
+    return 0;  /* nil reply */
+  usr1=(swig_lua_userdata*)lua_touserdata(L,1);  /* get data */
+  usr2=(swig_lua_userdata*)lua_touserdata(L,2);  /* get data */
+  /*result=(usr1->ptr==usr2->ptr && usr1->type==usr2->type); only works if type is the same*/
+  result=(usr1->ptr==usr2->ptr);
+   lua_pushboolean(L,result);
+  return 1;
+}
+
 /* populate table at the top of the stack with metamethods that ought to be inherited */
 SWIGINTERN void SWIG_Lua_populate_inheritable_metamethods(lua_State *L)
 {
@@ -1439,6 +1456,7 @@ SWIGINTERN void SWIG_Lua_add_class_user_metamethods(lua_State *L, swig_lua_class
   int metatable_index;
   int metamethods_info_index;
   int tostring_undefined;
+  int eq_undefined = 0;
 
   SWIG_Lua_get_class_metatable(L, clss->fqname);
   metatable_index = lua_gettop(L);
@@ -1471,6 +1489,18 @@ SWIGINTERN void SWIG_Lua_add_class_user_metamethods(lua_State *L, swig_lua_class
     lua_pop(L,1); /* remove copy of the key */
   }
 
+  /* Special handling for __eq method */
+  lua_pushstring(L, "__eq");
+  lua_pushvalue(L,-1);
+  lua_rawget(L,metatable_index);
+  eq_undefined = lua_isnil(L,-1);
+  lua_pop(L,1);
+  if( eq_undefined ) {
+    lua_pushcfunction(L, SWIG_Lua_class_equal);
+    lua_rawset(L, metatable_index);
+  } else {
+    lua_pop(L,1); /* remove copy of the key */
+  }
   /* Warning: __index and __newindex are SWIG-defined. For user-defined operator[]
    * a __getitem/__setitem method should be defined
    */
@@ -1788,23 +1818,6 @@ SWIGRUNTIME int SWIG_Lua_type(lua_State *L)
   return 1;
 }
 
-/* lua callable function to compare userdata's value
-the issue is that two userdata may point to the same thing
-but to lua, they are different objects */
-SWIGRUNTIME int SWIG_Lua_equal(lua_State *L)
-{
-  int result;
-  swig_lua_userdata *usr1,*usr2;
-  if (!lua_isuserdata(L,1) || !lua_isuserdata(L,2))  /* just in case */
-    return 0;  /* nil reply */
-  usr1=(swig_lua_userdata*)lua_touserdata(L,1);  /* get data */
-  usr2=(swig_lua_userdata*)lua_touserdata(L,2);  /* get data */
-  /*result=(usr1->ptr==usr2->ptr && usr1->type==usr2->type); only works if type is the same*/
-  result=(usr1->ptr==usr2->ptr);
-   lua_pushboolean(L,result);
-  return 1;
-}
-
 /* -----------------------------------------------------------------------------
  * global variable support code: class/struct typemap functions
  * ----------------------------------------------------------------------------- */

Lib/lua/luaruntime.swg

@@ -40,7 +40,7 @@ SWIGEXPORT int SWIG_init(lua_State* L) /* default Lua action */
 #if ((SWIG_LUA_TARGET != SWIG_LUA_FLAVOR_ELUA) && (SWIG_LUA_TARGET != SWIG_LUA_FLAVOR_ELUAC)) || defined(SWIG_LUA_ELUA_EMULATE)
   /* add a global fn */
   SWIG_Lua_add_function(L,"swig_type",SWIG_Lua_type);
-  SWIG_Lua_add_function(L,"swig_equals",SWIG_Lua_equal);
+  SWIG_Lua_add_function(L,"swig_equals",SWIG_Lua_class_equal);
 #endif
 
 #if (SWIG_LUA_TARGET != SWIG_LUA_FLAVOR_ELUAC)