LI76822: OVERLAPING CSECTS CAUSING LINKER ERROR

XL C/C++ for Linux Fix Pack 9 (August 2013 Update) for 11.1
June 2012 Update for XL C/C++ for Linux, V11.1
October 2012 Update for XL C/C++ for Linux, V11.1
XL C/C++ for Linux Fix Pack 8 (June 2013 Update) for 11.1

APAR status

• Closed as program error.

Error description

• When compiling with both -qfuncsect and -qminimaltoc, the newer
  linkers (ie bos.rte.bind_cmds 7.1.0.16 and above)
  start complaining about overlaping csect symbols in the object
  file.
  
  After looking at the .s file, you can see the overlap between
  csect H.12 and H.22:
  .
  .
          .csect  H.22.NO_SYMBOL{RO}, 3         <----start of H.22
          .long   0x00000054              # "\0\0\0T"
          .long   0x00000060              # "\0\0\0`"
          .long   0x0000006c              # "\0\0\0l"
          .long   0x00000078              # "\0\0\0x"
  
          .toc
  T.12.NO_SYMBOL:
          .tc     H.12.NO_SYMBOL{TC},0x00000084     <----start of
  H.12
          .long   0x00000090              # "\0\0\0\220"
          .long   0x0000009c              # "\0\0\0\234"
          .long   0x000000a8              # "\0\0\0\250"
  # End   csect   H.22.NO_SYMBOL{RO}          <----end of H.22
  
  
  
  
  ===== COMPILE COMMAND:
  $xlC -qfuncsect -qminimaltoc test.cpp
  
  ===== TESTCASE:
  $cat test.cpp
  int Z(int val)
  {
   int ret=0;
   switch(val)
   {
   case 0:
    ret=5;
    break;
   case 1:
    ret=10;
    break;
   case 2:
    ret=7;
    break;
   case 3:
    ret=2;
    break;
   case 4:
    ret=17;
    break;
   case 5:
    ret=1;
    break;
   case 6:
    ret=47;
    break;
   case 7:
    ret=99;
    break;
   default:
    ret=98;
    break;
   }
   return ret;
  }
  
  int main(int argc)
  {
   return Z(argc);
  }
  $
  
  
  ===== ACTUAL OUTPUT:
  $xlC -qfuncsect -qminimaltoc test.cpp
  ld: 0711-552 SEVERE ERROR: Object test.o:
   Csects with symbol numbers 22 and 12 overlap.
  $
  
  ===== EXPECTED OUTPUT:
  Should not cause a link error.
  

Local fix

• Avoid using the -qfuncsect -qminimaltoc option combination as a
  workaround with the 7.1.0.16 (and above) linkers.
  

Problem summary

• USERS AFFECTED:
  Clients using -qfuncsect and -qminimaltoc together to compile a
  program with switch statements may be affected by this issue.
  
  PROBLEM DESCRIPTION:
  The compiler internally generates a branch table for the switch
  statement when -qfuncsect is used.
  When -qminimaltoc is used, relocatable addresses are created
  and put into data CSECTs and should not generate TOC slots.
  When both are used together, the compiler generates incorrect
  addresses that overlap the branch table causing the linker to
  complain.
  

Problem conclusion

• The fix is to not emit the sym table entries for the incorrect
  TOC slot.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  IV13924

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  XL C/C++ FOR LI

• Fixed component ID

  5724X1400

Applicable component levels

• RB10 PSN IV13924

     UP06/09/13