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There's a lot of history behind this, so here's a summary: 1. I stopped forcing -fPIC when building the runtimes in 30f305efe279, before the LLVM 9 release back in 2019. 2. Someone complained that libc++.a couldn't be used in shared libraries built without -fPIC (http://llvm.org/PR43604) since the LLVM 9 release. This had been caused by my removal of -fPIC when building libc++.a in (1). 3. I suggested two ways of fixing the issue, the first being to force -fPIC back unconditionally (http://llvm.org/D104328), and the second being to specify that option explicitly when building the LLVM release (http://llvm.org/D104327). We converged on the first solution. 4. I landed D104328, which forced building the runtimes with -fPIC. This was included in the LLVM 13.0 release. 5. People complained about that and requested that we be able to customize this setting (basically we should have done the second solution). This patch makes it such that the LLVM release script will specifically ask for building with -fPIC using CMAKE_POSITION_INDEPENDENT_CODE, however by default the runtimes will not force that option onto users. This patch has the unintended effect that Clang and the LLVM libraries (not only the runtime ones like libc++) will also be built with -fPIC in the release. It would be better if we could specify that -fPIC is to be used only when building the runtimes, however this is left as a future improvement. The release should probably be using a bootstrapping build and passing those options to the stage that builds the runtimes only, see https://reviews.llvm.org/D112748 for that change. Differential Revision: https://reviews.llvm.org/D110261
libc++ Documentation ==================== The libc++ documentation is written using the Sphinx documentation generator. It is currently tested with Sphinx 1.1.3. To build the documents into html configure libc++ with the following cmake options: * -DLLVM_ENABLE_SPHINX=ON * -DLIBCXX_INCLUDE_DOCS=ON After configuring libc++ with these options the make rule `docs-libcxx-html` should be available. The documentation in this directory is published at https://libcxx.llvm.org. It is kept up-to-date by a build bot: https://lab.llvm.org/buildbot/#/builders/publish-sphinx-docs. If you notice that the documentation is not updating anymore, please contact one of the maintainers.