[llvm-dev] How to build LLVM linked to libc++abi?

[ardi via llvm-dev]

Thanks a lot, but tried it and I get this:

CMake Error at projects/libcxx/CMakeLists.txt:361 (message):

  LIBCXX_ENABLE_STATIC_ABI_LIBRARY is not supported on OS X

Why is it not supported? If I manually embed libc++abi.a inside
libc++.a it seems to work.

Thanks!

ardi

On Mon, Oct 1, 2018 at 4:20 AM Petr Hosek <phosek at chromium.org> wrote:
>
> You can use LIBCXX_ENABLE_STATIC_ABI_LIBRARY=ON CMake option to statically link libc++abi into libc++.a. You can also use LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY=OFF to disable statically linking libc++abi into libc++.so (i.e. libc++abi will only be merged into libc++.a, not libc++.so).
>
> Similarly, you can also use LIBCXXABI_ENABLE_STATIC_UNWINDER=ON and LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY=OFF to the same for libunwind.
>
> Alternatively, you could rename libc++.a to libc++_internal.a and then create a linker script named libc++.a with the following content:
>
> INPUT(libc++_internal.a libc++abi.a)
>
> There's no support to do so in CMake at the moment, but it's something we've already discussed within Fuchsia as it'd be also useful for sanitizer runtimes so I might start a (separate) discussion about adding such support.
>
> On Sun, Sep 30, 2018 at 2:40 PM ardi via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>
>> Hi!
>>
>> I sometimes build LLVM with a static libc++.a in MacOS, so that I use
>> the LLVM libc++ instead of the system-wide one. However, when doing
>> so, I always get link errors when building LLVM, because the build
>> system links with libc++.a, but not with libc++abi.a and so there are
>> quite a few missing symbols that the linker cannot find.
>>
>> My workaround (which always seems to work) is to embed libc++abi
>> inside of libc++ (with libtool, for example), but that's a hack for
>> being in a hurry. BTW, note that I'm talking about building LLVM
>> itself, not my programs (when you build your programs it doesn't hurt
>> to add  -lc++abi to your link line, but when building LLVM, how are
>> you supposed to do it? I've searched for a cleaner solution to this,
>> but couldn't find any.
>>
>> Isn't there any LLVM build option for simply telling "hey! don't
>> forget to add -lc++abi whenever you link to libc++" ?
>>
>> Thanks!
>>
>> ardi
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