[Bug c++/44906] g++ is giving error: parse error in template argument list while using a c++ code.

[Bug c++/44906] g++ is giving error: parse error in template argument list while using a c++ code.

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44906

Paolo Carlini <paolo.carlini at oracle dot com> changed:

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

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-09-23 12:43:53 UTC ---
Closing as invalid.

[Bug c++/44906] g++ is giving error: parse error in template argument list while using a c++ code.

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44906

--- Comment #8 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-09-23 13:59:07 UTC ---
(In reply to comment #6)
> Honestly, nothing similar will happen any time soon, it means changing
> completely the semantics of templates. Maybe we can produce a better
> diagnostics, let's add Manuel in CC to hear his opinion...

The code is invalid but the diagnostic could be much better (I only have GCC
4.5.2, so perhaps it is better in trunk).

Smaller testcase:

template<typename T>
class MISC{
public:
    T vec1;
    template<T* vc> void addVecVals(){};
    void add(void) { addVecVals<&vec1>();  };
};

void foo(void) {
    MISC<int> m;
    m.add();
}

Clang++ gives a somewhat better message:

/tmp/webcompile/_14512_0.cc:6:22: error: no matching member function for call
to 'addVecVals'
    void add(void) { addVecVals<&vec1>();  };
                     ^~~~~~~~~~~~~~~~~
/tmp/webcompile/_14512_0.cc:11:7: note: in instantiation of member function
'MISC<int>::add' requested here
    m.add();
      ^
/tmp/webcompile/_14512_0.cc:5:26: note: candidate template ignored: invalid
explicitly-specified argument for template parameter 'vc'
    template<T* vc> void addVecVals(){};
                         ^
1 error generated.


I would argue for reopening it...

[Bug c++/44906] g++ is giving error: parse error in template argument list while using a c++ code.

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44906

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
   Last reconfirmed|                            |2011-09-23
         Resolution|INVALID                     |
     Ever Confirmed|0                           |1

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-09-23 14:43:26 UTC ---
Hey, you woke up! ;) Sure, let's re-open is a diagnostic issue, your call.

[Bug c++/44906] g++ is giving error: parse error in template argument list

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44906

--- Comment #10 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-10-19 22:24:12 UTC ---
The problem seems to be the tentative parsing in cp_parse_template_id, which
tries every crazy thing it can, and when nothing works, it just gives this
catch all diagnostic. 

But debugging the C++ parser is an absolute pain, I hope someone with more
patience takes a shot at this. The current diagnostic is just awful.

[Bug c++/44906] g++ is giving error: parse error in template argument list

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44906

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |NEW
   Last reconfirmed|2011-09-23 00:00:00         |2021-8-3

--- Comment #11 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
For the testcase in comment #8:

Ok, this is interesting as at first I thought this was fixed in GCC 11 but then
I looked to see what the different standards do as GCC 11's default is C++17.

With C++17 and C++20, we get:
<source>:8:34: error: use of 'this' in a constant expression
    8 |     void add(void) { addVecVals<&vec1>();  }
      |                                  ^~~~
<source>: In instantiation of 'void MISC<T>::add() [with T = int]':
<source>:13:10:   required from here
<source>:8:39: error: no matching function for call to
'MISC<int>::addVecVals<(&((MISC<int>*)this)->MISC<int>::vec1)>()'
    8 |     void add(void) { addVecVals<&vec1>();  }
      |                      ~~~~~~~~~~~~~~~~~^~
<source>:7:26: note: candidate: 'template<int* vc> void MISC<T>::addVecVals()
[with T* vc = vc; T = int]'
    7 |     template<T* vc> void addVecVals(){}
      |                          ^~~~~~~~~~
<source>:7:26: note:   template argument deduction/substitution failed:
<source>:8:34: error: '&((MISC<int>*)this)->MISC<int>::vec1' is not a valid
template argument of type 'int*' because '((MISC<int>*)this)->MISC<int>::vec1'
is not a variable
    8 |     void add(void) { addVecVals<&vec1>();  }
      |                                  ^~~~


But for C++98, C++11, C++14, we get:
<source>: In member function 'void MISC<T>::add()':
<source>:8:22: error: parse error in template argument list
    8 |     void add(void) { addVecVals<&vec1>();  }
      |                      ^~~~~~~~~~~~~~~~~