[Bug c++/38681] New: Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[Bug c++/38681] New: Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[juvvij at gmail dot com]

While trying to reinvent some suitablu smart technique for routing Gtk's static
callbacks to object methods, I thought I had created a suitably brilliant
solution. Gcc could not digest it. While I am looking at smarter solutions from
boost or loki, I would like to see if I really was onto a workable solution.

I'm not sure if the triplet info above is useful enough. The bug posting
guidelines promised eternal shame if I didn't do my very best. So ading more
info, hopefully it is not all wasteful!

I have the as-packaged-for-ubuntu 8.10, g++-4.3.2 version.


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           Summary: Internal compiler error. expr.c:6956 [Template
                    instantiation with non-type value of member function
                    ptr]
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: juvvij at gmail dot com
 GCC build triplet: i486-linux-gnu
  GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681

[Bug c++/38681] Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[juvvij at gmail dot com]

------- Comment #2 from juvvij at gmail dot com  2008-12-31 07:43 -------
Created an attachment (id=17018)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17018&action=view)
Details of gcc from output of g++ -v -save-temps


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681

[Bug c++/38681] Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[juvvij at gmail dot com]

------- Comment #1 from juvvij at gmail dot com  2008-12-31 07:42 -------
Created an attachment (id=17017)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17017&action=view)
Preprocessed test case that causes the compiler error.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681

[Bug c++/38681] Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2008-12-31 07:49 -------
>        ulong ConnectCB(GtkWidget* pWidget, const char* sigName, _R(_ClassType::*MemFun)(GtkWidget*, _A1))
 >       {
>            typedef CBFamily2<_ClassType, _R, GtkWidget*, _A1, MemFun> TCallbackType;


This code is invalid code, you are using a non constant expression for a
template argument.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681

[Bug c++/38681] Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2008-12-31 16:10 -------
This is close to duplicate of bug 37093.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681

[Bug c++/38681] Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[juvvij at gmail dot com]

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------- Comment #5 from juvvij at gmail dot com  2008-12-31 17:31 -------
>From the C++ standards doc (Latest download form the website) (excerpt listed
below), I thought that member functions could be allowed. I am not entirely
sure if *function* can also refer to *member-function*.

--------------------
4.  A non-type template-parameter shall have one of the following (optionally
cv-qualified) types:
    — integral or enumeration type,
    — pointer to object or pointer to function,
    — reference to object or reference to function,
    — pointer to member., or
    — in a constrained template (14.10), a type archetype T for which the
concept requirement std::NonTypeTemplateParamet
       is part of the template’s requirements.
--------------------

Did I understand this wrong ? Does the correct interpretation of the standard
not allow for member-function-pointers as non-type arguments ?

The following links point to a different interpretation.

http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=101628

http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=196204

http://objectmix.com/c/382443-samples-non-type-template-argument-other-than-integral-types.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681

[Bug c++/38681] Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[pinskia at gcc dot gnu dot org]

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------- Comment #6 from pinskia at gcc dot gnu dot org  2008-12-31 17:40 -------
>    — pointer to member., or

This includes pointer to member functions.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681

[Bug c++/38681] Internal compiler error. expr.c:6956 [Template instantiation with non-type value of member function ptr]

[bangerth at gmail dot com]

------- Comment #7 from bangerth at gmail dot com  2009-01-30 15:51 -------
(In reply to comment #5)
> Did I understand this wrong ? Does the correct interpretation of the standard
> not allow for member-function-pointers as non-type arguments ?

It does, but it requires them to be in a constant-expression context -- i.e.
informally speaking the compiler needs to know *at compile time* which member
function you refer to. You can use a function argument as a template
argument.

I think this is indeed a duplicate of PR 37093.

W.

W.

*** This bug has been marked as a duplicate of 37093 ***


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bangerth at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at gmail dot com
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38681