[llvm-dev] How to build LLVM linked to libc++abi? (original) (raw)

ardi via llvm-dev llvm-dev at lists.llvm.org
Sun Sep 30 22:24:07 PDT 2018

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 LIBCXXENABLESTATICABILIBRARY=ON CMake option to statically link libc++abi into libc++.a. You can also use LIBCXXSTATICALLYLINKABIINSHAREDLIBRARY=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 LIBCXXABIENABLESTATICUNWINDER=ON and LIBCXXABISTATICALLYLINKUNWINDERINSHAREDLIBRARY=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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