From 5ea679485d0952d5d0d657ce4d6ab05bcfbb6e70 Mon Sep 17 00:00:00 2001
From: Randy Eckenrode <randy@largeandhighquality.com>
Date: Sun, 13 Apr 2025 13:57:35 -0400
Subject: [PATCH] llvmPackages.clang: add `systemLibcxxClang` (primarily for
 Darwin)

---
 pkgs/development/compilers/llvm/common/default.nix | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/pkgs/development/compilers/llvm/common/default.nix b/pkgs/development/compilers/llvm/common/default.nix
index 5de10bf97f0e..e3f8c25ad46c 100644
--- a/pkgs/development/compilers/llvm/common/default.nix
+++ b/pkgs/development/compilers/llvm/common/default.nix
@@ -222,6 +222,15 @@ let
         extraBuildCommands = mkExtraBuildCommands cc;
       };
 
+      # Darwin uses the system libc++ by default. It is set up as its own clang definition so that `libcxxClang`
+      # continues to use the libc++ from LLVM.
+      systemLibcxxClang = wrapCCWith rec {
+        cc = tools.clang-unwrapped;
+        libcxx = darwin.libcxx;
+        extraPackages = [ targetLlvmLibraries.compiler-rt ];
+        extraBuildCommands = mkExtraBuildCommands cc;
+      };
+
       lld = callPackage ./lld {
       };