Poison non-POD memset & non-trivially-copyable memcpy/memmove

This patch catches invalid initialization of non-POD types with
memset, at compile time.

This is what I used to catch the problems fixed by the previous
patches in the series:

  $ make -k 2>&1 | grep "deleted function"
  src/gdb/breakpoint.c:951:53: error: use of deleted function ‘void* memset(T*, int, size_t) [with T = bp_location; <template-parameter-1-2> = void; size_t = long unsigned int]’
  src/gdb/breakpoint.c:7325:32: error: use of deleted function ‘void* memset(T*, int, size_t) [with T = bp_location; <template-parameter-1-2> = void; size_t = long unsigned int]’
  src/gdb/btrace.c:1153:42: error: use of deleted function ‘void* memset(T*, int, size_t) [with T = btrace_insn; <template-parameter-1-2> = void; size_t = long unsigned int]’
...

gdb/ChangeLog:
2017-04-25  Pedro Alves  <palves@redhat.com>

	* common/common-defs.h: Include "common/poison.h".
	* common/function-view.h: (Not, Or, Requires): Move to traits.h
	and adjust.
	* common/poison.h: New file.
	* common/traits.h: Include <type_traits>.
	(Not, Or, Requires): New, moved from common/function-view.h.

1 files changed, 4 insertions, 36 deletions

diff --git a/gdb/common/function-view.h b/gdb/common/function-view.h
index 66a691b..de9a634 100644
--- a/gdb/common/function-view.h
+++ b/gdb/common/function-view.h
@@ -153,34 +153,6 @@
 
 namespace gdb {
 
-namespace traits {
-  /* A few trait helpers.  */
-  template<typename Predicate>
-  struct Not : public std::integral_constant<bool, !Predicate::value>
-  {};
-
-  template<typename...>
-  struct Or;
-
-  template<>
-  struct Or<> : public std::false_type
-  {};
-
-  template<typename B1>
-  struct Or<B1> : public B1
-  {};
-
-  template<typename B1, typename B2>
-  struct Or<B1, B2>
-    : public std::conditional<B1::value, B1, B2>::type
-  {};
-
-  template<typename B1,typename B2,typename B3, typename... Bn>
-  struct Or<B1, B2, B3, Bn...>
-    : public std::conditional<B1::value, B1, Or<B2, B3, Bn...>>::type
-  {};
-} /* namespace traits */
-
 namespace fv_detail {
 /* Bits shared by all function_view instantiations that do not depend
    on the template parameters.  */
@@ -209,9 +181,9 @@ class function_view<Res (Args...)>
 {
   template<typename From, typename To>
   using CompatibleReturnType
-    = traits::Or<std::is_void<To>,
-		 std::is_same<From, To>,
-		 std::is_convertible<From, To>>;
+    = Or<std::is_void<To>,
+	 std::is_same<From, To>,
+	 std::is_convertible<From, To>>;
 
   /* True if Func can be called with Args, and either the result is
      Res, convertible to Res or Res is void.  */
@@ -227,10 +199,6 @@ class function_view<Res (Args...)>
     : std::is_same<function_view, typename std::decay<Callable>::type>
   {};
 
-  /* Helper to make SFINAE logic easier to read.  */
-  template<typename Condition>
-  using Requires = typename std::enable_if<Condition::value, void>::type;
-
  public:
 
   /* NULL by default.  */
@@ -248,7 +216,7 @@ class function_view<Res (Args...)>
      compatible.  */
   template
     <typename Callable,
-     typename = Requires<traits::Not<IsFunctionView<Callable>>>,
+     typename = Requires<Not<IsFunctionView<Callable>>>,
      typename = Requires<IsCompatibleCallable<Callable>>>
   function_view (Callable &&callable) noexcept
   {