Interactive Debugging With dbx and Sun WorkShop

The Sun WorkShop provides a tightly integrated development environment for building and browsing, as well as debugging applications written in Fortran, C, and C++.

The Sun WorkShop debugging facility is a window-based interface to dbx, while dbx itself is an interactive, line-oriented, source-level symbolic debugger. Either can be used to determine where a program crashed, to view or trace the values of variables and expressions in a running code, and to set breakpoints.

Sun WorkShop adds a sophisticated graphical environment to the debugging process that is integrated with tools for editing, building, and source code version control. It includes a data visualization capability to display and explore large and complex datasets, simulate results, and interactively steer computations.

For details, see the Sun manuals Using Sun WorkShop and Debugging a Program With Sun WorkShop, and the dbx(1) man pages.

The dbx program provides event management, process control, and data inspection. You can watch what is happening during program execution, and perform the following tasks:

• Fix one routine, then continue executing without recompiling the others

• Set watchpoints to stop or trace if a specified item changes

• Collect data for performance tuning

• Graphically monitor variables, structures, and arrays

• Set breakpoints (set places to halt in the program) at lines or in functions

• Show values--once halted, show or modify variables, arrays, structures

• Step through a program, one source or assembly line at a time

• Trace program flow--show sequence of calls taken

• Invoke procedures in the program being debugged

• Step over or into function calls; step up and out of a function call

• Run, stop, and continue execution at the next line or at some other line

• Save and then replay all or part of a debugging run

• Examine the call stack, or move up and down the call stack

• Program scripts in the embedded Korn shell

• Follow programs as they fork(2) and exec(2)

To debug optimized programs, use the dbx fix command to recompile the routines you want to debug:

1. Compile the program with the appropriate -On optimization level.

2. Start the execution under dbx.

3. Use fix -g any.f without optimization on the routine you want to debug.

4. Use continue with that routine compiled.

Some optimizations will be inhibited by the presence of --g on the compilation command. For example, --g suppresses the automatic inlining usually obtained with- -O4. --g cancels any parallelization option (--autopar, --explicitpar, --parallel), as well as --depend and --reduction. Debugging is facilitated by specifying --g without any optimization options. See the dbx documentation for details.