JNA Error at Program Exit

So I have the following in c++

__declspec(dllexport) extern "C"
char** get_prop_types( int* count ) {
  const vector<string>& r = prop_manager::get_prop_types();
  char **p = (char**)malloc( r.size() );
  char **ptr = p;
  for( vector<string>::const_iterator it = r.begin(); it!=r.end() ; ++it ) {
    *p = (char*)malloc( it->size() );
    strcpy(*p++,it->c_str());
  }
  *count = r.size();
  return ptr;
}

and in java

public interface Arch extends Library {
    public Pointer get_prop_types( IntByReference size );
}
static Arch theLib; //initialization not shown

public static String[] getPropTypes() {
    IntByReference size = new IntByReference();
    Pointer strs = theLib.get_prop_types(size);
    //free is apparently handled for us?
    return strs.getStringArray(0, size.getValue());
}

public static void main( String[] args ) {
    System.out.println( Arrays.toString(getPropTypes()) );
}

The above will print out a list of Strings. So far so good. But after main returns (during finalization?) I get an error along the lines of

The instruction at "%08X" referenced memory at "%08x". The memory could not be "read".

I get the same error when trying to ma开发者_高级运维nually free() the char** or each individual char*

Can someone tell me what I've done wrong? Or at least point we to some more resources?

This:

 *p = (char*)malloc( it->size() );

should be:

 *p = (char*)malloc( it->size() + 1);

And I just noticed that:

 char **p = (char**)malloc( r.size() );

should be:

 char **p = (char**)malloc( r.size() * sizeof(char *) );

which shows how often I use malloc these days!