The function bfd_hash_lookup is used both to look up a
string in the hash table and to create a new entry.
If the create argument is FALSE, bfd_hash_lookup
will look up a string. If the string is found, it will
returns a pointer to a struct bfd_hash_entry. If the
string is not found in the table bfd_hash_lookup will
return NULL. You should not modify any of the fields in
the returns struct bfd_hash_entry.
If the create argument is TRUE, the string will be
entered into the hash table if it is not already there.
Either way a pointer to a struct bfd_hash_entry will be
returned, either to the existing structure or to a newly
created one. In this case, a NULL return means that an
error occurred.
If the create argument is TRUE, and a new entry is
created, the copy argument is used to decide whether to
copy the string onto the hash table objalloc or not. If
copy is passed as FALSE, you must be careful not to
deallocate or modify the string as long as the hash table
exists.