[libcxx-commits] [PATCH] D114473: [runtimes] Remove support for building in 32 bits mode on a 64 bit target

Thu Nov 25 12:17:53 PST 2021

ldionne marked an inline comment as done.
ldionne added a comment.

In D114473#3149875 <https://reviews.llvm.org/D114473#3149875>, @MaskRay wrote:

>> [runtimes] Remove support for building in 32 bits mode on a 64 bit target
>
> I think this needs to be clarified. It is about the GCC multilib style -m32 (inherited to Clang), not about the general cross-compilation feature.

Yes, indeed, I'll clarify the commit message. In fact, I wan't 100% aware of the backstory before you folks commented -- I'm glad I pinged several people now.

> I think there are still users with 32-bit cross compilation need on 64-bit host. Do you have a supported build  instruction for them?
>
> AIUI, some compiler-rt sanitizer tests (e.g. `%clangxx_asan`) need -m32 for i686-pc-linux-gnu testing on x86_64-pc-linux-gnu. If -m32 is unsupported, they need a fallback.

I assume it should be possible to build the runtimes using the target they actually need, i.e. `i686-pc-linux-gnu`. They should be able to add `-DLLVM_RUNTIME_TARGETS=i686-pc-linux-gnu` when configuring their build of the runtimes to achieve that.

================
Comment at: libcxx/docs/ReleaseNotes.rst:144
+    still work (i.e. we haven't done anything that would break that configuration), but it isn't
+    officially supported anymore.
----------------
mstorsjo wrote:
> Would it be good to be a bit more helpful and suggest how to build for such a configuration, if that's needed? I.e. `-DLLVM_ENABLE_RUNTIMES=libcxx` and the corresponding `-DLLVM_RUNTIME_TARGETS=your-32-bit-triple`, or pointing cmake at `llvm-project/runtimes` and just passing `-m32` in `CMAKE_CXXFLAGS`?
Good suggestion, I improved the release note. Please LMK if that's still not enough after I update.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D114473/new/

https://reviews.llvm.org/D114473