llvm dev - Apr 2005 - [LLVMdev] isa and friends as an alternative to dynamic cast?

On Thu, 21 Apr 2005, Jeff Cohen wrote:
> That's a good point.
I think there are some issues with doing this (e.g. EH doesn't work, so 
the very few places we use it would have to be modified), but other than 
that I fully support the idea.

-Chris
> Evan Jones wrote:
>
>> On Thu, 2005-21-04 at 19:43 -0700, Reid Spencer wrote:
>> 
>>> In case it wasn't obvious from Misha's answer, the main
reason for
>>> doing this is speed. RTTI is not very quick.
>>> 
>> 
>> Right. This is why I was somewhat suprized to see the "isa"
facilities
>> included in LLVM without also disabling rtti. It will reduce the memory
>> footprint a fair bit if you do disable it, at least based on my
>> experience with other C++ projects.
>> 
>> Evan Jones
>> 
>> 
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>
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-Chris

-- 
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http://llvm.cs.uiuc.edu/

This may be the case with GCC, but VC++ allows exception handling to be 
enabled while RTTI is disabled.  According to VC++ documentation, RTTI 
is needed only to support dynamic_cast, the typeid operator, and the 
type_info class.

Chris Lattner wrote:
> On Thu, 21 Apr 2005, Jeff Cohen wrote:
>
>> That's a good point.
>
>
> I think there are some issues with doing this (e.g. EH doesn't work, 
> so the very few places we use it would have to be modified), but other 
> than that I fully support the idea.
>
> -Chris

As far as I can tell, exceptions work just fine without RTTI when using 
gcc 3.4.2.  dynamic_cast, on the hand, crashes without RTTI (no 
compilation error or warning is generated).

Jeff Cohen wrote:
> This may be the case with GCC, but VC++ allows exception handling to 
> be enabled while RTTI is disabled.  According to VC++ documentation, 
> RTTI is needed only to support dynamic_cast, the typeid operator, and 
> the type_info class.
>
> Chris Lattner wrote:
>
>> On Thu, 21 Apr 2005, Jeff Cohen wrote:
>>
>>> That's a good point.
>>
>>
>>
>> I think there are some issues with doing this (e.g. EH doesn't
work,
>> so the very few places we use it would have to be modified), but 
>> other than that I fully support the idea.
>>
>> -Chris
>
>
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>