title: Why some global variables' size is zero in symbol table?
body: <p>Here is code:</p>
  
  <p>wubing@ubuntu:~/Downloads$ readelf -s testVar1.o</p>
  
  <pre><code>Symbol table '.symtab' contains 13 entries:
     Num:    Value          Size Type    Bind   Vis      Ndx Name
       0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
       1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS testVar1.cc
       2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1 
       3: 0000000000000000     0 SECTION LOCAL  DEFAULT    2 
       4: 0000000000000000     0 SECTION LOCAL  DEFAULT    3 
       5: 0000000000000000     0 SECTION LOCAL  DEFAULT    5 
       6: 0000000000000000     0 SECTION LOCAL  DEFAULT    6 
       7: 0000000000000000     0 SECTION LOCAL  DEFAULT    4 
       **8: 0000000000000000     4 OBJECT  GLOBAL DEFAULT    3 uninit1
       9: 0000000000000004     4 OBJECT  GLOBAL DEFAULT    3 uninit2
      10: 0000000000000000     4 OBJECT  GLOBAL DEFAULT    2 uninit3
      11: 0000000000000004     4 OBJECT  GLOBAL DEFAULT    2 unitit4**
      12: 0000000000000000    11 FUNC    GLOBAL DEFAULT    1 main
  </code></pre>
  
  <p>wubing@ubuntu:~/Downloads$ cat testVar1.cc </p>
  
  <pre><code>int uninit1;
  int uninit2;
  int uninit3=3;
  int unitit4=4;
  int main()
  {
    ;
  }
  </code></pre>