c++ – Comparing pointers for self-assignment – Education Career Blog

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I am trying to overload the = operator on a simple C++ class called Set that contains a dynamic array of ints. For the = operator, I first want to check for self assignment, so I wanted to compare 2 pointers to make see if they have the same memory address. Here’s the code:

Set& Set::operator=(const Set& setEqual)
{
//first check for self assignment
if(setEqual == this*)
    cout << "this is self assignment";
}

The error spat out is error: expected primary-expression before ')' token

I believe I’m having a misunderstanding of pointers again, so if anyone could point (ha!) me in the right direction, I’d appreciate it.

,

The error is becuase this* is not valid – * is either infix (in multiplication) or prefix (in dereferencing pointers).

You probably want &setEqual == this – that is assigning from an object at the same memory address or setEqual==*this – comparing equality using whatever operator== you have defined

,

To detect self-assignment you need

if(&setEqual == this)

you should never use

if(setEqual == *this)

for detecting self-assignment as the latter statement will invoke comparison of the objects, which might be overloaded in the way you don’t expect and is likely slower as well.

,

If you want to compare the address of the thing pointed too you really want this:

Set& Set::operator=(const Set& setEqual)
{
//first check for self assignment
if(&setEqual == this)
    cout << "this is self assignment";
}

Using (setEqual==*this) as sugested by some of the solutions compares if the objects are equal under operator==.

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