Hi,
With the piece of code:

1 #include <stdio.h>
  2 
  3 typedef struct {
  4         int x;
  5         int y;
  6 } addr;
  7 
  8 typedef struct addr a;
  9  
10 int main() {
 11         addr array[5]; 
 12.        printf("%d\n", sizeof(array)/sizeof(addr));
 13.        return 0;
 14. }

Having this error:

nettest.cpp:8: error: using typedef-name ‘addr’ after ‘struct’
nettest.cpp:6: error: ‘addr’ has a previous declaration here
nettest.cpp:8: error: invalid type in declaration before ‘;’ token
nettest.cpp: In function ‘int main()’:
nettest.cpp:12: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’

How to do it correctly?

in line #8, you no longer need to typedef a second time... just go ahead and create your object:

addr a;