[Bug libstdc++/34105] New: [4.3 Regression] Confusing error message with missing #include <algorithm>

[rguenth at gcc dot gnu dot org]

For

#include <vector>
#include <string>

int main()
{
  std::vector<std::string> x;
  std::string s("hello");
  return std::find(x.begin(), x.end(), s) - x.begin();
}

we now get "interesting" linker errors with trunk:

> g++-4.3 -o t t.C
/tmp/cc3Vq2t8.o: In function `main':
t.C:(.text+0x65): undefined reference to
`__gnu_cxx::__normal_iterator<std::basic_string<char, std::char_traits<char>,
std::allocator<char> >*, std::vector<std::basic_string<char,
std::char_traits<char>, std::allocator<char> >,
std::allocator<std::basic_string<char, std::char_traits<char>,
std::allocator<char> > > > >
std::find<__gnu_cxx::__normal_iterator<std::basic_string<char,
std::char_traits<char>, std::allocator<char> >*,
std::vector<std::basic_string<char, std::char_traits<char>,
std::allocator<char> >, std::allocator<std::basic_string<char,
std::char_traits<char>, std::allocator<char> > > > >, std::basic_string<char,
std::char_traits<char>, std::allocator<char> >
>(__gnu_cxx::__normal_iterator<std::basic_string<char, std::char_traits<char>,
std::allocator<char> >*, std::vector<std::basic_string<char,
std::char_traits<char>, std::allocator<char> >,
std::allocator<std::basic_string<char, std::char_traits<char>,
std::allocator<char> > > > >,
__gnu_cxx::__normal_iterator<std::basic_string<char, std::char_traits<char>,
std::allocator<char> >*, std::vector<std::basic_string<char,
std::char_traits<char>, std::allocator<char> >,
std::allocator<std::basic_string<char, std::char_traits<char>,
std::allocator<char> > > > >, std::basic_string<char, std::char_traits<char>,
std::allocator<char> > const&)'
collect2: ld returned 1 exit status

where it is not exactly obvious that just the #include <algorithm> is missing
here.  With 4.2 and 4.2 at least the program linked fine (I guess algorithm
was pulled in anyway).

Can we improve this situation by not making algorithm half-way available so
we can raise a meaningful error instead?


-- 
           Summary: [4.3 Regression] Confusing error message with missing
                    #include <algorithm>
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid, diagnostic
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34105