On Thu, Mar 3, 2016 at 8:41 PM, Jason Merrill <ja...@redhat.com> wrote:
> When we instantiate an element of a pack expansion, we replace the argument
> pack in the template argument vec with an ARGUMENT_PACK_SELECT which
> indicates the desired element of the vec. If the args have been used to
> instantiate other templates as well, the args of those instances get
> modified as well, which can lead to strange results when we run into
> ARGUMENT_PACK_SELECT in inappropriate places. This patch fixes this issue
> by making a copy of the template args before we start messing with them.
...so we don't need to deal with ARGUMENT_PACK_SELECT in the hash
tables anymore.
commit b5cb8944e6feb6f4c53170c5d58bc50e4fa5503a
Author: Jason Merrill <ja...@redhat.com>
Date: Tue Jul 19 12:49:53 2016 -0400
PR c++/67164 - clean up dead code
* pt.c (iterative_hash_template_arg, template_args_equal): Don't
handle ARGUMENT_PACK_SELECT.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 916fd7b..7c7024c 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -1704,9 +1704,7 @@ iterative_hash_template_arg (tree arg, hashval_t val)
STRIP_NOPS (arg);
if (TREE_CODE (arg) == ARGUMENT_PACK_SELECT)
- /* We can get one of these when re-hashing a previous entry in the middle
- of substituting into a pack expansion. Just look through it. */
- arg = ARGUMENT_PACK_SELECT_FROM_PACK (arg);
+ gcc_unreachable ();
code = TREE_CODE (arg);
tclass = TREE_CODE_CLASS (code);
@@ -7894,17 +7892,7 @@ template_args_equal (tree ot, tree nt)
return 1;
}
else if (ot && TREE_CODE (ot) == ARGUMENT_PACK_SELECT)
- {
- /* We get here probably because we are in the middle of substituting
- into the pattern of a pack expansion. In that case the
- ARGUMENT_PACK_SELECT temporarily replaces the pack argument we are
- interested in. So we want to use the initial pack argument for
- the comparison. */
- ot = ARGUMENT_PACK_SELECT_FROM_PACK (ot);
- if (nt && TREE_CODE (nt) == ARGUMENT_PACK_SELECT)
- nt = ARGUMENT_PACK_SELECT_FROM_PACK (nt);
- return template_args_equal (ot, nt);
- }
+ gcc_unreachable ();
else if (TYPE_P (nt))
{
if (!TYPE_P (ot))
