[Bug c++/57397] New: Off-by-one error in diagnostic when calling variadic function template with too few arguments

[Bug c++/57397] New: Off-by-one error in diagnostic when calling variadic function template with too few arguments

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

            Bug ID: 57397
           Summary: Off-by-one error in diagnostic when calling variadic
                    function template with too few arguments
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org

template<class T1, class T2, class... Tn>
void foo(T1, Tn...)
{ }

int main()
{
    foo();
}

t.cc: In function 'int main()':
t.cc:7:9: error: no matching function for call to 'foo()'
     foo();
         ^
t.cc:7:9: note: candidate is:
t.cc:2:6: note: template<class T1, class T2, class ... Tn> void foo(T1, Tn ...)
 void foo(T1, Tn...)
      ^
t.cc:2:6: note:   template argument deduction/substitution failed:
t.cc:7:9: note:   candidate expects 2 arguments, 0 provided
     foo();
         ^


The function expects 1 or more arguments, saying 2 is entirely bogus.

[Bug c++/57397] Off-by-one error in diagnostic when calling variadic function template with too few arguments

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-05-24
           Assignee|unassigned at gcc dot gnu.org      |paolo.carlini at oracle dot com
     Ever confirmed|0                           |1

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Gosh, we must fix this.

[Bug c++/57397] Off-by-one error in diagnostic when calling variadic function template with too few arguments

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |4.7.3, 4.8.1, 4.9.0

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm amazed I've never noticed it before, but it's present on all active
branches.

[Bug c++/57397] Off-by-one error in diagnostic when calling variadic function template with too few arguments

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #3 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
I simply guess that it had been noticed but no-one cared enough to file a
bugzilla entry for it.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idU701

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-05-24
                 CC|                            |ramana at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
Confirmed.

[Bug c++/57397] Off-by-one error in diagnostic when calling variadic function template with too few arguments

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
The core issue is very simple. Funny however the error messages you can get for
some other invalid cases, like I tried:

template<class T1, class... T2, class... Tn>
void boo(T1, T2..., Tn...)
{ }

int main()
{
  boo(1);
}

then my clang++ (not very up to date) says at least 2 arguments are needed. For
fun you give 2 and it says that 1 is required ;) ICC doesn't even try
suggesting the right number ;) I guess that while we are at it we want to say
"at least 2" for the original testcase filed by Jon (thus we can't just call
unify_arity with the right arguments) and then better handle in the diagnostic
parameters which can't be deduced anyway.

[Bug c++/57397] Off-by-one error in diagnostic when calling variadic function template with too few arguments

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Of course I meant "at least 1" for the original testcase.

[Bug c++/57397] Off-by-one error in diagnostic when calling variadic function template with too few arguments

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

--- Comment #6 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> ---
Author: paolo
Date: Wed Jul 30 20:06:29 2014
New Revision: 213310

URL: https://gcc.gnu.org/viewcvs?rev=213310&root=gcc&view=rev
Log:
/cp
2014-07-30  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/57397
    * pt.c (unify_arity): Add boolean parameter.
    (unify_too_few_arguments): Likewise.
    (type_unification_real): Diagnose correctly insufficient
    arguments in the presence of trailing variadic parameters;
    deducing multiple trailing packs as empty is fine.

/testsuite
2014-07-30  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/57397
    * g++.dg/cpp0x/vt-57397-1.C: New.
    * g++.dg/cpp0x/vt-57397-2.C: Likewise.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/vt-57397-1.C
    trunk/gcc/testsuite/g++.dg/cpp0x/vt-57397-2.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/57397] Off-by-one error in diagnostic when calling variadic function template with too few arguments

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57397

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
           Assignee|paolo.carlini at oracle dot com    |unassigned at gcc dot gnu.org
   Target Milestone|---                         |4.10.0

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed.