On 7/19/23 14:05, Patrick Palka wrote:
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/13?
-- >8 --
Since the arguments 'pargs' passed to the coerce_template_parms from
coerce_template_template_parms are always a full set, we need to make sure
we always pass the parameters of the most general template because if the
template is partially instantiated then the levels won't match up.
Hmm, so then my comment "In that case we might end up adding more levels
than needed, but that shouldn't be a problem; any args we need to refer
to are at the right level." is wrong for auto template parms?
So I guess we likely need to do more to assure that pargs has the right
number of levels if there are autos in the innermost arg parms.
Also, most_general_template doesn't work for TTPs, so that probably
won't help handle their partial instantiations.
And is it right for an alias template in a partial specialization?
In the
testcase below during said call to coerce_template_parms the parameters
are {X, Y} both level 1, but the arguments are {{int}, {N, M}}, which
leads to a crash during auto deduction of X and Y.
PR c++/110566
Since this is a regression from the patch for PR c++/108179, please list
that PR here as well, to help avoid backporting that patch without this one.
gcc/cp/ChangeLog:
* pt.cc (coerce_template_template_parms): Simplify by using
DECL_INNERMOST_TEMPLATE_PARMS and removing redundant asserts.
Always pass the parameters of the most general template to
coerce_template_parms.
gcc/testsuite/ChangeLog:
* g++.dg/template/ttp38.C: New test.
---
gcc/cp/pt.cc | 12 +++++-------
gcc/testsuite/g++.dg/template/ttp38.C | 12 ++++++++++++
2 files changed, 17 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/template/ttp38.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index d882e9dd117..8723868823e 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -8073,12 +8073,10 @@ coerce_template_template_parms (tree parm_tmpl,
tree parm, arg;
int variadic_p = 0;
- tree parm_parms = INNERMOST_TEMPLATE_PARMS (DECL_TEMPLATE_PARMS (parm_tmpl));
- tree arg_parms_full = DECL_TEMPLATE_PARMS (arg_tmpl);
- tree arg_parms = INNERMOST_TEMPLATE_PARMS (arg_parms_full);
-
- gcc_assert (TREE_CODE (parm_parms) == TREE_VEC);
- gcc_assert (TREE_CODE (arg_parms) == TREE_VEC);
+ tree parm_parms = DECL_INNERMOST_TEMPLATE_PARMS (parm_tmpl);
+ tree arg_parms = DECL_INNERMOST_TEMPLATE_PARMS (arg_tmpl);
+ tree gen_arg_tmpl = most_general_template (arg_tmpl);
+ tree gen_arg_parms = DECL_INNERMOST_TEMPLATE_PARMS (gen_arg_tmpl);
nparms = TREE_VEC_LENGTH (parm_parms);
nargs = TREE_VEC_LENGTH (arg_parms);
@@ -8134,7 +8132,7 @@ coerce_template_template_parms (tree parm_tmpl,
scope_args = TI_ARGS (tinfo);
pargs = add_to_template_args (scope_args, pargs);
- pargs = coerce_template_parms (arg_parms, pargs, NULL_TREE, tf_none);
+ pargs = coerce_template_parms (gen_arg_parms, pargs, NULL_TREE, tf_none);
if (pargs != error_mark_node)
{
tree targs = make_tree_vec (nargs);
diff --git a/gcc/testsuite/g++.dg/template/ttp38.C
b/gcc/testsuite/g++.dg/template/ttp38.C
new file mode 100644
index 00000000000..7d25d291e81
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/ttp38.C
@@ -0,0 +1,12 @@
+// PR c++/110566
+// { dg-do compile { target c++20 } }
+
+template<template<int N, int M> class>
+struct A;
+
+template<class T>
+struct B {
+ template<int X, int Y> struct C;
+};
+
+using type = A<B<int>::C>;
