QSORT Segmentation Fault

[chauvjo]

The following code is generating a segmentation fault during the call to QSORT.  It appears QSORT is calling the routine COMPARE without assigning a value to arg1. I tried adding USE IFPORT to the main routine but this did not solve the problem.  This identical code worked without errors on another UNIX system.  I have compiled the code using Intel Compiler Version 2013 SP1 Update 4 and Intel Compiler Version 2015 Update 1 without success. I am running on RHEL 6.6.  Any ideas?   Thanks...

      SUBROUTINE BuildArray(array_values,number_values,min_value,max_value,delta_value,special_array,n_special_array)

      IMPLICIT NONE
C     ..
C     .. Scalar Arguments ..
      DOUBLE PRECISION min_value,max_value,delta_value
      INTEGER number_values,n_special_array
C     ..
C     .. Array Arguments ..
      DOUBLE PRECISION array_values(2000),special_array(10)
C     ..
C     .. Local Scalars ..
      INTEGER J,K
C     ..
C     .. External Functions ..
      EXTERNAL QSORT,Compare
      INTEGER*2 Compare
C     ..
C     .. Executable Statements ..

      number_values = (INT((max_value - min_value) / delta_value) + 1) 

      DO J=1,number_values
          array_values(J) = min_value + DBLE(J-1) * delta_value
      END DO

      DO J=1,n_special_array
         K = number_values + J
         array_values(K) = special_array(J) 
      END DO

      number_values = number_values + n_special_array

      CALL QSORT(array_values,number_values,8,Compare)

      RETURN
      END
      INTEGER*2 FUNCTION Compare(arg1,arg2)

      IMPLICIT NONE
C     ..
C     .. Scalar Arguments ..
      DOUBLE PRECISION arg1,arg2
C     ..
C     .. Executable Statements ..
C
      IF(arg1.LT.arg2) THEN
          Compare = -1
      ELSE IF(arg1.EQ.arg2) THEN
          Compare = 0
      ELSE IF(arg1.GT.arg2) THEN
          Compare = 1
      ENDIF

      RETURN
      END

[chauvjo]

I forgot to add the compiler options:

-O0 -fpe0 -extend_source 132 -g -check bounds -u -traceback

Thanks....

[mecej4]

If you are targeting x64 rather than IA32, you need to declare the integer arguments to QSORT as integer(8), or use a compiler option to select as default 8-byte integers. Failing to do so is probably the cause of the failure that you noted. Perhaps, the "another Unix system" is a 32-bit installation?

[jimdempseyatthecove]

mecej4 is likely correct.

You should have (make one if you do not) a module defining the interface to QSORT. Had you USEed this, it would have told you of the incorrect types.

Avoid using EXTERNAL if at all possible.

Jim Dempsey