Re: KDE hackers, please read (was [nathan@codesourcery.com: Re: GCC3.0.3: Bugs to Fix]) (fwd)

[Mark Mitchell <mark at codesourcery dot com>]

--On Tuesday, December 11, 2001 03:09:53 PM -0200 Alexandre Oliva 
<aoliva@redhat.com> wrote:

> On Dec 10, 2001, Mark Mitchell <mark@codesourcery.com> wrote:
>
>>> 3) Persuade gcc folks to add compiler switch that makes gcc use string
>>> comparing when doing rtti, and simply compile whole KDE with this switch
>>> turned on.
>
>> All code in the application -- including the C++ run-time library --
>> needs to be compiled the same way, so you would have to rebuild
>> everything to do this.
>
> Err...  Wouldn't it be enough to link with a modified version of the
> object file that implements rtti comparison?  Or are such comparisons
> ever inlined in the generated code?

They are typically inlined.  From <typeinfo>:

  class type_info {
    ...
    bool operator==(const type_info& __arg) const
    { return __name == __arg.__name; }
  };

There you have it.  We certainly want to inline these; they are
almost free.

The point I tried to make yesterday, but apparently somewhat
unsuccessfully, is that RTTI is only the tip of the iceberg.
You might be able to fix this -- but you can't fix all the
problems, and it's not easy to specify what subset of the
language you can support.

It's a mistake to try.  It's much better to tell your customers
how to use your product successfully than to encourage them to
use a technique likely to fail.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com