[Bug middle-end/105849] A couple of new clang warnings

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105849

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to David Binderman from comment #0)
> Standard practice is to have virtual destructor in the presence of virtual
> functions.

Or a protected destructor, or to make the class final.

int_range cannot be final, but it looks as though value_range_equiv can be.

But I think the warning for int_range<1> is a false positive anyway. The
warning comes from instantiating finalizer<int_range<1>> in ggc_alloc, but it's
not actually used, because that class has a trivial destructor. So this should
work:

diff --git a/gcc/ggc.h b/gcc/ggc.h
index aeec1bafb9b..af0a4c005d7 100644
--- a/gcc/ggc.h
+++ b/gcc/ggc.h
@@ -160,14 +160,7 @@ extern void dump_ggc_loc_statistics ();
     ((T *) ggc_realloc ((P), (N) * sizeof (T) MEM_STAT_INFO))

 template<typename T>
-void
-finalize (void *p)
-{
-  static_cast<T *> (p)->~T ();
-}
-
-template<typename T>
-inline bool
+constexpr bool
 need_finalization_p ()
 {
 #if GCC_VERSION >= 4003
@@ -177,6 +170,19 @@ need_finalization_p ()
 #endif
 }

+template<typename T>
+typename std::enable_if<need_finalization_p<T> ()>::type
+finalize (void *p)
+{
+  static_cast<T *> (p)->~T ();
+}
+
+template<typename T>
+typename std::enable_if<!need_finalization_p<T> ()>::type
+finalize (void *)
+{
+}
+
 template<typename T>
 inline T *
 ggc_alloc (ALONE_CXX_MEM_STAT_INFO)
diff --git a/gcc/value-range-equiv.h b/gcc/value-range-equiv.h
index 0a52d1372a1..95a129124b2 100644
--- a/gcc/value-range-equiv.h
+++ b/gcc/value-range-equiv.h
@@ -24,7 +24,7 @@ along with GCC; see the file COPYING3.  If not see

 /* Note value_range_equiv cannot currently be used with GC memory,
    only value_range is fully set up for this.  */
-class GTY((user)) value_range_equiv : public value_range
+class GTY((user)) value_range_equiv final : public value_range
 {
  public:
   value_range_equiv () : value_range () { m_equiv = NULL; }


(It would be better to use "if constexpr" in ggc_alloc, but that's a C++17
feature, so overloading with std::enable_if is needed for C++11.)