Mismatch delete

Question

I have program which implements database of peoples and his companies. I have created dynamic array of pointer to class members instead of dynamic array of class members, cause copying is quicker with it.

I have version which works but valgrind shows mismatch delete in destructor (delete db)

CCompany** db;

~CCompanyIndex ( void )
{
    for(unsigned i=0;i<len;i++)
    {
        /*cout<<"dealloc:"<<db[i]<<endl;*/
        delete db[i];
    }
    delete db;
}

CCompanyIndex ( void )
{
    max=1000;
    len=0;
    db=new CCompany*[max];
}

I use also to add

CCompany* newIt=new CCompany(oName,oAddr,cName,cAddr);

So I have tried following code which I consider correct previously

~CCompanyIndex ( void )
{
    delete [] db;
}

But then all memory allocated by adding method is not deallocated.

Solution 1

The first sample is almost correct. You're deleting each element in a for loop, but then you attempt to delete the array.

for(unsigned i=0;i<len;i++) { delete db[i]; }
delete db;

It should instead be:

for(unsigned i=0;i<len;i++) { delete db[i]; }
delete[] db;

Whenever you use new ...[], you should be using delete[].

Also, don't forget the Rule of Three (or Five (or Zero)).

Solution 2

You are using the wrong delete. Do this:

CCompanyIndex::~CCompanyIndex()
{
    for(unsigned i=0; i<len;i++) delete db[i];
    delete [] db;
}

Note the delete [] call.

Solution 3

You need delete db[i] for each element but delete[] db for the array itself, so neither destructor was correct.

Arrays allocated with new Foo[n] must be deallocated with the array form, delete[], that's what valgrind means about mismatch new/delete

Comments

[Jerry Coffin]

Better still, don't use new[] or delete[]. Use a vector and be happy.