[Bug c++/34886] New: Strangeness of name lookup in template function

[Bug c++/34886] New: Strangeness of name lookup in template function

[rvovsd at mail dot ru]

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On compiling that code:

--- begin code ---
class Y {};

void f(Y*) { } // line 3. If comment - all ok

template < typename T>
void sel(T* a) { f(a); } //line 6

void f(void*) {}

int main(int argc, char **argv)
{
        sel((void*)0); //line 12
}
--- end code ---

Àppears error:
../main.cpp: In function ‘void sel(T*) [with T = void]’:
../main.cpp:12:   instantiated from here
../main.cpp:6: error: invalid conversion from ‘void*’ to ‘Y*’
../main.cpp:6: error:   initializing argument 1 of ‘void f(Y*)’

If comment line 3, then work.
Also work, if line 3 move after line 6.

If functions f(Y*), f(void*) and sel(T*) placed in different header files, then
arise dependency on order including headers.


-- 
           Summary: Strangeness of name lookup in template function
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rvovsd at mail dot ru
  GCC host triplet: openSuse 10.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34886

[Bug c++/34886] Strangeness of name lookup in template function

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2008-01-20 21:55 -------
GCC is correct here.  Well partly.  It should reject it no matter what.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34886

[Bug c++/34886] Strangeness of name lookup in template function

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2008-01-20 22:30 -------
*** Bug 34893 has been marked as a duplicate of this bug. ***


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34886

[Bug c++/34886] Strangeness of name lookup in template function

[rvovsd at mail dot ru]

------- Comment #3 from rvovsd at mail dot ru  2008-01-21 14:43 -------
This case is similar to the bug 31047
(http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31047).

There Andrew Pinski wrote (comment 4):
>14.6.4.2/1 says this is invalid code.
>For a function call that depends on a template parameter, if the function is an
>unqualified-id but not a template-id, the candiate functions are found using
>the usual lookup rules (3.4.1, 3.4.2) except that:
>....
>
>Paraphasing since I don't want to type it all in
>* non argument dependent lookup (3.4.1: template definition context
>* argument dependent lookup (3.4.2):  template definition context and template
>instation context

This case is argument dependent lookup, therefore should used both contexts -
definition and instantiation.
Point of instantiation "sel(T* a) with T = void" - after "void f(void*)" and
before "int main()".
Thus should be visible both f(void*) and f(Y*), whether not so?
Why gcc does not see "void f (void *)"?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34886

[Bug c++/34886] Strangeness of name lookup in template function

[redi at gcc dot gnu dot org]

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------- Comment #4 from redi at gcc dot gnu dot org  2009-12-08 21:58 -------
In resolving dependent names, names from the following sources are considered:
— Declarations that are visible at the point of definition of the
template.
— Declarations from namespaces associated with the types of the function
arguments both from the instantiation context (14.7.4.1) and from the
definition context.

— If T is a fundamental type, its associated sets of namespaces and classes are
both empty.
— If T is a pointer to U or an array of U, its associated namespaces and
classes are those associated with U.

void* is a pointer to fundamental type so has no associated namespaces, so only
the first source is considered, and only f(T*) is visible at the point of
definition. This is invalid.


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redi at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34886

[Bug c++/34886] Strangeness of name lookup in template function

[pinskia at gcc dot gnu dot org]

------- Comment #5 from pinskia at gcc dot gnu dot org  2009-12-08 22:01 -------
Actually ....


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34886

[Bug c++/34886] Strangeness of name lookup in template function

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2009-12-08 22:02 -------
> void* is a pointer to fundamental type so has no associated namespaces

Well there is a still open defect report that says this might not be true :).

*** This bug has been marked as a duplicate of 29131 ***


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34886