error: cannot initialize return object of type 'Type *' with an rvalue of type 'bool'

Question

I have this code in JavaScript:

// ...

 findNode: function(root, w, h) {
    if (root.used)
      return this.findNode(root.right, w, h) || this.findNode(root.down, w, h);
},

// ...

I'm developing an equivalent code in C++ like this:

Block *GrowingPacker::findNode(Block *root, float w, float h)
{
    if (root->m_used)
        return findNode(root->m_right, w, h) || findNode(root->m_down, w, h);
}

However C++ throws this error at return line:

error: cannot initialize return object of type 'Block *' with an rvalue of type 'bool'

I wonder what is the most elegant approach to prevent the error!

Answer 1

if (root->m_used)
    return findNode(root->m_right, w, h) || findNode(root->m_down, w, h);

returns a boolean but your function expects to return a Block* . In Javascript it doesn't matter because there is no strong typing but in C++ the return type of || is bool .

I think you want this

if (root->m_used)
{
    Block* tmp = findNode(root->m_right, w, h);
    if (tmp)
        return tmp;
    else
        return findNode(root->m_down, w, h);
}

AND you need to add some code to deal with the case when root->m_used is false ( return nullptr; presumably).

Unlike Javascript, C++ is a strongly typed language. Therefore it's really important to enable all the warnings you can on your compiler, so you can catch as many type mismatches and other gotchas as possible.