[Bug c++/20212] New: attribute unused vs. member function template

["bkoz at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

Works with: 3.4.2
Fails with: 4.0.0

For some reason, the attached output warns (oddly) with the attached code:

%COMP.sh "-g -O2 -Wunused -Wextra" debug.ii
/mnt/hd/src/gcc/libstdc++-v3/src/debug.cc: In instantiation of 'void
__gnu_debug::_Error_formatter::_M_format_word(char*, int, const char*, _Tp)
const [with _Tp = const void*]':
/mnt/hd/src/gcc/libstdc++-v3/src/debug.cc:274:   instantiated from here
/mnt/hd/bld/gcc.disable-c99/i686-pc-linux-gnu/libstdc++-v3/include/debug/formatter.h:363:
warning: unused parameter '__n'
/mnt/hd/src/gcc/libstdc++-v3/src/debug.cc: In instantiation of 'void
__gnu_debug::_Error_formatter::_M_format_word(char*, int, const char*, _Tp)
const [with _Tp = const char*]':
/mnt/hd/src/gcc/libstdc++-v3/src/debug.cc:383:   instantiated from here
/mnt/hd/bld/gcc.disable-c99/i686-pc-linux-gnu/libstdc++-v3/include/debug/formatter.h:363:
warning: unused parameter '__n'
/mnt/hd/src/gcc/libstdc++-v3/src/debug.cc: In instantiation of 'void
__gnu_debug::_Error_formatter::_M_format_word(char*, int, const char*, _Tp)
const [with _Tp = unsigned int]':
/mnt/hd/src/gcc/libstdc++-v3/src/debug.cc:473:   instantiated from here
/mnt/hd/bld/gcc.disable-c99/i686-pc-linux-gnu/libstdc++-v3/include/debug/formatter.h:363:
warning: unused parameter '__n'
/usr/bin/ld: cannot find -lv3test
collect2: ld returned 1 exit status

I believe this code to be fine (indeed, with 3.4.x I have no warning.)

I tried to reduce this down but didn't hit anything with the obvious reduction.
So, I file this instead.

-benjamin

-- 
           Summary: attribute unused vs. member function template
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bkoz at gcc dot gnu dot org
                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=20212