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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/47342] New: misleading diagnostic for member of undeclared class template partial specialization Date: Tue, 18 Jan 2011 13:00:00 -0000 [thread overview] Message-ID: <bug-47342-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47342 Summary: misleading diagnostic for member of undeclared class template partial specialization Product: gcc Version: 4.6.0 Status: UNCONFIRMED Keywords: diagnostic Severity: enhancement Priority: P3 Component: c++ AssignedTo: unassigned@gcc.gnu.org ReportedBy: redi@gcc.gnu.org g++ does not distinguish between invalid uses of an incomplete partial specialization and an undeclared partial specialization: template<class T> struct X : T { void f(); }; template<class T> inline void X<T>::f() { } template<typename T> struct Y { }; #ifdef CORRECT template<class T> struct X< Y<T> > : Y<T> { void f(); }; #endif template<class T> inline void X< Y<T> >::f() // xxx { } $ g++ ps.cc ps.cc:26: error: invalid use of incomplete type 'struct X<Y<T> >' ps.cc:3: error: declaration of 'struct X<Y<T> >' The diagnostic is rather unhelpful. The problem is not that the type is incomplete, but that there is not even a declaration of the class template partial specialization X<Y<T>> (which can be fixed by defining CORRECT). The second error referring to line 3 is wrong, that's the declaration of the primary template, not the partial specialization. The diagnostic would be almost correct (apart from the line number) if the class template partial specialization had been declared but not defined, like so template<class T> struct X< Y<T> >; but that is not the case here. This is a regression since 4.1 which correctly states the type is undefined, not incomplete: ps.cc:27: error: invalid use of undefined type `struct X<Y<T> >' ps.cc:3: error: declaration of `struct X<Y<T> >' ps.cc:27: error: template definition of non-template `void X<Y<T> >::f()' EDG gives: "ComeauTest.c", line 26: error: template argument list must match the parameter list X< Y<T> >::f() // xxx ^ This isn't very informative but is more accurate, referring to the wording in [temp.class.spec.mfunc]p1: The template argument list of a member of a class template partial specialization shall match the template argument list of the class template partial specialization. Clang++ gives a more helpful diagnostic: ps.cc:26:14: error: nested name specifier 'X<Y<T> >::' for declaration does not refer into a class, class template or class template partial specialization X< Y<T> >::f() // xxx ~~~~~~~~~~~^ 1 error generated. Sun CC gives arguably the best diagnostic: "ps.cc", line 27: Error: Could not find partial specialization matching X<Y<T>>. 1 Error(s) detected. (N.B. clang++ gives a worse diagnostic for the case where the class template partial specialization has been declared but not defined and CC accepts it without error)
next reply other threads:[~2011-01-18 12:52 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-01-18 13:00 redi at gcc dot gnu.org [this message] 2011-01-18 13:27 ` [Bug c++/47342] " redi at gcc dot gnu.org 2021-05-12 14:52 ` redi at gcc dot gnu.org
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