TotalView Users Guide - CI Wiki

Defining Eval Points and Conditional Breakpoints
Defining Eval Points and
Conditional Breakpoints
TotalView lets you define eval points. These are action points at which you
have added a code fragment that TotalView executes. You can write the
code fragment in C, Fortran, or assembler.
Assembler support is currently available on the HP Alpha Tru64 UNIX, IBM AIX, and
SGI IRIX operating systems. You can enable or disable TotalView’s ability to compile
eval points.
When running on many AIX systems, you can speed up the performance of compiled
expressions by using the –use_aix_fast_trap command when you start TotalView. For
more information, see the TotalView Release Notes. Search for “fast trap”.
Topics in this section are:
� “Setting Eval Points” on page 367
� “Creating Conditional Breakpoint Examples” on page 368
� “Patching Programs” on page 368
� “About Interpreted and Compiled Expressions” on page 370
� “Allocating Patch Space for Compiled Expressions” on page 371
You can do the following when you use eval points:
� Include instructions that stop a process and its relatives. If the code
fragment can make a decision whether to stop execution, it is called a
conditional breakpoint.
� Test potential fixes for your program.
� Set the values of your program’s variables.
� Automatically send data to the Visualizer. This can produce animated
displays of the changes in your program’s data.
You can set an eval point at any source line that generates executable code
(marked with a box surrounding a line number) or a line that contains
assembler-level instructions. This means that if you can set a breakpoint,
you can set an eval point.
At each eval point, TotalView or your program executes the code contained
in the eval point before your program executes the code on that line.
Although your program can then go on to execute this source line or
instruction, it can do the following instead:
� Include a goto in C or Fortran that transfers control to a line number in
your program. This lets you test program patches.
� Execute a TotalView function. These functions let you stop execution,
create barriers, and countdown breakpoints. For more information on
these statements, see “Using Built-in Variables and Statements” on page 394.
366 Chapter 16: Setting Action Points