[fpc-devel] Debug info for SEH exceptions (64 bit and upcoming 3.2 32 bit)
fpc at mfriebe.de
Wed Jan 9 14:54:43 CET 2019
Marco V wrote (
> Current holdup is enabling SEH by default for 32-bit windows, so that
> it is COM compatible
This reminds me of an unsolved issued, debugging exceptions with SEH
(currently Win64, but apparently soon Win32 too)
The debugger (IDE + gdb/lldb, // todo for fpdebug) can currently "step
to except" and "step to finally" (except Win64 / seh).
If an exception is raised the debugger stops on fpc_raiseexception. (and
re-raise if needed)
- If stopped F8 will step to next except or finally
- If it is ignored during a step-over, the debugger will step to the
next except/finally enclosing the line where the step started. (stepping
over any except/finally inside function calls)
To do this the debugger will set breakpoints at fpc_popaddrstack,
If it reaches fpc_popaddrstack, fpc_catches, it needs to step-out once,
and will be in finally or except.
With SEH that does not work.
And with SEH, I am unaware of sufficient debug info to implement all of
this in any other fashion. (some of it can be done)
On Win64 a breakpoint can be set to RtlUnwindEx
This will be called with the "except" handle address as 2nd argument.
(IIRC, 2nd arg)
The address can be extracted, and a breakpoint can be set to it.
=> except block can be stepped to.
As for the finally block, I have not yet found a way.
__FPC_specific_handler will be called. And somewhere within it, it will
call the finally handler. No way to intercept by the debugger. (It would
need to set a breakpoint in the middle of __FPC_specific_handler, but
there is no debug info to find the line that calls "finally")
On Win32 I did some testing with SEH, and IIRC (but not sure its a while
ago) I could catch neither except nor finally.
Afaik/IIRC the 2 handlers are...
The __FPC_default_handler calls the except handler directly. So again
would need a breakpoint in the middle of it)
Same for __FPC_finally_handler
Any idea how to add/use debug info, so a debugger can deal with the above?
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