Add test for global variable that is nested by another DSO

This is just a testcase addition that I am proposing for upstream GDB.
We have this in our internal tree, and the related RH bug is:

  <https://bugzilla.redhat.com/show_bug.cgi?id=809179>

(You might not be able to see all the comments without privileges.)

This bug is about a global variable that got incorrectly displayed by
GDB.  This bug has already been fixed a long time ago by Joel's
commit:

  commit 19630284f570790ebf6d50bfb43caa1f125ee88a
  Author: Joel Brobecker <brobecker@gnat.com>
  Date:   Tue Jun 5 13:50:50 2012 +0000

But I think a testcase for it wouldn't hurt.

So, consider the following scenario:

  $ cat solib1.c
  int test;
  void c_main (void)
  {
    test = 42;
  }

  $ cat solib2.c
  int test;
  void b_main (void)
  {
    test = 42;
  }

  $ cat main.c
  int main (int argc, char *argv[])
  {
    c_main ();
    b_main ();
    return 0;
  }

  $ gcc -g -fPIC -shared -o libSO1.so -c solib1.c
  $ gcc -g -fPIC -shared -o libSO2.so -c solib2.c
  $ gcc -g -o main -L$PWD -lSO1 -lSO2 main.c
  $ LD_LIBRARY_PATH=. gdb -q -batch -ex 'b c_main' -ex r -ex n -ex 'p test' ./main
  ...
  $1 = 0

This happened with GDB before Joel's commit above.  Now, things work
and GDB is able to correctly display the nested global variable:

  $ LD_LIBRARY_PATH=. gdb -q -batch -ex 'b c_main' -ex r -ex n -ex 'p test' ./main
  ...
  $1 = 42

The testcase attached tests this behavior.

gdb/testsuite/ChangeLog:
2014-09-16  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.base/global-var-nested-by-dso-solib1.c: New file.
	* gdb.base/global-var-nested-by-dso-solib2.c: Likewise.
	* gdb.base/global-var-nested-by-dso.c: Likewise.
	* gdb.base/global-var-nested-by-dso.exp: Likewise.

1 files changed, 24 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/global-var-nested-by-dso.c b/gdb/testsuite/gdb.base/global-var-nested-by-dso.c
new file mode 100644
index 0000000..3b63096
--- /dev/null
+++ b/gdb/testsuite/gdb.base/global-var-nested-by-dso.c
@@ -0,0 +1,24 @@
+/* Copyright 2014 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+int
+main (int argc, char *argv[])
+{
+  c_main ();
+  b_main ();
+  return 0;
+}