[cfe-dev] [llvm-dev] JIT - Resolve obj file without a main

Tue Jun 13 08:13:04 PDT 2017

Hi Björn

I am not aware of any symbol query issue that depends on the presence of
a main function. However, if you call IRCompileLayer::findSymbol(const
std::string &Name, bool ExportedSymbolsOnly) you should make sure to
pass "false" as the second argument if you are running on Windows.

If you look for a working demo on Windows, that may be interesting for
you (incl. a step-by-step guide in branches):
https://github.com/weliveindetail/JitFromScratch

Cheers
Stefan

Am 29.05.17 um 09:08 schrieb via llvm-dev:

> Hello Lang,
>
> so you are part of the "Jitter-Team"?
> I'm really interested in this whole jitting-process. I wanted to know,
> is there a way to load other obj-files, than the one created with
> clang? Could I load - for example - a obj-File from VisualStudio? Or
> will the namemangeling fail?
>
> Kind regards
> Björn
>
>
>
> From:        Lang Hames <lhames at gmail.com>
> To:        bjoern.gaier at horiba.com
> Cc:        Clang Dev <cfe-dev at lists.llvm.org>, LLVM Developers Mailing
> List <llvm-dev at lists.llvm.org>
> Date:        24.05.2017 01:19
> Subject:        Re: JIT - Resolve obj file without a main
> ------------------------------------------------------------------------
>
>
>
> Hi Bjoern,
>
> Could you please tell me, if there is a way to allocate the memory for
> the codemodules more precise? I would like to allocate the memory for
> strings from a separated memory-pool. But how can I detect a string?
> The only moment I can do this is in "notifyObjectLoaded" via the names
> of the symbols. But than it is impossible for my to get the address of
> the symbols. I noticed that some strings are stored in .rdata, but
> this is no guarantee. 
>
> There is no easy way to do this at the moment, any it will always be
> limited by what the object format allows (as you said: you need the
> object format to tell you what's a string and what isn't, and they
> don't do that in all situations).
>
> If you can identify strings at the IR level you could do this by
> allocating the strings in your own memory and marking the IR
> definitions as weak, but this would also require LLVM to be more
> careful about picking strong definitions, so it would require some
> non-trivial LLVM improvements. These improvements are on the drawing
> board, but there is no schedule for them to be implemented yet.
>
> Cheers,
> Lang.
>
> On Wed, May 17, 2017 at 7:03 AM, <_bjoern.gaier at horiba.com_
> <mailto:bjoern.gaier at horiba.com>> wrote:
> Hi Lang,
>
> I'm using Windows. I was parsing an IR-File and added the Module to
> the ExectuionEngine. If I than searched for a function, I just got 0.
> But when the module had a main, I got an address. I solved the problem
> via a call to "generateCodeForModule". The JIT didn't even called my
> SymbolResolver in this special case.
>
> Could you please tell me, if there is a way to allocate the memory for
> the codemodules more precise? I would like to allocate the memory for
> strings from a separated memory-pool. But how can I detect a string?
> The only moment I can do this is in "notifyObjectLoaded" via the names
> of the symbols. But than it is impossible for my to get the address of
> the symbols. I noticed that some strings are stored in .rdata, but
> this is no guarantee.
>
> Kind regards
> Björn
>
>
>
> From:        Lang Hames <_lhames at gmail.com_ <mailto:lhames at gmail.com>>
> To:        _bjoern.gaier at horiba.com_ <mailto:bjoern.gaier at horiba.com>
> Cc:        Clang Dev <_cfe-dev at lists.llvm.org_
> <mailto:cfe-dev at lists.llvm.org>>, LLVM Developers Mailing List
> <_llvm-dev at lists.llvm.org_ <mailto:llvm-dev at lists.llvm.org>>
> Date:        16.05.2017 18:37
> Subject:        Re: JIT - Resolve obj file without a main
> ------------------------------------------------------------------------
>
>
>
>
> Hi Björn,
>
> I don't recall ever seeing this behavior before. Can you describe the
> situation in more detail?
>
> Is this specifically for object files loaded via
> RTDyldLinkingLayer::addObjectSet, or does it apply to IR Modules
> without a main too?
>
> When you say the JIT won't resolve an address, do you mean that you
> can't find anything when you call findSymbol on the JIT, or that the
> JIT isn't calling your SymbolResolver back to find addresses?
>
> Was this for MacOS, Linux, or Windows?
>
> Cheers,
> Lang. 
>
> On Fri, May 12, 2017 at 6:47 AM, <_bjoern.gaier at horiba.com_
> <mailto:bjoern.gaier at horiba.com>> wrote:
> Hello Lang,
>
> I noticed, if I load a obj-File without a main-function, the Jitter
> won't resolve any address. But if I have a main, everything works
> fine. Why is this so? Is there a way to stop this?
>
> Kind regards
> Björn
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
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>
>
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
> USt.ID-Nr. DE 114 165 789
> Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode,
> Heiko Lampert, Takashi Nagano, Takeshi Fukushima.
>
>
>
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
> USt.ID-Nr. DE 114 165 789
> Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode,
> Heiko Lampert, Takashi Nagano, Takeshi Fukushima.
>
>
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-- 
https://about.me/stefan.graenitz
https://cryptup.org/pub/stefan.graenitz@gmail.com

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