Possible flaw in handling of object references

Consider the C++ function below. The MyStruct and MyMember classes are both mapped into Lua.

 

struct MyMember
{
 int value;
};

 

struct MyStruct
{
 MyMember x;
};

 

void foo(MyStruct &m, const MyMember &x)
{
 m.x.value = 1;
 m.x.value += x;
}

 

Now we call the function from Lua:

local m = MyStruct()
local x = MyMember()
foo(m, x)

 

It seems correct at first, but the API is flawed. Parameter x might get altered if function is used as follows:

local m = MyStruct()
m.x = 3
foo(m, m.x)

 

Expected value of m.x: 4
Actual value of m.x: 2

 

What is the best practice to avoid this 'fake-const' problem?


I understand you can change the signature of foo to "void foo(MyStruct &m, MyMember x)", but that implies a possible performance hit, doesn't it? Is there a better way?

 

My feeling is that all bound functions should have non-reference parameters IF parameter type exists in 'this' AND is bound to lua. Correct? Is it possible that luabind could handle this automatically to avoid semantic errors?

 

Thanks
 		 	   		  
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