Re: [PATCH/RFC] Simplify adjust_pc_after_break?

[Daniel Jacobowitz <drow@false.org>]

[Trying again with Mark's current email.]

On Mon, May 17, 2004 at 01:28:36AM +0200, Mark Kettenis wrote:
> The signal tests are failing horribly on Solaris x86.  The problem is
> that upon hitting a breakpoint in the signal handler, we don't
> properly back up the PC.

Hi Mark,

While sorting through old mail I found this message.  Andrew explained
why your patch was wrong; has this been fixed some other way, or are we
still broken on Solaris x86?

> The problem here seems to stem from the fact that we were
> single-stepping when the signal arrived.  The signal takes us out of
> the single-stepping range, and when we hit the breakpoint, we're atan
> address that's miles away from PREV_PC.  As a result
> adjust_pc_after_break decides that there is no reason to back up the
> PC.
> 
> Why don't we see this on other i386 targets?  There is some code in
> handle_inferior_event() that notices when a signal takes us out of the
> single-stepping range.  However, procfs(4) has this nice feature that
> you can tell it what signals to report.  We tell it to only report
> signals that we're interested in.  In this particular case we're not
> interested in the SIGALRM, so GDB never sees it, and the code in
> handle_inferior_event() is never executed.
> 
> Looking at adjust_pc_after_break() I couldn't figure out why we're
> trying do.  I could imagine that we shouldn't back up the PC if a
> breakpoint and single-step coalesce, but that's exactly the condition
> where we *do* back up the PC.  So why not simplify things and just
> back up the PC if we detect an inserted breakpoint?
> 
> The attached patch works for me on Solaris x86 and various other i386
> and amd64 targets.  But I'm probably overlooking something.

-- 
Daniel Jacobowitz
CodeSourcery, LLC