LI75610: APPLICATION SEGFAULT WITH -O -Q

June 2011 Update for XL C/C++ for Linux, V10.1
XL C/C++ for Linux Fix Pack 8 (January 2014 Update) for 10.1
August 2010 Update for XL C/C++ for Linux, V10.1
January 2011 Update for XL C/C++ for Linux, V10.1
January 2012 Update for XL C/C++ for Linux, V10.1
July 2012 Update for XL C/C++ for Linux, V10.1

APAR status

• Closed as program error.

Error description

• The following test case (3 source files) have application
  runtime segmentation fault if the program is compiled on AIX5.3
  with -O -Q.
  
  Removing -Q compiles and runs fine.
  
  
  xlc -O -Q -c bug.c -o bug_inline.o
  xlc -O -Q -c main.c -o main_inline.o
  xlc -O -Q bug_inline.o main_inline.o -o bug_inline
  
  ./bug_inline
  (segmentation fault)
  
  
  ===== TESTCASE:
  /*******$ cat bug.h*******/
  typedef struct {
    int x;
  } SYMBOL;
  
  /*********$ cat bug.c*******/
  #include <stddef.h>
  #include <stdlib.h>
  #include "bug.h"
  
  //Workaround: __attribute__((noinline))
  int
  allocate(SYMBOL **symbol)
  {
    SYMBOL *temp_symbol;
  
    if ((temp_symbol = malloc(sizeof(SYMBOL))) == NULL) return -1;
    temp_symbol->x = 1;
    *symbol = temp_symbol;
  
    return 0;
  }
  
  void
  create(SYMBOL **symptr)
  {
    if (allocate(symptr)) return;
    (*symptr)->x = 1;
  }
  
  
  void create(SYMBOL **symptr);
  
  
  /*********$ cat main.c*********/
  #include "bug.h"
  
  int
  main()
  {
    SYMBOL *sym;
    create(&sym);
    return 0;
  }
  

Local fix

• 1) Removing -Q on compile line on AIX 5.3.
  
  2) Compiling with -O -Q on AIX6.1.
  
  3) Combining the 3 source files into one file and compiliing
  with -O -Q on AIX 5.3.
  
  4) Adding __attribute__((noinline))to int allocate(SYMBOL
  **symbol) in bug.c.
  

Problem summary

• PROBLEM DESCRIPTION: Memory corruption due to bad load/store
  swap.
  
  USERS AFFECTED:
  Programs using inlining with multiple levels of indirection for
  an argument to a function,
  some combination of pointers for the associated parameter in
  the
  function body for the compiler to generate a sequence of
  Pointer Aliasing directves
  which does not work out when using inlining.
  

Problem conclusion

• Fixed a corner case in Intermediate Language generation which
  affects how the Inliner
  patches arguments to parameters.
  

Temporary fix

Comments

APAR Information

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

  IZ66403

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

Fix information

• Fixed component name

  XL C/C++ SLES10

• Fixed component ID

  5724U8300

Applicable component levels

• RA10 PSN IZ66403

     UP06/09/13