llvm dev - Oct 2019 - Function name demangle on clang vs clang++

Hi all,

I'm a LLVM newbie and am working on a LLVM 3.5 code base. The project (
https://github.com/zhguanw/lin-analyzer) makes use of clang and reads C
code. I'm trying to make it read C++ code. When I compile a kernel written
in C with clang++, I get the following difference in the IR for a function
declaration:

When compiled with clang:
declare void @convolution3d(float*, float*) #1

When compiled with clang++:
declare void @_Z13convolution3dPfS_(float*, float*) #2

The project breaks if I compile with clang++ because it expects the
function name to not have the @_Z13*PfS. Does anyone know how I can get the
function name in the IR generated by clang++ to not have the mangled
characters? Once again, this is in LLVM 3.5.

Best,

Syed Ahmed
PhD Student
Implementation of Computation Group
UPenn
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This is more of a general C and C++ question than one suitable to the LLVM
discussion list, I think?

You can modify the source itself -
https://en.cppreference.com/w/cpp/language/language_linkage - discusses the
extern "C" directive and how it can be used to expose C-linkage
functions
from C++ translation units (so, if you have a function with C API, but an
implementation written in C++, this is how to do that)

On Mon, Oct 28, 2019 at 3:37 PM Syed Ahmed via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi all,
>
> I'm a LLVM newbie and am working on a LLVM 3.5 code base. The project (
> https://github.com/zhguanw/lin-analyzer) makes use of clang and reads C
> code. I'm trying to make it read C++ code. When I compile a kernel
written
> in C with clang++, I get the following difference in the IR for a function
> declaration:
>
> When compiled with clang:
> declare void @convolution3d(float*, float*) #1
>
> When compiled with clang++:
> declare void @_Z13convolution3dPfS_(float*, float*) #2
>
> The project breaks if I compile with clang++ because it expects the
> function name to not have the @_Z13*PfS. Does anyone know how I can get
> the function name in the IR generated by clang++ to not have the mangled
> characters? Once again, this is in LLVM 3.5.
>
> Best,
>
> Syed Ahmed
> PhD Student
> Implementation of Computation Group
> UPenn
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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On Mon, Oct 28, 2019 at 06:36:45PM -0400, Syed Ahmed via llvm-dev
wrote:
> I'm a LLVM newbie and am working on a LLVM 3.5 code base. The project (
> https://github.com/zhguanw/lin-analyzer) makes use of clang and reads C
> code. I'm trying to make it read C++ code. When I compile a kernel
written
> in C with clang++, I get the following difference in the IR for a function
> declaration:
clang++ will implicitly force C++ mode for all input. If you really want
to use it to compile C code and not have mangled names, you need to add
the appropiate extern "C" markers.

Joerg

Thank you David and Joerg!

Best,

Syed

On Mon, Oct 28, 2019 at 6:45 PM Joerg Sonnenberger via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> On Mon, Oct 28, 2019 at 06:36:45PM -0400, Syed Ahmed via llvm-dev wrote:
> > I'm a LLVM newbie and am working on a LLVM 3.5 code base. The
project (
> > https://github.com/zhguanw/lin-analyzer) makes use of clang and reads
C
> > code. I'm trying to make it read C++ code. When I compile a kernel
> written
> > in C with clang++, I get the following difference in the IR for a
> function
> > declaration:
>
> clang++ will implicitly force C++ mode for all input. If you really want
> to use it to compile C code and not have mangled names, you need to add
> the appropiate extern "C" markers.
>
> Joerg
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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