[RFC] First 3.5 project: don't assign _S_terminal in string::c_str()

[Paolo Carlini]

Paolo Carlini wrote:

> By the way, due to 21.3.4 this is a *bug*, that we should fix in
> 3.4 (3.3?) too. Testcase:

This is more robust (fails when i ~ 500 on both i686 and
x86_64, mainline and branch):

#include <string>
#include <cassert>

int main()
{
  for (int i = 0; i < 2000; ++i)
    {
      std::string a;

      for (int j = 0; j < i; ++j)
        a += 'a';

      a.reserve(i + 10);

      const std::string b(a);
      assert( b[i] == '\0' );
    }
}

Paolo.