PR c++/81073 - constexpr and static var in statement-expression.

	* typeck2.c (store_init_value): Always call
	require_potential_constant_expression.
	* pt.c (convert_nontype_argument): Likewise.
	* constexpr.c (potential_constant_expression_1): Adjust message.
	Use decl_maybe_constant_var_p instead of decl_constant_var_p.
	* decl2.c (decl_maybe_constant_var_p): Consider initializer.

From-SVN: r249382

gcc/cp/ChangeLog

+2017-06-19  Jason Merrill  <jason@redhat.com>
+
+	PR c++/81073 - constexpr and static var in statement-expression.
+	* typeck2.c (store_init_value): Always call
+	require_potential_constant_expression.
+	* pt.c (convert_nontype_argument): Likewise.
+	* constexpr.c (potential_constant_expression_1): Adjust message.
+	Use decl_maybe_constant_var_p instead of decl_constant_var_p.
+	* decl2.c (decl_maybe_constant_var_p): Consider initializer.
+
 2017-06-19  Nathan Sidwell  <nathan@acm.org>
 
 	* pt.c (coerce_template_parms): Fix indentation.

gcc/cp/constexpr.c

@@ -5212,10 +5212,11 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict,
       if (want_rval
 	  && !var_in_maybe_constexpr_fn (t)
 	  && !type_dependent_expression_p (t)
-	  && !decl_constant_var_p (t)
+	  && !decl_maybe_constant_var_p (t)
 	  && (strict
 	      || !CP_TYPE_CONST_NON_VOLATILE_P (TREE_TYPE (t))
-	      || !DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (t))
+	      || (DECL_INITIAL (t)
+		  && !DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (t)))
 	  && COMPLETE_TYPE_P (TREE_TYPE (t))
 	  && !is_really_empty_class (TREE_TYPE (t)))
         {
@@ -5540,21 +5541,21 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict,
 	    {
 	      if (flags & tf_error)
 		error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared "
-			  "%<static%> in %<constexpr%> function", tmp);
+			  "%<static%> in %<constexpr%> context", tmp);
 	      return false;
 	    }
 	  else if (CP_DECL_THREAD_LOCAL_P (tmp))
 	    {
 	      if (flags & tf_error)
 		error_at (DECL_SOURCE_LOCATION (tmp), "%qD declared "
-			  "%<thread_local%> in %<constexpr%> function", tmp);
+			  "%<thread_local%> in %<constexpr%> context", tmp);
 	      return false;
 	    }
 	  else if (!DECL_NONTRIVIALLY_INITIALIZED_P (tmp))
 	    {
 	      if (flags & tf_error)
 		error_at (DECL_SOURCE_LOCATION (tmp), "uninitialized "
-			  "variable %qD in %<constexpr%> function", tmp);
+			  "variable %qD in %<constexpr%> context", tmp);
 	      return false;
 	    }
 	}

gcc/cp/decl2.c

@@ -4145,10 +4145,19 @@ decl_maybe_constant_var_p (tree decl)
     /* A proxy isn't constant.  */
     return false;
   if (TREE_CODE (type) == REFERENCE_TYPE)
-    /* References can be constant.  */
+    /* References can be constant.  */;
+  else if (CP_TYPE_CONST_NON_VOLATILE_P (type)
+	   && INTEGRAL_OR_ENUMERATION_TYPE_P (type))
+    /* And const integers.  */;
+  else
+    return false;
+
+  if (DECL_INITIAL (decl)
+      && !DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (decl))
+    /* We know the initializer, and it isn't constant.  */
+    return false;
+  else
     return true;
-  return (CP_TYPE_CONST_NON_VOLATILE_P (type)
-	  && INTEGRAL_OR_ENUMERATION_TYPE_P (type));
 }
 
 /* Complain that DECL uses a type with no linkage.  In C++98 mode this is

gcc/cp/pt.c

@@ -6585,10 +6585,10 @@ convert_nontype_argument (tree type, tree expr, tsubst_flags_t complain)
 	  if (complain & tf_error)
 	    {
 	      int errs = errorcount, warns = warningcount + werrorcount;
-	      if (processing_template_decl
-		  && !require_potential_constant_expression (expr))
-		return NULL_TREE;
-	      expr = cxx_constant_value (expr);
+	      if (!require_potential_constant_expression (expr))
+		expr = error_mark_node;
+	      else
+		expr = cxx_constant_value (expr);
 	      if (errorcount > errs || warningcount + werrorcount > warns)
 		inform (loc, "in template argument for type %qT ", type);
 	      if (expr == error_mark_node)

gcc/cp/typeck2.c

@@ -821,8 +821,7 @@ store_init_value (tree decl, tree init, vec<tree, va_gc>** cleanups, int flags)
 	  || (DECL_IN_AGGR_P (decl) && !DECL_VAR_DECLARED_INLINE_P (decl)))
 	{
 	  /* Diagnose a non-constant initializer for constexpr.  */
-	  if (processing_template_decl
-	      && !require_potential_constant_expression (value))
+	  if (!require_potential_constant_expression (value))
 	    value = error_mark_node;
 	  else
 	    value = cxx_constant_value (value, decl);

gcc/testsuite/g++.dg/cpp0x/constexpr-diag1.C

@@ -16,5 +16,5 @@ constexpr int i = ai.f();
 constexpr int b = A<B>().f();	// { dg-error "" }
 
 template <class T>
-constexpr int f (T t) { return 42; } // { dg-error "parameter" }
-constexpr int x = f(B());	     // { dg-error "constexpr" }
+constexpr int f (T t) { return 42; }
+constexpr int x = f(B());	     // { dg-error "non-literal" }

gcc/testsuite/g++.dg/cpp0x/constexpr-trivial2.C

@@ -10,5 +10,5 @@ struct T
 
 int main()
 {
-    constexpr T t = (T{} = T{});
+    constexpr T t = (T{} = T{}); // { dg-error "" "" { target c++11_only } }
 }

gcc/testsuite/g++.dg/ext/stmtexpr19.C

+// PR c++/81073
+// { dg-options "" }
+// { dg-do compile { target c++11 } }
+
+struct test { const int *addr; };
+
+const test* setup()
+{
+  static constexpr test atest =
+    {
+      ({ static const int inner = 123; &inner; }) // { dg-error "static" }
+    };
+
+  return &atest;
+}
+
+int main(){}