$ gfortran -g test.f -o test.exe
$ gdb test.exe
GNU gdb (GDB) 7.5.50.20130309-cvs (cygwin-special)
Copyright (C) 2013 Free Software Foundation, Inc.
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This GDB was configured as "i686-cygwin".
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<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /cygdrive/c/DOCUME~1/harryr/d62/B1900/svn/B1900/test.exe...done.
(gdb) tb test:1
Temporary breakpoint 1 at 0x401176: file test.f, line 7.
(gdb) r
Starting program: /cygdrive/c/DOCUME~1/harryr/d62/B1900/svn/B1900/test.exe 
[New Thread 800.0x1834]
[New Thread 800.0x1abc]

Temporary breakpoint 1, test () at test.f:7
7             foo = 99
(gdb) n
10               call sleep(0)
(gdb) b
Breakpoint 2 at 0x401180: file test.f, line 10.
(gdb) n
12               total_ticks=22
(gdb) 
13               loopcounter = 0
(gdb) 
14               do while (loopcounter .lt. total_ticks)
(gdb) 
15                  loopcounter = loopcounter + 1
(gdb) b
Breakpoint 3 at 0x4011af: file test.f, line 15.
(gdb) b
Note: breakpoint 3 also set at pc 0x4011af.
Breakpoint 4 at 0x4011af: file test.f, line 15.
(gdb) so .gdbtest
(gdb) c
Continuing.
$1 = 2
$2 = 2
$3 = 3
$4 = 3
$5 = 3
$6 = 3
$7 = 3
$8 = 3
$9 = 3
$10 = 3
$11 = 3
$12 = 3
$13 = 3

Breakpoint 2, test () at test.f:10
10               call sleep(0)