Debugging A Program

4

Sun WorkShop provides an integrated debugging service that can run a program in a controlled fashion and to inspect the state of a stopped program. WorkShop gives you complete control of the dynamic execution of a program, including the collection of performance data.

You can determine where a program crashed, view the values of variables and expressions, set breakpoints in the code, and run and trace a program. In addition, machine-level and other commands are available to help you debug code. You can use standard dbx commands in the Dbx Commands window.

This chapter is organized into the following sections:

Debugging Features

page 27

Quick Start

page 29

Quick Mode

page 32

Debugging Features	page 27
Quick Start	page 29
Quick Mode	page 32

Debugging Features

When debugging in WorkShop, you have access to an extensive range of event management, process control, and data inspection features. You can:

Run a program in Quick Mode with the debugger in the background, ready to take over processing when a program is about to core dump
Run, stop, and continue execution
Set breakpoints at lines or in functions; trace program execution line by line across a whole program or within a function; set watchpoints to stop or trace a program if a specified value or expression changes or meets some other condition
Set multiple breakpoints or trace tags in C++ code--in all member functions of the same name across a class, in all members of a specified class, or in all overloaded functions
Single-step through program code one line at a time; step over or into function calls; step up and out of a function call arriving at the line of the calling function line after the call
Collect data for use with the Analyzer using the Collector
Automatically detect runtime errors in an application using runtime checking to detect memory access errors, memory leaks, and memory block usage
Look up declarations of identifiers and definitions of types, classes, and templates
Spot check the value of variables or expressions whenever the program is stopped; monitor variables or expressions for changes over time; examine the call stack; move up and down the call stack; and call functions in the program
Graphically examine program variables including complex structures and arrays, and monitor values during program execution using the Data Grapher and the Data Display window
Debug multithreaded programs
Use the Fix and Continue feature to edit a file, recompile it with the same options, install the new code in the program, and continue
Support C++ by supporting virtual functions, supporting C++ exceptions, debugging with C++ Templates, using function overloading for argument resolution, and using default arguments
Use an embedded Korn shell for programmability
Use the Program Input/Output window to provide an I/O command interface separate from the dbx interaction in the Dbx Commands window
Follow programs as they fork

Quick Start

WorkShop simplifies the debugging task by providing you with an intuitive, easy-to-use interface to ease the task.

The following shows the basic steps to follow when debugging a program. For more detailed information on any of the steps, see the online help for WorkShop.

Table 4-1 Task List: Debugging a Program

Task
Description

Build the application

Compile the application using the -g or -g0 (zero) option, which instructs the compiler to generate debugging information during compilation.

Start debugging

1. Select a debugging state. Choose Debug Quick Mode to run a program normally, with the option of switching to debugging at any point.
Choose Debug Debug Mode to debug the program using the full functionality of the debugger.

For more information on Quick Mode, see "Using Quick Mode" later in this chapter.

2. If you just built your program, it is considered the current program and is the top menu item in the Debug menu picklist. To start debugging the current program, choose Debug path name/program name, or click the Debug button on the WorkShop main window tool bar.

3. If you want to debug a program other than the current program, load a new program using Debug New Program, attach to a process using Debug Attach Process, or debug a core file using Debug Load Core File.

4. Change program information such as arguments, the run directory, and environment variables.

5. Debug multiple processes at once using the Active Debugging Sessions dialog box to manage the sessions.

6. Run your program by clicking either the Start or Go button on the tool bar.

View code

1. Wait until your program stops, or interrupt execution by clicking the Interrupt button or pressing Control + Break.

2. In the editor window, step through your code one line at a time, through functions, around functions, or out of functions.

3. Continue executing your program by clicking Go or choosing Execute Go.

Set breakpoints

1. Open the Breakpoints window by choosing Windows Breakpoints or Execute Set Breakpoints.

2. Set breakpoints to force the debugger to stop execution. You can set simple breakpoints to stop at a line of code or in a procedure or function.

3. Set advanced breakpoints to break in C++ classes, track changes in data, break on a condition, break on special events, or create your own custom breakpoints.

4. Disable and re-enable breakpoints as you move through your program.

Trace code

1. In the Breakpoints window, set a trace handler so that you can view each line of source code as it is executed.

2. Add a filter to your trace to view just calls to a function, every member function of a name, every function in a class, or each exit from a function.

3. Control the speed of the trace using the Debugging Options dialog box.

Check values and data

1. Spot-check the value of expressions using the Data History pane of the Debugging window.

2. Select variables or expressions from the editor window, and click the Evaluate button or choose Data Evaluate Selected to find their value.

3. Copy a variable or expression into the Expressions field and evaluate it for value and type.

4. Copy a variable or expression into the Expressions field and click Display to open the Data Display window to monitor changes in its value.

5. While the program is stopped, change the value of a variable or expression using the Assign button.

Monitor data values

1. Use the Data Display window to watch the changes in the value of an expression while a program runs. Choose Windows Data Display.

2. Enter expressions in the window using the Display button in the Data History pane.

3. Follow changes in the value of an expression, compare current and previous values, view static information, and graph arrays.

Examine the call stack

1. View the call stack in the Stack pane of the Debugging window.

2. Navigate around the call stack using the Up and Down buttons, or click the hypertext link.

3. Remove the function you are stopped in from the stack by choosing Stack Pop.

4. Remove multiple frames by placing your cursor next to the frame you want to return to and choosing Stack Pop to Current Frame.

Debug multithreaded programs

1. When a multithreaded program is detected, the Threads pane on the Debugging window opens listing information about the threads in the program.

2. Click a thread in the Threads pane to view its context.

3. Hide and expose threads to help in managing them.

Customize debugging sessions

Set new defaults for debugging performance, output, language, and so on by choosing Debug Debugging Options.

Table 4-1 Task List: Debugging a Program
Task	Description
Build the application	Compile the application using the `-g` or `-g0` (zero) option, which instructs the compiler to generate debugging information during compilation.

Start debugging	1. Select a debugging state. Choose Debug Quick Mode to run a program normally, with the option of switching to debugging at any point. Choose Debug Debug Mode to debug the program using the full functionality of the debugger. For more information on Quick Mode, see "Using Quick Mode" later in this chapter.
	2. If you just built your program, it is considered the current program and is the top menu item in the Debug menu picklist. To start debugging the current program, choose Debug path name/program name, or click the Debug button on the WorkShop main window tool bar.
	3. If you want to debug a program other than the current program, load a new program using Debug New Program, attach to a process using Debug Attach Process, or debug a core file using Debug Load Core File.
	4. Change program information such as arguments, the run directory, and environment variables.
	5. Debug multiple processes at once using the Active Debugging Sessions dialog box to manage the sessions.
	6. Run your program by clicking either the Start or Go button on the tool bar.

View code	1. Wait until your program stops, or interrupt execution by clicking the Interrupt button or pressing Control + Break.
	2. In the editor window, step through your code one line at a time, through functions, around functions, or out of functions.
	3. Continue executing your program by clicking Go or choosing Execute Go.

Set breakpoints	1. Open the Breakpoints window by choosing Windows Breakpoints or Execute Set Breakpoints.
	2. Set breakpoints to force the debugger to stop execution. You can set simple breakpoints to stop at a line of code or in a procedure or function.
	3. Set advanced breakpoints to break in C++ classes, track changes in data, break on a condition, break on special events, or create your own custom breakpoints.
	4. Disable and re-enable breakpoints as you move through your program.

Trace code	1. In the Breakpoints window, set a trace handler so that you can view each line of source code as it is executed.
	2. Add a filter to your trace to view just calls to a function, every member function of a name, every function in a class, or each exit from a function.
	3. Control the speed of the trace using the Debugging Options dialog box.

Check values and data	1. Spot-check the value of expressions using the Data History pane of the Debugging window.
	2. Select variables or expressions from the editor window, and click the Evaluate button or choose Data Evaluate Selected to find their value.
	3. Copy a variable or expression into the Expressions field and evaluate it for value and type.
	4. Copy a variable or expression into the Expressions field and click Display to open the Data Display window to monitor changes in its value.
	5. While the program is stopped, change the value of a variable or expression using the Assign button.

Monitor data values	1. Use the Data Display window to watch the changes in the value of an expression while a program runs. Choose Windows Data Display.
	2. Enter expressions in the window using the Display button in the Data History pane.
	3. Follow changes in the value of an expression, compare current and previous values, view static information, and graph arrays.

Examine the call stack	1. View the call stack in the Stack pane of the Debugging window.
	2. Navigate around the call stack using the Up and Down buttons, or click the hypertext link.
	3. Remove the function you are stopped in from the stack by choosing Stack Pop.
	4. Remove multiple frames by placing your cursor next to the frame you want to return to and choosing Stack Pop to Current Frame.

Debug multithreaded programs	1. When a multithreaded program is detected, the Threads pane on the Debugging window opens listing information about the threads in the program.
	2. Click a thread in the Threads pane to view its context.
	3. Hide and expose threads to help in managing them.

Customize debugging sessions	Set new defaults for debugging performance, output, language, and so on by choosing Debug Debugging Options.

Quick Mode

Quick Mode is a new debugging feature that allows you to run your program normally but keep debugging ready in the background to take over the process at any point. Think of Quick Mode like a safety net. If you fall--your program terminates abnormally--the Debugger is there to save the program before it core dumps, just like the net. If you decide you want to debug the program you are running, you can interrupt and turn control over to the Debugger.

If all you want to do is run your program as quickly as possible, but you are afraid you might still need some debugging, select Quick Mode. There may be a short delay while the Debugging window opens, but otherwise your program runs exactly as if you were running it from the shell. Only when you switch back to Debug mode through a termination or interrupt are the symbols for the program loaded, causing a delay.

By providing this rescue capability, Quick Mode reduces the guesswork when you are testing your program.

Debugging A Program

4

Debugging Features

Quick Start

Table 4-1 Task List: Debugging a Program

Quick Mode

Advantages of Quick Mode

When to Use Quick Mode

How to Switch to Quick Mode

Quick Mode Example