Watchpoints
To create a watchpoint expression with the CLI, use the -e argument on the dwatch command, and enter an expression. The expression is compiled into interpreted code that is executed each time the watchpoint triggers.
TotalView has two variables used exclusively with watchpoint expressions:
• $oldval: The value of the memory locations before a change is made.
• $newval: The value of the memory locations after a change is made.
NOTE >> Watchpoints are not available on the Mac OS X platform.
For example:
{if ($newval > 2) $stop}
This watchpoint triggers when the updated value of the variable arg_count equals more than two.
At this point, you can see in the VAR panel that
arg_count equals 1:
The watchpoint is now reflected in the Action Points view with the watchpoint
icon:
When you advance the program by choosing
Go,
Next or
Step, for instance, TotalView stops at this watchpoint when the value of
arg_count has been incremented past 2.
• The Processes & Threads view reports the Process State stopped at this watchpoint.
• The Source view identifies the location of the PC.
• The VAR panel reports that arg_count’s value is at 3.
• The Command Line view reports that watchpoint 2 has been hit.
• The Action Point view displays a pale yellow background to identify the stopped watchpoint.