Any application (either a Windows' native executable, or a
Winelib application) can be run through
winedbg. Command line options and tricks
are the same as for wine:
winedbg can also be launched without any
command line argument: winedbg is started
without any attached process. You can get a list of running
W-processes (and their
wpid's) using the info
process command, and then, with the
attach command, pick up the
wpid of the W-process
you want to debug. This is a neat feature as it allows you
to debug an already started application.
When something goes wrong, Windows tracks this as an
exception. Exceptions exist for segmentation violation,
stack overflow, division by zero, etc.
When an exception occurs, Wine checks if the
W-process is debugged. If so, the
exception event is sent to the debugger, which takes care of
it: end of the story. This mechanism is part of the standard
Windows' debugging API.
If the W-process is not debugged, Wine
tries to launch a debugger. This debugger (normally
winedbg, see III Configuration for more
details), at startup, attaches to the
W-process which generated the exception
event. In this case, you are able to look at the causes of
the exception, and either fix the causes (and continue
further the execution) or dig deeper to understand what went
wrong.
If winedbg is the standard debugger, the
pass and cont commands
are the two ways to let the process go further for the
handling of the exception event.
To be more precise on the way Wine (and Windows) generates
exception events, when a fault occurs (segmentation
violation, stack overflow...), the event is first sent to
the debugger (this is known as a first chance exception).
The debugger can give two answers:
continue
the debugger had the ability to correct what's
generated the exception, and is now able to continue
process execution.
pass
the debugger couldn't correct the cause of the
first chance exception. Wine will now try to walk
the list of exception handlers to see if one of them
can handle the exception. If no exception handler is
found, the exception is sent once again to the
debugger to indicate the failure of the exception
handling.
Note: since some of Wine's code uses exceptions and
try/catch blocks to provide some
functionality, winedbg can be entered
in such cases with segv exceptions. This happens, for
example, with IsBadReadPtr function.
In that case, the pass command shall be
used, to let the handling of the exception to be done by
the catch block in
IsBadReadPtr.
You can stop the debugger while it's running by hitting
Ctrl-C in its window. This will stop the debugged process,
and let you manipulate the current context.
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