[Bug c++/17152] New: Useless error message

[Bug c++/17152] New: Useless error message

[paavola at skycomputers dot com]

The following program compiles without errors using gcc 3.3, but 3.4.1 complains:

Reading specs from /usr/lib64/gcc/x86_64-suse-linux/3.4.1/specs
Configured with: /net/monday_ad2/tools/gcc-3.4.1/configure --enable-threads=posix --prefix=/usr 
--with-local-prefix=/usr/local --infodir=/usr/share/info --mandir=/usr/share/man --libdir=/usr/
lib64 --enable-languages=c,c++,f77,objc,java,ada --disable-checking --enable-libgcj --with-gxx-
include-dir=/usr/include/g++ --with-slibdir=/lib64 --with-system-zlib --enable-shared --enable-
__cxa_atexit x86_64-suse-linux
Thread model: posix
gcc version 3.4.1
 /usr/libexec/gcc/x86_64-suse-linux/3.4.1/cc1plus -E -quiet -v -D_GNU_SOURCE foo.cpp 
-mtune=k8 -o foo.ii
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/g++
 /usr/include/g++/x86_64-suse-linux
 /usr/include/g++/backward
 /usr/local/include
 /usr/lib64/gcc/x86_64-suse-linux/3.4.1/include
 /usr/lib64/gcc/x86_64-suse-linux/3.4.1/../../../../x86_64-suse-linux/include
 /usr/include
End of search list.
 /usr/libexec/gcc/x86_64-suse-linux/3.4.1/cc1plus -fpreprocessed foo.ii -quiet -dumpbase foo.cpp 
-mtune=k8 -auxbase foo -version -o foo.s
GNU C++ version 3.4.1 (x86_64-suse-linux)
        compiled by GNU C version 3.3.1 (SuSE Linux).
GGC heuristics: --param ggc-min-expand=63 --param ggc-min-heapsize=63559
foo.cpp:12: error: declaration of `operator==' as non-function
foo.cpp:12: error: expected `;' before '<' token
foo.cpp:13: error: declaration of `operator!=' as non-function
foo.cpp:13: error: expected `;' before '<' token

Removing the <> in the program produces some useful information - adding function prototypes 
makes the error go away. If the function prototypes are truly required, please add some useful text to 
this error to make programs written using directions from various texts easier to debug. For example, 
Stroustrup's "The C++ Programming Language" doesn't provide any indication on how to fix this 
problem.

-- 
           Summary: Useless error message
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: paavola at skycomputers dot com
                CC: gcc-bugs at gcc dot gnu dot org,leblanc at skycomputers
                    dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152

[Bug c++/17152] Useless error message

[paavola at skycomputers dot com]

------- Additional Comments From paavola at skycomputers dot com  2004-08-23 13:58 -------
I neglected to include the source code:

template <int N, class T>
 class vec
 {
    public:
  int size() const { return N; }

  vec(const T & t = T())
  { for(int i = 0; i < N; i++) v[i] = t; }
  vec(const T * tp)
  { for(int i = 0; i < N; i++) v[i] = tp[i]; }

  friend bool operator == <> ( const vec<N,T> &v1, const vec<N,T> &v2 );
  friend bool operator != <> ( const vec<N,T> &v1, const vec<N,T> &v2 );

  T v[N];
 };


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152

[Bug c++/17152] Useless error message

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-08-23 14:07 -------
I think the error message is actually quite clear: you try to make 
something a friend which isn't known: for a friend declaration, if 
name lookup doesn't find an existing name, and if it is a declaration 
of either a function or a function template, then this injects the 
name into the surrounding namespace. However, this doesn't apply for 
a function template specialization, as in your case, if the actual 
template declaration isn't available. Thus the compiler complains 
that you are trying to declare something you can't declare (a non-function, 
non-template). It should be obvious that the compiler can't do anything 
about it unless you provide a declaration of the general template. 
 
I leave it to others to decide whether we want to keep this PR and if so 
how to change the error message. I personally would vote for closing it. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152

[Bug c++/17152] Useless error message

[paavola at skycomputers dot com]

------- Additional Comments From paavola at skycomputers dot com  2004-08-23 14:22 -------
Subject: Re:  Useless error message

Hmmm - the message says "declaration of `operator==' as non-function". 
It looks like a function declaration to me.

It also says "expected `;' before '<' token", so I do get a clue that 
there's a problem with the "<>". Putting a `;' into the code would 
clearly be wrong.

I won't claim to be a C++ template wizard - perhaps someone more 
experienced would figure this out. In addition, gcc 3.3 was happy 
enough with this. As a minimum, you should document it in your 3.4 
release notes as a change from 3.3. I got the code that caused this bug 
report off the web. I suspect there's more of it out there.

Steve

On Aug 23, 2004, at 10:07 AM, bangerth at dealii dot org wrote:

>
> ------- Additional Comments From bangerth at dealii dot org  
> 2004-08-23 14:07 -------
> I think the error message is actually quite clear: you try to make
> something a friend which isn't known: for a friend declaration, if
> name lookup doesn't find an existing name, and if it is a declaration
> of either a function or a function template, then this injects the
> name into the surrounding namespace. However, this doesn't apply for
> a function template specialization, as in your case, if the actual
> template declaration isn't available. Thus the compiler complains
> that you are trying to declare something you can't declare (a 
> non-function,
> non-template). It should be obvious that the compiler can't do anything
> about it unless you provide a declaration of the general template.
>
> I leave it to others to decide whether we want to keep this PR and if 
> so
> how to change the error message. I personally would vote for closing 
> it.
>
> W.
>
> -- 
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152
>
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
>



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152

[Bug c++/17152] Useless error message

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-08-31 05:29 -------
I agree with  Wolfgang about this error so closing as invalid.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152

[Bug c++/17152] Useless error message

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-11-05 19:27 -------
These are all duplicates of PR 15552 

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152

[Bug c++/17152] Useless error message

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-11-05 19:33 -------
Na, that was wrong, of course. 
W. 

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17152