[llvm-dev] Shipping LLVM.dll for the C API with the Windows installer.

Jakob Bornecrantz via llvm-dev llvm-dev at lists.llvm.org
Wed Apr 5 11:40:50 PDT 2017

On Wed, Apr 5, 2017 at 5:20 PM, John Brawn <John.Brawn at arm.com> wrote:
> We already half-have this, the LLVM_BUILD_LLVM_C_DYLIB cmake option builds
> a shared object which exports the llvm-c interface but it only works on
> Darwin.
> tools/llvm-shlib/CMakeLists.txt is where how this is done is defined, and it
> looks like it does it by:
>  * build LLVM.so
>  * use nm+awk+sed to pick out the symbols starting with LLVM
>  * build LLVM-C.so using a -reexport_library linker option
> I'm thinking that maybe we could make this not-darwin-specific by making
> use of utils/extract_symbols.py:
>  * edit extract_symbols.py to add a --only_unmangled option (or maybe
>    --only_prefix=LLVM or something like that)
>  * on non-darwin use that instead of the existing command to get the
>    symbols to export (or: make extract_symbols.py work on Darwin)
>  * instead of building LLVM-C.so from LLVM.so using this -reexport_library
>    option, instead build LLVM-C.so from the same libraries that LLVM.so
>    is built from
>  (where I use .so above, it also applies to .dll)
> John

Thanks for the info John!

I tried to enable LLVM_BUILD_LLVM_C_DYLIB on my linux machine
to play around a little bit. I disabled the APPLE check to get past that.
The config failed if I had BUILD_SHARED_LIBS also set to true.
If I tried that without the flag it complained about missing:

Which is a bit weird since it builds a lib/libLLVM-5.0svn.so.

I have to admit I'm a tiny bit in over my head here with the cmake scripts here.

Cheers, Jakob.

>> -----Original Message-----
>> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
>> Jakob Bornecrantz via llvm-dev
>> Sent: 05 April 2017 12:51
>> To: llvm-dev
>> Subject: Re: [llvm-dev] Shipping LLVM.dll for the C API with the Windows
>> installer.
>> On Thu, Mar 30, 2017 at 4:46 PM, Jakob Bornecrantz
>> <wallbraker at gmail.com> wrote:
>> > Hello list!
>> >
>> > So I'm wondering if there is a will to ship a DLL with the C API
>> > exported? LLVM currently ships with LTO.dll which has some C api
>> > functions exported, made from the export file tools/lto/lto.exports,
>> > so it would not be the first DLL LLVM shipped.
>> >
>> > Currently I (and the users of my project[1]) are building it ourselves
>> > using this script[2] derived from the LLVMSharp script[3]. Which adds
>> > a extra long step for all users of ours and other projects like
>> > LLVMSharp in order to use them.
>> >
>> > The resulting LLVM.dll exports 809 functions and weighs in at around
>> > 18mb, so it would make the installer larger. There is also the cost of
>> > maintaining a lists of export for the DLL, but hopefully we can use
>> > the llvm-echo to test it on the windows nodes so any failure to add
>> > new exports gets detected early.
>> >
>> > Now for the bike-shed questions, do we call it LLVM-c.dll or just
>> > LLVM.dll? Annotate all functions with a LLVM_EXPORT define or use a
>> > llvm-c.exports file?
>> >
>> > Thoughts and feedback welcome.
>> >
>> > Cheers, Jakob.
>> >
>> > [1] http://volt-lang.org
>> > [2] https://github.com/VoltLang/GenLLVMDLLPy/blob/master/GenLLVMDLL.py
>> > [3]
>> https://github.com/Microsoft/LLVMSharp/blob/master/tools/GenLLVMDLL.ps1
>> Ping? Any thoughts?
>> What would be the best way to proceed? My cmake-fu is very weak so any
>> pointers here from those knowledgeable and stakeholders in the code
>> would be greatly appreciated.
>> Cheers, Jakob.
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