ldionne added inline comments.
Herald added a subscriber: Enna1.

================
Comment at: clang/cmake/caches/Fuchsia-stage2.cmake:124
     set(RUNTIMES_${target}_LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
-    set(RUNTIMES_${target}_LIBCXX_ENABLE_STATIC_ABI_LIBRARY ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXX_ABI_VERSION 2 CACHE STRING "")
----------------
phosek wrote:
> ldionne wrote:
> > ldionne wrote:
> > > phosek wrote:
> > > > ldionne wrote:
> > > > > phosek wrote:
> > > > > > ldionne wrote:
> > > > > > > Note that I am removing these options here because I don't think 
> > > > > > > they are required -- since we specify 
> > > > > > > `LIBCXXABI_ENABLE_SHARED=OFF`, there is no shared libc++abi to 
> > > > > > > link against, so we should already be linking against 
> > > > > > > `libc++abi.a` regardless of this change.
> > > > > > This option was set to merge `libc++abi.a` into `libc++.a` so to 
> > > > > > achieve the same effect, presumably we would need to set 
> > > > > > `-DLIBCXX_CXX_ABI=libcxxabi-objects`?
> > > > > I agree this is suspicious, but why is there no 
> > > > > `LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY` specified here then? I 
> > > > > can add `-DLIBCXX_CXX_ABI=libcxxabi-objects`, I just want to make 
> > > > > sure we both understand what's going on.
> > > > This is intentional. We are merging `libc++abi.a` into `libc++.a` but 
> > > > we ship `libc++abi.so` and `libc++.so` as separate (and use the 
> > > > generated linker script to pull in `libc++abi.so` when you pass `-lc++` 
> > > > to linker). I'd be fine merging `libc++abi.so` into `libc++.so` as 
> > > > well, but we'll need to figure out a transition plan since there are 
> > > > several places in our build right now that expect `libc++abi.so` to 
> > > > exist. We cannot land this change as is because that would break the 
> > > > `-static-libstdc++` use case, since Clang driver only passes `-lc++` to 
> > > > the linker and not `-lc++abi` and there's nothing that would pull 
> > > > `libc++abi.a` in.
> > > I see, so to summarize, basically you want to use `libcxxabi-objects` for 
> > > the static `libc++.a`, but `libcxxabi` for the dynamic `libc++.so`. This 
> > > change as currently laid out does not permit that to happen, since 
> > > `libcxxabi-objects` implies that the objects are merged both in the 
> > > static and in the shared library. I guess we could introduce a new 
> > > `libcxxabi-objects-static` option, however that would be kind of strange. 
> > > We can either do that, or wait for you to stop relying on `libc++abi.so` 
> > > existing and switch to `libcxxabi-objects` wholesale for Fuchsia. WDYT?
> > Gentle ping. It would be nice to land this in one form or another. If you 
> > don't think Fuchsia can stop relying on `libc++abi.so` being there, I could 
> > add yet another `libcxxabi-objects-static` -- I still feel like that's 
> > better than the status quo.
> We discussed this on our team and we don't have any issues switching towards 
> combined `libc++.so`, we just need to figure out a transition plan. Let me 
> test this change locally to see if landing this as is will break anything.
Gentle ping -- did you get any time to investigate this?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D125683/new/

https://reviews.llvm.org/D125683

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