[PATCH 1/9] Do not pass NULL to memcpy

[Tom Tromey <tom@tromey.com>]

-fsanitize=undefined pointed out a couple of spots that pass NULL to
memcpy, which is undefined behavior according to the C standard.

ChangeLog
2018-08-27  Tom Tromey  <tom@tromey.com>

	* namespace.c (add_using_directive): Don't pass NULL to memcpy.
	* dwarf2-frame.h (struct dwarf2_frame_state_reg_info): Don't pass
	NULL to memcpy.
---
 gdb/ChangeLog      | 6 ++++++
 gdb/dwarf2-frame.h | 3 ++-
 gdb/namespace.c    | 5 +++--
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/gdb/dwarf2-frame.h b/gdb/dwarf2-frame.h
index 52316e5e168..6844010c8df 100644
--- a/gdb/dwarf2-frame.h
+++ b/gdb/dwarf2-frame.h
@@ -110,7 +110,8 @@ struct dwarf2_frame_state_reg_info
     size_t size = src.num_regs * sizeof (struct dwarf2_frame_state_reg);
 
     reg = (struct dwarf2_frame_state_reg *) xmalloc (size);
-    memcpy (reg, src.reg, size);
+    if (size > 0)
+      memcpy (reg, src.reg, size);
   }
 
   /* Assignment operator for both move-assignment and copy-assignment.  */
diff --git a/gdb/namespace.c b/gdb/namespace.c
index be998d9d491..85c0c4b14d7 100644
--- a/gdb/namespace.c
+++ b/gdb/namespace.c
@@ -111,8 +111,9 @@ add_using_directive (struct using_direct **using_directives,
   else
     newobj->declaration = declaration;
 
-  memcpy (newobj->excludes, excludes.data (),
-	  excludes.size () * sizeof (*newobj->excludes));
+  if (!excludes.empty ())
+    memcpy (newobj->excludes, excludes.data (),
+	    excludes.size () * sizeof (*newobj->excludes));
   newobj->excludes[excludes.size ()] = NULL;
 
   newobj->next = *using_directives;
-- 
2.13.6