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, 55 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/global-var-nested-by-dso.exp b/gdb/testsuite/gdb.base/global-var-nested-by-dso.exp
new file mode 100644
index 0000000..e1e208a
--- /dev/null
+++ b/gdb/testsuite/gdb.base/global-var-nested-by-dso.exp
@@ -0,0 +1,55 @@
+# Copyright 2014 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/>.
+
+if { [skip_shlib_tests] } {
+    return 0
+}
+
+standard_testfile
+
+set lib1name $testfile-solib1
+set srcfile_lib1 $srcdir/$subdir/$lib1name.c
+set binfile_lib1 [standard_output_file $lib1name.so]
+
+set lib2name $testfile-solib2
+set srcfile_lib2 $srcdir/$subdir/$lib2name.c
+set binfile_lib2 [standard_output_file $lib2name.so]
+
+if { [gdb_compile_shlib $srcfile_lib1 $binfile_lib1 \
+	[list debug additional_flags=-fPIC]] != "" } {
+  untested "Could not compile $binfile_lib1."
+  return -1
+}
+
+if { [gdb_compile_shlib $srcfile_lib2 $binfile_lib2 \
+	[list debug additional_flags=-fPIC]] != "" } {
+  untested "Could not compile $binfile_lib2."
+  return -1
+}
+
+if { [gdb_compile $srcdir/$subdir/$srcfile $binfile executable \
+	[list debug shlib=$binfile_lib1 shlib=$binfile_lib2]] != "" } {
+  return -1
+}
+
+clean_restart $binfile
+
+if { ![runto_main] } {
+  return -1
+}
+
+gdb_test "next" "$decimal.*b_main \\(\\);"
+gdb_test "next" "$decimal.*return 0;"
+gdb_test "print test" " = 42"