gcc 4.3.1 fails to diagnose the following ill-formed program:
template <class T> struct S { T foo (); };
template <class T> T S<T>::foo () { return T (); }
template struct S<int>;
extern template struct S<int>;
int main () { return S<int>().foo (); }
See the discussion thread below for more detail:
John H. Spicer wrote:
>
> On Dec 30, 2008, at 2:10 PM, Martin Sebor wrote:
>
>> To: C++ core language mailing list
>> Message c++std-core-13732
>>
>> The discussion on the subject of extern template and vtables
>> reminded me of the case below that still passes with at least
>> one recent compiler and fails with another and which I'm still
>> not sure is intended to be well-formed or not. I'm hoping this
>> is a good time to revisit it and get the issue settled.
>
> 14.7.2p10 says:
>
> If an entity is the subject of both an explicit instantiation
> declaration and an explicit instantiation definition
> in the same translation unit, the definition shall follow the declaration.
>
>
> This makes your example ill-formed.
>
> John Spicer
> Edison Design Group
>
>>
>>
>> Thanks!
>> Martin
>>
>> Martin Sebor wrote:
>>> To: C++ core language mailing list
>>> Message c++std-core-11080
>>> The following piece of code compiles successfully with 2 compilers
>>> and fails with 2 others. I can't tell from N1448 whether it was
>>> intended to be well-formed or (if so) what the expected behavior
>>> should be. Could someone clarify?
>>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1448.pdf
>>> Thanks in advance!
>>> Martin
>>> template <class T> struct S { T foo (); };
>>> template <class T> T S<T>::foo () { return T (); };
>>> template struct S<int>;
>>> extern template struct S<int>;
>>> int main () { return S<int>().foo (); }
--
Summary: extern template declaration accepted after explicit
instantiation
Product: gcc
Version: 4.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: sebor at roguewave dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38677
