XL Fortran Enterprise Edition for AIX : User's Guide - IBM

A Sample dbx Session for an XL Fortran Program
You can debug XL Fortran programs with any dbx-compatible symbolic debugger.
For background information on dbx, see the AIX General Concepts and Procedures
document . For information on dbx subcommands, see the AIX Commands
Reference.
The following example represents a typical XL Fortran problem that you may be
able to resolve through dbx. Although it demonstrates only a small subset of dbx
features and uses memory-allocation techniques made obsolete by Fortran
90/Fortran 95 allocatable arrays, it can serve as an introduction if you have not
used this debugger before.
Problem with Dynamic Memory Allocation
The following program tries to allocate an array at run time by using the AIX
system subroutine malloc. When you use the following command to compile the
program and then run the program, the program produces a core dump:
xlf95 -qddim testprog.f -o testprog
At this point, you may be wondering whether the C malloc routine is working
correctly or whether this is the right way to allocate an array in a main program
when the dimensions are not known until run time.
program main
pointer(p, array(nvar,nrec))
real*8 array
nvar = 2
nrec = 3
p = malloc(nvar*nrec*8)
call test_sub(array, nvar, nrec)
end
subroutine test_sub(array, nvar, nrec)
dimension array(nvar, nrec)
array(1,1) = 1.
array(2,1) = 2.
array(1,2) = 3.
array(2,2) = 4.
array(1,3) = 5.
array(2,3) = 6.
write(*, 100) array(1,1), array(2,1), array(1,2),
1 array(2,2), array(1,3), array(2,3)
100 format(//t2,f4.1/t2,f4.1/t2,f4.1/t2,f4.1/
1 t2,f4.1/t2,f4.1)
return
end
You might go through the debugging process as follows:
1. Compile the program with the -g option, to allow debugging under dbx:
Problem Determination and Debugging 377