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Subject: Re: [boost] [1.44][Serialization] fails to compile on OSX universal
From: David Irvine (david.irvine_at_[hidden])
Date: 2010-08-21 13:04:37

On Sat, Aug 21, 2010 at 6:08 PM, Robert Ramey <ramey_at_[hidden]> wrote:
> Dave Abrahams wrote:
>> Sent from my iPhone
>> On Aug 20, 2010, at 9:09 PM, Emil Dotchevski
>> <emil_at_[hidden]> wrote:
>>> One option is to "fix" them anyway. Unfortunately, a lot of times
>>> this involves casting, and in general I find it ill-advised to use a
>>> cast to suppress a warning. Think about it: casts are used to tell
>>> the compiler to do something it wouldn't normally do because it is
>>> dangerous. This is true for all casts, including the ones people
>>> sprinkle around to "fix" warnings.
>> True, but you can often avoid those casts by allowing (presumably
>> safer) implicit conversions to do the same work,e.g. instead of
>> static_cast<Base&>(derived), declare and initialize a named Base&.
> Here is what I did.
> I had a bunch of warnings that I could have fixed with casts.  In some
> cases I did.  But in most cases I felt I was "Hiding the problem" by
> puting in a cast.
> What I ended up doing in many cases was make a special type such as
> // a special type of integer.  This is used as an 'id" so it makes no
> // sense to apply arithmetic operation or to compare it to other integers
> // which are not this type of id
> class special_type {
>    int m_i;
> public:
>    // trap uninitialized values
>    special_type(int i) : m_i(i) {}
>    // trap erroneous comparisons
>    bool operator==(const & special_type rhs) const {
>        return m_i == rhs.m_i
>   }
>   // don't permit id to change - don't define assignment
>   // but copying is ok
>   special_type(const special_type & s) : m_i(s.m_i) ;
> };
> Now compile your program and all the warning are now errors.
> (plus a whole new raft of errors).  Then start doing things like
> replace
>    int id;
>    if(id == original_id)
>        ...
> with
>    special_type id(... ah think about this - this is a good thing);
>    if(id == original_id)
>        ...
> Now
> a) your warnings disappear
> b) you might have fixed a bug
> c) you have set things up to avoid future bugs
> d) at no cost in execution time
> This might look like a lot of work.  But it really isn't.  You
> have to think carefully about what kind of operations you
> want to actually permit and/or trap which is some work.
> But fixing the generated errors is very easy as the whole
> system almost tells you what to fix.  I can do it while participating
> in an otherwise mind numbing phone conference.  In fact
> it's a good way to do as it makes me sound less disinterested.
> Robert Ramey
> _______________________________________________
This looks like a good move and I think very efficient, although I
think perhaps for completeness you should declare the assignment
operator private, to prevent the compiler declaring if for you.

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