[cfe-dev] Fwd: Clang comparison page

Joel Nelson joelnn at gmail.com
Mon Dec 10 06:34:34 PST 2007

Sorry missed the reply all button, forwarding to the group


Sent from my phone

Begin forwarded message:

> From: Joel Nelson <joelnn at gmail.com>
> Date: December 10, 2007 9:30:39 AM EST
> To: Chris Lattner <clattner at apple.com>
> Subject: Re: [cfe-dev] Clang comparison page

> Sent from my phone
> On Dec 10, 2007, at 1:04 AM, Chris Lattner <clattner at apple.com> wrote:
>> On Dec 9, 2007, at 9:27 PM, Joel Nelson wrote:
>>> I have no stake in Elsa, and I've never used it,
>> Your opinion is welcome!  I've made some edits in response to your  
>> feedback:
>> http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20071210/003255.html
>>> but my thoughts:
>>> Elsa is not a compiler, so I'm not sure that the following point  
>>> is appropriate:
>>> "Elsa does not support native code generation."
>> Right.  This gets to the "differences in goals" aspect of the  
>> comparison.  I should mention explicitly at the top that whether  
>> you consider one of these to be a big deal depends on what your  
>> personal goals are.  I clarified this in the intro
> Thanks I think that is well done
>>> Also the following point seems to be a political (and practical,
>>> granted) rather than a technical criticism:
>>> "The Elsa community is extremely small and major development work
>>> seems to have ceased in 2005, though it continues to be used by  
>>> other
>>> projects (e.g. Oink). Clang has a vibrant community including
>>> developers that are paid to work on it full time."
>>> A small community is only a problem for those who do not have the
>>> resources to contribute to the project themselves.
>> I mention this because it is a very big disadvantage for a lot of  
>> people: it basically means that if you hit a bug in Elsa, you have  
>> to fix it yourself or just work around it.  In clang, you can  
>> report the bug and it quite possible someone will fix it for you.   
>> This means that even if you *could* fix the bug yourself, you might  
>> find out that you don't have to, meaning you get more done in less  
>> of *your* time.
>>> Since as you say
>>> Clang has plenty of resources,
>> There is no such thing as "plenty" :)
>>> then I think Elsa could be adopted as
>>> the C++ parser if there were no technical issues, or if the cost of
>>> resolving the technical issues was less than the cost of a
>>> reimplementation.
>> If a reader has the ability to reimplement an entire C++ compiler  
>> from scratch and has the desire to do so, presumably they wouldn't  
>> be looking at either clang or elsa :).  The rest of the bullets  
>> explain technical problems that prevent clang from adopting Elsa.
> The only reason someone would be comparing Elsa and Clang today  
> would be if they are interested in helping to implement a c++ parser  
> themselves in clang (as you basically said).
> If you are not including that audience, then there is really no  
> comparison to be made today since clang and elsa are completely  
> disjoint with respect to the ability to parse c++, and every other  
> thing.
> Therefore you are speaking to the group of people who have the  
> ability to contribute to a c++ parser. If they disagree with your  
> technical arguments, they themselves have the power to correct the  
> problem of the small Elsa community.
> The issue I have with this argument in general is that it seems to  
> be the same fallacious argument made by popular American  
> politicians: "get with the winning team."
>> I updated the bullet to try to make it more clear what I'm getting  
>> at, please take a look and let me know if it helps.
>>> I just thought these two points may be unfair given the scope of  
>>> this
>>> doc is stated as "We restrict the discussion to very specific
>>> technical points to avoid controversy where possible." Maybe its  
>>> this
>>> statement which should be changed, instead.
>> I think it is true that the Elsa community is "extremely small", do  
>> you disagree with that part?
> No I think you are completely correct. I just wouldn't call that a  
> technical point. That may be the *result* of technical weaknesses  
> (as you argue well), or it could be the result of a lack of the kind  
> of promotion you do for clang. Either way I think it is not itself  
> material.
> Basically I think Clang can win on technical merits, so why not  
> leave it at that?
> Thanks,
> Joel
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