Question

I have an if/else if statement that looks like this:

if(myNode->left->is_red){
    //CODE TO EXECUTE
}               
else if(myNode->right->is_red){
    //CODE TO EXECUTE
}

The conditions I am checking are whether certain data fields in each node are set. BUT, the problem is, if I access a NULL pointer and try to access its members (which don’t exist), then I run into a segmentation fault issue. But if I do an if statement before the if, and again before the else if, to check whether or not the node is NULL, then I lose the ability to use an if/else if statement.

Is there any way I can achieve a solution to both problems?

Answer 1

I’m assuming the issue is that left and/or right is NULL, hence your segfault?

If so, then use AND.

e.g:

if((myNode->left != NULL) && myNode->left->is_red){
    //CODE TO EXECUTE
}               
else if((myNode->right != NULL) && myNode->right->is_red){
    //CODE TO EXECUTE
}

This uses short-circuit evaluation: although the myNode->left->is_red and myNode->right->is_red are still in the if conditions, if myNode->left is NULL (or myNode->right respectively), they wont be evaluated and you will not have your segfault.