[Bug c++/38888] New: [C++0x] badly readable diagnostic output with variadic templates

[Bug c++/38888] New: [C++0x] badly readable diagnostic output with variadic templates

[bangerth at dealii dot org]

Maybe it isn't too late yet to change the specification in the ABI (or
maybe there isn't even one yet) for cases like this -- consider
------------------------
template <typename... T> struct X {
    template <typename... U> int f() { this->error; }
};
template int X<int,double>::f<int,double>();
------------------------
We get this error message:

g/x> c++ -std=c++0x -c x.cc
x.cc: In member function 'int X<T>::f() [with U = int, double, T = int,
double]':
x.cc:4:   instantiated from here
x.cc:2: error: 'struct X<int, double>' has no member named 'error'

What bothers me is this bit:
  [with U = int, double, T = int, double]
where it isn't quite clear due to lack of parentheses/braces/... which types
belong where. I think it would be a lot clearer if it read like this:
  [with U = {int, double}, T = {int, double}]

I'm sure it would also make automated parsing of such strings a lot simpler
if someone wanted to do that.

Best
 Wolfgang


-- 
           Summary: [C++0x] badly readable diagnostic output with variadic
                    templates
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bangerth at dealii dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2009-01-16 22:38 -------
Well the diagnostic mechanism does not demangle anything, we have the whole
expression in memory still.  So changing the diagnostic is no issue.  Now I
wonder how we (c++filt) demange "_ZN1XIIidEE1fIIidEEEiv" anyways.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[jason at gcc dot gnu dot org]

------- Comment #2 from jason at gcc dot gnu dot org  2009-01-16 22:45 -------
We demangle it as int X<int, double>::f<int, double>()

The suggestion seems reasonable to me.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2009-01-16 22:46 -------
(In reply to comment #2)
> We demangle it as int X<int, double>::f<int, double>()

I have to update my c++filt even though it is from August 2008.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[jason at gcc dot gnu dot org]

------- Comment #4 from jason at gcc dot gnu dot org  2009-01-16 22:50 -------
Yep, I've been making a bunch of mangling changes recently.  Should be all done
now though.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[bangerth at gmail dot com]

------- Comment #5 from bangerth at gmail dot com  2009-01-30 15:29 -------
I think Jason confirmed this already...


-- 

bangerth at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-01-30 15:29:16
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[jason at gcc dot gnu dot org]

-- 

jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[jason at gcc dot gnu dot org]

------- Comment #6 from jason at gcc dot gnu dot org  2009-10-17 06:12 -------
Subject: Bug 38888

Author: jason
Date: Sat Oct 17 06:11:21 2009
New Revision: 152925

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=152925
Log:
        PR c++/38888
        * error.c (dump_template_bindings): Wrap argument packs in {}.

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


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888

[Bug c++/38888] [C++0x] badly readable diagnostic output with variadic templates

[jason at gcc dot gnu dot org]

------- Comment #7 from jason at gcc dot gnu dot org  2009-10-17 15:41 -------
Fixed for 4.5.0.


-- 

jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38888