[PATCH] Fix breakpoints on symbols with multiple trampoline symbols

[PATCH] Fix breakpoints on symbols with multiple trampoline symbols

[Hannes Domani]

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

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

[Hannes Domani]

 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

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

[Hannes Domani]

 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

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

[Tom Tromey]

>>>>> "Hannes" == Hannes Domani <ssbssa@yahoo.de> writes:

Hannes> On mingw targets it's possible that there are multiple trampoline
Hannes> symbols for __cxa_throw, in each module where a throw is done, but
Hannes> without a corresponding global symbol.
Hannes> Since commit 77f2120b200be6cabbf6f610942fc1173a8df6d3 they cancel each
Hannes> other out in search_minsyms_for_name, which makes it impossible to set
Hannes> a breakpoint there:

Thank you for the patch.  This is ok.
Approved-By: Tom Tromey <tom@tromey.com>

Tom

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

[Hannes Domani]

 Am Dienstag, 5. Dezember 2023, 16:21:58 MEZ hat Tom Tromey <tom@tromey.com> Folgendes geschrieben:

> >>>>> "Hannes" == Hannes Domani <ssbssa@yahoo.de> writes:
>
> Hannes> On mingw targets it's possible that there are multiple trampoline
> Hannes> symbols for __cxa_throw, in each module where a throw is done, but
> Hannes> without a corresponding global symbol.
> Hannes> Since commit 77f2120b200be6cabbf6f610942fc1173a8df6d3 they cancel each
> Hannes> other out in search_minsyms_for_name, which makes it impossible to set
> Hannes> a breakpoint there:
>
> Thank you for the patch.  This is ok.
> Approved-By: Tom Tromey <tom@tromey.com>

Pushed, thanks.