Question

I would like to add pointers to a hash table using hsearch_r. At the moment it does not work using the following code segment (without variable declarations and checks):

// Allocate hash table
htab = calloc( INITIAL_HASH_SIZE, sizeof(struct hsearch_data) );
hcreate_r( INITIAL_HASH_SIZE, htab );

// Add first pointer to hash table
he.key = (char *)&pointer_some_complex_struct1;
if ( hsearch_r( he, FIND, &hep, htab ) == 0) {
  he.data = pointer_some_complex_struct1->data;
  hsearch_r( he, ENTER, &hep, htab );
}

// Add second pointer to hash table
he.key = (char *)&pointer_some_complex_struct2;
if ( hsearch_r( he, FIND, &hep, htab ) ) {
  // CODE ENTERS HERE
}

The second call finds the object regardless it is not present. Any ideas what could be the problem with the above code segment?

Answer 1

The problem is that the keys in hsearch/hsearch_r are NUL-terminated strings, not arbitrary data.