Still assertion failure in boost::format for empty strings

[daniel_kruegler]

The assertion failure of boost::format in case of empty
string arguments that occured since VS2005 has been
partly fixed by cepstein in March 2006. This fix was
partial, because there still exists a corner case,
where this assertion can take place:

#include <iostream>
#include <ostream>
#include <string>
#include <boost/format.hpp>

int main() {
  std::string arg; // empty string
  boost::format fmt = boost::format("%=8s") % arg;
  std::string s = fmt.str();
  std::cout << s << std::endl;
}

The proposed patch looks in unified syntax:
Index: feed_args.hpp
===================================================================
RCS file: /cvsroot/boost/boost/boost/format/feed_args.hpp,v
retrieving revision 1.29
diff -u -r1.29 feed_args.hpp
--- feed_args.hpp	22 Mar 2006 15:13:25 -0000	1.29
+++ feed_args.hpp	15 Jun 2006 19:49:37 -0000
@@ -63,7 +63,8 @@
             if(n_before) res.append(n_before, fill_char);
             if(prefix_space) 
               res.append(1, prefix_space);
-            res.append(beg, size);
+            if (size)
+              res.append(beg, size);
             if(n_after) res.append(n_after, fill_char);
         }
     } // -mk_str(..) 


and in standard syntax:

Index: feed_args.hpp
===================================================================
RCS file: /cvsroot/boost/boost/boost/format/feed_args.hpp,v
retrieving revision 1.29
diff -r1.29 feed_args.hpp
66c66,67
<             res.append(beg, size);
---
>             if (size)
>               res.append(beg, size);

[joaquintides]

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user_id=911241

Applied fixes according to Daniel's instructions