llvmPackages.stdenv: make Darwin a “system” libc++ platform #347388
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Applying `overrideLibcxx` by default allows various LLVM versions to use the same underlying libc++ on Darwin. This works because libc++ is built by default with the stable ABI. Using the same libc++ regardless of LLVM version avoids potential ODR violations from linking multiple libc++ versions in the same process. This is similar to the default on Linux, which uses libstdc++ instead of libc++. On both platforms, to force a stdenv to link against that LLVM version’s libc++, use `libcxxStdenv`.
Take advantage of the fact that an overriden libc++ has the “system” version prepended to the new version, so it doesn’t get overriden again.
Darwin’s linkers support text-based stubs, which allows the override to use the “system” libc++ while limiting the symbols to those in the original version.
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6.topic: darwin
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This was split off from #346043. It updates
overrideLibcxxto usetapito restrict symbols and updates LLVM to always apply the adapter on Darwin. This aligns Darwin’s behavior regarding LLVM with Linux, which always uses libstdc++ unless you use llvmPackages.libcxxStdenv.Whether to apply this to pkgsLLVM is an open question. It makes sense to do that there as well.
Things done
nix.conf? (See Nix manual)sandbox = relaxedsandbox = truenix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage./result/bin/)Add a 👍 reaction to pull requests you find important.