[Bug libstdc++/58415] New: __sso_string_base move constructor does not null terminate local data when moving from empty string

[mkirzinger at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58415

            Bug ID: 58415
           Summary: __sso_string_base move constructor does not null
                    terminate local data when moving from empty string
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mkirzinger at gmail dot com

When doing a move construct using a sso_string_base versa_string where it is
moving from an empty string, the contents of the string it is moving from are
not copied, leaving the local data uninitialized (and later calling c_str() on
it may produce invalid output).

Code that demonstrates one of the situations this problem can show up (compile
with -std=c++11):

------------------------------------------
#include <ext/vstring.h>
#include <cstdio>

typedef __gnu_cxx::__versa_string<char> string;

int main(int argc, char* argv[])
{
    string s1("string");
    string s2("");
    std::swap(s1, s2);
    printf("%s%s\n", s1.c_str(), s2.c_str());
}
------------------------------------------

Expected output:
string
Actual output:
stringstring