[RFA] Clear entire "location" in value constructor

[Tom Tromey <tom@tromey.com>]

My recent change to allocate values with "new" may have introduced a
small bug.  In particular, the previous code allocated with XCNEW, but
the new code only clears a part of the "location" field in the
constructor.  I didn't try very hard to actually trigger a bug here,
the problem remains theoretical.

This patch changes the constructor to clear the entire "location".

Regression tested by the buildbot.

2018-04-10  Tom Tromey  <tom@tromey.com>

	* value.c (value::value): Clear "location".
---
 gdb/ChangeLog | 4 ++++
 gdb/value.c   | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d46ecdd120..8cc1486c87 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2018-04-10  Tom Tromey  <tom@tromey.com>
+
+	* value.c (value::value): Clear "location".
+
 2018-04-10  Pedro Alves  <palves@redhat.com>
 
 	* gdbthread.h (finish_thread_state_cleanup): Delete declaration.
diff --git a/gdb/value.c b/gdb/value.c
index 12aa2b8bb4..64e3eaca22 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -180,7 +180,7 @@ struct value
       type (type_),
       enclosing_type (type_)
   {
-    location.address = 0;
+    memset (&location, 0, sizeof (location));
   }
 
   ~value ()
-- 
2.13.6