[Bug c++/18354] New: expression "+1" not considered constant (as template parameter).

["fsm at robots dot ox dot ac dot uk" <gcc-bugzilla at gcc dot gnu dot org>]

Have class templated over "int". Compiler does not accept "+1" as template
parameter on the grounds that it is not a constant expression. Compiler accepts
both "-1" and "1".

This bug appears in:  gcc version 4.0.0 20041107 (experimental)
                      gcc version 4.0.0 20041106 (experimental)

It did not appear in: gcc version 4.0.0 20040927 (experimental)

The following code reproduces the problem.
---------------------8<-------------------
template <int N>
struct X { };

void f()
{
  X< 1> a;
  X<-1> b;
  X<+1> c;  // <-- error here.
}
---------------------8<-------------------


$ g++ -c f.cxx
f.cxx: In function ?void f()?:
f.cxx:8: error: ?1? is not a valid template argument for type ?int? because it
is a non-constant expression
f.cxx:8: error: invalid type in declaration before ?;? token



$ uname -a
Linux theseus 2.4.20-8smp #1 SMP Thu Mar 13 17:45:54 EST 2003 i686 i686 i386
GNU/Linux




$ g++ -v
Reading specs from /lvm/fred/gcc/cvs/install/lib/gcc/i686-pc-linux-gnu/4.0.0/specs
Configured with: ../gcc/configure --prefix=/lvm/fred/gcc/cvs/install
--enable-static --enable-shared --enable-languages=c,c++,f95
--with-mpfr=/lvm/fred/pkg/gmp/install
Thread model: posix
gcc version 4.0.0 20041107 (experimental)

-- 
           Summary: expression "+1" not considered constant (as template
                    parameter).
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: fsm at robots dot ox dot ac dot uk
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18354