[Bug debug/49167] New: dwarf marker for function return instruction

[Bug debug/49167] New: dwarf marker for function return instruction

[fche at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49167

           Summary: dwarf marker for function return instruction
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: aoliva@gcc.gnu.org
        ReportedBy: fche@redhat.com
                CC: tromey@redhat.com


It would be desirable to have a DWARF marker of some sort emitted
for the point(s) of a function that correspond to the logical moment
of its return.  This would ideally be a point where all the nearby
variables are still in scope, so the last-gasp variable state may be
examined.

Ideally, tail call sites would also have this marker, and so would
inlined functions.  One can dream...

[Bug debug/49167] dwarf marker for function return instruction

[jistone at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49167

Josh Stone <jistone at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jistone at redhat dot com

--- Comment #1 from Josh Stone <jistone at redhat dot com> 2011-06-03 18:56:06 UTC ---
(In reply to comment #0)
> Ideally, tail call sites would also have this marker, and so would
> inlined functions.  One can dream...

Besides nearby variables, we'd also like to know what is the imminent return
value.  I imagine that's fine for a typical function, and perhaps for inlines
too if optimization didn't morph it away.  But it's not clear to me how DWARF
could help us with the return value from a tail call.  If the callee is
statically known, then perhaps some indirection to that site, but in general I
don't know...

[Bug debug/49167] dwarf marker for function return instruction

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49167

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-06-03 19:09:04 UTC ---
For tail calls, you have in GCC 4.7 (and 4.6-RH in Fedora 16) the
DW_TAG_GNU_call_site* stuff from which you can (sometimes) reconstruct the
actual backtrace.  The return value from the function that tail called another
one is by definition the same as from the tail callee.

[Bug debug/49167] dwarf marker for function return instruction

[fche at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49167

--- Comment #3 from Frank Ch. Eigler <fche at redhat dot com> 2012-05-22 14:30:35 UTC ---
test comment