llvm dev - Jun 2016 - LLVMLinkModules2() C-API question

Hey all,

A quick question about the LLVM C-Api and using LinkModules. In a normal
situation where I have 2 LLVM modules and 1 depends on the other using
LLVMLinkModules2() works perfectly.

LLVMLinkModules2() "Links the source module into the destination module.
The source module is destroyed." according to the comment of the function.
That is all fine when you only have 2 modules.

But how are you supposed to act in a triangulary dependency like below?

                                                    CommonModule
                                                                |
                                                        -----------------
                                                        |               |
                                                 ModuleA      Module B

1) Create and verify common module.
2) Create ModuleA, Link CommonModule to ModuleA and verify the new module.
3) Now we have a problem. Even though we wanted to repeat step (2) for
Module B this fails due to CommonModule being "damaged" as the
documentation says. Even though LLVMLinkModules2() function returns
success, Module B is lacking structs and functions that were defined in the
CommonModule.


I am probably doing this the wrong way and am missing something obvious.
Any tips on how to do this the right way? Thanks in advance!

---

Best Regards,

Lefteris(Eleftherios) Karapetsas
About me: My Website <http://lefteris.refu.co>

Keep in touch: Twitter <https://twitter.com/LefterisJP>, Github
<https://github.com/LefterisJP>, Blog <http://blog.refu.co>
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Hi Lefteris,

I’m not sure how _right_ my solution is, but it should work, at least as a
workaround.

To prevent a CommonModule from being destroyed you can make a copy of the
module. You can do so using LLVMCloneModule method, so that the code may look
like this:

let commonModuleForA = LLVMCloneModule(CommonModule)
LLVMLinkModule2(commonModuleForA, ModuleA)

let commonModuleForB = LLVMCloneModule(CommonModule)
LLVMLinkModule2(commonModuleForB, ModuleB)

Hope that will help you.

Best regards,
Alex.
> On 04 Jun 2016, at 14:01, Lefteris Karapetsas via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hey all,
> 
> A quick question about the LLVM C-Api and using LinkModules. In a normal
situation where I have 2 LLVM modules and 1 depends on the other using
LLVMLinkModules2() works perfectly.
> 
> LLVMLinkModules2() "Links the source module into the destination
module. The source module is destroyed." according to the comment of the
function. That is all fine when you only have 2 modules.
> 
> But how are you supposed to act in a triangulary dependency like below?
> 
>                                                     CommonModule
>                                                                 |
>                                                         -----------------
>                                                         |               |
>                                                  ModuleA      Module B
> 
> 1) Create and verify common module.
> 2) Create ModuleA, Link CommonModule to ModuleA and verify the new module.
> 3) Now we have a problem. Even though we wanted to repeat step (2) for
Module B this fails due to CommonModule being "damaged" as the
documentation says. Even though LLVMLinkModules2() function returns success,
Module B is lacking structs and functions that were defined in the CommonModule.
> 
> 
> I am probably doing this the wrong way and am missing something obvious.
> Any tips on how to do this the right way? Thanks in advance!
> 
> ---
> 
> Best Regards,
> 
> Lefteris(Eleftherios) Karapetsas
> About me: My Website
> 
> Keep in touch: Twitter, Github, Blog
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
--
AlexDenisov
Software Engineer, http://lowlevelbits.org

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Hello Alex,

This sounds like a workaround that should do the trick! I will try it out
today.

Thank you for the reply.

Best Regards,

Lefteris(Eleftherios) Karapetsas
About me: My Website <http://lefteris.refu.co>

Keep in touch: Twitter <https://twitter.com/LefterisJP>, Github
<https://github.com/LefterisJP>, Blog <http://blog.refu.co>

On Sat, Jun 4, 2016 at 4:24 PM, Alex Denisov <1101.debian at gmail.com>
wrote:
> Hi Lefteris,
>
> I’m not sure how _right_ my solution is, but it should work, at least as a
> workaround.
>
> To prevent a CommonModule from being destroyed you can make a copy of the
> module. You can do so using LLVMCloneModule method, so that the code may
> look like this:
>
> let commonModuleForA = LLVMCloneModule(CommonModule)
> LLVMLinkModule2(commonModuleForA, ModuleA)
>
> let commonModuleForB = LLVMCloneModule(CommonModule)
> LLVMLinkModule2(commonModuleForB, ModuleB)
>
> Hope that will help you.
>
> Best regards,
> Alex.
>
> > On 04 Jun 2016, at 14:01, Lefteris Karapetsas via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > Hey all,
> >
> > A quick question about the LLVM C-Api and using LinkModules. In a
normal
> situation where I have 2 LLVM modules and 1 depends on the other using
> LLVMLinkModules2() works perfectly.
> >
> > LLVMLinkModules2() "Links the source module into the destination
module.
> The source module is destroyed." according to the comment of the
function.
> That is all fine when you only have 2 modules.
> >
> > But how are you supposed to act in a triangulary dependency like
below?
> >
> >                                                     CommonModule
> >                                                                 |
> >                                                        
-----------------
> >                                                         |             
|
> >                                                  ModuleA      Module B
> >
> > 1) Create and verify common module.
> > 2) Create ModuleA, Link CommonModule to ModuleA and verify the new
> module.
> > 3) Now we have a problem. Even though we wanted to repeat step (2) for
> Module B this fails due to CommonModule being "damaged" as the
> documentation says. Even though LLVMLinkModules2() function returns
> success, Module B is lacking structs and functions that were defined in the
> CommonModule.
> >
> >
> > I am probably doing this the wrong way and am missing something
obvious.
> > Any tips on how to do this the right way? Thanks in advance!
> >
> > ---
> >
> > Best Regards,
> >
> > Lefteris(Eleftherios) Karapetsas
> > About me: My Website
> >
> > Keep in touch: Twitter, Github, Blog
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
> --
> AlexDenisov
> Software Engineer, http://lowlevelbits.org
>
>
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