Re: RFA: Breakpoint infrastructure cleanups [0/8]

[Michael Snyder <msnyder@redhat.com>]

Eli Zaretskii wrote:
>>Date: Fri, 17 Oct 2003 14:38:52 -0700
>>From: Michael Snyder <msnyder@redhat.com>
>>
>>Debugging using tracepoints is a totally different process
>>than debugging with breakpoints.  It's like planning and
>>setting up a photo or video shoot, going away while someone
>>else does the filming, then coming back and looking at
>>the results.
> 
> 
> Debugging with tracepoints indeed uses a different paradigm, but
> _operations_ on tracepoints are almost identical to those for
> breakpoints: they have the same syntax and a very similar semantics.

That's true -- by design.

> Like breakpoints, each tracepoint is a trap in some point of code,
> designed to do something when the program gets to that point.

_May_ be a trap.  That part of the implementation is on the target,
and gdb doesn't know how it is implemented.

We're both right -- the interface is very similar, but the
concept and the way it is used is very different.

> 
> 
>>Asynchronous signals aren't like traps at all.
> 
> 
> I didn't mean to say they were.  I meant to say that catching forks,
> signals, longjmps, and syscalls works by setting traps in some
> specific portions of the program's code. 

Except for asynchronous signals.  I haven't tried real hard
to find other exceptions, but that's one.


> So it's the same as setting
> a breakpoint, we just give the user a convenience feature to ease the
> way of specifying the place where to set the trap.
> 
> In other words, all these features use breakpoints of some kind, it's
> only their use in the higher-level view of the debugging process is
> different.  When discussing the syntax and semantics of these
> commands, I think the lower-level similarity is what matters, not the
> higher-level distinction of their application.

Well, again, the interface may be the same.  The implementation
may be similar (although in many cases we're actually setting a
"mystery breakpoint" at a location the user knows nothging about).
But conceptually they are very different.