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

[Hannes Domani <ssbssa@yahoo.de>]

 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