Re: [PATCH] Fix breakpoints on symbols with multiple trampoline symbols

[Hannes Domani <ssbssa@yahoo.de>]

 Ping.


Am Dienstag, 21. November 2023, 18:28:28 MEZ hat Hannes Domani <ssbssa@yahoo.de> Folgendes geschrieben:

> Ping.
>
>
> Am Montag, 6. November 2023, 20:31:22 MEZ hat Hannes Domani <ssbssa@yahoo.de> Folgendes geschrieben:
>
> > On mingw targets it's possible that there are multiple trampoline
> > symbols for __cxa_throw, in each module where a throw is done, but
> > without a corresponding global symbol.
> > Since commit 77f2120b200be6cabbf6f610942fc1173a8df6d3 they cancel each
> > other out in search_minsyms_for_name, which makes it impossible to set
> > a breakpoint there:
> >
> > (gdb) b __cxa_throw
> > Function "__cxa_throw" not defined.
> > Make breakpoint pending on future shared library load? (y or [n]) y
> > Breakpoint 2 (__cxa_throw) pending.
> > (gdb) c
> > Continuing.
> > [Inferior 1 (process 10004) exited with code 03]
> >
> > With catch throw it also doesn't work, and you don't even get an error
> > message:
> >
> > (gdb) catch throw
> > Catchpoint 2 (throw)
> > (gdb) c
> > Continuing.
> > [Inferior 1 (process 5532) exited with code 03]
> > (gdb)
> >
> > The fix is to simply ignore other trampoline symbols when looking for
> > corresponding global symbols, and it's working as expected:
> >
> > (gdb) b __cxa_throw
> > Breakpoint 2 at 0x13f091590 (2 locations)
> > (gdb) c
> > Continuing.
> >
> > Breakpoint 2.1, 0x000000013f091590 in __cxa_throw ()
> > (gdb)
> >
> > And catch throw also works again:
> >
> > (gdb) catch throw
> > Catchpoint 2 (throw)
> > (gdb) c
> > Continuing.
> >
> > Catchpoint 2.1 (exception thrown), 0x000000013f181590 in __cxa_throw ()
> > (gdb)
> >
> > Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29548
> > ---
> > gdb/linespec.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/gdb/linespec.c b/gdb/linespec.c
> > index fa733d880e3..2aa01819812 100644
> > --- a/gdb/linespec.c
> > +++ b/gdb/linespec.c
> > @@ -4281,6 +4281,10 @@ search_minsyms_for_name (struct collect_info *info,
> >           if (&item2 == &item)
> >         continue;
> >
> > +          /* Ignore other trampoline symbols.  */
> > +          if (item2.minsym->type () == mst_solib_trampoline)
> > +        continue;
> > +
> >           /* Trampoline symbols can only jump to exported
> >         symbols.  */
> >           if (msymbol_type_is_static (item2.minsym->type ()))
> > --
> > 2.35.1