[Bug c++/56377] New: [4.8 Regression] <missing> template args in substitution-failure diagnostics

[Bug c++/56377] New: [4.8 Regression] <missing> template args in substitution-failure diagnostics

[pl.smith.mail at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

             Bug #: 56377
           Summary: [4.8 Regression] <missing> template args in
                    substitution-failure diagnostics
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pl.smith.mail@gmail.com


When a candidate function for which substituion failed is listed in a
diagnostic, if the failure stems from a template parameter that have an
explicit argument, the explicit arguments are listed as <missing>.

For example:

template <typename T>
typename T::type f();

int main () {
  f<int>();
}

Produces (4.8, no flags):

test.cpp: In function ג€˜int main()ג€™:
test.cpp:5:10: error: no matching function for call to 'f()'
   f<int>();
          ^
test.cpp:5:10: note: candidate is:
test.cpp:2:18: note: template<class T> typename T::type f()
 typename T::type f();
                  ^
test.cpp:2:18: note:   template argument deduction/substitution failed:
  *************
test.cpp: In substitution of 'template<class T> typename T::type f() [with T =
<missing>]':
  *************
test.cpp:5:10:   required from here
test.cpp:2:18: error: 'int' is not a class, struct, or union type

In 4.7 it is "[with T = int]".

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[pl.smith.mail at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

--- Comment #1 from Paul Smith <pl.smith.mail at gmail dot com> 2013-02-18 16:12:00 UTC ---
Looks like this was introduced in rev. 190664, with the merging of
'deduction_tsubst_fntype' into 'fn_type_unification'.

The instantiation context is constructed with 'targs' as the vector of template
arguments, which is still empty when substituting the explicit arguments into
the function type the first time. This can be fixed by either constructing the
instantiation context using 'explicit_targs' when non-null, or by copying
'explicit_targs' into 'targs' before the substitution.

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-02-18
                 CC|                            |jason at gcc dot gnu.org
     Ever Confirmed|0                           |1

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.8.0

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-19 09:58:16 UTC ---
Yeah, diff between r190663 and r190664 output is:
-pr56377.C: In substitution of ‘template<class T> typename T::type f() [with T
= int]’:
+pr56377.C: In substitution of ‘template<class T> typename T::type f() [with T
= <missing>]’:

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
           Priority|P3                          |P1

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> 2013-02-22 22:24:40 UTC ---
Author: jason
Date: Fri Feb 22 22:24:27 2013
New Revision: 196230

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=196230
Log:
    PR c++/56377
    * pt.c (fn_type_unification): Use explicit args in template
    instantiation context.

Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> 2013-02-23 01:59:20 UTC ---
Fixed.

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[pl.smith.mail at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Paul Smith <pl.smith.mail at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |

--- Comment #5 from Paul Smith <pl.smith.mail at gmail dot com> 2013-02-23 15:15:47 UTC ---
There can still be <missing> arguments before the substitution:

template <int N>
void f() {
  f<N + 1>();
}

int main() {
  f<0>();
}

Output:

test.cpp:3:11: error: template instantiation depth exceeds maximum of 900 (use
-ftemplate-depth= to increase the maximum) substituting ‘template<int N> void
f() [with int N = <missing>]’
  f<N + 1>();
           ^
...

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> 2013-02-26 04:28:04 UTC ---
Author: jason
Date: Tue Feb 26 04:27:51 2013
New Revision: 196275

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=196275
Log:
    PR c++/56377
    * pt.c (fn_type_unification): Wait to call push_tinst_level until
    we know what args we're looking at.

Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c

[Bug c++/56377] [4.8 Regression] <missing> template args in substitution-failure diagnostics

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56377

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2013-02-26 04:29:17 UTC ---
Should really be fixed now.