Fix 'catch exception' with -flto

A user noticed that when an Ada program (including the runtime) is
compiled with -flto, then "catch exception" does not work -- even
though setting the equivalent breakpoint by hand does work.

Looking into this, it turns out that GCC puts the exception functions
from the Ada runtime into a CU that uses the C language, not Ada.
Then, when trying to look up the relevant symbol,
lookup_name_info::search_name_hash uses the "verbatim" form of the
symbol name (like "<__gnat_debug_raise_exception>") rather than the
"<>"-less form, causing the symbol not to be found.

This patch fixes the problem in two steps.

First, lookup_name_info::search_name_hash is changed to use the same
hack that language_defn::get_symbol_name_matcher uses.  That is, when
the current language is Ada, verbatim-mode lookups are special-cased.
(This is a bit unfortunate; perhaps a better long term approach would
be to promote verbatim mode to a fundamental mode of
lookup_name_info.)

Second, although the above fixes the problem in the Ada language mode,
the code still fails in other languages.  However, due to the way
these lookups are coded in ada-lang.c, I think it makes sense to
temporarily set the current language to Ada in
create_ada_exception_catchpoint.

Tested on x86-64 Fedora 38.

A new test case that mimics the -flto scenario is included.

Reviewed-By: Alexandra Petlanova Hajkova <ahajkova@redhat.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.ada/exception-lto.c b/gdb/testsuite/gdb.ada/exception-lto.c
new file mode 100644
index 0000000..c5ee69d
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/exception-lto.c
@@ -0,0 +1,40 @@
+/* This test program is part of GDB, the GNU debugger.
+
+   Copyright 2024 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* We need a few extra functions here to ensure that the dictionary
+   for the global block has more than one slot.  */
+
+void f1 () { }
+void f2 () { }
+void f3 () { }
+void f4 () { }
+
+void
+__gnat_debug_raise_exception ()
+{
+}
+
+void
+__gnat_begin_handler_v1 ()
+{
+}
+
+int
+main ()
+{
+  return 0;
+}