Run dw2-var-zero-addr.exp with --readnow

This patch is to extend dw2-var-zero-add.exp to cover the case that
partial symtabl is not used while full symtab is used, in order to
cover the changes in patch 2/3.  This patch restarts GDB with
--readnow and does the same test again.

gdb/testsuite:

2014-09-19  Yao Qi  <yao@codesourcery.com>

	* gdb.dwarf2/dw2-var-zero-addr.exp: Move test into new proc test.
	Invoke test.  Restart GDB with --readnow and invoke test again.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2014-09-19  Yao Qi  <yao@codesourcery.com>
+
+	* gdb.dwarf2/dw2-var-zero-addr.exp: Move test into new proc test.
+	Invoke test.  Restart GDB with --readnow and invoke test again.
+
 2014-09-19  Yao Qi  <yao@codesourcery.com>
 
 	* gdb.base/break-on-linker-gcd-function.exp: Move test into new

gdb/testsuite/gdb.dwarf2/dw2-var-zero-addr.exp

@@ -26,6 +26,19 @@ if [prepare_for_testing ${testfile}.exp ${testfile} \
     return -1
 }
 
-# FAIL was: = (int *) 0x0
-# Such DIE record can be produced using: gcc -fdata-sections -Wl,-gc-sections
-gdb_test "print &var" {No symbol "var" in current context\.}
+proc test { } {
+    # FAIL was: = (int *) 0x0
+    # Such DIE record can be produced using: gcc -fdata-sections -Wl,-gc-sections
+    gdb_test "print &var" {No symbol "var" in current context\.}
+}
+
+test
+
+set saved_gdbflags $GDBFLAGS
+set GDBFLAGS "$GDBFLAGS --readnow"
+clean_restart ${binfile}
+set GDBFLAGS $saved_gdbflags
+
+with_test_prefix "readnow" {
+    test
+}