Re: Lifetime of local variables

[Momchil Velikov <velco at fadata dot bg>]

Martin Baulig <martin@gnome.org> writes:

> Daniel Jacobowitz <drow@mvista.com> writes:
> 
> > No.  I'd strongly object to adding any DWARF-2 tags without at least
> > discussing them with the DWARF committee (which is quite responsive, I
> > believe).
> 
> Yeah, good point.
> 
> > Also, I believe that this should be entirely subsumed by .debug_loc. 
> > The first variable's value may no longer be available, but it has not
> > actually gone out of scope, has it?  We should list it but claim that
> > its value is unavailable.
> 
> It has actually gone out of scope. 

I think ypu are mixing two different concepts here, the language
notion of scope and the compiler/runtime notion of lifetime.  I guess
the lifetime is of interest for a debugger.

> I want to use this to debug machine
> generated IL code and the JIT may want to create local variables
> on-the-fly. For variables which have actually been defined by a human
> programmer, listing them and claiming that their value is no longer
> available is IMHO the right thing to do - but I'd like to tell the
> debugger to make a machine-generated variable disappear when it's no
> longer used, otherwise you'd get a large number of automatic variables
> (having numbers, not names, which makes it even more confusing to the
> user) and only a very few of them are actually used.
> 

One can use DT_AT_artificial to distinguish machine generated
temporaries and the .debug_loc ranges to decide whether to display the
variable.