Re: [RFA] enable software single step on alpha-osf

[Andrew Cagney <ac131313@ges.redhat.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