stdcxx-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Martin Sebor <se...@roguewave.com>
Subject Re: [STDCXX-550] Please peer review this change.
Date Mon, 02 Jun 2008 22:20:47 GMT
Eric Lemings wrote:
>  
> 
>> -----Original Message-----
>> From: Martin Sebor [mailto:sebor@roguewave.com] 
>> Sent: Monday, June 02, 2008 2:44 PM
>> To: dev@stdcxx.apache.org
>> Subject: Re: [STDCXX-550] Please peer review this change.
>>
>> Eric Lemings wrote:
>>>  
>>> Would like to get another set of eyes on this before I submit.
>>>
>>> $ svn diff include/deque
>>> Index: include/deque
>>> ===================================================================
>>> --- include/deque       (revision 662487)
>>> +++ include/deque       (working copy)
>>> @@ -749,7 +749,7 @@
>>>      void _C_insert (const iterator &__it,
>>>                      _IntType __n, _IntType __x, int) {
>>>          // see 23.1.1, p9 and DR 438
>>> -        _C_insert_n (__it, __n, __x);
>>> +        _C_insert_n (__it, __n, const_reference (__x));
>> I suspect this is not correct. Suppose the type of __x is
>> a 4 byte int and const_reference is an 8 byte long. The cast
>> will make _C_insert_n() to read 4 bytes past the end of __x.
>> A better fix might be to cast __x to value_type, as long as
>> doing so doesn't violate [sequence.reqmts].
> 
> Yep.  Good call.  Will change to value_type() cast.

Do read DR 438 before applying the cast. There are some obscure
corner cases here, e.g., IntType being a user-defined "integer-
like" type. I don't know if we support this case now, or if we
do, if it's being tested, but suffice it to say that there are
subtle differences between direct-initialization either via
a function-style cast or static_cast, or copy-initialization
(passing arguments to functions).

Martin

> 
> Brad.
> 
>> See also LWG DR 438 for some background:
>> http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#438
>>
>> Martin
>>


Mime
View raw message