re PR c++/92695 (P1064R0 - virtual constexpr fails if object taken from array)

	PR c++/92695
	* constexpr.c (cxx_bind_parameters_in_call): For virtual calls,
	adjust the first argument to point to the derived object rather
	than its base.

	* g++.dg/cpp2a/constexpr-virtual14.C: New test.

From-SVN: r278921

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 9ca25aea63561f651ab71f6071ca9cd82651ff66..1565d72b45583193f572968120f0abe08bbcfea8 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2019-12-03  Jakub Jelinek  <jakub@redhat.com>
+
+       PR c++/92695
+       * constexpr.c (cxx_bind_parameters_in_call): For virtual calls,
+       adjust the first argument to point to the derived object rather
+       than its base.
+
 2019-12-02  Jakub Jelinek  <jakub@redhat.com>
 
        PR c++/92695

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index cc3ef1056f2816a743a5533acec8892398de516e..39118200285c67c892a05fc0e1ebfa841abef7ed 100644 (file)
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1441,6 +1441,26 @@ cxx_bind_parameters_in_call (const constexpr_ctx *ctx, tree t,
            arg = adjust_temp_type (type, arg);
          if (!TREE_CONSTANT (arg))
            *non_constant_args = true;
+         /* For virtual calls, adjust the this argument, so that it is
+            the object on which the method is called, rather than
+            one of its bases.  */
+         if (i == 0 && DECL_VIRTUAL_P (fun))
+           {
+             tree addr = arg;
+             STRIP_NOPS (addr);
+             if (TREE_CODE (addr) == ADDR_EXPR)
+               {
+                 tree obj = TREE_OPERAND (addr, 0);
+                 while (TREE_CODE (obj) == COMPONENT_REF
+                        && DECL_FIELD_IS_BASE (TREE_OPERAND (obj, 1))
+                        && !same_type_ignoring_top_level_qualifiers_p
+                                       (TREE_TYPE (obj), DECL_CONTEXT (fun)))
+                   obj = TREE_OPERAND (obj, 0);
+                 if (obj != TREE_OPERAND (addr, 0))
+                   arg = build_fold_addr_expr_with_type (obj,
+                                                         TREE_TYPE (arg));
+               }
+           }
          TREE_VEC_ELT (binds, i) = arg;
        }
       parms = TREE_CHAIN (parms);

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 520581de661c21afaf9a0f938374cb57f6bc458f..edd1869f384bda1ed581883a31e6684adc7b5757 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-03  Jakub Jelinek  <jakub@redhat.com>
+
+       PR c++/92695
+       * g++.dg/cpp2a/constexpr-virtual14.C: New test.
+
 2019-12-03  Luo Xiong Hu  <luoxhu@linux.ibm.com>
 
        * gcc.target/powerpc/pr72804.c: Fix missing space.

diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual14.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual14.C
new file mode 100644 (file)
index 0000000..b29d3f6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual14.C
@@ -0,0 +1,27 @@
+// PR c++/92695
+// { dg-do compile { target c++2a } }
+
+struct A {
+  virtual int get () = 0;
+  virtual int set (A *o) = 0;
+};
+struct B : A {
+  constexpr int get () override { return 10; }
+  constexpr int set (A *o) override { a = o; return 20; }
+  A *a {};
+};
+constexpr auto addressof = [] (A &n) { return &n; };
+struct C {
+  B b;
+  A *c { addressof (b) };
+  constexpr int add () { return c->set (addressof (b)); }
+};
+struct D {
+  B b[2];
+  A *c { addressof (b[0]) };
+  constexpr int add () { return c->set (addressof (b[0])); }
+};
+template <typename T>
+constexpr int get () { T f; return f.add (); }
+static_assert (get<C> () == 20);
+static_assert (get<D> () == 20);