LI75926: SEGFAULT DUE TO SEGMENT VIOLATION

January 2012 Update for XL Fortran for Linux, V12.1
January 2011 Update for XL Fortran for Linux, V12.1
June 2011 Update for XL Fortran for Linux, V12.1
XL Fortran for Linux Fix Pack 8 (January 2014 Update) for 12.1

APAR status

• Closed as program error.

Error description

• The following test case segfaults due to a pointer violation
  created by the compiler:
  
  ===== COMPILE COMMAND:
  $xlc -c zc.c
  $xlf90 -c -qsource,list zom.f
  $xlf90 -c -qsource,list zz.f
  $xlf90 zz.o zom.o zc.o
  
  ===== TESTCASE:
  $ cat zc.c
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  void zc(long long ii)
  {
    fprintf(stderr,"ii = %ld\n",ii);
  }
  $
  
  $ cat zom.f
  MODULE ZOM
  
  INTEGER :: JPNOTP
  
  parameter(jpnotp=10)
  
  !       JOT JO table, derived type
  TYPE jotsub_t
    CHARACTER(len=32) :: sname         ! name of sub-table
    REAL*8 , POINTER :: cost(:,:)      ! cost function value
    INTEGER, POINTER :: count(:,:)     ! data count
    REAL*8 , POINTER :: obimpact(:,:)  ! obs impact
  END TYPE jotsub_t
  
  TYPE jot_t
    CHARACTER(len=32)       :: name    ! name of table entry
    INTEGER                 :: size    ! size of sub-table
    TYPE(jotsub_t), POINTER :: jost(:) ! Jo sub-table
  END TYPE jot_t
  
  TYPE(jot_t) :: jot(JPNOTP)           ! Jo-table
  
  INTEGER :: NPRTBINS=1
  INTEGER :: JPXVAR=10
  
  end module zom
  
  $
  
  $ cat zz.f
  call zzz()
  end
  
  @PROCESS NOOPT
  SUBROUTINE zzz
  
    USE ZOM
    IMPLICIT NONE
  
  
    INTEGER :: INOCTP,JCTP,IOBTYP
  
    INOCTP=10
    IOBTYP=10
  
  
          ALLOCATE(JOT(IOBTYP)%jost(INOCTP))
  
          do jctp=1,10
  
            ALLOCATE(JOT(IOBTYP)%jost(JCTP)%cost
  (JPXVAR,NPRTBINS))
  
  ALLOCATE(JOT(IOBTYP)%jost(JCTP)%count(JPXVAR,NPRTBINS))
  
  ALLOCATE(JOT(IOBTYP)%jost(JCTP)%obimpact(JPXVAR,NPRTBINS))
  
            write(0,*) "IOBTYP,JCTP=",IOBTYP,JCTP
            call zc(JOT(IOBTYP)%jost(JCTP)%cost(1,1))
            JOT(IOBTYP)%jost(JCTP)%cost(:,:)= 0.0
            JOT(IOBTYP)%jost(JCTP)%count(:,:)= 0.0
            JOT(IOBTYP)%jost(JCTP)%obimpact(:,:) = 0.0
  
          enddo
  
  END
  $
  
  
  
  ===== ACTUAL OUTPUT:
  $ ./a.out
   IOBTYP,JCTP= 10 1
  ii = 51245076
  Segmentation fault
  $
  
  ===== EXPECTED OUTPUT:
  $ ./a.out
   IOBTYP,JCTP= 10 1
  ii = 536876824
   IOBTYP,JCTP= 10 2
  ii = 537003080
   IOBTYP,JCTP= 10 3
  ii = 537003320
   IOBTYP,JCTP= 10 4
  ii = 537003560
   IOBTYP,JCTP= 10 5
  ii = 537003800
   IOBTYP,JCTP= 10 6
  ii = 537004040
   IOBTYP,JCTP= 10 7
  ii = 537004280
   IOBTYP,JCTP= 10 8
  ii = 537004520
   IOBTYP,JCTP= 10 9
  ii = 537004760
   IOBTYP,JCTP= 10 10
  ii = 537005000
  $
  

Local fix

• n/a
  

Problem summary

• USERS AFFECTED:
  Users who use modules to declare variables of types containing
  pointer alike components will be affected.
  
  PROBLEM DESCRIPTION:
  The execution of the program fails in a particular situation.
  1. The program contains a reference to a variable that is of
  derived type containing a allocatable/pointer
  component and declared in a module, and
  
  2. There is a variable declared in the same module and
  appearing before the affected variable.
  

Problem conclusion

• When computing base address of an internal component, the
  compiler needed to take module variables into consideration.
  

Temporary fix

Comments

APAR Information

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

  IZ72918

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

Fix information

• Fixed component name

  XL FORTRAN RHEL

• Fixed component ID

  5724U8410

Applicable component levels

• RC10 PSN IZ72918

     UP06/09/13