[PATCH] c++: ICE in TARGET_EXPR evaluation in cp_fold_r [PR117980]

[Marek Polacek]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
This ICE started with the recent prvalue optimization (r15-6052).  In
cp_fold_r we have:

      if (tree &init = TARGET_EXPR_INITIAL (stmt))
        {
          cp_walk_tree (&init, cp_fold_r, data, NULL);
          // ...
          tree folded = maybe_constant_init (init, TARGET_EXPR_SLOT (stmt));

What can happen here is that originally the TARGET_EXPR is:

    TARGET_EXPR <D.2747, <<< Unknown tree: aggr_init_expr
      5
      __ct_comp
      D.2747
      (struct subrange *) <<< Unknown tree: void_cst >>>
      &TARGET_EXPR <D.2707, {.it=TARGET_EXPR <D.2695, ...>}> >>>>

but after the first cp_walk_tree we fold the D.2707 TARGET_EXPR into:

    TARGET_EXPR <D.2707, <<< Unknown tree: expr_stmt
      D.2707.it = TARGET_EXPR <D.2695, ...> >>>>

and then we pass the EXPR_STMT to maybe_constant_init, with D.2707 as
the object.  But their types don't match anymore, so we crash.  We'd
have to pass D.2707.it as the object for it to work.

But I don't think we need to pass any object to maybe_constant_init;
it'll grab the appropriate one itself.

constexpr-prvalue3.C is reduced from a large std::ranges libstdc++ test.

        PR c++/117980

gcc/cp/ChangeLog:

        * cp-gimplify.cc (cp_fold_r) <case TARGET_EXPR>: Don't pass an object
        to maybe_constant_init.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/constexpr-prvalue2.C: New test.
        * g++.dg/cpp0x/constexpr-prvalue3.C: New test.
---
 gcc/cp/cp-gimplify.cc                         |  2 +-
 .../g++.dg/cpp0x/constexpr-prvalue2.C         | 15 +++++++++++
 .../g++.dg/cpp0x/constexpr-prvalue3.C         | 26 +++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue2.C
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue3.C

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index 623e2ee6e96..a861331c7c7 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -1477,7 +1477,7 @@ cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data_)
          *walk_subtrees = 0;
          if (!flag_no_inline)
            {
-             tree folded = maybe_constant_init (init, TARGET_EXPR_SLOT (stmt));
+             tree folded = maybe_constant_init (init);
              if (folded != init && TREE_CONSTANT (folded))
                init = folded;
            }
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue2.C 
b/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue2.C
new file mode 100644
index 00000000000..46053231cf8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue2.C
@@ -0,0 +1,15 @@
+// PR c++/117980
+// { dg-do compile { target c++11 } }
+// { dg-options "-O" }
+
+struct S {
+  constexpr S(S &); // { dg-warning "used but never defined" }
+  ~S();
+};
+struct B {
+  S s;
+};
+struct A {
+  B b;
+};
+void fn(B b) { A{b}; }
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue3.C 
b/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue3.C
new file mode 100644
index 00000000000..a2eb12c02d7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-prvalue3.C
@@ -0,0 +1,26 @@
+// PR c++/117980
+// { dg-do compile { target c++11 } }
+// { dg-options "-O" }
+
+struct _Safe_iterator  {
+ _Safe_iterator();
+  ~_Safe_iterator();
+};
+template <typename _Tp>
+struct vector {
+  vector(int) {}
+  constexpr _Safe_iterator end() {
+    return _Safe_iterator();
+  }
+};
+template <typename It> struct sentinel {
+  It it;
+};
+template <typename _Sent>
+struct subrange {
+  subrange(sentinel<_Safe_iterator>) {}
+};
+void test01() {
+  vector<int> v{0};
+  subrange<sentinel<_Safe_iterator>>{sentinel<_Safe_iterator>{v.end()}};
+}

base-commit: 2cbb2408a830a63fbd901a4da3bfd341cec4b6ef
-- 
2.47.1