[LTP] [RFC PATCH v2 0/2] Libclang based analyzer

[Joerg Vehlow]

Hi Richard,

On 6/7/2021 12:20 PM, Richard Palethorpe wrote:
> Hello Joerg,
>
> On ubuntu 20.04, this file is part of libclang-dev, but installing it
> did not help either, because it is installed to an include path not
> know to gcc (/usr/lib/llvm-10/include/clang-c).
> Is part of this path the same that 'clang -print-resource-dir' prints?
>
> Either way I guess we can search for this during configuration. LLVM has
> a CMake module (or w/e) which probably finds all this automatically.
resource dir is /usr/lib/llvm-12/lib/clang/12.0.1.

The llvm-config tool can be used to find the locations of the include 
and lib directory.
On my ubuntu, I installed clang-12 from apt.llvm.org and clang-10 from 
ubuntu repos.
In the path there is the llvm-config tool from ubuntu pointing to 
/usr/lib/llvm-10/bin/llvm-config and llvm-config-10 and llvm-config-12 
pointing to the respective llvm-config tool.

I guess using llvm-config from the path to detect the correct include 
and library path would be the best way to go.
If someone wants to use a different version, he can still set prepend it 
to the path during configuration:

$ llvm-config --includedir
/usr/lib/llvm-10/include

$ llvm-config --libdir
/usr/lib/llvm-10/lib

$ PATH="/usr/lib/llvm-12/bin:$PATH" llvm-config --includedir
/usr/lib/llvm-12/include


Both includedir and libdir are required, to correctly link libclang. In 
the default library search paths, there are only versioned versiones of 
libclang (eg. libclang-12.so).

>> I added it to the include path and it was found, but the next problem
>> is, that some used functions (like clang_Cursor_getVarDeclInitializer)
>> are only available starting with libclang 12.
>>
> I guess that we could replace that function by recursing further into
> the AST to find the initializer ourselves.
>
> Probably we can restrict ourselves to only use functions from before
> libclang 11.
Sounds good, but how to force this? I don't think there is a "allow only 
libclang 10 symbols"...
>
>> So in conclusion, I do not think we can assume libclang to be
>> available for all developers and installing it is probably more work,
>> at least when newer functions from libclang are used, than installing
>> coccinelle.
> IIRC Cyril said the Coccinelle package on Gentoo is not maintained
> anymore. AFAICT it exists, but it is on an old version. I don't think
> many people are interested in or want to maintain Ocaml
> stuff. LLVM/Clang OTOH looks to be very active.
Right, it actually is removed now from gentoo portage tree ([1]). But is 
it used by the kernel developers?

Jörg

[1] 
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=58395d3a0c06e060a0a40182fff4bf39f1910529