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

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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>
>

My understanding is that EH works fine without RTTI. However, we use
typeid in LLVM in a few limited spots like lib/VMCore/Pass.cpp

Reid.

On Sat, 2005-04-23 at 20:12 -0700, Jeff Cohen wrote:
> 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
> >
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
> >
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
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That requires RTTI.

Anyway, I verified exceptions really don't need RTTI in VC++ also.  
Furthermore, VC++ complains when dynamic_cast is used with RTTI disabled.

Reid Spencer wrote:
>My understanding is that EH works fine without RTTI. However, we use
>typeid in LLVM in a few limited spots like lib/VMCore/Pass.cpp
>
>Reid.
>
>On Sat, 2005-04-23 at 20:12 -0700, Jeff Cohen wrote:
>  
>
>>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
>>>>        
>>>>
>>>_______________________________________________
>>>LLVM Developers mailing list
>>>LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>>http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>
>>>
>>>      
>>>
>>_______________________________________________
>>LLVM Developers mailing list
>>LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
>>    
>>