IV13924: OVERLAPING CSECTS CAUSING LINKER ERROR

April 2012 PTF for XL C for AIX, V11.1
April 2012 PTF for XL C/C++ for AIX, V11.1
July 2012 PTF for XL C/C++ for AIX, V11.1
October 2012 PTF for XL C/C++ for AIX, V11.1
October 2012 PTF for XL C for AIX, V11.1
February 2013 PTF for XL C for AIX, V11.1
February 2013 PTF for XL C/C++ for AIX, V11.1
XL C/C++ for AIX Fix Pack 14 (May 2013 PTF) for 11.1
XL C for AIX Fix Pack 14 (May 2013 PTF) for 11.1
XL C/C++ for AIX Fix Pack 15 (August 2013 PTF) for 11.1
XL C for AIX Fix Pack 15 (August 2013 PTF) for 11.1
XL C/C++ for AIX Fix Pack 16 (November 2013 PTF) for 11.1
XL C for AIX Fix Pack 17 (February 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 17 (February 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 18 (May 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 19 (August 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 20 (November 2014 PTF) for 11.1
XL C for AIX Fix Pack 21 (April 2015 PTF) for 11.1
XL C/C++ for AIX Fix Pack 21 (April 2015 PTF) for 11.1
XL C/C++ for AIX Fix Pack 22 (September 2015 PTF) for 11.1
XL C for AIX Fix Pack 23 (March 2016 PTF) for 11.1
XL C/C++ for AIX Fix Pack 23 (March 2016 PTF) for 11.1
XL C for AIX Fix Pack 24 (September 2016 PTF) for 11.1
XL C/C++ for AIX Fix Pack 24 (September 2016 PTF) for 11.1
July 2012 PTF for XL C for AIX, V11.1
XL C for AIX Fix Pack 16 (November 2013 PTF) for 11.1
XL C for AIX Fix Pack 18 (May 2014 PTF) for 11.1
XL C for AIX Fix Pack 19 (August 2014 PTF) for 11.1
XL C for AIX Fix Pack 20 (November 2014 PTF) for 11.1
XL C for AIX Fix Pack 22 (September 2015 PTF) 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:

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

  LI76822

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5724X1200

Applicable component levels