Casting/dereferencing member variable pointer from void*, is this safe?
- by Damien
Hi all,
I had a problem while hacking a bigger project so I made a simpel test case. If I'm not omitting something, my test code works fine, but maybe it works accidentally so I wanted to show it to you and ask if there are any pitfalls in this approach.
I have an OutObj which has a member variable (pointer) InObj. InObj has a member function. I send the address of this member variable object (InObj) to a callback function as void*. The type of this object never changes so inside the callback I recast to its original type and call the aFunc member function in it. In this exampel it works as expected, but in the project I'm working on it doesn't. So I might be omitting something or maybe there is a pitfall here and this works accidentally. Any comments? Thanks a lot in advance.
(The problem I have in my original code is that InObj.data is garbage).
#include <stdio.h>
class InObj
{
public:
int data;
InObj(int argData);
void aFunc()
{
printf("Inside aFunc! data is: %d\n", data);
};
};
InObj::InObj(int argData)
{
data = argData;
}
class OutObj
{
public:
InObj* objPtr;
OutObj(int data);
~OutObj();
};
OutObj::OutObj(int data)
{
objPtr = new InObj(data);
}
OutObj::~OutObj()
{
delete objPtr;
}
void callback(void* context)
{
((InObj*)context)->aFunc();
}
int main ()
{
OutObj a(42);
callback((void*)a.objPtr);
}
