[Bug c++/16582] New: Wrong diagnostic when using "&a[1]" as template argument

[Bug c++/16582] New: Wrong diagnostic when using "&a[1]" as template argument

[giovannibajo at libero dot it]

Compiling the following code:

-----------------------------------------
template<class T, char* p> struct X {
  X();
  X(const char* q) { /* ... */ }
};

char p[] = "Vivisectionist";
X<int, p> x2; // OK
X<int, &p[0]> x3; // ERROR
-----------------------------------------

I get this error on mainline:

nontype1.cc: At global scope:
nontype1.cc:8: error: missing `>' to terminate the template argument list
nontype1.cc:8: error: template argument 2 is invalid
nontype1.cc:8: error: expected init-declarator before '>' token
nontype1.cc:8: error: expected `,' or `;' before '>' token

The message is totally bogus. The real problem is that a call to operator[] is 
not be allowed within a template argument.

This happens with both 3.4 and mainline. Not a regression though since older 
versions even incorrectly accepted the code (in fact, I fixed this very issue 
within the new parser).

-- 
           Summary: Wrong diagnostic when using "&a[1]" as template argument
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: giovannibajo at libero dot it
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16582

[Bug c++/16582] Wrong diagnostic when using "&a[1]" as template argument

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-07-16 03:36 -------
Confirmed. This is about the worst message I've seen in a long 
while :) 
 
Here's what icc says: 
g/x> icc -c -Xc -ansi x.cc 
x.cc(8): error: this operator is not allowed in a template argument expression 
  X<int, &p[0]> x3; // ERROR 
           ^ 
 
compilation aborted for x.cc (code 2) 
 
W. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-07-16 03:36:36
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16582

[Bug c++/16582] Wrong diagnostic when using "&a[1]" as template argument

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16582

[Bug c++/16582] Wrong diagnostic when using "&a[1]" as template argument

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=16582

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
C++11/C++14/C++98 gives:
<source>:8:13: error: template argument 2 is invalid
    8 | X<int, &p[0]> x3; // ERROR
      |             ^

While C++17 gives:
<source>:8:8: error: '& p[0]' is not a valid template argument of type 'char*'
because 'p[0]' is not a variable
    8 | X<int, &p[0]> x3; // ERROR
      |        ^~~~~

And C++20 accepts the code.

Note clang accepts the code for C++17 and C++20.

[Bug c++/16582] Wrong diagnostic when using "&a[1]" as template argument

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-02-26 19:29 -------
the mainline gives:
t.cc:9: error: template argument 2 is invalid
t.cc:9: error: invalid type in declaration before ';' token

Which might be an ok enough error message.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16582