llvm dev - Feb 2008 - [LLVMdev] Calling functions

Hello!


I'm trying LLVM for generating code and I found something I cannot figure
out or find in the documentation:

I'm doing something like this to call "sin" from std:

  std::vector<const Type*> params;
  params.push_back( Type::FloatTy );
  FunctionType *FT = FunctionType::get( Type::FloatTy, params, false);
  Function *F = new Function( FT, Function::ExternalLinkage, "sin", M
);
  CallInst *CallExternal = new CallInst( F, SomeValue,
"external_call", BB  );


I can make some calls to functions like glclear() as I'm using opengl:
...
  Function *F = new Function( FT, Function::ExternalLinkage,
"glclear", M );
...

But if I want to call any function inside a C++ namespace I don't find the
way to do it. Imagine you want to call

othernamespace::globalFunction()

How should I do it?
I've tried all the linkage types, but it's clear that's not the
solution.

And another question:
is it possible to call a function of an instance of a C++ class? Which are the
limits of interaction between generated code and "precompiled" code (I
mean any library for example)?
I want to generate code able to use functionality from c/c++ libraries...

like:
classinstance.memberFunction()



Thank you very much,

.alvaro.castro.




       
______________________________________________ 
¿Con Mascota por primera vez? Sé un mejor Amigo. Entra en Yahoo! Respuestas
http://es.answers.yahoo.com/info/welcome

On Feb 22, 2008, at 11:43, Álvaro Castro wrote:
> I'm trying LLVM for generating code and I found something I cannot  
> figure out or find in the documentation:
>
> But if I want to call any function inside a C++ namespace I don't  
> find the way to do it. Imagine you want to call
>
> othernamespace::globalFunction()
>
> How should I do it?
> I've tried all the linkage types, but it's clear that's not the
> solution.
Hi Álvaro,

Google for C++ name mangling to understand why what you're attempting  
doesn't work. Looking at the output of llvm-gcc may help you get it  
right, but it's probably easier to write C wrappers for your C++ code.

— Gordon

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Álvaro Castro wrote:
| Hello!
|
|
| I'm trying LLVM for generating code and I found something I cannot figure
out or find in the documentation:
|
| I'm doing something like this to call "sin" from std:
|
|   std::vector<const Type*> params;
|   params.push_back( Type::FloatTy );
|   FunctionType *FT = FunctionType::get( Type::FloatTy, params, false);
|   Function *F = new Function( FT, Function::ExternalLinkage, "sin",
M );
|   CallInst *CallExternal = new CallInst( F, SomeValue,
"external_call", BB  );
|
|
| I can make some calls to functions like glclear() as I'm using opengl:
| ...
|   Function *F = new Function( FT, Function::ExternalLinkage,
"glclear", M );
| ...
|
| But if I want to call any function inside a C++ namespace I don't find the
way to do it. Imagine you want to call
|
| othernamespace::globalFunction()

See this older message:

http://lists.cs.uiuc.edu/pipermail/llvmdev/2007-December/011616.html

| And another question:
| is it possible to call a function of an instance of a C++ class? Which are
the limits of interaction between generated code and "precompiled"
code (I
mean any library for example)?
| I want to generate code able to use functionality from c/c++ libraries...
|
| like:
| classinstance.memberFunction()

This is... not simple. If you take the address of a member function you
don't actually get back a simple pointer, you get back a
member-pointer-to-function which has metadata about whether the function is
virtual or not and other details.

C++ member functions calls also use a special calling convention. See
http://en.wikipedia.org/wiki/Stdcall#thiscall for details. LLVM currently
does not support MSVC-style thiscall convention.

If the function you want to call is virtual, you can call it through a
function pointer by dereferencing the vtable. If the function is
non-virtual, you'll need to get it's address somehow (using the mangled
name, perhaps) and then call it using the thiscall convention.

- --BDS

- --

Benjamin Smedberg
Platform Guru
Mozilla Corporation
benjamin at smedbergs.us
http://benjamin.smedbergs.us/
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (Darwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFHv0BoSSwGp5sTYNkRAuW6AKDYIiiEMZo7ZghN11qjAxHMY3fYlgCfe4QF
xTF0Tx/8808bsSgRu6SCkTs=ujKD
-----END PGP SIGNATURE-----