[PATCH] c++: Fix tsubst ICE with invalid static_cast [PR95728]

[Marek Polacek via Gcc-patches]

Since r11-423 tsubst_copy_and_build/TREE_LIST uses tsubst_tree_list
instead of open coding it.  While the latter could return an error
node wrapped in a TREE_LIST, the former can return a naked error node.

That broke in tsubst_copy_and_build/NEW_EXPR:
  tree placement = RECUR (TREE_OPERAND (t, 0));
  // placement is now error_mark_node, so...
  for (; placement != NULL_TREE; placement = TREE_CHAIN (placement))
  // ... this crashes

If we just return, we avoid the ICE and improve the diagnostic a bit.

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

gcc/cp/ChangeLog:

        PR c++/95728
        * pt.c (tsubst_copy_and_build) <case NEW_EXPR>: Return error_mark_node
        if placement is erroneous.

gcc/testsuite/ChangeLog:

        PR c++/95728
        * g++.dg/template/cast6.C: New test.
---
 gcc/cp/pt.c                           |  2 ++
 gcc/testsuite/g++.dg/template/cast6.C | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/template/cast6.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 07b9956c6b0..9732e3b78c7 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -19633,6 +19633,8 @@ tsubst_copy_and_build (tree t,
 
        if (placement == NULL_TREE)
          placement_vec = NULL;
+       else if (placement == error_mark_node)
+         RETURN (error_mark_node);
        else
          {
            placement_vec = make_tree_vector ();
diff --git a/gcc/testsuite/g++.dg/template/cast6.C 
b/gcc/testsuite/g++.dg/template/cast6.C
new file mode 100644
index 00000000000..743eadaa5dd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/cast6.C
@@ -0,0 +1,19 @@
+// PR c++/95728
+
+template<typename T>
+  void
+  construct(T* p)
+  { ::new(static_cast<void*>(p)) T; } // { dg-error "invalid .static_cast." }
+
+template<typename T>
+void
+f(const T* t)
+{
+  construct(t);
+}
+
+int main()
+{
+  int i[1];
+  f(i);
+}

base-commit: 4f2ab6b89e170f1343f935761481c3745fe603b1
-- 
Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA