LI78458: RETURN VALUE FROM SETJMP NOT SAVED

XL C/C++ for Linux Fix Pack 2 (February 2015 Update) for 13.1

APAR status

• Closed as program error.

Error description

• When compiling with optimization, the return value from a
  call/jump to setjmp is not saved.  This may result in incorrect
  program behaviour, or invalid looping between setjmp/longjmp.
  
  
     === TEST CASE ===
  
  #include <stdio.h>
  #include <setjmp.h>
  #include <stdlib.h>
  
  int main(int argc, char *argv[])
  {
   int ret;
   jmp_buf jmpbuf;
  
   ret = _setjmp(jmpbuf);
   //__fence();    // WORKAROUND
   if (ret == 0)
   {
    int raise = argc > 1 ? atoi(argv[1]) : 0;
    printf("Expected Code Path ... 1\n");
  
    if (raise) _longjmp(jmpbuf, 100);
   }
  
   if (ret == 100)  printf("Expected Code Path ... 2\n");
  
   return 0;
  }
  
  
  $ xlc -q64 tc2.c
  $ ./a.out 11
  Expected Code Path ... 1
  Expected Code Path ... 2
  $
  
  $ xlc -q64 tc2.c -O2
  $ ./a.out 11
  Expected Code Path ... 1
  $
  

Local fix

• Compile without optimization, or insert an optimization
  __fence() call after the setjmp() call.
  

Problem summary

• PROBLEM DESCRIPTION:
  The result from __setjmp is not saved and if the result
  variable is accessed later it may not produce the correct
  result.
  
  USERS AFFECTED:
  Only a problem if the return value from __setjmp is used.
  

Problem conclusion

• The fix will make volatile declaration unnecessary as the
  compiler will know to treat the result of __setjmp differently.
  

Temporary fix

Comments

APAR Information

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

  IV62226

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

Fix information

• Fixed component name

  XL C/C++ FOR LI

• Fixed component ID

  5725C7300

Applicable component levels

• RD10 PSN IV62226

     UP06/09/13