re PR c++/64356 (Some constexpr expressions not recognized as constexpr)

	PR c++/64356
	PR libstdc++/58777
	* constexpr.c (cxx_eval_binary_expression): Don't VERIFY_CONSTANT
	pointer expressions.
	(cxx_eval_increment_expression): Likewise.

From-SVN: r219559

4 files changed, 45 insertions, 6 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 668b13b..013c432 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,11 @@
 2015-01-13  Jason Merrill  <jason@redhat.com>
 
+	PR c++/64356
+	PR libstdc++/58777
+	* constexpr.c (cxx_eval_binary_expression): Don't VERIFY_CONSTANT
+	pointer expressions.
+	(cxx_eval_increment_expression): Likewise.
+
 	PR c++/64514
 	* pt.c (coerce_template_parameter_pack): Return NULL for a
 	zero-length fixed parameter pack with a pack expansion arg.
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 650250b..1432506 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1616,10 +1616,15 @@ cxx_eval_binary_expression (const constexpr_ctx *ctx, tree t,
   tree lhs, rhs;
   lhs = cxx_eval_constant_expression (ctx, orig_lhs, /*lval*/false,
 				      non_constant_p, overflow_p);
-  VERIFY_CONSTANT (lhs);
+  /* Don't VERIFY_CONSTANT if this might be dealing with a pointer to
+     a local array in a constexpr function.  */
+  bool ptr = POINTER_TYPE_P (TREE_TYPE (lhs));
+  if (!ptr)
+    VERIFY_CONSTANT (lhs);
   rhs = cxx_eval_constant_expression (ctx, orig_rhs, /*lval*/false,
 				      non_constant_p, overflow_p);
-  VERIFY_CONSTANT (rhs);
+  if (!ptr)
+    VERIFY_CONSTANT (lhs);
 
   location_t loc = EXPR_LOCATION (t);
   enum tree_code code = TREE_CODE (t);
@@ -1634,7 +1639,8 @@ cxx_eval_binary_expression (const constexpr_ctx *ctx, tree t,
     }
   else if (cxx_eval_check_shift_p (loc, ctx, code, type, lhs, rhs))
     *non_constant_p = true;
-  VERIFY_CONSTANT (r);
+  if (!ptr)
+    VERIFY_CONSTANT (lhs);
   return r;
 }
 
@@ -2704,7 +2710,11 @@ cxx_eval_increment_expression (const constexpr_ctx *ctx, tree t,
   tree val = rvalue (op);
   val = cxx_eval_constant_expression (ctx, val, false,
 				      non_constant_p, overflow_p);
-  VERIFY_CONSTANT (val);
+  /* Don't VERIFY_CONSTANT if this might be dealing with a pointer to
+     a local array in a constexpr function.  */
+  bool ptr = POINTER_TYPE_P (TREE_TYPE (val));
+  if (!ptr)
+    VERIFY_CONSTANT (val);
 
   /* The modified value.  */
   bool inc = (code == PREINCREMENT_EXPR || code == POSTINCREMENT_EXPR);
@@ -2719,7 +2729,8 @@ cxx_eval_increment_expression (const constexpr_ctx *ctx, tree t,
     }
   else
     mod = fold_build2 (inc ? PLUS_EXPR : MINUS_EXPR, type, val, offset);
-  VERIFY_CONSTANT (mod);
+  if (!ptr)
+    VERIFY_CONSTANT (mod);
 
   /* Storing the modified value.  */
   tree store = build2 (MODIFY_EXPR, type, op, mod);
diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-local2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-local2.C
new file mode 100644
index 0000000..fd6143b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-local2.C
@@ -0,0 +1,22 @@
+// PR c++/64356
+// { dg-do compile { target c++14 } }
+
+typedef unsigned long size_t;
+
+template<size_t N>
+constexpr size_t f(const char (&x)[N]) {
+  size_t s = 0;
+  for(size_t c : x)
+    s += c;
+  return s;
+}
+
+template<size_t N>
+constexpr size_t g(const char (&x)[N]) {
+  char y[N] = {0};
+  for(size_t i = 0; i < N; ++i)
+    y[i] = x[i];
+  return f(y);
+}
+
+constexpr auto x = g(__DATE__);
diff --git a/gcc/testsuite/g++.dg/cpp1y/pr63996.C b/gcc/testsuite/g++.dg/cpp1y/pr63996.C
index d0bf9b5..8f66cdc 100644
--- a/gcc/testsuite/g++.dg/cpp1y/pr63996.C
+++ b/gcc/testsuite/g++.dg/cpp1y/pr63996.C
@@ -6,5 +6,5 @@ foo (int i)
   int a[i] = { }; // { dg-error "forbids variable length" }
 }
 
-constexpr int j = foo (1); // { dg-error "is not a constant expression" }
+constexpr int j = foo (1); // { dg-error "flows off the end" }