[Bug libstdc++/48355] New: Assigning NULL to string segfaults

[amr.ali.cc at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48355

           Summary: Assigning NULL to string segfaults
           Product: gcc
           Version: 4.5.1
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: amr.ali.cc@gmail.com
              Host: Linux 2.6.35-28-generic #49-Ubuntu SMP x86_64


Created attachment 23813
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23813
Bug reproducible code

When trying to call the ctor of string() or basic_string<char,
char_traits<char>, allocator<char> >() with a NULL pointer parameter (instead
of the char pointer), it would abort() with a logic_error saying that NULLs
aren't allowed.

Which is the result of the following code:

basic_string.tcc
 133     // NB: Not required, but considered best practice.
 134     if (__gnu_cxx::__is_null_pointer(__beg) && __beg != __end)
 135       __throw_logic_error(__N("basic_string::_S_construct null not
valid"));

However, when trying to assign NULL to a string, it doesn't do
__is_null_pointer() check and tries to call __builtin_strlen on the pointer,
which of course, results in the infamous SIGSEGV.

I'd say either make the behavior for the assign() equal to the ctor or
preferably instead just have an empty string when assigned a NULL pointer.

I'd happily write a patch for this myself, I just need a few pointers of where
this should be fixed. I've looked around in basic_string.{h,tcc} and
char_traits.h but still a little confused.

NOTE:
Attached a code snippet to reproduce the behavior mentioned above.

Checked Against:
OSX v10.6.7 - GCC v4.2.1
Linux v2.6.35-28-generic - GCC v4.4.5/v4.5.1