[Bug libstdc++/48257] std::string::assign() corrupts std::string static data when called on emptyString1 using emptyString2.data()

["mohsinrzaidi at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48257

Mohsin <mohsinrzaidi at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |

--- Comment #4 from Mohsin <mohsinrzaidi at gmail dot com> 2011-03-24 06:19:52 UTC ---
(In reply to comment #3)
> In C++03 see 21.3.5.3 [lib.string.assign] paragraph 6 where 
> string::assign(const char* s, size_t n) is defined to return
> assign( string(s, n) ) and that constructor:
> 
> Constructs an object of class basic_string and determines its initial string
> value from the array of charT of length n whose first element is designated by
> s, 
> 
> In C++0x the requirement is explicit, [string::assign] paragraph 8 says
> 
> Requires: s points to an array of at least n elements of charT.

I believe this is what you were referring to (from N3242=11-0012):

basic_string& assign(const charT* s, size_type n);
8 Requires: s points to an array of at least n elements of charT.
9 Throws: length_error if n > max_size().
10 Effects: Replaces the string controlled by *this with a string of length n
whose elements are a copy
of those pointed to by s.
11 Returns: *this.

Thanks for pointing this out. However, does libstdc++ throw and error if "n >
max_size()"? I don't think it does.

>From the latest libstdc++ documentation:

<snip>

template<typename _CharT, typename _Traits , typename _Alloc >
basic_string< _CharT, _Traits, _Alloc > & std::basic_string< _CharT, _Traits,
_Alloc >::assign     (     const _CharT *      __s,
        size_type      __n     
    )             

Set value to a C substring.

Parameters:
        s     The C string to use.
        n     Number of characters to use.

Returns:
    Reference to this string.

This function sets the value of this string to the first n characters of s. If
n is is larger than the number of available characters in s, the remainder of s
is used.

Definition at line 261 of file basic_string.tcc.

References std::basic_string< _CharT, _Traits, _Alloc >::size().

</snip>

I don't see this as saying that the string has to have at least n elements OR
that an error will be thrown if it isn't.

>From the latest basic_string code:

<snip>

  template<typename _CharT, typename _Traits, typename _Alloc>
00259     basic_string<_CharT, _Traits, _Alloc>&
00260     basic_string<_CharT, _Traits, _Alloc>::
00261     assign(const _CharT* __s, size_type __n)
00262     {
00263       __glibcxx_requires_string_len(__s, __n);
00264       _M_check_length(this->size(), __n, "basic_string::assign");
00265       if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
00266     return _M_replace_safe(size_type(0), this->size(), __s, __n);
00267       else
00268     {
00269       // Work in-place.
00270       const size_type __pos = __s - _M_data();
00271       if (__pos >= __n)
00272         _M_copy(_M_data(), __s, __n);
00273       else if (__pos)
00274         _M_move(_M_data(), __s, __n);
00275       _M_rep()->_M_set_length_and_sharable(__n);
00276       return *this;
00277     }
00278      }

</snip>

I don't see any errors being thrown. I am not trying to nit-pick but I've
raised this issue because I was affected by it and had to spend several days
isolating it. It would have made my life a whole lot easier if, as you claim,
libstdc++ had thrown an error.

Just a request, but please let the discussion complete before you go ahead and
mark the bug as Resolved-Invalid. I don't mind it being marked invalid, but I
consider it disrespectful for you to not even wait for my response and rushing
to mark it as invalid. Once we're through discussing, I will mark it invalid
myself if necessary.