Re: libstdc++/5133: Problems with toupper

[Philip Martin <philip at codematters dot co dot uk>]

> #include <string>
> #include <iostream> // does work, when this line is removed
> #include <algorithm>
> #include <cctype>
> 
> int main()
> {
>     std::string s("Hallo");
>     std::transform (s.begin(), s.end(), s.begin(), std::tolower);
>     std::transform (s.begin(), s.end(), s.begin(), ::tolower);
> }
 
Using gcc the include of <iostream> brings in a declaration of the
function template

  namespace std { template<class T> T tolower(T, const locale&); }

and the include of <cctype> brings in the functions

  extern "C" int tolower(int);
  namespace std { using ::tolower; }

[The global scope tolower function is a separate problem, but doesn't
affect this PR.]

Now, I believe you are trying to call the tolower function, rather
than the tolower function template. I don't understand template
argument deduction well enough to be able to say whether the compiler
should work out that this is what you want, but you can tell it
explicitly

  typedef std::string::iterator I;
  std::transform<I,I,int(*)(int)>transform(s.begin(),s.end(),s.begin(),std::tolower);

This compiles with gcc 3.0.3 and gcc 3.1. However it doesn't address
the "C"/"C++" linkage point mentioned by Martin. One can avoid that by
using the function template, however using the function template is
tricky because the second parameter is a reference. One would like to
try

  // this won't work
  std::locale loc;
  std::transform(s.begin(),s.end().s.begin(),
                 std::bind2nd(std::ptr_fun(std::tolower<char>),loc));

but this will suffer from the reference to a reference problem. If you
wish to pursue this you should consider using the bind library from
boost (http://www.boost.org) instead of std::bind2nd

-- 
Philip