[PATCH] Fix PR c++/30044

[PATCH] Fix PR c++/30044

[Patrick Palka]

The crux of the issue causing PR 30044 is that, in the middle of
processing a template parameter list, current_template_parms is not
up-to-date.  This causes problems particularly when we attempt to
instantiate a type that's defined within the very parameter list we are
processing.  Of course, more details to follow...

When processing the default template argument C<1> in (this is not the
reproducer in the PR but it better exhibits the same problem)

  template <class A, class B, template <B> class C, class D = C<1> >
  struct Z { };

we try to "instantiate" B with itself before the parameter list that B
resides has been finished.  At that point B is not even in
current_template_parms because we only update current_template_parms
when the entire parameter list is finished.  So when tsubst gets called
on B with an incomplete template argument list (because
current_template_parms hasn't been updated), tsubst ICEs with an
out-of-bounds error when trying to look up the template argument to
substitute for B, which has level=1 and index=1.

[ Note that we don't ICE for the similar test case

    template <class B, template <B> class C, class D = C<1> >
    struct Z { };

  because of a hack in template_parms_to_args() to add a dummy argument
  corresponding to level=1 and index=0 in the template argument list of a
  template template.  Here tsubst() has to look up the argument
  corresponding to B, which now has level=1 and index=0.  The lookup
  succeeds (returning NULL_TREE) and tsubst proceeds. ]

To fix this PR, this patch attempts to more frequently update
current_template_parms.  Instead of updating current_template_parms only
after the whole parameter list has been processed, this patch makes
current_template_parms get updated as soon as each template parameter is
processed.

Aside from directly fixing the PR, this approach allows us to remove two
now-obsolete hacks (there may be more) which attempted to work around
this delay in updating.  One hack is in the aforementioned
template_parms_to_args() and another is in splite_lat_return_type().

As a plus, we now detect shadowing of template variables across nested
template parameter lists, e.g.

   template <typename T, template <typename T> class> struct A { };

and now we no longer bogusly error out on late-specified return types
inside nested template parameter lists:

    template <template <auto f()->int> class> struct A { };

[ We can't use vec_grow() (which uses ggc_realloc()) to update
  current_template_parms because of sharing issues that I haven't
  investigated deeply.  ]

[ In check_default_tmpl_args we now have to account for nested template
  parameter lists the same way we account for template class depth, so
  that we don't inspect default template args not belonging to the nested
  parameter list we just finished.  last_level_to_check now defaults to 1
  instead of 0 since template "level"s are 1-based anyway.  ]

Does this approach make sense?

OK to install after bootstrap + regtesting succeeds?

gcc/cp/ChangeLog:

	* parser.c (cp_parser_template_parameter_list): Update
	current_template_parms right after processing a paramater.
	* pt.c (template_parms_to_args): Remove obsolete hack for
	giving template template arguments the proper level.
	(check_default_tmpl_args): Account for tested template
	parameter_lists.
	(splite_late_return_type): Remove obsolete hack for giving
	template template arguments the proper level.

gcc/testsuite/ChangeLog

	* g++.dg/cpp0x/auto45.C: New test.
	* g++.dg/template/pr30044.C: New test.
	* g++.dg/template/crash83.C: Accept any error string.
	* g++.dg/cpp0x/variadic18.C: Adjust to not shadow template
	parameters.
	* g++.dg/cpp0x/variadic18.C: Likewise
	* g++.dg/template/canon-type-13.C: Likewise.
	* g++.old-deja/g++.pt/ttp42.C: Likewise.
---
 gcc/cp/parser.c                               | 25 ++++++++++++++++++++
 gcc/cp/pt.c                                   | 33 ++++++++-------------------
 gcc/testsuite/g++.dg/cpp0x/auto45.C           |  5 ++++
 gcc/testsuite/g++.dg/cpp0x/variadic18.C       |  2 +-
 gcc/testsuite/g++.dg/cpp0x/variadic19.C       |  2 +-
 gcc/testsuite/g++.dg/template/canon-type-13.C |  2 +-
 gcc/testsuite/g++.dg/template/crash83.C       |  2 +-
 gcc/testsuite/g++.dg/template/pr30044.C       | 14 ++++++++++++
 gcc/testsuite/g++.old-deja/g++.pt/ttp42.C     |  2 +-
 9 files changed, 58 insertions(+), 29 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/auto45.C
 create mode 100644 gcc/testsuite/g++.dg/template/pr30044.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 5fdb2a7..d0a3c09 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -13259,6 +13259,11 @@ cp_parser_template_parameter_list (cp_parser* parser)
 
   begin_template_parm_list ();
 
+  current_template_parms
+    = tree_cons (size_int (processing_template_decl),
+		 make_tree_vec (0),
+		 current_template_parms);
+
   /* The loop below parses the template parms.  We first need to know
      the total number of template parms to be able to compute proper
      canonical types of each dependent type. So after the loop, when
@@ -13271,6 +13276,7 @@ cp_parser_template_parameter_list (cp_parser* parser)
       bool is_non_type;
       bool is_parameter_pack;
       location_t parm_loc;
+      tree parameter_vec;
 
       /* Parse the template-parameter.  */
       parm_loc = cp_lexer_peek_token (parser->lexer)->location;
@@ -13295,8 +13301,27 @@ cp_parser_template_parameter_list (cp_parser* parser)
 	break;
       /* Otherwise, consume the `,' token.  */
       cp_lexer_consume_token (parser->lexer);
+
+      /* Add the parameter we just processed to current_template_parms.  */
+
+      parameter_vec = make_tree_vec
+	(TREE_VEC_LENGTH (TREE_VALUE (current_template_parms)) + 1);
+
+      for (int i = 0; i < TREE_VEC_LENGTH (parameter_vec) - 1; i++)
+	TREE_VEC_ELT (parameter_vec, i)
+	  = TREE_VEC_ELT (TREE_VALUE (current_template_parms), i);
+
+      TREE_VEC_ELT (parameter_vec, TREE_VEC_LENGTH (parameter_vec) - 1)
+	= tree_last (parameter_list);
+
+      current_template_parms
+	= tree_cons (TREE_PURPOSE (current_template_parms),
+		     parameter_vec,
+		     TREE_CHAIN (current_template_parms));
     }
 
+  current_template_parms = TREE_CHAIN (current_template_parms);
+
   return end_template_parm_list (parameter_list);
 }
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 7f04fe6..d1eb833 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -3990,21 +3990,6 @@ template_parms_to_args (tree parms)
 	args = a;
     }
 
-    if (length > 1 && TREE_VEC_ELT (args, 0) == NULL_TREE)
-      /* This can happen for template parms of a template template
-	 parameter, e.g:
-
-	 template<template<class T, class U> class TT> struct S;
-
-	 Consider the level of the parms of TT; T and U both have
-	 level 2; TT has no template parm of level 1. So in this case
-	 the first element of full_template_args is NULL_TREE. If we
-	 leave it like this TMPL_ARGS_DEPTH on args returns 1 instead
-	 of 2. This will make tsubst wrongly consider that T and U
-	 have level 1. Instead, let's create a dummy vector as the
-	 first element of full_template_args so that TMPL_ARGS_DEPTH
-	 returns the correct depth for args.  */
-      TREE_VEC_ELT (args, 0) = make_tree_vec (1);
   return args;
 }
 
@@ -4647,6 +4632,9 @@ check_default_tmpl_args (tree decl, tree parms, bool is_primary,
   else
     msg = G_("default argument for template parameter for class enclosing %qD");
 
+  /* By default check everything.  */
+  last_level_to_check = 1;
+
   if (current_class_type && TYPE_BEING_DEFINED (current_class_type))
     /* If we're inside a class definition, there's no need to
        examine the parameters to the class itself.  On the one
@@ -4656,10 +4644,12 @@ check_default_tmpl_args (tree decl, tree parms, bool is_primary,
 	 struct S { template <class U> void f(U); };
        Here the default argument for `S' has no bearing on the
        declaration of `f'.  */
-    last_level_to_check = template_class_depth (current_class_type) + 1;
-  else
-    /* Check everything.  */
-    last_level_to_check = 0;
+    last_level_to_check += template_class_depth (current_class_type);
+
+  if (processing_template_parmlist)
+    /* Likewise for parameters outside of the nested parameter list we have
+       just finished defining.  */
+    last_level_to_check += processing_template_parmlist;
 
   for (parm_level = parms;
        parm_level && TMPL_PARMS_DEPTH (parm_level) >= last_level_to_check;
@@ -22348,11 +22338,6 @@ splice_late_return_type (tree type, tree late_return_type)
     return type;
   argvec = make_tree_vec (1);
   TREE_VEC_ELT (argvec, 0) = late_return_type;
-  if (processing_template_parmlist)
-    /* For a late-specified return type in a template type-parameter, we
-       need to add a dummy argument level for its parmlist.  */
-    argvec = add_to_template_args
-      (make_tree_vec (processing_template_parmlist), argvec);
   if (current_template_parms)
     argvec = add_to_template_args (current_template_args (), argvec);
   return tsubst (type, argvec, tf_warning_or_error, NULL_TREE);
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto45.C b/gcc/testsuite/g++.dg/cpp0x/auto45.C
new file mode 100644
index 0000000..5f539a2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto45.C
@@ -0,0 +1,5 @@
+// Addendum to auto23.C, now with nested template parameter lists
+// { dg-do compile { target c++11 } }
+
+template<template <auto f()->int> class> struct A { };
+template<template <template <auto f()->int> class> class> struct A { };
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic18.C b/gcc/testsuite/g++.dg/cpp0x/variadic18.C
index fc0e2dd..57fdc86 100644
--- a/gcc/testsuite/g++.dg/cpp0x/variadic18.C
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic18.C
@@ -1,7 +1,7 @@
 // { dg-do compile { target c++11 } }
 template<typename...> class tuple { };
 
-template<typename T, template<typename T> class... Metafunctions>
+template<typename T, template<typename U> class... Metafunctions>
 struct apply_all
 {
   typedef tuple<typename Metafunctions<T>::type...> type;
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic19.C b/gcc/testsuite/g++.dg/cpp0x/variadic19.C
index 0ae2672..3be9bb0 100644
--- a/gcc/testsuite/g++.dg/cpp0x/variadic19.C
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic19.C
@@ -4,7 +4,7 @@ struct tuple {
   static const int value = 0;
 };
 
-template<typename T, template<class T> class... Metafunctions>
+template<typename T, template<class U> class... Metafunctions>
 struct tuple<Metafunctions<T>...> {
   static const int value = 1;
 };
diff --git a/gcc/testsuite/g++.dg/template/canon-type-13.C b/gcc/testsuite/g++.dg/template/canon-type-13.C
index 4f3702b..5a8d37d 100644
--- a/gcc/testsuite/g++.dg/template/canon-type-13.C
+++ b/gcc/testsuite/g++.dg/template/canon-type-13.C
@@ -11,7 +11,7 @@ struct S1
 {
 };
 
-template<class T, template<class T>  class A, template<class T>  class B = A>
+template<class T, template<class U>  class A, template<class U>  class B = A>
 struct C
 {
   B<T> m;
diff --git a/gcc/testsuite/g++.dg/template/crash83.C b/gcc/testsuite/g++.dg/template/crash83.C
index b83dd21..7dcbed9 100644
--- a/gcc/testsuite/g++.dg/template/crash83.C
+++ b/gcc/testsuite/g++.dg/template/crash83.C
@@ -2,4 +2,4 @@
 
 template<int> struct A {};
 
-template<typename = class A<0>: > struct B {}; // { dg-error "explicit specialization|expected" }
+template<typename = class A<0>: > struct B {}; // { dg-error "" }
diff --git a/gcc/testsuite/g++.dg/template/pr30044.C b/gcc/testsuite/g++.dg/template/pr30044.C
new file mode 100644
index 0000000..c1d0d29
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/pr30044.C
@@ -0,0 +1,14 @@
+template <typename T1, typename T2, template <T2> class Comp, class Result = Comp<1> >
+struct sort { };
+
+
+template <typename Type, template <Type, Type> class Comp, class Result = Comp<1, 2> >
+struct sort2 { };
+
+template <typename Type, template <int, Type> class Comp, class Result = Comp<1, 2> >
+struct sort3 { };
+
+template <template <typename T1, typename T2, template <T2> class Comp, class Result = Comp<1> > class Foo>
+struct sort4 { };
+
+
diff --git a/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C b/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
index 53bdae1..a2ac239 100644
--- a/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
+++ b/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
@@ -1,5 +1,5 @@
 // { dg-do run  }
-template <class T, template <class T> class C>
+template <class T, template <class U> class C>
 struct X
 {};
 
-- 
2.4.3.413.ga5fe668

Re: [PATCH] Fix PR c++/30044

[Jason Merrill]

On 06/11/2015 09:25 PM, Patrick Palka wrote:
> +      parameter_vec = make_tree_vec
> +	(TREE_VEC_LENGTH (TREE_VALUE (current_template_parms)) + 1);
> +
> +      for (int i = 0; i < TREE_VEC_LENGTH (parameter_vec) - 1; i++)
> +	TREE_VEC_ELT (parameter_vec, i)
> +	  = TREE_VEC_ELT (TREE_VALUE (current_template_parms), i);
> +
> +      TREE_VEC_ELT (parameter_vec, TREE_VEC_LENGTH (parameter_vec) - 1)
> +	= tree_last (parameter_list);

Any reason not to use grow_tree_vec?

Re: [PATCH] Fix PR c++/30044

[Patrick Palka]

On Mon, Jun 15, 2015 at 2:05 PM, Jason Merrill <jason@redhat.com> wrote:
> On 06/11/2015 09:25 PM, Patrick Palka wrote:
>>
>> +      parameter_vec = make_tree_vec
>> +       (TREE_VEC_LENGTH (TREE_VALUE (current_template_parms)) + 1);
>> +
>> +      for (int i = 0; i < TREE_VEC_LENGTH (parameter_vec) - 1; i++)
>> +       TREE_VEC_ELT (parameter_vec, i)
>> +         = TREE_VEC_ELT (TREE_VALUE (current_template_parms), i);
>> +
>> +      TREE_VEC_ELT (parameter_vec, TREE_VEC_LENGTH (parameter_vec) - 1)
>> +       = tree_last (parameter_list);
>
>
> Any reason not to use grow_tree_vec?

Doing so causes a lot of ICEs in the testsuite.  I think it's because
grow_tree_vec invalidates the older parameter_vec which some trees may
still be holding a reference to in their DECL_TEMPLATE_PARMS field.

>
>

Re: [PATCH] Fix PR c++/30044

[Jason Merrill]

On 06/15/2015 02:32 PM, Patrick Palka wrote:
> On Mon, Jun 15, 2015 at 2:05 PM, Jason Merrill <jason@redhat.com> wrote:
>> Any reason not to use grow_tree_vec?
>
> Doing so causes a lot of ICEs in the testsuite.  I think it's because
> grow_tree_vec invalidates the older parameter_vec which some trees may
> still be holding a reference to in their DECL_TEMPLATE_PARMS field.

Hmm, that's unfortunate, as doing it this way means we get a bunch of 
garbage TREE_VECs in the process.  But I guess the patch is OK as is.

Jason

Re: [PATCH] Fix PR c++/30044

[Patrick Palka]

On Tue, Jun 23, 2015 at 12:38 AM, Jason Merrill <jason@redhat.com> wrote:
> On 06/15/2015 02:32 PM, Patrick Palka wrote:
>>
>> On Mon, Jun 15, 2015 at 2:05 PM, Jason Merrill <jason@redhat.com> wrote:
>>>
>>> Any reason not to use grow_tree_vec?
>>
>>
>> Doing so causes a lot of ICEs in the testsuite.  I think it's because
>> grow_tree_vec invalidates the older parameter_vec which some trees may
>> still be holding a reference to in their DECL_TEMPLATE_PARMS field.
>
>
> Hmm, that's unfortunate, as doing it this way means we get a bunch of
> garbage TREE_VECs in the process.  But I guess the patch is OK as is.

Yeah, though I can't think of a simple way to work around this -- any
solution I think of seems to require a change in the representation of
current_template_parms, something that would be quite invasive....
Will commit the patch shortly.

>
> Jason
>

Re: [PATCH] Fix PR c++/30044

[Markus Trippelsdorf]

[-- Attachment #1: Type: text/plain, Size: 1527 bytes --]

On 2015.06.23 at 19:40 -0400, Patrick Palka wrote:
> On Tue, Jun 23, 2015 at 12:38 AM, Jason Merrill <jason@redhat.com> wrote:
> > On 06/15/2015 02:32 PM, Patrick Palka wrote:
> >>
> >> On Mon, Jun 15, 2015 at 2:05 PM, Jason Merrill <jason@redhat.com> wrote:
> >>>
> >>> Any reason not to use grow_tree_vec?
> >>
> >>
> >> Doing so causes a lot of ICEs in the testsuite.  I think it's because
> >> grow_tree_vec invalidates the older parameter_vec which some trees may
> >> still be holding a reference to in their DECL_TEMPLATE_PARMS field.
> >
> >
> > Hmm, that's unfortunate, as doing it this way means we get a bunch of
> > garbage TREE_VECs in the process.  But I guess the patch is OK as is.
> 
> Yeah, though I can't think of a simple way to work around this -- any
> solution I think of seems to require a change in the representation of
> current_template_parms, something that would be quite invasive....
> Will commit the patch shortly.

Your patch causes LLVM build to hang on the attached testcase. (I killed
gcc after ~10 minutes compile time.)

perf shows:
  23.03%  cc1plus  cc1plus              [.] comp_template_parms
  19.41%  cc1plus  cc1plus              [.] structural_comptypes
  16.28%  cc1plus  cc1plus              [.] cp_type_quals
  15.89%  cc1plus  cc1plus              [.] comp_template_parms_position
  14.01%  cc1plus  cc1plus              [.] comp_type_attributes
   6.58%  cc1plus  cc1plus              [.] comptypes
...

To reproduce just run:
 g++ -c -O3 -std=c++11 gtest-all.ii

-- 
Markus

[-- Attachment #2: gtest-all.ii.bz2 --]
[-- Type: application/x-bzip2, Size: 262490 bytes --]

Re: [PATCH] Fix PR c++/30044

[Patrick Palka]

On Wed, Jun 24, 2015 at 5:08 AM, Markus Trippelsdorf
<markus@trippelsdorf.de> wrote:
> On 2015.06.23 at 19:40 -0400, Patrick Palka wrote:
>> On Tue, Jun 23, 2015 at 12:38 AM, Jason Merrill <jason@redhat.com> wrote:
>> > On 06/15/2015 02:32 PM, Patrick Palka wrote:
>> >>
>> >> On Mon, Jun 15, 2015 at 2:05 PM, Jason Merrill <jason@redhat.com> wrote:
>> >>>
>> >>> Any reason not to use grow_tree_vec?
>> >>
>> >>
>> >> Doing so causes a lot of ICEs in the testsuite.  I think it's because
>> >> grow_tree_vec invalidates the older parameter_vec which some trees may
>> >> still be holding a reference to in their DECL_TEMPLATE_PARMS field.
>> >
>> >
>> > Hmm, that's unfortunate, as doing it this way means we get a bunch of
>> > garbage TREE_VECs in the process.  But I guess the patch is OK as is.
>>
>> Yeah, though I can't think of a simple way to work around this -- any
>> solution I think of seems to require a change in the representation of
>> current_template_parms, something that would be quite invasive....
>> Will commit the patch shortly.
>
> Your patch causes LLVM build to hang on the attached testcase. (I killed
> gcc after ~10 minutes compile time.)
>
> perf shows:
>   23.03%  cc1plus  cc1plus              [.] comp_template_parms
>   19.41%  cc1plus  cc1plus              [.] structural_comptypes
>   16.28%  cc1plus  cc1plus              [.] cp_type_quals
>   15.89%  cc1plus  cc1plus              [.] comp_template_parms_position
>   14.01%  cc1plus  cc1plus              [.] comp_type_attributes
>    6.58%  cc1plus  cc1plus              [.] comptypes
> ...
>
> To reproduce just run:
>  g++ -c -O3 -std=c++11 gtest-all.ii

Thanks.  I don't think infinite recursion is going on.  Rather, it
seems that this patch causes a quadratic slowdown (in the number of
template template parameters in a parameter list and in the number of
partial specializations of a template) in the structural_comptypes ->
comp_template_parms -> comptypes loop when comparing two
TEMPLATE_TEMPLATE_PARMs to find the canonical template template
parameter of a partial specialization.  The test case has a good
amount of mechanical partial specializations of templates with big
parameter lists containing lots of template template parameters so
it's very sensitive to this quadratic slowdown.

To compare two template template parameters for structural equality,
structural_comptypes must compare their DECL_TEMPLATE_PARMS for
structural equality.  Since the patch gives the DECL_TEMPLATE_PARMS
field a level containing all previously declared template parameters
in the parameter list it's defined in, this comparison becomes
recursive and quadratic if all the parameters of the template are
template template parameters which is what the test has starting at
line 48518.

In the meantime I will revert this patch since I won't be able to find
a solution in time.

What should be done about the PR?  I suppose I should reopen it...

>
> --
> Markus

[PATCH] Fix PR c++/30044

[Patrick Palka]

Here is a more modest approach to fixing this PR.  Instead of updating
current_template_parms with each newly processed template parameter,
this patch just updates it with a "dummy" parameter level once per
parameter list.  So now in tsubst(), to fix the reported ICE we just
have to avoid substituting a template parameter if it corresponds to an
empty "dummy" argument level.

One caveat with this approach is that since template template decls will
now have dummy parameter levels in their DECL_TEMPLATE_PARMS fields, we
have to avoid emitting such dummy levels inside error messages when
printing template template parameters.  Otherwise the parameter B in

  template<template<class A> class B> struct Foo { };

would get printed in error messages as

  template<> template <class A> class B>

Two new test files are added in this version: shadow2.C, which checks
that we emit a shadowing error for identical template parameter names
across nested parameter lists, and error55.C, which checks that we
correctly emit template template decls in error messages.

With this approach the test case provided by Markus no longer takes
forever to compile because the added parameter lists are always empty so
when doing structural type comparison of a TEMPLATE_TEMPLATE_PARM there
is nothing extra to recurse into.

Does this approach seem sensible?

gcc/cp/ChangeLog:

	PR c++/30044
	* pt.c (begin_template_parm_list): Add a dummy parameter level
	to current_template_parms.
	(end_template_parm_list): Remove the dummy parameter level
	before adding the real one.
	(tsubst): Don't attempt to substitute for template parameters
	corresponding to a dummy argument level.
	(template_parms_to_args): Remove obsolete hack for
	giving template template arguments the proper level.
	(splite_late_return_type): Remove obsolete hack for giving
	template template arguments the proper level.
	* error.c (dump_template_decl): Don't print dummy template
	levels.

gcc/testsuite/ChangeLog

	PR c++/30044
	* g++.dg/cpp0x/auto45.C: New test.
	* g++.dg/template/pr30044.C: New test.
	* g++.dg/template/shadow2.C: New test.
	* g++.dg/template/error55.C: New test.
	* g++.dg/template/crash83.C: Accept any error string.
	* g++.dg/cpp0x/variadic18.C: Adjust to avoid shadowing template
	parameters.
	* g++.dg/cpp0x/variadic18.C: Likewise
	* g++.dg/template/canon-type-13.C: Likewise.
	* g++.old-deja/g++.pt/ttp42.C: Likewise.
	* g++.dg/torture/20070621-1.C: Likewise.
---
 gcc/cp/error.c                                |  7 ++++++
 gcc/cp/pt.c                                   | 32 +++++++++------------------
 gcc/testsuite/g++.dg/cpp0x/auto45.C           |  5 +++++
 gcc/testsuite/g++.dg/cpp0x/variadic18.C       |  2 +-
 gcc/testsuite/g++.dg/cpp0x/variadic19.C       |  2 +-
 gcc/testsuite/g++.dg/template/canon-type-13.C |  2 +-
 gcc/testsuite/g++.dg/template/crash83.C       |  2 +-
 gcc/testsuite/g++.dg/template/error55.C       |  8 +++++++
 gcc/testsuite/g++.dg/template/pr30044.C       | 14 ++++++++++++
 gcc/testsuite/g++.dg/template/shadow2.C       |  3 +++
 gcc/testsuite/g++.dg/torture/20070621-1.C     |  2 +-
 gcc/testsuite/g++.old-deja/g++.pt/ttp42.C     |  2 +-
 12 files changed, 54 insertions(+), 27 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/auto45.C
 create mode 100644 gcc/testsuite/g++.dg/template/error55.C
 create mode 100644 gcc/testsuite/g++.dg/template/pr30044.C
 create mode 100644 gcc/testsuite/g++.dg/template/shadow2.C

diff --git a/gcc/cp/error.c b/gcc/cp/error.c
index 96fa94d..b21befe 100644
--- a/gcc/cp/error.c
+++ b/gcc/cp/error.c
@@ -1296,6 +1296,13 @@ dump_template_decl (cxx_pretty_printer *pp, tree t, int flags)
 	  tree inner_parms = INNERMOST_TEMPLATE_PARMS (parms);
 	  int len = TREE_VEC_LENGTH (inner_parms);
 
+	  if (len == 0)
+	    {
+	      /* Skip over the dummy template levels of a template template parm.  */
+	      gcc_assert (TREE_CODE (TREE_TYPE (t)) == TEMPLATE_TEMPLATE_PARM);
+	      continue;
+	    }
+
 	  pp_cxx_ws_string (pp, "template");
 	  pp_cxx_begin_template_argument_list (pp);
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index fe5fc14..e7c35d3 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -658,6 +658,12 @@ begin_template_parm_list (void)
   ++processing_template_decl;
   ++processing_template_parmlist;
   note_template_header (0);
+
+  /* Add a dummy parameter level while we process the parameter list.  */
+  current_template_parms
+    = tree_cons (size_int (processing_template_decl),
+		 make_tree_vec (0),
+		 current_template_parms);
 }
 
 /* This routine is called when a specialization is declared.  If it is
@@ -3854,6 +3860,9 @@ end_template_parm_list (tree parms)
   tree parm, next;
   tree saved_parmlist = make_tree_vec (list_length (parms));
 
+  /* Pop the dummy parameter level and add the real one.  */
+  current_template_parms = TREE_CHAIN (current_template_parms);
+
   current_template_parms
     = tree_cons (size_int (processing_template_decl),
 		 saved_parmlist, current_template_parms);
@@ -3989,21 +3998,6 @@ template_parms_to_args (tree parms)
 	args = a;
     }
 
-    if (length > 1 && TREE_VEC_ELT (args, 0) == NULL_TREE)
-      /* This can happen for template parms of a template template
-	 parameter, e.g:
-
-	 template<template<class T, class U> class TT> struct S;
-
-	 Consider the level of the parms of TT; T and U both have
-	 level 2; TT has no template parm of level 1. So in this case
-	 the first element of full_template_args is NULL_TREE. If we
-	 leave it like this TMPL_ARGS_DEPTH on args returns 1 instead
-	 of 2. This will make tsubst wrongly consider that T and U
-	 have level 1. Instead, let's create a dummy vector as the
-	 first element of full_template_args so that TMPL_ARGS_DEPTH
-	 returns the correct depth for args.  */
-      TREE_VEC_ELT (args, 0) = make_tree_vec (1);
   return args;
 }
 
@@ -12029,7 +12023,8 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	template_parm_level_and_index (t, &level, &idx); 
 
 	levels = TMPL_ARGS_DEPTH (args);
-	if (level <= levels)
+	if (level <= levels
+	    && TREE_VEC_LENGTH (TMPL_ARGS_LEVEL (args, level)) > 0)
 	  {
 	    arg = TMPL_ARG (args, level, idx);
 
@@ -22394,11 +22389,6 @@ splice_late_return_type (tree type, tree late_return_type)
     return type;
   argvec = make_tree_vec (1);
   TREE_VEC_ELT (argvec, 0) = late_return_type;
-  if (processing_template_parmlist)
-    /* For a late-specified return type in a template type-parameter, we
-       need to add a dummy argument level for its parmlist.  */
-    argvec = add_to_template_args
-      (make_tree_vec (processing_template_parmlist), argvec);
   if (current_template_parms)
     argvec = add_to_template_args (current_template_args (), argvec);
   return tsubst (type, argvec, tf_warning_or_error, NULL_TREE);
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto45.C b/gcc/testsuite/g++.dg/cpp0x/auto45.C
new file mode 100644
index 0000000..09e9f44
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto45.C
@@ -0,0 +1,5 @@
+// Addendum to auto23.C, now with nested template parameter lists
+// { dg-do compile { target c++11 } }
+
+template<template <auto f()->int> class> struct A { };
+template<template <template <auto f()->int> class> class> struct B { };
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic18.C b/gcc/testsuite/g++.dg/cpp0x/variadic18.C
index fc0e2dd..57fdc86 100644
--- a/gcc/testsuite/g++.dg/cpp0x/variadic18.C
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic18.C
@@ -1,7 +1,7 @@
 // { dg-do compile { target c++11 } }
 template<typename...> class tuple { };
 
-template<typename T, template<typename T> class... Metafunctions>
+template<typename T, template<typename U> class... Metafunctions>
 struct apply_all
 {
   typedef tuple<typename Metafunctions<T>::type...> type;
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic19.C b/gcc/testsuite/g++.dg/cpp0x/variadic19.C
index 0ae2672..3be9bb0 100644
--- a/gcc/testsuite/g++.dg/cpp0x/variadic19.C
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic19.C
@@ -4,7 +4,7 @@ struct tuple {
   static const int value = 0;
 };
 
-template<typename T, template<class T> class... Metafunctions>
+template<typename T, template<class U> class... Metafunctions>
 struct tuple<Metafunctions<T>...> {
   static const int value = 1;
 };
diff --git a/gcc/testsuite/g++.dg/template/canon-type-13.C b/gcc/testsuite/g++.dg/template/canon-type-13.C
index 4f3702b..5a8d37d 100644
--- a/gcc/testsuite/g++.dg/template/canon-type-13.C
+++ b/gcc/testsuite/g++.dg/template/canon-type-13.C
@@ -11,7 +11,7 @@ struct S1
 {
 };
 
-template<class T, template<class T>  class A, template<class T>  class B = A>
+template<class T, template<class U>  class A, template<class U>  class B = A>
 struct C
 {
   B<T> m;
diff --git a/gcc/testsuite/g++.dg/template/crash83.C b/gcc/testsuite/g++.dg/template/crash83.C
index b83dd21..7dcbed9 100644
--- a/gcc/testsuite/g++.dg/template/crash83.C
+++ b/gcc/testsuite/g++.dg/template/crash83.C
@@ -2,4 +2,4 @@
 
 template<int> struct A {};
 
-template<typename = class A<0>: > struct B {}; // { dg-error "explicit specialization|expected" }
+template<typename = class A<0>: > struct B {}; // { dg-error "" }
diff --git a/gcc/testsuite/g++.dg/template/error55.C b/gcc/testsuite/g++.dg/template/error55.C
new file mode 100644
index 0000000..41f9595
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/error55.C
@@ -0,0 +1,8 @@
+// Check that template template parameters get printed properly in error
+// messages.
+
+template <template <class A> class B>
+struct Y
+{
+  B<5> y;  // { dg-error "for 'template<class A> class B'" }
+};
diff --git a/gcc/testsuite/g++.dg/template/pr30044.C b/gcc/testsuite/g++.dg/template/pr30044.C
new file mode 100644
index 0000000..415e6f0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/pr30044.C
@@ -0,0 +1,14 @@
+// PR c++/30044
+
+template <typename T1, typename T2, template <T2> class Comp, class Result = Comp<1> >
+struct sort { };
+
+
+template <typename Type, template <Type, Type> class Comp, class Result = Comp<1, 2> >
+struct sort2 { };
+
+template <typename Type, template <int, Type> class Comp, class Result = Comp<1, 2> >
+struct sort3 { };
+
+template <template <typename T1, typename T2, template <T2> class Comp, class Result = Comp<1> > class Foo>
+struct sort4 { };
diff --git a/gcc/testsuite/g++.dg/template/shadow2.C b/gcc/testsuite/g++.dg/template/shadow2.C
new file mode 100644
index 0000000..7f6a6dc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/shadow2.C
@@ -0,0 +1,3 @@
+template <class A, // { dg-error "shadows template parm 'class A'" }
+          template <class A> class B> // { dg-error "declaration of 'class A'" }
+class X;
diff --git a/gcc/testsuite/g++.dg/torture/20070621-1.C b/gcc/testsuite/g++.dg/torture/20070621-1.C
index 15d1ac7..9bd8cc3 100644
--- a/gcc/testsuite/g++.dg/torture/20070621-1.C
+++ b/gcc/testsuite/g++.dg/torture/20070621-1.C
@@ -89,7 +89,7 @@ namespace __gnu_test {
         SharedInfo->first=ptr;
       }
     };
-    template <class T, template<class T> class ItType>   struct test_container   {
+    template <class T, template<class U> class ItType>   struct test_container   {
       typename ItType<T>::ContainerType bounds;
       test_container(T* _first, T* _last):bounds(_first, _last)     {
   }
diff --git a/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C b/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
index 53bdae1..a2ac239 100644
--- a/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
+++ b/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
@@ -1,5 +1,5 @@
 // { dg-do run  }
-template <class T, template <class T> class C>
+template <class T, template <class U> class C>
 struct X
 {};
 
-- 
2.5.0.rc0.5.g91e10c5.dirty

Re: [PATCH] Fix PR c++/30044

[Patrick Palka]

On Fri, Jun 26, 2015 at 7:40 AM, Patrick Palka <patrick@parcs.ath.cx> wrote:
> Here is a more modest approach to fixing this PR.  Instead of updating
> current_template_parms with each newly processed template parameter,
> this patch just updates it with a "dummy" parameter level once per
> parameter list.  So now in tsubst(), to fix the reported ICE we just
> have to avoid substituting a template parameter if it corresponds to an
> empty "dummy" argument level.
>
> One caveat with this approach is that since template template decls will
> now have dummy parameter levels in their DECL_TEMPLATE_PARMS fields, we
> have to avoid emitting such dummy levels inside error messages when
> printing template template parameters.  Otherwise the parameter B in
>
>   template<template<class A> class B> struct Foo { };
>
> would get printed in error messages as
>
>   template<> template <class A> class B>
>
> Two new test files are added in this version: shadow2.C, which checks
> that we emit a shadowing error for identical template parameter names
> across nested parameter lists, and error55.C, which checks that we
> correctly emit template template decls in error messages.
>
> With this approach the test case provided by Markus no longer takes
> forever to compile because the added parameter lists are always empty so
> when doing structural type comparison of a TEMPLATE_TEMPLATE_PARM there
> is nothing extra to recurse into.
>
> Does this approach seem sensible?
>
> gcc/cp/ChangeLog:
>
>         PR c++/30044
>         * pt.c (begin_template_parm_list): Add a dummy parameter level
>         to current_template_parms.
>         (end_template_parm_list): Remove the dummy parameter level
>         before adding the real one.
>         (tsubst): Don't attempt to substitute for template parameters
>         corresponding to a dummy argument level.
>         (template_parms_to_args): Remove obsolete hack for
>         giving template template arguments the proper level.
>         (splite_late_return_type): Remove obsolete hack for giving
>         template template arguments the proper level.
>         * error.c (dump_template_decl): Don't print dummy template
>         levels.
>
> gcc/testsuite/ChangeLog
>
>         PR c++/30044
>         * g++.dg/cpp0x/auto45.C: New test.
>         * g++.dg/template/pr30044.C: New test.
>         * g++.dg/template/shadow2.C: New test.
>         * g++.dg/template/error55.C: New test.
>         * g++.dg/template/crash83.C: Accept any error string.
>         * g++.dg/cpp0x/variadic18.C: Adjust to avoid shadowing template
>         parameters.
>         * g++.dg/cpp0x/variadic18.C: Likewise
>         * g++.dg/template/canon-type-13.C: Likewise.
>         * g++.old-deja/g++.pt/ttp42.C: Likewise.
>         * g++.dg/torture/20070621-1.C: Likewise.
> ---
>  gcc/cp/error.c                                |  7 ++++++
>  gcc/cp/pt.c                                   | 32 +++++++++------------------
>  gcc/testsuite/g++.dg/cpp0x/auto45.C           |  5 +++++
>  gcc/testsuite/g++.dg/cpp0x/variadic18.C       |  2 +-
>  gcc/testsuite/g++.dg/cpp0x/variadic19.C       |  2 +-
>  gcc/testsuite/g++.dg/template/canon-type-13.C |  2 +-
>  gcc/testsuite/g++.dg/template/crash83.C       |  2 +-
>  gcc/testsuite/g++.dg/template/error55.C       |  8 +++++++
>  gcc/testsuite/g++.dg/template/pr30044.C       | 14 ++++++++++++
>  gcc/testsuite/g++.dg/template/shadow2.C       |  3 +++
>  gcc/testsuite/g++.dg/torture/20070621-1.C     |  2 +-
>  gcc/testsuite/g++.old-deja/g++.pt/ttp42.C     |  2 +-
>  12 files changed, 54 insertions(+), 27 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/cpp0x/auto45.C
>  create mode 100644 gcc/testsuite/g++.dg/template/error55.C
>  create mode 100644 gcc/testsuite/g++.dg/template/pr30044.C
>  create mode 100644 gcc/testsuite/g++.dg/template/shadow2.C
>
> diff --git a/gcc/cp/error.c b/gcc/cp/error.c
> index 96fa94d..b21befe 100644
> --- a/gcc/cp/error.c
> +++ b/gcc/cp/error.c
> @@ -1296,6 +1296,13 @@ dump_template_decl (cxx_pretty_printer *pp, tree t, int flags)
>           tree inner_parms = INNERMOST_TEMPLATE_PARMS (parms);
>           int len = TREE_VEC_LENGTH (inner_parms);
>
> +         if (len == 0)
> +           {
> +             /* Skip over the dummy template levels of a template template parm.  */
> +             gcc_assert (TREE_CODE (TREE_TYPE (t)) == TEMPLATE_TEMPLATE_PARM);
> +             continue;
> +           }
> +
>           pp_cxx_ws_string (pp, "template");
>           pp_cxx_begin_template_argument_list (pp);
>
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index fe5fc14..e7c35d3 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -658,6 +658,12 @@ begin_template_parm_list (void)
>    ++processing_template_decl;
>    ++processing_template_parmlist;
>    note_template_header (0);
> +
> +  /* Add a dummy parameter level while we process the parameter list.  */
> +  current_template_parms
> +    = tree_cons (size_int (processing_template_decl),
> +                make_tree_vec (0),
> +                current_template_parms);
>  }
>
>  /* This routine is called when a specialization is declared.  If it is
> @@ -3854,6 +3860,9 @@ end_template_parm_list (tree parms)
>    tree parm, next;
>    tree saved_parmlist = make_tree_vec (list_length (parms));
>
> +  /* Pop the dummy parameter level and add the real one.  */
> +  current_template_parms = TREE_CHAIN (current_template_parms);
> +
>    current_template_parms
>      = tree_cons (size_int (processing_template_decl),
>                  saved_parmlist, current_template_parms);
> @@ -3989,21 +3998,6 @@ template_parms_to_args (tree parms)
>         args = a;
>      }
>
> -    if (length > 1 && TREE_VEC_ELT (args, 0) == NULL_TREE)
> -      /* This can happen for template parms of a template template
> -        parameter, e.g:
> -
> -        template<template<class T, class U> class TT> struct S;
> -
> -        Consider the level of the parms of TT; T and U both have
> -        level 2; TT has no template parm of level 1. So in this case
> -        the first element of full_template_args is NULL_TREE. If we
> -        leave it like this TMPL_ARGS_DEPTH on args returns 1 instead
> -        of 2. This will make tsubst wrongly consider that T and U
> -        have level 1. Instead, let's create a dummy vector as the
> -        first element of full_template_args so that TMPL_ARGS_DEPTH
> -        returns the correct depth for args.  */
> -      TREE_VEC_ELT (args, 0) = make_tree_vec (1);
>    return args;
>  }
>
> @@ -12029,7 +12023,8 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>         template_parm_level_and_index (t, &level, &idx);
>
>         levels = TMPL_ARGS_DEPTH (args);
> -       if (level <= levels)
> +       if (level <= levels
> +           && TREE_VEC_LENGTH (TMPL_ARGS_LEVEL (args, level)) > 0)
>           {
>             arg = TMPL_ARG (args, level, idx);
>
> @@ -22394,11 +22389,6 @@ splice_late_return_type (tree type, tree late_return_type)
>      return type;
>    argvec = make_tree_vec (1);
>    TREE_VEC_ELT (argvec, 0) = late_return_type;
> -  if (processing_template_parmlist)
> -    /* For a late-specified return type in a template type-parameter, we
> -       need to add a dummy argument level for its parmlist.  */
> -    argvec = add_to_template_args
> -      (make_tree_vec (processing_template_parmlist), argvec);
>    if (current_template_parms)
>      argvec = add_to_template_args (current_template_args (), argvec);
>    return tsubst (type, argvec, tf_warning_or_error, NULL_TREE);
> diff --git a/gcc/testsuite/g++.dg/cpp0x/auto45.C b/gcc/testsuite/g++.dg/cpp0x/auto45.C
> new file mode 100644
> index 0000000..09e9f44
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/auto45.C
> @@ -0,0 +1,5 @@
> +// Addendum to auto23.C, now with nested template parameter lists
> +// { dg-do compile { target c++11 } }
> +
> +template<template <auto f()->int> class> struct A { };
> +template<template <template <auto f()->int> class> class> struct B { };
> diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic18.C b/gcc/testsuite/g++.dg/cpp0x/variadic18.C
> index fc0e2dd..57fdc86 100644
> --- a/gcc/testsuite/g++.dg/cpp0x/variadic18.C
> +++ b/gcc/testsuite/g++.dg/cpp0x/variadic18.C
> @@ -1,7 +1,7 @@
>  // { dg-do compile { target c++11 } }
>  template<typename...> class tuple { };
>
> -template<typename T, template<typename T> class... Metafunctions>
> +template<typename T, template<typename U> class... Metafunctions>
>  struct apply_all
>  {
>    typedef tuple<typename Metafunctions<T>::type...> type;
> diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic19.C b/gcc/testsuite/g++.dg/cpp0x/variadic19.C
> index 0ae2672..3be9bb0 100644
> --- a/gcc/testsuite/g++.dg/cpp0x/variadic19.C
> +++ b/gcc/testsuite/g++.dg/cpp0x/variadic19.C
> @@ -4,7 +4,7 @@ struct tuple {
>    static const int value = 0;
>  };
>
> -template<typename T, template<class T> class... Metafunctions>
> +template<typename T, template<class U> class... Metafunctions>
>  struct tuple<Metafunctions<T>...> {
>    static const int value = 1;
>  };
> diff --git a/gcc/testsuite/g++.dg/template/canon-type-13.C b/gcc/testsuite/g++.dg/template/canon-type-13.C
> index 4f3702b..5a8d37d 100644
> --- a/gcc/testsuite/g++.dg/template/canon-type-13.C
> +++ b/gcc/testsuite/g++.dg/template/canon-type-13.C
> @@ -11,7 +11,7 @@ struct S1
>  {
>  };
>
> -template<class T, template<class T>  class A, template<class T>  class B = A>
> +template<class T, template<class U>  class A, template<class U>  class B = A>
>  struct C
>  {
>    B<T> m;
> diff --git a/gcc/testsuite/g++.dg/template/crash83.C b/gcc/testsuite/g++.dg/template/crash83.C
> index b83dd21..7dcbed9 100644
> --- a/gcc/testsuite/g++.dg/template/crash83.C
> +++ b/gcc/testsuite/g++.dg/template/crash83.C
> @@ -2,4 +2,4 @@
>
>  template<int> struct A {};
>
> -template<typename = class A<0>: > struct B {}; // { dg-error "explicit specialization|expected" }
> +template<typename = class A<0>: > struct B {}; // { dg-error "" }
> diff --git a/gcc/testsuite/g++.dg/template/error55.C b/gcc/testsuite/g++.dg/template/error55.C
> new file mode 100644
> index 0000000..41f9595
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/error55.C
> @@ -0,0 +1,8 @@
> +// Check that template template parameters get printed properly in error
> +// messages.
> +
> +template <template <class A> class B>
> +struct Y
> +{
> +  B<5> y;  // { dg-error "for 'template<class A> class B'" }
> +};
> diff --git a/gcc/testsuite/g++.dg/template/pr30044.C b/gcc/testsuite/g++.dg/template/pr30044.C
> new file mode 100644
> index 0000000..415e6f0
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/pr30044.C
> @@ -0,0 +1,14 @@
> +// PR c++/30044
> +
> +template <typename T1, typename T2, template <T2> class Comp, class Result = Comp<1> >
> +struct sort { };
> +
> +
> +template <typename Type, template <Type, Type> class Comp, class Result = Comp<1, 2> >
> +struct sort2 { };
> +
> +template <typename Type, template <int, Type> class Comp, class Result = Comp<1, 2> >
> +struct sort3 { };
> +
> +template <template <typename T1, typename T2, template <T2> class Comp, class Result = Comp<1> > class Foo>
> +struct sort4 { };
> diff --git a/gcc/testsuite/g++.dg/template/shadow2.C b/gcc/testsuite/g++.dg/template/shadow2.C
> new file mode 100644
> index 0000000..7f6a6dc
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/shadow2.C
> @@ -0,0 +1,3 @@
> +template <class A, // { dg-error "shadows template parm 'class A'" }
> +          template <class A> class B> // { dg-error "declaration of 'class A'" }
> +class X;
> diff --git a/gcc/testsuite/g++.dg/torture/20070621-1.C b/gcc/testsuite/g++.dg/torture/20070621-1.C
> index 15d1ac7..9bd8cc3 100644
> --- a/gcc/testsuite/g++.dg/torture/20070621-1.C
> +++ b/gcc/testsuite/g++.dg/torture/20070621-1.C
> @@ -89,7 +89,7 @@ namespace __gnu_test {
>          SharedInfo->first=ptr;
>        }
>      };
> -    template <class T, template<class T> class ItType>   struct test_container   {
> +    template <class T, template<class U> class ItType>   struct test_container   {
>        typename ItType<T>::ContainerType bounds;
>        test_container(T* _first, T* _last):bounds(_first, _last)     {
>    }
> diff --git a/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C b/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
> index 53bdae1..a2ac239 100644
> --- a/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
> +++ b/gcc/testsuite/g++.old-deja/g++.pt/ttp42.C
> @@ -1,5 +1,5 @@
>  // { dg-do run  }
> -template <class T, template <class T> class C>
> +template <class T, template <class U> class C>
>  struct X
>  {};
>
> --
> 2.5.0.rc0.5.g91e10c5.dirty
>

Ping.

Re: [PATCH] Fix PR c++/30044

[Jason Merrill]

OK, thanks.

Jason