[PATCH] PR c++/80473 allow suppressing notes about over-aligned new

[Jonathan Wakely]

This suppresses the notes about over-aligned new when the
corresponding warning is suppressed, either by -w or because it's in a
system header (as in PR 80390, which I originally tried to fix in the
library).

OK for trunk? And gcc-7-branch after 7.1 is released?

Is this the right place for the new test?


gcc/cp:

        PR c++/80473
        * init.c (build_new_1): Suppress notes about over-aligned new when
        the warning is suppressed.

gcc/testsuite:

        PR c++/80473
        * init.c (build_new_1): Suppress notes in system headers.
        PR c++/80473
        * g++.dg/diagnostic/pr80473.C: New test.

commit 66697a6551dd13715c2156ac6b2d5969010c12db
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Apr 20 15:24:09 2017 +0100

    PR c++/80473 allow suppressing notes about over-aligned new
    
    gcc/cp:
    
    	PR c++/80473
    	* init.c (build_new_1): Suppress notes about over-aligned new when
    	the warning is suppressed.
    
    gcc/testsuite:
    
    	PR c++/80473
    	* g++.dg/diagnostic/pr80473.C: New test.

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index bfa9020..2e72451 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -3128,11 +3128,14 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
     {
       warning (OPT_Waligned_new_, "%<new%> of type %qT with extended "
 	       "alignment %d", elt_type, TYPE_ALIGN_UNIT (elt_type));
-      inform (input_location, "uses %qD, which does not have an alignment "
-	      "parameter", alloc_fn);
-      if (!aligned_new_threshold)
-	inform (input_location, "use %<-faligned-new%> to enable C++17 "
-				"over-aligned new support");
+      if (diagnostic_report_warnings_p (global_dc, input_location))
+	{
+	  inform (input_location, "uses %qD, which does not have an alignment "
+		  "parameter", alloc_fn);
+	  if (!aligned_new_threshold)
+	    inform (input_location, "use %<-faligned-new%> to enable C++17 "
+				    "over-aligned new support");
+	}
     }
 
   /* If we found a simple case of PLACEMENT_EXPR above, then copy it
diff --git a/gcc/testsuite/g++.dg/diagnostic/pr80473.C b/gcc/testsuite/g++.dg/diagnostic/pr80473.C
new file mode 100644
index 0000000..6a739f5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/pr80473.C
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++11 } }
+// { dg-bogus "over-aligned new" "PR c++/80473" { target *-*-* } 0 }
+template<typename T> T&& declval();
+
+template<typename T, typename U, typename = void>
+struct is_constructible { enum { value = 0 }; };
+
+template<typename T, typename U>
+struct is_constructible<T, U, decltype(::new T(declval<U>()), void())>
+{ enum { value = 1 }; };
+
+struct alignas(64) A { int i; };
+
+constexpr bool b = is_constructible<A, A>::value;