swift-corelibs: don’t link against libcurl

swift-corelibs uses libcurl to implement `NSURLSession` in Foundation
via the symbols exported by CF. Foundation is not build on Darwin, and
these symbols are not exported by the system CoreFoundation.

By not linking against libcurl, this breaks a cycle between CF and
libcurl. That should allow libcurl to drop the patch disabling
linking against the SystemConfiguration and restore NAT64 support.

Unfortunately, the Darwin stdenv bootstrap still needs to build
dependencies that use `fetchFromGitHub`. While it can drop curl from the
final stdenv, it still needs to use it during the stdenv bootstrap.

2 files changed, 53 insertions, 0 deletions

diff --git a/pkgs/os-specific/darwin/swift-corelibs/0008-Dont-link-libcurl.patch b/pkgs/os-specific/darwin/swift-corelibs/0008-Dont-link-libcurl.patch
new file mode 100644
index 0000000000000..4207bf1a82f59
--- /dev/null
+++ b/pkgs/os-specific/darwin/swift-corelibs/0008-Dont-link-libcurl.patch
@@ -0,0 +1,46 @@
+diff -u a/CoreFoundation/CMakeLists.txt b/CoreFoundation/CMakeLists.txt
+--- a/CoreFoundation/CMakeLists.txt	1969-12-31 19:00:01.000000000 -0500
++++ b/CoreFoundation/CMakeLists.txt	2023-06-29 19:39:30.074449222 -0400
+@@ -104,7 +104,6 @@
+                 # URL
+                 URL.subproj/CFURL.inc.h
+                 URL.subproj/CFURLPriv.h
+-                URL.subproj/CFURLSessionInterface.h
+               PUBLIC_HEADERS
+                 # FIXME: PrivateHeaders referenced by public headers
+                 Base.subproj/CFKnownLocations.h
+@@ -120,7 +119,6 @@
+                 String.subproj/CFRegularExpression.h
+                 String.subproj/CFRunArray.h
+                 URL.subproj/CFURLPriv.h
+-                URL.subproj/CFURLSessionInterface.h
+ 
+                 # AppServices
+                 AppServices.subproj/CFNotificationCenter.h
+@@ -280,8 +278,7 @@
+                 URL.subproj/CFURL.c
+                 URL.subproj/CFURLAccess.c
+                 URL.subproj/CFURLComponents.c
+-                URL.subproj/CFURLComponents_URIParser.c
+-                URL.subproj/CFURLSessionInterface.c)
++                URL.subproj/CFURLComponents_URIParser.c)
+ if(CMAKE_SYSTEM_NAME STREQUAL Linux OR CMAKE_SYSTEM_NAME STREQUAL Android)
+   target_compile_definitions(CoreFoundation
+                              PRIVATE
+@@ -341,8 +338,6 @@
+                              PRIVATE
+                                ${CURL_INCLUDE_DIRS})
+ elseif(CMAKE_SYSTEM_NAME STREQUAL Darwin)
+-  find_package(CURL REQUIRED)
+-  target_include_directories(CoreFoundation PRIVATE ${CURL_INCLUDE_DIRS})
+   find_package(ICU COMPONENTS uc i18n data REQUIRED)
+   find_package(LibXml2 REQUIRED)
+   target_include_directories(CoreFoundation PRIVATE ${LIBXML2_INCLUDE_DIR})
+@@ -377,7 +372,6 @@
+                           ${LIBXML2_LIBRARIES})
+ elseif(CMAKE_SYSTEM_NAME STREQUAL Darwin)
+   target_link_libraries(CoreFoundation PRIVATE
+-    ${CURL_LIBRARIES}
+     ICU::uc
+     ICU::i18n
+     ICU::data
diff --git a/pkgs/os-specific/darwin/swift-corelibs/corefoundation.nix b/pkgs/os-specific/darwin/swift-corelibs/corefoundation.nix
index 90282b391d90a..5bd3e201056ac 100644
--- a/pkgs/os-specific/darwin/swift-corelibs/corefoundation.nix
+++ b/pkgs/os-specific/darwin/swift-corelibs/corefoundation.nix
@@ -40,6 +40,13 @@ stdenv.mkDerivation {
     ./0006-System-CF-framework-compatibility.patch
     # Link against the nixpkgs ICU instead of using Apple’s vendored version.
     ./0007-Use-nixpkgs-icu.patch
+    # Don’t link against libcurl. This breaks a cycle between CF and curl, which depends on CF and
+    # uses the SystemConfiguration framework to support NAT64.
+    # This is safe because the symbols provided in CFURLSessionInterface are not provided by the
+    # system CoreFoundation. They are meant to be used by the implementation of `NSURLSession` in
+    # swift-corelibs-foundation, which is not built because it is not fully compatible with the
+    # system Foundation used on Darwin.
+    ./0008-Dont-link-libcurl.patch
   ];
 
   postPatch = ''