[C++ PATCH] PR c++/86398

[Ville Voutilainen]

This has been buggy for a while, but since we were implementing
the library triviality traits in terms of just the intrinsic since GCC 8,
not too many users ran into it. The bug has been worked around
in the library, but I'd rather have the intrinsic give the right
answer and not require the library work-around.

Tested on Linux-PPC64, ok for trunk and the gcc-8 branch?

2018-07-04  Ville Voutilainen  <ville.voutilai...@gmail.com>

    gcc/cp/

    PR c++/86398
    * method.c (is_trivially_xible): Return false
    if is_xible_helper returns a NULL_TREE.

    testsuite/

    PR c++/86398
    * g++.dg/ext/is_trivially_constructible1.C: Add new tests.

diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index 858655b..0b208a8 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -1216,7 +1216,7 @@ is_trivially_xible (enum tree_code code, tree to, tree from)
   tree expr;
   expr = is_xible_helper (code, to, from, /*trivial*/true);
 
-  if (expr == error_mark_node)
+  if (expr == NULL_TREE || expr == error_mark_node)
     return false;
   tree nt = cp_walk_tree_without_duplicates (&expr, check_nontriv, NULL);
   return !nt;
diff --git a/gcc/testsuite/g++.dg/ext/is_trivially_constructible1.C b/gcc/testsuite/g++.dg/ext/is_trivially_constructible1.C
index 175eae9..191b696 100644
--- a/gcc/testsuite/g++.dg/ext/is_trivially_constructible1.C
+++ b/gcc/testsuite/g++.dg/ext/is_trivially_constructible1.C
@@ -39,6 +39,11 @@ SA(!__is_trivially_constructible(void,int));
 SA(!__is_trivially_constructible(const void,int));
 SA(!__is_trivially_constructible(volatile void,int));
 SA(!__is_trivially_constructible(const volatile void,int));
+SA(!__is_trivially_constructible(int, void*));
+SA(!__is_trivially_constructible(int, int*));
+SA(!__is_trivially_constructible(int, const int*));
+SA(!__is_trivially_constructible(int*, void*));
+SA(!__is_trivially_constructible(int*, const int*));
 
 SA(!__is_trivially_constructible(D));