From efdf4e9d1f05d6587230d1b71fab1e5000bed22a Mon Sep 17 00:00:00 2001
From: Randy Eckenrode <randy@largeandhighquality.com>
Date: Sun, 23 Jul 2023 20:40:26 -0400
Subject: [PATCH] swift: use stdenv libc++ on Darwin

Swift uses libc++ 15, but it should really be using the same libc++ from
the stdenv. While not strictly needed currently, Swift 5.9 will support
C++ interop. If Swift is not using the stdenv C++, any C++ library used
with interop would need to be rebuilt against the Swift libc++.
---
 pkgs/development/compilers/swift/default.nix | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/pkgs/development/compilers/swift/default.nix b/pkgs/development/compilers/swift/default.nix
index 2df883095cf1..0da2510f09a0 100644
--- a/pkgs/development/compilers/swift/default.nix
+++ b/pkgs/development/compilers/swift/default.nix
@@ -2,11 +2,14 @@
 , pkgs
 , newScope
 , darwin
+, llvmPackages
 , llvmPackages_15
 , overrideCC
 }:
 
 let
+  swiftLlvmPackages = llvmPackages_15;
+
   self = rec {
 
     callPackage = newScope self;
@@ -24,12 +27,25 @@ let
     # used in Swift, and applies the same libc overrides as `apple_sdk.stdenv`.
     clang = if pkgs.stdenv.isDarwin
       then
-        llvmPackages_15.clang.override rec {
+        swiftLlvmPackages.clang.override rec {
           libc = apple_sdk.Libsystem;
           bintools = pkgs.bintools.override { inherit libc; };
+          # Ensure that Swift’s internal clang uses the same libc++ and libc++abi as the
+          # default Darwin stdenv. Using the default libc++ avoids issues (such as crashes)
+          # that can happen when a Swift application dynamically links different versions
+          # of libc++ and libc++abi than libraries it links are using.
+          inherit (llvmPackages) libcxx;
+          extraPackages = [
+            llvmPackages.libcxxabi
+            # Use the compiler-rt associated with clang, but use the libc++abi from the stdenv
+            # to avoid linking against two different versions (for the same reasons as above).
+            (swiftLlvmPackages.compiler-rt.override {
+              inherit (llvmPackages) libcxxabi;
+            })
+          ];
         }
       else
-        llvmPackages_15.clang;
+        swiftLlvmPackages.clang;
 
     # Overrides that create a useful environment for swift packages, allowing
     # packaging with `swiftPackages.callPackage`. These are similar to