TotalView Users Guide - CI Wiki

Defining Eval Points and Conditional Breakpoints
eval point unless, for example, you declare it in some other scope or
declare it to be a static variable.
Creating Conditional Breakpoint Examples
The following are examples that show how you can create conditional
breakpoints:
� The following example defines a breakpoint that is reached whenever the
counter variable is greater than 20 but less than 25:
if (counter > 20 && counter < 25) $stop;
� The following example defines a breakpoint that stops execution every
tenth time that TotalView executes the $count function
$count 10
� The following example defines a breakpoint with a more complex expression:
$count my_var * 2
When the my_var variable equals 4, the process stops the eighth time it
executes the $count function. After the process stops, TotalView reevaluates
the expression. If my_var equals 5, the process stops again after the
process executes the $count function ten more times.
The TotalView internal counter is a “static” variable, which means that
TotalView remembers its value every time it executes the eval point. Suppose
you create an eval point within a loop that executes 120 times and the eval
point contains $count 100. Also assume that the loop is within a subroutine.
As expected, TotalView stops execution the 100th time the eval point executes.
When you resume execution, the remaining 20 iterations occur.
The next time the subroutine executes, TotalView stops execution after 80
iterations because it will have counted the 20 iterations from the last time
the subroutine executed.
This isn't a bug that we're documenting as a feature. Suppose you have a
function that is called from lots of different places from within your program.
Because TotalView remembers every time a statement executes, you
could, for example, stop execution every 100 times the function is called.
In other words, while $count is most often used within loops, you can use it
outside of them as well.
For descriptions of the $stop, $count, and variations on $count, see “Using
Built-in Variables and Statements” on page 394.
Patching Programs
You can use expressions in eval points to patch your code if you use the
goto (C) and GOTO (Fortran) statements to jump to a different program
location. This lets you do the following:
� Branch around code that you don’t want your program to execute.
� Add new statements.
368 Chapter 16: Setting Action Points