TotalView Users Guide - CI Wiki

Using Watchpoints
Computer Constraints
Linux x86, You can create up to four watchpoints and each must be 1, 2, or 4
bytes in length, and a memory address must be aligned for the
byte length. That is, you must align a 4-byte watchpoint on a 4byte
address boundary, and you must align 2-byte watchpoint on
a 2-byte boundary, and so on.
Linux x86-64 (AMD
and Intel)
HP-UX IA-64 and
Linux IA-64
Typically, a debugging session doesn’t use many watchpoints. In most cases,
you are only monitoring one memory location at a time. Consequently,
restrictions on the number of values you can watch seldom cause problems.
Creating Watchpoints
You can create up to four watchpoints and each must be 1, 2, 4,
or 8 bytes in length, and a memory address must be aligned for
the byte length. For example, you must align a 4-byte watchpoint
on a 4-byte address boundary.
You can create up to four watchpoints. The length of the memory
being watched must be a power of 2 and the address must be
aligned to that power of 2; that is, (address % length) == 0.
Solaris SPARC TotalView supports watchpoints on Solaris 7 or later operating
systems. These operating system let you create hundreds of
watchpoints, and there are no alignment or size constraints.
However, watchpoints can’t overlap.
Watchpoints are created by using either the Action Points> Create
Watchpoint command in the Process Window or the Tools > Create
Watchpoint Dialog Box. (If your platform doesn’t support watchpoints,
TotalView dims this menu item.) Here are some things you should know:
� You can also set watchpoints by right-clicking within the Process and
Variable Windows and then select Create Watchpoint from the context
menu.
� You can select an expression within the Source and Stack Frame panes
and then use a context menu or select the Action Points > Create
Watchpoint command. If you invoke either of these commands and
TotalView cannot determine where to set the expression, it displays a dialog
box into which you type the variable’s name.
� If you select the Tools > Create Watchpoint command and a compound
variable such an array or structure is being displayed, TotalView sets the
watchpoint on the first element. However, it you select an element before
invoking this command, TotalView sets the watchpoint on that element.
If you set a watchpoint on a stack variable, TotalView that lets you know
that you’re trying to set a watchpoint on “non-global” memory. For example,
the variable is on the stack or in a block and the variable will no longer
exist when the stack is popped or control leaves the block. In either of
these cases, it is likely that your program will overwrite the memory and the
watchpoint will no longer be meaningful. See “Watching Memory” on
page 377for more information.
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