Assembler Expression Facility is new in TPF/GI 2.2

Assembler debugging takes a big step forward with the release of TPF/GI 2.2. That’s because of a new TPF/GI feature called the assembler expression facility.

Using the assembler expression facility, programmers can watch and edit the results of assembler expressions while they step through their source code; this new feature brings the power of "high-level-language" debugging to assembler code?and assembler is still the kind of code that TPF systems use most.

This new feature is integrated into SourceView®, TPF Software’s ground-breaking source code debugger for TPF. The new feature has been in the hands of some TPF/GI customers since early 1999.

Easy to use

Using the assembler expression facility is easy. Programmers begin by stepping through their source code. When they see an assembler expression they want to watch, they click the right mouse button and select "Edit Expression" from the popup menu (Figure 1).

Figure 1: In this detail from the SourceView window, the user has clicked with the right mouse button and is about to select "Edit Expression" from the popup menu.

An assembler expression can be many things: a DSECT name, the name of an EQUATE; or some combination of field, register, length, and displacement, such as "EBW001+3(16,R13)" (for examples of valid assembler expressions, see the "Expressing Yourself" sidebar on this page).

The assembler expression facility brings the power of "higher-level-language" debugging to assembler source code.

At any rate, since the expression format is one most programmers already know, learning to use the new feature is guaranteed to be easy.

Figure 2: The Edit Assembler Expression dialog allows users to fine tune the expression before beginning to watch it. Most users will just need to press the Enter key.

Even Easier

Actually, programmers may never have to type in an expression themselves. TPF/GI first offers them the expression that is located where they clicked in their source code (Figure 2). Since this text is usually correct, most programmers will need only to press the Enter key to begin watching the expression.

The assembler expression format is one most programmers already know . . . but programmers may never have to type in an expression themselves.

Power users, of course, will want to fine tune the assembler expression by editing its text. In addition, TPF/GI makes recalling an old expression a breeze by remembering a "history list" of expressions the programmer has watched in the past (Figure 3).

Figure 3: The user has clicked the drop-down arrow of the combo box to access the history list of expressions watched before.

Watching and Editing

Once programmers have supplied an assembler expression, an editor window pops up to display the character and hex values addressed by that expression. Programmers can keep this editor window open as they step through their code. The window will update when the underlying values change (Figure 4).

But the editor window is much more than a colorful watch window. At any time, programmers can alter the contents of the window, press Enter, and poke new values into core to facilitate their debugging.

Figure 4: In this detail from the editor/watch window, the user has just stepped in the source code. Values that changed are shown in red. Note that field names and comments are shown above the data.

Friendly Display

A great deal of thought has gone into making the editor windows friendly and efficient.

For example, programmers can open as many editor windows as they like without a loss of screen real estate, because editor windows dock together in a structure called a "tabbed notebook," keeping the screen clutter free (Figure 5). Of course, when programmers want to view an editor window by itself, they can separate the window using the mouse.

Finally, the editor window is friendly because it displays more than just a hex dump. Whenever possible, field names and code comments are displayed above the hex and character data (Figures 4 & 5) making it easier for programmers to locate what they need.

Figure 5: A detail from two editor windows docked together. Two windows occupy the space of only one window.