Re: [boost] [function] function wrapping with no exception safetyguarantee

Subject: Re: [boost] [function] function wrapping with no exception safetyguarantee
From: Emil Dotchevski (emil_at_[hidden])
Date: 2010-10-08 11:12:27

On Thu, Oct 7, 2010 at 7:56 PM, OvermindDL1 <overminddl1_at_[hidden]> wrote:
> On Thu, Oct 7, 2010 at 8:37 PM, Emil Dotchevski <emil_at_[hidden]> wrote:
>> On Thu, Oct 7, 2010 at 6:22 PM, Peter Dimov <pdimov_at_[hidden]> wrote:
>>> Daniel Walker wrote:
>>>
>>>> void do_stuff(boost::function<int(int)> f)
>>>> {
>>>>   // ...
>>>>   if(f) {
>>>>       // Remove the exception safety guarantee for this block.
>>>>       boost::unsafe_function<int(int)> g = f;
>>>>       for(int i = 0; i < INT_MAX; ++i)
>>>>           g(i);
>>>>   }
>>>>   // ...
>>>> }
>>>
>>> This example implies that unsafe_function is inherently more efficient, but
>>> this need not be so. An empty function may point to throw_bad_function_call
>>> instead of NULL.
>>
>> Right, and what the empty boost::function does needs not be decided at
>> compile time, it can be done in the constructor.
>
> However the empty built-in Boost.Function still does an if(isnull)
> test on every operator call, whether you assigned something in the
> constructor or not...

Like Peter said, this need not be the case.

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode