PR c++/69496

	* constexpr.c (cxx_eval_array_reference): Evaluate the number of
	elements of the array.

	* g++.dg/ext/constexpr-vla1.C: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@232875 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 0c490d5..9f8d91a 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2016-01-27  Marek Polacek  <polacek@redhat.com>
+
+       PR c++/69496
+       * constexpr.c (cxx_eval_array_reference): Evaluate the number of
+       elements of the array.
+
 2016-01-26  Jason Merrill  <jason@redhat.com>
 
        PR c++/68949

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index bbb8ccf..fd80000 100644 (file)
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1846,7 +1846,12 @@ cxx_eval_array_reference (const constexpr_ctx *ctx, tree t,
 
   if (!found)
     {
-      if (tree_int_cst_lt (index, array_type_nelts_top (TREE_TYPE (ary))))
+      tree nelts = array_type_nelts_top (TREE_TYPE (ary));
+      /* For VLAs, the number of elements won't be an integer constant.  */
+      nelts = cxx_eval_constant_expression (ctx, nelts, false, non_constant_p,
+                                           overflow_p);
+      VERIFY_CONSTANT (nelts);
+      if (tree_int_cst_lt (index, nelts))
        {
          if (TREE_CODE (ary) == CONSTRUCTOR
              && CONSTRUCTOR_NO_IMPLICIT_ZERO (ary))

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8559a78..2ff4f7d 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-01-27  Marek Polacek  <polacek@redhat.com>
+
+       PR c++/69496
+       * g++.dg/ext/constexpr-vla1.C: New test.
+
 2016-01-20  Christian Bruel  <christian.bruel@st.com>
 
        PR target/69245

diff --git a/gcc/testsuite/g++.dg/ext/constexpr-vla1.C b/gcc/testsuite/g++.dg/ext/constexpr-vla1.C
new file mode 100644 (file)
index 0000000..a5615bb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/constexpr-vla1.C
@@ -0,0 +1,30 @@
+// PR c++/69496
+// { dg-do compile { target c++14 } }
+
+constexpr int
+fn_ok (int n)
+{
+    __extension__ int a[n] = { };
+    int z = 0;
+
+    for (unsigned i = 0; i < sizeof (a) / sizeof (int); ++i)
+      z += a[i];
+
+    return z;
+}
+
+
+constexpr int
+fn_not_ok (int n)
+{
+    __extension__ int a[n] = { };
+    int z = 0;
+
+    for (unsigned i = 0; i < sizeof (a); ++i)
+      z += a[i];
+
+    return z;
+}
+
+constexpr int n1 = fn_ok (3);
+constexpr int n2 = fn_not_ok (3); // { dg-error "array subscript out of bound" }