[LLVMdev] me being stupid: me vs the llvm codebase...

[BGB]

----- Original Message ----- 
From: "Chris Lattner" <sabre at nondot.org>
To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
Sent: Wednesday, October 24, 2007 11:30 AM
Subject: Re: [LLVMdev] me being stupid: me vs the llvm codebase...


> On Wed, 24 Oct 2007, BGB wrote:
>> even more interestingly: if the same compiler were also used for static
>> compilation, it could be used as a special feature to make such dynamic
>> movability available even for statically compiled and linked code (as
>> is, in my case, parts of the app which are statically compiled and
>> linked, can't currently be relinked...).
>
> LLVM handles function pointers currently.  It just overwrites the first
> instruction of the old code with an unconditional branch to the new
> implementation.  Thus, any code branching to the old location will still
> work.
>

yes, that works so long as one has write access to the text section (or the 
code is otherwise in a writable area).

at least with typical compilation, afaik this is not the case (I think both 
linux and windows by default have .text being read only, which may limit 
applicability of this approach...).

so, nearly any option works for dynamic land, but fewer options are around 
for static linking (this is partly what I was addressing as well, that in 
some cases one makes available a "universal proxy", and the VM is smart 
enough to figure this out, for example, by first trying to adjust the proxy 
before falling back to more drastic measures, such as patching or 
relinking...).


> It would be possible to implement more aggressive solutions, and if you
> are interested, llvmdev is a great place to talk about how to do it.
>

yes, maybe.

well, maybe I can fammiliarize myself with the project more, and maybe be 
able to say something actually useful at some point...


> Are you interested in using LLVM for your project?  If not, llvmdev isn't
> a very appropriate place to talk about your project.  If you are, this is
> a great place to ask questions or discuss design issues of LLVM itself.
>

I am still undecided mostly.


a major detractor at this point for me and LLVM, is that it is written in 
C++, and I am not so good with C++, and I am otherwise not so fammiliar with 
the codebase...


(as for myself and my project, well, my issue is partly one of isolation, 
namely that not really anyone cares about much of this, so I don't have all 
that many people to talk to...).
(not too much interesting goes on on usenet is all...).


well, this is among other issues, like homework, lack of female interest, 
and 'future'...

so, I am just some lame hobbyist is all I guess, may stay around or may go 
away, or may use LLVM or continue using my own compiler (and at some point 
have to get a job or something, parents want me to be a school teacher, but 
I had hoped to be a programmer, maybe games or 3D modeling software or 
something, but they think there is no future in this, or that there is too 
much competition and no real jobs, or such...).

this is life I guess...


> -Chris
>
> -- 
> http://nondot.org/sabre/
> http://llvm.org/
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