Breakpoints

• Setting Breakpoints:
• Deleting Breakpoints:
• Disabling Breakpoints:
• Temporary Breakpoints:
• Editing Breakpoint Properties:
• Breakpoint Conditions:
• Breakpoint Ignore Counts:
• Breakpoint Commands:
• Moving and Copying Breakpoints:
• Looking up Breakpoints:
• Editing all Breakpoints:
• Hardware-Assisted Breakpoints:

Node:Setting Breakpoints, Next:Deleting Breakpoints, Up:Breakpoints

Setting Breakpoints

You can set breakpoints by location or by name.

Setting Breakpoints by Location

Breakpoints are set at a specific location in the program.

If the source line is visible, click with mouse button 1 on the left of the source line and then on the Break button.

As a faster alternative, you can simply press mouse button 3 on the left of the source line and select the Set Breakpoint item from the line popup menu.

As an even faster alternative, you can simply double-click on the left of the source line to set a breakpoint.

As yet another alternative, you can select Source => Breakpoints. Click on the Break button and enter the location.

(If you find this number of alternatives confusing, be aware that DDD users fall into three categories, which must all be supported. Novice users explore DDD and may prefer to use one single mouse button. Advanced users know how to use shortcuts and prefer popup menus. Experienced users prefer the command line interface.)

Breakpoints are indicated by a plain stop sign, or as #Illegal HTML tag removed : n, where Illegal HTML tag removed : n is the breakpoint number. A greyed out stop sign (or _Illegal HTML tag removed : n_) indicates a disabled breakpoint. A stop sign with a question mark (or ?Illegal HTML tag removed : n?) indicates a conditional breakpoint or a breakpoint with an ignore count set.

If you set a breakpoint by mistake, use Edit => Undo to delete it again.

Setting Breakpoints by Name

If the function name is visible, click with mouse button 1 on the function name. The function name is then copied to the argument field. Click on the Break button to set a breakpoint there.

As a shorter alternative, you can simply press mouse button 3 on the function name and select the Break at item from the popup menu.

As yet another alternative, you can click on Break... from the Breakpoint editor (invoked through Source => Breakpoints) and enter the function name.

Setting Regexp Breakpoints

Using GDB, you can also set a breakpoint on all functions that match a given string. Break => Set Breakpoints at Regexp () sets a breakpoint on all functions whose name matches the regular expression given in (). Here are some examples:

• To set a breakpoint on every function that starts with Xm, set () to ^Xm.
• To set a breakpoint on every member of class Date, set () to ^Date::.
• To set a breakpoint on every function whose name contains _fun, set () to _fun.
• To set a breakpoint on every function that ends in _test, set () to _test$.

Node:Deleting Breakpoints, Next:Disabling Breakpoints, Previous:Setting Breakpoints, Up:Breakpoints

Deleting Breakpoints

To delete a visible breakpoint, click with mouse button 1 on the breakpoint. The breakpoint location is copied to the argument field. Click on the Clear button to delete all breakpoints there.

If the function name is visible, click with mouse button 1 on the function name. The function name is copied to the argument field. Click on the Clear button to clear all breakpoints there.

As a faster alternative, you can simply press mouse button 3 on the breakpoint and select the Delete Breakpoint item from the popup menu.

As yet another alternative, you can select the breakpoint and click on Delete in the Breakpoint editor (invoked through Source => Breakpoints).

As an even faster alternative, you can simply double-click on the breakpoint while holding <Ctrl>.

Node:Disabling Breakpoints, Next:Temporary Breakpoints, Previous:Deleting Breakpoints, Up:Breakpoints

Disabling Breakpoints

Rather than deleting a breakpoint or watchpoint, you might prefer to Illegal HTML tag removed : disable it. This makes the breakpoint inoperative as if it had been deleted, but remembers the information on the breakpoint so that you can Illegal HTML tag removed : enable it again later.¹²

To disable a breakpoint, press mouse button 3 on the breakpoint symbol and select the Disable Breakpoint item from the breakpoint popup menu. To enable it again, select Enable Breakpoint.

As an alternative, you can select the breakpoint and click on Disable or Enable in the Breakpoint editor (invoked through Source => Breakpoints.

Disabled breakpoints are indicated by a grey stop sign, or _Illegal HTML tag removed : n_, where Illegal HTML tag removed : n is the breakpoint number.

The Disable Breakpoint item is also accessible via the Clear button. Just press and hold mouse button 1 on the button to get a popup menu.

Node:Temporary Breakpoints, Next:Editing Breakpoint Properties, Previous:Disabling Breakpoints, Up:Breakpoints

Temporary Breakpoints

A Illegal HTML tag removed : temporary breakpoint is immediately deleted as soon as it is reached.¹³

To set a temporary breakpoint, press mouse button 3 on the left of the source line and select the Set Temporary Breakpoint item from the popup menu.

As a faster alternative, you can simply double-click on the left of the source line while holding <Ctrl>.

Temporary breakpoints are convenient to make the program continue up to a specific location: just set the temporary breakpoint at this location and continue execution.

The Continue Until Here item from the popup menu sets a temporary breakpoint on the left of the source line and immediately continues execution. Execution stops when the temporary breakpoint is reached.

The Set Temporary Breakpoint and Continue Until Here items are also accessible via the Break button. Just press and hold mouse button 1 on the button to get a popup menu.

Node:Editing Breakpoint Properties, Next:Breakpoint Conditions, Previous:Temporary Breakpoints, Up:Breakpoints

Editing Breakpoint Properties

You can change all properties of a breakpoint by pressing mouse button 3 on the breakpoint symbol and select Properties from the breakpoint popup menu. This will pop up a dialog showing the current properties of the selected breakpoint.

As an even faster alternative, you can simply double-click on the breakpoint.

• Click on Lookup to move the cursor to the breakpoint's location.
• Click on Enable to enable the breakpoint.
• Click on Disable to disable the breakpoint.
• Click on Temp to make the breakpoint temporary.¹⁴
• Click on Delete to delete the breakpoint.

Node:Breakpoint Conditions, Next:Breakpoint Ignore Counts, Previous:Editing Breakpoint Properties, Up:Breakpoints

Breakpoint Conditions

The simplest sort of breakpoint breaks every time your program reaches a specified place. You can also specify a Illegal HTML tag removed : condition for a breakpoint. A condition is just a Boolean expression in your programming language. A breakpoint with a condition evaluates the expression each time your program reaches it, and your program stops only if the condition is true.

This is the converse of using assertions for program validation; in that situation, you want to stop when the assertion is violated-that is, when the condition is false. In C, if you want to test an assertion expressed by the condition Illegal HTML tag removed : assertion, you should set the condition !Illegal HTML tag removed : assertion on the appropriate breakpoint.

Break conditions can have side effects, and may even call functions in your program. This can be useful, for example, to activate functions that log program progress, or to use your own print functions to format special data structures. The effects are completely predictable unless there is another enabled breakpoint at the same address. (In that case, DDD might see the other breakpoint first and stop your program without checking the condition of this one.)

Note that breakpoint commands are usually more convenient and flexible for the purpose of performing side effects when a breakpoint is reached. See Breakpoint Commands, for details.

Node:Breakpoint Ignore Counts, Next:Breakpoint Commands, Previous:Breakpoint Conditions, Up:Breakpoints

Breakpoint Ignore Counts

A special case of a breakpoint condition is to stop only when the breakpoint has been reached a certain number of times. This is so useful that there is a special way to do it, using the Illegal HTML tag removed : ignore count of the breakpoint. Every breakpoint has an ignore count, which is an integer. Most of the time, the ignore count is zero, and therefore has no effect. But if your program reaches a breakpoint whose ignore count is positive, then instead of stopping, it just decrements the ignore count by one and continues. As a result, if the ignore count value is Illegal HTML tag removed : n, the breakpoint does not stop the next Illegal HTML tag removed : n times your program reaches it.

In the field Ignore Count of the Breakpoint Properties panel, you can specify the breakpoint ignore count.¹⁵

If a breakpoint has a positive ignore count and a condition, the condition is not checked. Once the ignore count reaches zero, DDD resumes checking the condition.

Node:Breakpoint Commands, Next:Moving and Copying Breakpoints, Previous:Breakpoint Ignore Counts, Up:Breakpoints

Breakpoint Commands

You can give any breakpoint (or watchpoint) a series of DDD commands to execute when your program stops due to that breakpoint. For example, you might want to print the values of certain expressions, or enable other breakpoints.¹⁶

Using the Commands buttons of the Breakpoint Properties panel, you can edit commands to be executed when the breakpoint is hit.

To edit breakpoint commands, click on Edit >> and enter the commands in the commands editor. When done with editing, click on Edit << to close the commands editor.

Using GDB, you can also Illegal HTML tag removed : record a command sequence to be executed. To record a command sequence, follow these steps:

1. Click on Record to begin the recording of the breakpoint commands.
2. Now interact with DDD. While recording, DDD does not execute commands, but simply records them to be executed when the breakpoint is hit. The recorded debugger commands are shown in the debugger console.

3. To stop the recording, click on End or enter end at the GDB prompt. To

   Illegal HTML tag removed : cancel

   the recording, click on Interrupt or press <ESC>.

4. You can edit the breakpoint commands just recorded using Edit >>.

Node:Moving and Copying Breakpoints, Next:Looking up Breakpoints, Previous:Breakpoint Commands, Up:Breakpoints

Moving and Copying Breakpoints

To move a breakpoint to a different location, press mouse button 1 on the stop sign and drag it to the desired location.¹⁷ This is equivalent to deleting the breakpoint at the old location and setting a breakpoint at the new location. The new breakpoint inherits all properties of the old breakpoint, except the breakpoint number.

To copy a breakpoint to a new location, press <Shift> while dragging.

Node:Looking up Breakpoints, Next:Editing all Breakpoints, Previous:Moving and Copying Breakpoints, Up:Breakpoints

Looking up Breakpoints

If you wish to lookup a specific breakpoint, select Source => Breakpoints => Lookup. After selecting a breakpoint from the list and clicking the Lookup button, the breakpoint location is displayed.

As an alternative, you can enter #Illegal HTML tag removed : n in the argument field, where Illegal HTML tag removed : n is the breakpoint number, and click on the Lookup button to find its definition.

Node:Editing all Breakpoints, Next:Hardware-Assisted Breakpoints, Previous:Looking up Breakpoints, Up:Breakpoints

Editing all Breakpoints

To view and edit all breakpoints at once, select Source => Breakpoints. This will popup the Illegal HTML tag removed : Breakpoint Editor which displays the state of all breakpoints.

In the breakpoint editor, you can select individual breakpoints by clicking on them. Pressing <Ctrl> while clicking toggles the selection. To edit the properties of all selected breakpoints, click on Props.

Node:Hardware-Assisted Breakpoints, Previous:Editing all Breakpoints, Up:Breakpoints

Hardware-Assisted Breakpoints

Using GDB, a few more commands related to breakpoints can be invoked through the debugger console:

• hbreak

  Illegal HTML tag removed : position

• Sets a hardware-assisted breakpoint at

  Illegal HTML tag removed : position

  . This command requires hardware support and some target hardware may not have this support. The main purpose of this is EPROM/ROM code debugging, so you can set a breakpoint at an instruction without changing the instruction.

• thbreak

  Illegal HTML tag removed : pos

• Set a temporary hardware-assisted breakpoint at

  Illegal HTML tag removed : pos

  .

See Setting breakpoints, for details.

Node:Watchpoints, Next:Interrupting, Previous:Breakpoints, Up:Stopping