编译器报错：使用了未初始化的局部变量“T”？

/*
Args:
* s:the string of preorder traversal sequence.

for example:
if you want to obtain an element of s,you can write the code:
DataType data = *((*s));
if you want to obtain the second element of s,you can write the code:
(*s)++;
DataType data = *((*s));

Return:
* Pointer of the bitree node.
Description:
* Create a bitree from preorder traversal sequence.
*/
BinaryTree CreateBinaryTreeFromPreOrderSequence(DataType **s)
{
    DataType ch;
    BinaryTree *T;
    ch = (*(*s));

    if (ch == '*')
        *T = NULL;
    else
    {
        *T = (BinaryTree)malloc(sizeof(BinaryNode));
        if (!*T)
            exit(0);
        (*T)->data = ch;
        (*s)++;
        (*T)->left=CreateBinaryTreeFromPreOrderSequence(*(*s));
        (*T)->right= CreateBinaryTreeFromPreOrderSequence(*(*s));
    }
    return *T;
}

DataType ch;
BinaryTree *T;

这些你都顺手给个初始值