c++ - malloc issue with struct of containing an array of strings -

i've read other posts issue. when change top line:

typedef char key_type; 

to

typedef string key_type; 

i memory access error @ p->key[1] = x;

typedef char key_type; // change string , breaks typedef struct node_tag{     int count;     key_type key[maxsize + 1];     struct node_tag *branch[maxsize + 1]; }node_type;  node_type *insert(key_type newkey, node_type *root) {     key_type x; /* node reinserted new root    */     node_type *xr;  /* subtree on right of x        */     node_type *p;   /* pointer temporary use        */     bool pushup; /* has height of tree increased? */      pushup = pushdown(newkey, root, &x, &xr);     if (pushup) {   /* tree grows in height.*/         /* make new root: */         p = (node_type *)malloc(sizeof(node_type));         p->count = 1;         p->key[1] = x; // memory access error         p->branch[0] = root;         p->branch[1] = xr;         return p;     }     return root; } 

what small modification can made eliminate memory access error?

you didn't call constructor string. also, in habit of writing c++ , not c:

typedef string key_type; struct node_type{ // don't need typedef ...     int count;     key_type key[maxsize + 1];     node_type *branch[maxsize + 1]; };  node_type *insert(key_type newkey, node_type *root) {     key_type x; /* node reinserted new root    */     node_type *xr;  /* subtree on right of x        */     node_type *p;   /* pointer temporary use        */     bool pushup; /* has height of tree increased? */      pushup = pushdown(newkey, root, &x, &xr);     if (pushup) {   /* tree grows in height.*/         /* make new root: */         p = new node_type;         p->count = 1;         p->key[1] = x; // memory access error         p->branch[0] = root;         p->branch[1] = xr;         return p;     }     return root; } 

if don't provide ctor struct compiler create 1 (as dtor).