TotalView Users Guide - CI Wiki

Debugging UPC Programs
Figure 110: A Pointer to a
Shared Variable
Displaying Pointer to Shared Variables
TotalView understands pointer-to-shared data and displays the components
of the data, as well as the target of the pointer to shared variables.
For example,Figure 110 shows this data being displayed:
In this figure, notice the following:
� Because the Type field shows the full type name, TotalView is telling you
that this is a pointer to a shared int with a block size of 10.
� In this figure, TotalView also displays the upc_threadof ("T0"), the
upc_phaseof ("P0"), and the upc_addrfield (0x0x10010ec4) components of
this variable.
In the same way that TotalView normally shows the target of a pointer variable,
it also shows the target of a UPC pointer variable. When dereferencing
a UPC pointer, TotalView fetches the target of the pointer from the UPC
thread with which the pointer has affinity.
You can update the pointer by selecting the pointer value and editing the
thread, phase, or address values. If the phase is corrupt, you’ll see something
like the following in the Value area:
T0;P6;0x3ffc0003b00 ->
0xc0003c80 (-1073726336)
In this example, the pointer is invalid because the phase is outside the legal
range. TotalView displays a similar message if the thread is invalid.
Since the pointer itself is not shared, you can use the TView > Show Across
commands to display the value from each of the UPC threads. (See
Figure 111 on page 161.)
160 Chapter 7: Setting Up Parallel Debugging Sessions