Re: Howdy from Apple; Fix and Continue implemented Yet Again

["Kris Warkentin" <kewarken@qnx.com>]

That's pretty interesting.  Does it require any special os support in the
debug interface or is it all done with dlopen/dlclose, etc.?  Other than
compiling your app PIC, does it require any other special compiler features?

cheers,

Kris

----- Original Message -----
From: "Jason Molenda" <jason-swarelist@molenda.com>
To: <gdb@sources.redhat.com>
Sent: Friday, June 27, 2003 11:29 PM
Subject: Re: Howdy from Apple; Fix and Continue implemented Yet Again


> On Fri, Jun 27, 2003 at 12:40:04AM -0700, Jason Molenda wrote:
> `
> > Fix and continue is a feature implemented by many other debuggers,
> > which we added to our gdb for this release.
>
> It was pointed out that I never said what F&C _is_.  It's a feature
> for debugging your program, where you can modify your sources
> mid-debug-session, and the debugger will "patch" in the new code.
> At a very high level, the source file you're modifying is built as
> a shared library, gdb executes inferior function calls to load that
> shared library into the program, gdb finds all old versions of all
> functions contained in that shared library and writes trampolines
> in the prologues to jump to the new versions of those functions,
> and gdb redirects all file-static (including global) variables in
> that shared library to point to the statics/globals in the original
> executable.
>
> >From an end user's perspective, they're running their program, they
> see it misbehave or they know it's about to misbehave, but it took
> them fifteen minutes to get to this point -- they don't want to
> restart from the beginning and navigate all the way back here.
> With F&C, they make the source change, patch it in, and continue
> on with their work.
>
> I don't have anything interesting planned this weekend so maybe I'll
> write up a short ditty about how it is implemented in gdb and some
> of the more technical aspects of the feature.  I've been doing little
> else since winter, so I've got a pretty good idea of how it all fits
> together. :-)
>
>
> Jason
>