[gdb/testsuite] Add gdb.base/eh_return.exp

In PR25350, an internal error was reported:
...
(gdb) break *eh2+0x7e
Breakpoint 1 at 0x13e2: file small.c, line 38.
(gdb) run
Starting program: a.out
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".

Breakpoint 1, 0x00005555555553e2 in eh2 (
frame.c:558: internal-error: frame_id get_frame_id(frame_info*): \
  Assertion `stashed' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
...

The internal error does not reproduce after recent commit 547ce8f00b
"[gdb/backtrace] Fix printing of fortran string args".

Add the corresponding test-case as regression test, given that the code is
rather atypical.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2020-08-16  Tom de Vries  <tdevries@suse.de>

	PR gdb/25350
	* gdb.base/eh_return.c: New test.
	* gdb.base/eh_return.exp: New file.

3 files changed, 151 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index d855615..f0b7949 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2020-08-16  Tom de Vries  <tdevries@suse.de>
+
+	PR gdb/25350
+	* gdb.base/eh_return.c: New test.
+	* gdb.base/eh_return.exp: New file.
+
 2020-08-15  Tom de Vries  <tdevries@suse.de>
 
 	* gdb.fortran/mixed-lang-stack.c (fortran_charlen_t): New type.
diff --git a/gdb/testsuite/gdb.base/eh_return.c b/gdb/testsuite/gdb.base/eh_return.c
new file mode 100644
index 0000000..80eea9c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/eh_return.c
@@ -0,0 +1,98 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   It was copied from gcc repo, gcc/testsuite/gcc.target/aarch64/eh_return.c.
+
+   Copyright 2020 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/>.  */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+int val, test, failed;
+
+int main (void);
+
+void
+eh0 (void *p)
+{
+  val = (int)(long)p & 7;
+  if (val)
+    abort ();
+}
+
+void
+eh1 (void *p, int x)
+{
+  void *q = __builtin_alloca (x);
+  eh0 (q);
+  __builtin_eh_return (0, p);
+}
+
+void
+eh2a (int a,int b,int c,int d,int e,int f,int g,int h, void *p)
+{
+  val = a + b + c + d + e + f + g + h +  (int)(long)p & 7;
+}
+
+void
+eh2 (void *p)
+{
+  eh2a (val, val, val, val, val, val, val, val, p);
+  __builtin_eh_return (0, p);
+}
+
+
+void
+continuation (void)
+{
+  test++;
+  main ();
+}
+
+void
+fail (void)
+{
+  failed = 1;
+  printf ("failed\n");
+  continuation ();
+}
+
+void
+do_test1 (void)
+{
+  if (!val)
+    eh1 (continuation, 100);
+  fail ();
+}
+
+void
+do_test2 (void)
+{
+  if (!val)
+    eh2 (continuation);
+  fail ();
+}
+
+int
+main (void)
+{
+  if (test == 0)
+    do_test1 ();
+  if (test == 1)
+    do_test2 ();
+  if (failed || test != 2)
+    exit (1);
+  exit (0);
+}
diff --git a/gdb/testsuite/gdb.base/eh_return.exp b/gdb/testsuite/gdb.base/eh_return.exp
new file mode 100644
index 0000000..e38398e
--- /dev/null
+++ b/gdb/testsuite/gdb.base/eh_return.exp
@@ -0,0 +1,47 @@
+# Copyright 2020 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/>.  */
+
+# Check if executable generated from eh_return.c assert when setting a
+# breakpoint at the last insn of eh, and running to it.
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
+    return -1
+}
+
+set address -1
+
+# Get the address of the last insn in function eh2.
+gdb_test_multiple "disassemble eh2" "" {
+    -re -wrap "($hex)\[^\r\n\]*\r\nEnd of assembler dump." {
+	set address $expect_out(1,string)
+	pass $gdb_test_name
+    }
+}
+
+if { $address == -1 } {
+    return 0
+}
+
+clean_restart ${binfile}
+
+gdb_breakpoint "*$address" message
+
+# The assert did not reproduce when running to main, and continuing to the
+# breakpoint, so instead, run to the breakpoint.
+gdb_run_cmd
+
+gdb_test "" "Breakpoint .*" "hit breakpoint"