The following examples use a sample program called my_program.
Main program for debugging, a1.f:
PARAMETER ( n=2 ) REAL twobytwo(2,2) / 4 *-1 / CALL mkidentity( twobytwo, n ) PRINT *, determinant( twobytwo ) END
Subroutine for debugging, a2.f:
SUBROUTINE mkidentity ( array, m ) REAL array(m,m) DO 90 i = 1, m DO 20 j = 1, m IF ( i .EQ. j ) THEN array(i,j) = 1. ELSE array(i,j) = 0. END IF 20 CONTINUE 90 CONTINUE RETURN END
Function for debugging, a3.f:
REAL FUNCTION determinant ( a ) REAL a(2,2) determinant = a(1,1) * a(2,2) - a(1,2) * a(2,1) RETURN END
You can do this in one or two steps.
demo% f95 -o my_program -g a1.f a2.f a3.f
demo% f95 -c -g a1.f a2.f a3.f demo% f95 -o my_program a1.o a2.o a3.o
demo% dbx my_program Reading symbolic information…
To stop at the first executable statement in a main program.
(dbx) stop in MAIN (2) stop in MAIN
Although the main program MAIN must be all uppercase, the names of subroutines, functions, or block data subprogramas can be uppercase or lowercase.
(dbx) run Running: my_program stopped in MAIN at line 3 in file "a1.f" 3 call mkidentity( twobytwo, n )
When the breakpoint is reached, dbx displays a message showing where it stopped, in this case, at line 3 of the a1.f file.
Print the value of n:
(dbx) print n n = 2
To print the matrix twobytwo, the format might vary:
(dbx) print twobytwo twobytwo = (1,1) -1.0 (2,1) -1.0 (1,2) -1.0 (2,2) -1.0
Note that you cannot print the matrix array because array is not defined here, only in mkidentity.
(dbx) next stopped in MAIN at line 4 in file "a1.f" 4 print *, determinant( twobytwo ) (dbx) print twobytwo twobytwo = (1,1) 1.0 (2,1) 0.0 (1,2) 0.0 (2,2) 1.0 (dbx) quit demo%
The next command executes the current source line and stops at the next line. It counts subprogram calls as single statements.
(dbx)quit demo%