[Bug c++/23771] New: [4.0.2 regression] Constant template argument not recognized as such

[bangerth at dealii dot org]

This code 
---------------------- 
template <typename T> struct length { 
    static const int value = 3; 
}; 
 
template <typename T, int L = length<T>::value> struct S {}; 
 
template <typename T> 
S<T> bar (T); 
 
template <int dim> void foo () { 
  bar (1); 
} 
----------------------------- 
Used to compile with gcc 4.0.1pre (20050531), but it doesn't any more with 
today's snapshot of the 4.0.2 branch. It apparently doesn't recognize 
length<T>::value as an integer constant expression any more: 
 
> /home/bangerth/bin/gcc-4.0.2-pre/bin/c++ -c source/grid/grid_generator.cc  
source/grid/grid_generator.cc: In function &#8216;void foo()&#8217;: 
source/grid/grid_generator.cc:11: error: &#8216;length<int>::value&#8217; is 
not a valid 
template argument for type &#8216;int&#8217; because it is a non-constant 
expression 
source/grid/grid_generator.cc:11: error: no matching function for call to 
&#8216;bar(int)&#8217; 
 
I don't really see how to work around this problem short of specifying the 
value of the second template argument by hand. 
 
This bug will (again) prevent 4.0.2 from being able to compile one of the 
proposed SPEC 2005 benchmarks (4.0.1 couldn't do this due to PR 21799). It 
would be nice if this could be fixed before 4.0.2 comes out. 
 
Thanks 
  Wolfgang

-- 
           Summary: [4.0.2 regression] Constant template argument not
                    recognized as such
           Product: gcc
           Version: 4.0.2
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bangerth at dealii dot org
                CC: gcc-bugs at gcc dot gnu dot org,mmitchel at gcc dot gnu
                    dot org,nathan at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23771