IV65270: -O OPTIMIZES AWAY AN IF CLAUSE

XL C/C++ for AIX Fix Pack 1 (September 2014 PTF) for 13.1
XL C/C++ for AIX Fix Pack 2 (December 2014 PTF) for 13.1
XL C/C++ for AIX Fix Pack 3 (April 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 4 (July 2015 PTF) for 13.1
XL C for AIX Fix Pack 5 (November 2015 Update) for 13.1
XL C/C++ for AIX Fix Pack 5 (November 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 6 (February 2016 PTF) for 13.1
XL C for AIX Fix Pack 6 (February 2016 Update) for 13.1
XL C for AIX Fix Pack 7 (May 2016 Update) for 13.1
XL C/C++ for AIX Fix Pack 7 (May 2016 PTF) for 13.1
XL C for AIX Fix Pack 8 (August 2016 Update) for 13.1
XL C/C++ for AIX Fix Pack 8 (August 2016 PTF) for 13.1
XL C for AIX Fix Pack 9 (June 2017 Update) for 13.1
XL C/C++ for AIX Fix Pack 9 (June 2017 PTF) for 13.1
XL C for AIX Fix Pack 10 (February 2018 Update) for 13.1
XL C/C++ for AIX Fix Pack 10 (February 2018 PTF) for 13.1
XL C for AIX Fix Pack 1 (September 2014 PTF) for 13.1
XL C for AIX Fix Pack 2 (December 2014 PTF) for 13.1
XL C for AIX Fix Pack 3 (April 2015 PTF) for 13.1
XL C for AIX Fix Pack 4 (July 2015 PTF) for 13.1
XL C/C++ for AIX Fix Pack 11 (November 2018 PTF) for 13.1
XL C for AIX Fix Pack 11 (November 2018) for 13.1

APAR status

• Closed as program error.

Error description

• When compiling the following test case with -O2, the resulting
  binary leads to NnNincorrect outputN
  
  ===== COMPILE COMMAND:
  xlC_r -qmakedep=gcc -D_AIX51 -D_LARGE_FILES
  -D__NO_XLC_BUILTIN_VA -DOS_LEVEL=710 -D_Packed= -qnotempinc
  -U__unix -q64N-qtbtable=full -qhalt=e -qalias=noansi -qutf -+ -O
  -qfdpr -qstrict -qlibansi -qinlglue -qmaxmem=-1 -DNDEBUG
  -qarch=pwr4 -qtune=balanced -qsNill=2560 -qlonglong
  -qalign=natural -qldbl128  -qdebug=RNSSMALL -c -o test.o test.c
  
  xlC_r -o a.out -NcNtors:mbr::s -bweNklocal -q64 -brtl  -bbigtoc
  -lc -lc128 test.o  -lperfstat  -lrt -lwlm -lpthread -lm
  
  ===== TESTCASE:
  $ cat test.c
  #include <stdNo.h>
  #include <stdlib.h>
  #include <unistd.h>            N
  
  typedef unsigned short P_CHAR;
                  N N                N
  static bool isStandardChar(P_CHAR &c)
  {
          printf ("-->isStandardChar (%d: %c) a: %d z: %d
  \n",(P_CHAR) c, (P_CHAR) c, (P_CHAR)u'a', (P_CHAR)u'z');
      if ( (c >N (P_CHAR) u'a') && (c <= (P_CHAR) u'z') )
      {
          return true;           N
      }
      else if ( (c >= (P_CHAR) u'A') && (c <= (P_CHAR) u'Z') )
      {           N N                N
          return true;
      }
      else if ( (c >= (P_CHAR) u'0') && (c <= (P_CHAR) u'9') )
      {
          returN true;
      }
      else if ( ( c == u'_') || (Nc == u':') ||
                ( c == u'/') || ( c == u'-') ||
                ( c == u';') )
      {           N N                N
          return true;
      }
  
      return false;
  }            N
  
  int main(int argc, char** argv)N
  {
      P_CHAR c = 117;
      if ( isStandNrNChar(c) )       N
          printf ("%c is a StandardChar\n", (P_CHAR) c);
          else
          printf ("%c is NOT a StandardChar\n", (P_CHAR) c);
  
      return 0;N
  }
  $                              N
  
  
  ===== ACTUAL OUTNUN:               N
  $ ./restKrn
  -->isStandardChar (117: u) a: 97 z: 122
  u is NOT a StandardChar
  $
               N
  ===== EXPECTED OUTPUT:
  $ ./restKm                     N
  -->isStandardChar (117: u) a: 97 z: 122
  u is a StandardChar
  

Local fix

• N N                N
  Change
  
  typedef unsigned short P_CHAR;
  
  to           N
  
  typedef unsigned int P_CHAR;   N
  
  as a workaround.
  

Problem summary

• PROBLEM SUMMANY:
  USERS AFFECTED:
  Users who perform a range checkNof alphabetical ASCII
  characters (a-z,A-Z) in their code may be affected by this
  issue.
                  N N                N
  PROBLEM DESCRIPTION:
  The compiler optimizes out an IF clause under specific
  circumstances whenever a char is checked for the range of
  alphabetical ASCII characters (a-z,A-Z).
  This occured Necause a parameter passed was mangled without
  restoring to next parameter.
  

Problem conclusion

• N
  The compiler has been fixed to properly check the range of
  alphabetical ASCII characters (a-z,A-Z).
  

Temporary fix

• N N                N
  

Comments

APAR Information

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

  IV62591

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

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5725C7100

Applicable component levels

• RD10 PSY