GDB：如何在调试期间调用具有修改参数的函数

Question

考虑以下简单的Fortran程序，它通过子例程添加两个整数并打印结果：

      PROGRAM MAIN

      INTEGER I, J, SUM

      I = 1
      J = 1

      CALL ADD(I, J, SUM)

      WRITE(*,*) SUM

      END

      SUBROUTINE ADD(I, J, SUM)

      INTEGER I, J, SUM

      SUM = I + J

      END

通过gfortran -g -O0 gdb-mwe.f -o gdb-mwe编译并在GNU调试器中运行，我想在调试输出之前使用修改后的输入参数从调试器调用ADD。这是发生的事情：

Reading symbols from gdb-mwe...done.
(gdb) break 10
Breakpoint 1 at 0x4007dd: file gdb-mwe.f, line 10.
(gdb) r
Starting program: /home/username/Documents/Fortran/gdb-mwe 

Breakpoint 1, MAIN__ () at gdb-mwe.f:10
10        WRITE(*,*) SUM
(gdb) p j = j+1
$2 = 2
(gdb) call add(i,j,sum)

Program received signal SIGSEGV, Segmentation fault.
0x000000000040079a in add (
i=<error reading variable: Cannot access memory at address 0x1>, 
j=<error reading variable: Cannot access memory at address 0x2>, 
sum=<error reading variable: Cannot access memory at address 0x2>)
at gdb-mwe.f:18
18        SUM = I + J
The program being debugged was signaled while in a function called from GDB.
GDB remains in the frame where the signal was received.
To change this behavior use "set unwindonsignal on".
Evaluation of the expression containing the function
(add) will be abandoned.
When the function is done executing, GDB will silently stop.

我怎么做到这一点？