[cfe-dev] libclang shared library that exports all symbols

[Ivan Donchevskii via cfe-dev]

Hi!

I think I meant CLANG_PLUGIN_SUPPORT flag which enables export_executable_symbols(clang) in tools\clang\tools\driver\CMakeLists.txt

Probably in combination with LLVM_EXPORT_SYMBOLS_FOR_PLUGINS.


Ivan

________________________________
From: Pirama Arumuga Nainar <pirama at google.com>
Sent: Monday, August 6, 2018 10:53:29 PM
To: Ivan Donchevskii; cfe-dev list
Cc: Tzu-hsiang Chien; Stephen Hines
Subject: Re: [cfe-dev] libclang shared library that exports all symbols



On Fri, Aug 3, 2018 at 1:37 AM Ivan Donchevskii <ivan.donchevskii at qt.io<mailto:ivan.donchevskii at qt.io>> wrote:

Hi!
Why do you need to mix C++ symbols with what libclang exports?

My reasoning was that the C/C++ difference was already imposed by the headers included by a libclang.so user.  But I also see why limiting the exported symbols can catch user errors.


Doesn't it make sense to have separate clang.so instead? I also think there's already a possibility to build such library by providing some LLVM flags.

I think you mean LLVM_ENABLE_SHARED?  That builds each individual library (libclangAST, libclangDriver etc) as shared libraries, rather than producing a single shared library.  I am not aware of any other option that can help.

To clarify my proposal, I've uploaded a patch (https://reviews.llvm.org/D50359) that adds this new library.  The library is named libclang-cxx in that patch - which I think is slightly more informative than libclang-full.

Please add comments in the patch or to this discussions.



Kind regards,

Ivan

________________________________
From: cfe-dev <cfe-dev-bounces at lists.llvm.org<mailto:cfe-dev-bounces at lists.llvm.org>> on behalf of Pirama Arumuga Nainar via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>>
Sent: Thursday, August 2, 2018 11:48:16 PM
To: cfe-dev list
Cc: Tzu-hsiang Chien
Subject: Re: [cfe-dev] libclang shared library that exports all symbols

Ping for any thoughts on this proposal...

On Thu, Jul 26, 2018 at 3:59 PM Pirama Arumuga Nainar <pirama at google.com<mailto:pirama at google.com>> wrote:
libclang.so exports only the symbols needed by the C API.  This is in contrast to libLLVM.so that exports all symbols from the LLVM static libraries.  Would it be useful to provide a libclang shared library that exports all symbols for use by tools that use Clang's (admittedly non-backwards-compatible) C++ API?

We can either:
1. Add a new shared library (libclang_full.so?) that is built based on a CMake option.
2. Export all symbols from the current libclang.so.  We'd have to also include a few additional libraries such as libClangAnalysis.  Tools using the C API are still restricted to the stable interface if they use the clang-c headers.

Motivation:
There are a few Clang-based tools used by Android's build system (1, 2) that use the C++ API.  They are built using Android build rules but need to link against Android's Clang toolchain that's built with CMake.  We don't want to include the libclang static libraries with the toolchain for space considerations, and also to avoid exposing Clang's build internals (internal library dependences and changes to them) to downstream tools.

Do other Clang/LLVM toolchain maintainers face similar issues and have solutions that are applicable here?

[1] https://android.googlesource.com/platform/development/+/master/vndk/tools/header-checker/
[2] https://android.googlesource.com/platform/development/+/master/vndk/tools/vtable-dumper/
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