Re: gcc7 build error with recent tip

[John W. Eaton]

On 06/24/2017 02:23 PM, Daniel J Sebald wrote:
> On 06/24/2017 11:21 AM, Dmitri A. Sergatskov wrote:
> > On Sat, Jun 24, 2017 at 10:59 AM, John W. Eaton <address@hidden
> > <mailto:address@hidden>> wrote:
> >
> >
> >     I admit this code is a bit tricky.  I was trying to come up with a
> >     way to use a single template that would cover both of these cases:
> >
> >       static octave_value
> >       dump_container_map (const std::map<std::string,
> >     std::list<std::string>>&)
> >
> >       static octave_value
> >       dump_container_map (const std::map<std::string,
> >     std::map<std::string>>&)
> >
> >     It works for me with gcc version 6.3.0 20170516 (Debian 6.3.0-18).
> >
> >
> > ​It is quite possible this is a bug in gcc7.1.1.
> > I filled a bug:
> >
> > ​https://bugzilla.redhat.com/show_bug.cgi?id=1464612
> >
> > would like to see what Jakub has to say about it.
>
> Yes, that is quite possible, based upon the error message.  The compiler
> identifies the proper candidate, but it is telling us that the candidate
> expects only one argument.  I.e.,
>
> ../src/libinterp/corefcn/symtab.cc:1424:1: note: candidate:
> template<class V, template<class ...> class C> octave_value
> dump_container_map(const std::map<std::__cxx11::basic_string<char>, C<V>
> > &)
>  dump_container_map (const std::map<std::string, C<V>>& container_map)
>  ^~~~~~~~~~~~~~~~~~
> ../src/libinterp/corefcn/symtab.cc:1424:1: note:   template argument
> deduction/substitution failed:
> ../src/libinterp/corefcn/symtab.cc:1446:73: note:   candidate expects 1
> argument, 3 provided
>         {"precedence_table", dump_container_map
> (m_class_precedence_table)},
>
> but I don't understand where the compiler is getting those number 3
> from.  Here's the definition of m_class_precedence_table:

The template substitution that is failing is for std::set which takes 1, 
2, or 3 template parameters.  The other, for std::list, takes 1 or 2.

I checked in the following changeset and the problem seems to be fixed 
for both GCC 6 and 7:

  http://hg.savannah.gnu.org/hgweb/octave/rev/93371ce5378d

Now I'm not sure whether this is a bug in GCC 7 or if it was a bug in 
previous versions to accept the template without the "A..." argument.

jwe