[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 1:21 PM
Subject: Re: [LLVMdev] me being stupid: me vs the llvm codebase...


>>> 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...).
>>
>
> In the LLVM case, it generated the code in the first place, so it
> obviously had access to write it there.
>
> In any case, the JIT can use mprotect to map the page writable if it
> has to.
>

yes, ok (yes, on windows VirtualAlloc will probably also work here...).

so, yeah, I deal with a mixed case (some code my compiler, much of the rest 
gcc, some dynamicly linked, much of the rest with ld...). I think this way 
about things I guess...


>> 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...
>
> That sounds like an excellent reason to get more familiar with C++
> and the LLVM code base.  It's usually better to try to grow your
> capabilities than to limit what you can do by avoiding learning new
> things ;-)
>

yeah, I have spent enough of my life avoiding C++...
(personally, the language never seemed all that worthwhile, and back when I 
was a lot younger I had a run-in with the pain of writing stuff Java that 
made me despise OO for years...).


> LLVM has extensive documentation at http://llvm.org/docs
>

yes, may need to look through a lot of this.


>> (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...).
>
> Sure, but that isn't a good reason to fill the in-boxes of people who
> are interested in LLVM. :)
>

ok, ok, good point. if people want to write off-list, that is probably 
better...
I guess I will try to limit my on-list activity to more on-topic pursuits I 
guess...


>> 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.
>
> We certainly welcome "lame hobbists"!  That is not the point.  In
> fact, one significant goal of LLVM is to make it usable and
> approachable for people with all sorts of backgrounds.  We haven't
> necessarily done a great job at this, but it is a goal :).  I have no
> problem with discussing technical issues or answering questions on
> this list, just so long as they stay LLVM-related.
>
> Thanks, and welcome to the LLVM community!
>

yes, ok.


> -Chris
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