[libstdc++ patch] Fix basic_string::_S_construct null pointer check

[Phil Edwards]

Couple of comments, Doug:

1)  Can "Apple Mail" be told to do its attachments in text/plain instead
    of application/octet-stream?

> --Apple-Mail-16-444405215
> Content-Type: application/octet-stream; x-unix-mode=0644; name="string_construct_null.patch"
> Content-Disposition: attachment; filename="string_construct_null.patch"
> Content-Transfer-Encoding: 7bit
> 
> *** basic_string.tcc	2003-07-04 21:05:34.000000000 -0700
> --- /home/dgregor/basic_string.tcc	2003-07-14 11:46:46.000000000 -0700
> ***************
> *** 45,50 ****
> --- 45,60 ----
>   
>   namespace std
>   {
> +   template<typename _Type>
> +     inline bool
> +     __null_pointer(_Type* __ptr)
> +     { return __ptr == 0; }
> + 
> +   template<typename _Type>
> +     inline bool
> +     __null_pointer(const _Type&)
> +     { return false; }
> + 

I have a feeling these will come in handy in other files, but I can't
think of a better place to put them right now.  In the meantime:

2)  Please name the function __is_null_pointer or __null_pointer_p
    or something like that, to make it clear this is a predicate function.
    Reading the code where it was used made me think at first that the
    function creates and returns a null pointer.

3)  This should go in __gnu_cxx, not std.  Actually, this should go in
    our internal-details namespace, but we haven't invented that name yet.


> --Apple-Mail-16-444405215
> Content-Type: application/octet-stream; x-unix-mode=0644; name="string_construct_null.ChangeLog"
> Content-Disposition: attachment; filename="string_construct_null.ChangeLog"
> Content-Transfer-Encoding: 7bit
> 
> 2003-07-14  Doug Gregor <dgregor@apple.com>
> 	    * include/bits/basic_string.tcc (basic_string::_S_construct):
> 	    Fix null pointer check.
> 	    * include/bits/basic_string.tcc (__null_pointer): New.

Please put a blank line after the date/name/email bit, for the sake of
GNU-changelog-style parsers.


Phil

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