Question

here base->left is NULL, and base->right->height is 0:

((((base->left ? base->left->height : -1)) > ((base->right ? base->right->height : -1))) 
? 
((base->left ? base->left->height : -1) + 1) 
: 
((base->right ? base->right->height : -1) + 1))

IMO the result of the above expression should be 1,

but it turns out it’s 0 when I print it out.

Anyone knows the reason?

Is it a bug of gcc 4.3.2?

UPDATE

how the expression come?

#define MAX_PLUS_1(a, b) (((a) > (b)) ? (a + 1) : (b + 1))
#define BINARY_TREE_HEIGHT(node) (node ? node->height : -1)
#define BINARY_TREE_SYN_HEIGHT(left, right) \
    MAX_PLUS_1(\
        BINARY_TREE_HEIGHT(left),\
        BINARY_TREE_HEIGHT(right)\
    )

it’s really BINARY_TREE_SYN_HEIGHT(base->left, base->right)

And the problem is gone if I replace MAX_PLUS_1 with function:

int MAX_PLUS_1(int a, int b){
    return (((a) > (b)) ? (a + 1) : (b + 1));
}

Answer 1

From additional information in our Comments discussion, your height field is unsigned. That means that when you try to compare it to -1 you end up in trouble – (uint32_t)-1 == 0xFFFF_FFFF = Very Big Number, so the ‘left’ branch gets chosen over the ‘right’ branch at some point when you don’t expect it to.

Writing MAX_PLUS_1() as a function solves, or perhaps rather hides, this problem because you use int for the parameters. That means the comparison is done between the height value and (int)-1, which is what you wanted.