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Re: [RFA] enable software single step on alpha-osf
- From: Andrew Cagney <ac131313 at ges dot redhat dot com>
- To: Joel Brobecker <brobecker at gnat dot com>
- Cc: gdb-patches at sources dot redhat dot com
- Date: Mon, 05 Aug 2002 23:01:37 -0400
- Subject: Re: [RFA] enable software single step on alpha-osf
- References: <20020718203205.GB26990@gnat.com> <3D4DBBC8.5000906@ges.redhat.com> <20020805184920.GC892@gnat.com>
Can you confirm that the code is encountering a situtation where both
breakpoints_inserted and singlestep_breakpoints_inserted_p are true. I
think this occures when doing a single step after stepping off of a
breakpoint. When single stepping off a breakpoint, only
singlestep_breakpoints_inserted_p would be true.
If this is the case then the comments should make mention of it. It
also makes the re-ordered if statement part of the patch correct.
Yes, I can confirm this, and this should happen fairly often: suppose
you have inserted a regular breakpoint in your program, anywhere, and
then do a single step. Before resuming the inferior, GDB will re-insert
the breakpoints, and set breakpoints_inserted. At the same time, because
we are doing a s/w single step, singlestep_breakpoints_inserted_p will
be set too. Did I miss something?
Thanks. No you didn't miss anything, I just want to be sure WFI is nasty.
The problem won't have been noticed previously as only the older targets
use software single-step and I don't know how often their testsuite is
beaten on.
As for the re-ordering, I made it because I saw some regressions in the
testsuite after switching to s/w single step. Unfortunately, I don't
remember which ones, I would have to rerun the testsuite without this
change to find them again. But the following comment explains in which
cases the re-ordering was necessary:
Yes, ok, the part of the patch that re-orders the test is ok.
----
I've tried as much as I can to make sure this can not happen, but I am
not familiar enough to have a good level of confidence in my analysis.
All I can say is: this patch fixes all the regressions observed in the
testsuite after switching to software single step. I know this is no
absolute proof, but that gives me a certain level of confidence.
BTW, if someone ever claims to have a ``good level of confidence'' in
that code, assume that they are lieing :-^
I'm still thinking about this bit, trying to find a way of not so much
increasing our confidence but at least putting us in a position where we
are more sure about what to do when we next encounter a problem.
Andrew