SourceView Workshop: Using breakpoints

If your only tool is a hammer, someone has said, everything looks like a nail.

And if your only debugging tool is a core dump, someone might add, your eyes are going to get tired really fast.

Fortunately, learning how to use SourceView, TPF/GI?s source code debugger, can save a lot of eye strain. In this article, we set out to learn how to use breakpoints. By the time we?re done, we will have a new tool in our toolbox, and the world should be looking a lot less like it’s all nails.

Getting set up

For this task we are initiating our debugging in the following way. First, we are adding four control files to SourceView: TSTIP141, TSTIP241, TSTIP341, and TSTIP441. Second, we are entering the command ZTSTI into the Prime CRAS terminal, causing execution to enter and stop at the top of the TSTIP141 file.

TPF/GI lets you know which lines are eligible for breakpoints by placing a small blue dot in the left-hand margin of the SourceView window.

If you don?t have the TSTIP* files, you’ll need to add your own control files to SourceView in order to practice this task. To add control files, select Trace>Add SourceView Control Files from the main menu. Then, after the files you select appear in the SourceView window, use a TPF/GI terminal to enter a command that will cause execution to stop in one of your files.

Setting breakpoints

When you want SourceView to pause execution at a certain line of your program, you set a breakpoint there. TPF/GI lets you know which lines are eligible for breakpoints by placing a small blue dot in the left-hand "gutter" of the SourceView window (Figure 1).

Figure 1: Small blue dots in the margin show which lines are executable in SourceView.

To set or remove a breakpoint at a line, use your mouse to click the blue dot beside the line (Figure 2).

Figure 2: The easiest way to set or remove a breakpoint is by clicking the blue dot beside the SourceView line.

Viewing the breakpoint list

Once you have several breakpoints set--especially if they are set in several different files--you may want to look at the breakpoint window. The breakpoint window is simply a list of the breakpoints you have set, specified by filename and statement number. This list will allow you to navigate in your source code between the different breakpoints, and it will even let you remove breakpoints.

This breakpoint list will allow you to navigate in your source code between the different breakpoints, and it will even let you remove breakpoints.

You can view the breakpoint list in either of two ways: the first way is by selecting Trace>Debug Windows>Breakpoints from the TPF/GI main menu; the second way is by using the right mouse button to click the main area of the SourceView window, and then selecting Debug Windows>Breakpoints from the popup menu (Figure 3).

Figure 3: The user has clicked the SourceView window with the right mouse button, and is now selecting "Breakpoints" from the popup menu. This will cause the breakpoint list to appear.

The breakpoint list window will appear "docked" at the bottom of the SourceView window (Figure 4). To navigate between breakpoints in your source code, simply double click an item in the breakpoint list. To remove a breakpoint, click an item in the breakpoint list and press the Delete key.

To navigate between breakpoints in your source code, double click an item in the breakpoint list. To remove a breakpoint, click an item in the breakpoint list and press the Delete key.

You can adjust the size of the breakpoint list window by placing your mouse cursor over the area between the SourceView and breakpoint windows, waiting until the mouse cursor changes to a double horizontal bar, and then holding down the left mouse button and dragging up or down. Release the left mouse button to complete the sizing process.

Figure 4: The breakpoint list window appears at the bottom of the SourceView window. Double click an item in the list to navigate to that location in your source code.

To run to a breakpoint, click the Run Fast tool button on the TPF/GI main window, or press the F11 key. When execution stops at your breakpoint, the line color will change to whatever your execution point color is set to be in your TPF/GI preferences (by default, the execution point color is bright blue). Also the breakpoint icon in the SourceView gutter will be replaced at the point of execution by a bright red arrow (Figure 5).

Figure 5: The user has pressed F11 and run to a breakpoint. The bright blue color of the source code line and the bright red arrow in the margin show that execution has stopped at this breakpoint.