Specific Allocations

In Smalltalk MT 4.0 we introduced a new way to track allocations in a specific piece of code using the StDbgHandler class. In Smalltalk 4.2, we have extended this class to track allocations in blocks or between a start and an end point.

If you haven't used this class, now would be a good time to start. First, you must copy the debug version of the run time DLL from the Smalltalk MT subdirectory 'support' subdirectory 'debug' to where you will run your image.

Next you must file in 'Debug trace handler.sp' from the Smalltalk MT subdirectory 'source' subdirectory 'debug trace'.

In the Class Hierarchy Browser, locate the 'StDbgHandler' class. If you right click on this class, you will see menus at the bottom under 'Alloc Trace' to start and stop allocation tracing.

So for example I turned 'Alloc Trace' on and executed

10 timesRepeat: ['abc','def','ghi']

Then turned 'Alloc Trace' off. I see 159 allocations some of which are from turning the allocation handler on and off. If you want a more accurate measure of allocations, use

StDbgHandler resetAllocTrace.
StDbgHandler recordAllocationsFor: [
10 timesRepeat: ['abc','def','ghi']
].
StDbgHandler inspectAllocTrace

Or:

StDbgHandler startTraceAlloc.
10 timesRepeat: ['abc','def','ghi'].
StDbgHandler endTraceAlloc

Both of these show 20 allocations and using the trace window, you can drill down to where the allocation actually happened