Re: libstdc++/5133: Problems with toupper

[Philip Martin <philip@codematters.co.uk>]

The following reply was made to PR libstdc++/5133; it has been noted by GNATS.

From: Philip Martin <philip@codematters.co.uk>
To: gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org, paolo@gcc.gnu.org, schmid@snake.iap.physik.tu-darmstadt.de, sebor@roguewave.com
Cc:  
Subject: Re: libstdc++/5133: Problems with toupper
Date: 17 Dec 2001 16:01:28 +0000

 > #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