c++: unpropagated CONSTRUCTOR_MUTABLE_POISON [PR110463]

Here we're incorrectly accepting the mutable member accesses because
cp_fold neglects to propagate CONSTRUCTOR_MUTABLE_POISON when folding a
CONSTRUCTOR.

	PR c++/110463

gcc/cp/ChangeLog:

	* cp-gimplify.cc (cp_fold) <case CONSTRUCTOR>: Propagate
	CONSTRUCTOR_MUTABLE_POISON.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/constexpr-mutable6.C: New test.

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index 853b1e4423635881a8d05a415db0690cb622c58d..f57341977748dbef68355e492fc6d328fcea21a5 100644 (file)
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -3079,6 +3079,8 @@ cp_fold (tree x, fold_flags_t flags)
            x = build_constructor (TREE_TYPE (x), nelts);
            CONSTRUCTOR_PLACEHOLDER_BOUNDARY (x)
              = CONSTRUCTOR_PLACEHOLDER_BOUNDARY (org_x);
+           CONSTRUCTOR_MUTABLE_POISON (x)
+             = CONSTRUCTOR_MUTABLE_POISON (org_x);
          }
        if (VECTOR_TYPE_P (TREE_TYPE (x)))
          x = fold (x);

diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-mutable6.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-mutable6.C
new file mode 100644 (file)
index 0000000..2c946e3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-mutable6.C
@@ -0,0 +1,18 @@
+// PR c++/110463
+// { dg-do compile { target c++11 } }
+
+struct U {
+  mutable int x = 1;
+};
+
+struct V {
+  mutable int y = 1+1;
+};
+
+int main() {
+  constexpr U u = {};
+  constexpr int x = u.x; // { dg-error "mutable" }
+
+  constexpr V v = {};
+  constexpr int y = v.y; // { dg-error "mutable" }
+}