https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53360
Eric Gallager <egallager at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2017-08-19
CC| |egallager at gcc dot gnu.org
Summary|Problems with -std=gnu++0x |g++ prints 'invalid use of
| |incomplete type' error when
| |compiling code with
| |-std=gnu++0x and newer
Ever confirmed|0 |1
--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Alex from comment #0)
> I have such code:
>
>
> template<class CppType>
> struct make_literal;
>
> template<>
> struct make_literal<int> {
> typedef int type;
> };
>
> template<class T>
> struct make_expression {
> typedef typename make_literal<T>::type type;
> };
>
> struct column {
> template<class T>
> typename make_expression<T>::type operator= (const T& t) const {
> return typename make_expression<T>::type(t);
> }
> };
>
> struct expression : column
> {
> expression() { }
> using column::operator =;
> };
>
> int main()
> {
> expression ex;
> ex = 2;
>
> return 0;
> }
>
> which failed to compile with such command line:
> c++ -std=gnu++0x file.cpp
>
> Compiler produces such error:
> bug.cpp: In instantiation of ‘make_expression<column>’:
> bug.cpp:31:10: instantiated from here
> bug.cpp:12:42: error: invalid use of incomplete type ‘struct
> make_literal<column>’
> bug.cpp:3:8: error: declaration of ‘struct make_literal<column>’
(In reply to Marc Glisse from comment #1)
> clang and gcc reject it, but intel and oracle accept it.
The errors with gcc and clang are now:
$ /usr/local/bin/g++ -c -Wall -Wextra -pedantic -std=gnu++0x 53360.cc
53360.cc: In instantiation of ‘struct make_expression<column>’:
53360.cc:16:36: required by substitution of ‘template<class T> typename
make_expression<T>::type column::operator=(const T&) const [with T = column]’
53360.cc:30:10: required from here
53360.cc:11:41: error: invalid use of incomplete type ‘struct
make_literal<column>’
typedef typename make_literal<T>::type type;
^~~~
53360.cc:2:8: note: declaration of ‘struct make_literal<column>’
struct make_literal;
^~~~~~~~~~~~
$ /sw/opt/llvm-3.1/bin/clang++ -c -Wall -Wextra -pedantic -std=gnu++0x 53360.cc
53360.cc:11:19: error: implicit instantiation of undefined template
'make_literal<column>'
typedef typename make_literal<T>::type type;
^
53360.cc:16:11: note: in instantiation of template class
'make_expression<column>' requested here
typename make_expression<T>::type operator= (const T& t) const {
^
53360.cc:16:36: note: while substituting deduced template arguments into
function template 'operator=' [with T = column]
typename make_expression<T>::type operator= (const T& t) const {
^
53360.cc:2:8: note: template is declared here
struct make_literal;
^
1 error generated.
$
Note that it also fails with gnu++14 and gnu++1z. When compiled with
-std=gnu++98 and -Wc++11-compat, it prints no errors or warnings, which is odd,
because if it were actually supposed to error out with gnu++11, you'd think
-Wc++11-compat would at least warn about it. So, confirmed.
