From 90799cfdf73e69147baab6f92f934c3a74235c5e Mon Sep 17 00:00:00 2001
From: Yuta Saito <kateinoigakukun@gmail.com>
Date: Sat, 10 Aug 2024 13:29:48 +0000
Subject: [PATCH 1/2] Revert "[wasm] Fix ambiguous `errno` error when importing
 WASILibc module"

This reverts commit 164ec0adaa80e7a29d2a10fb31ee72baddeda6b2.
---
 stdlib/public/Platform/Platform.swift | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/stdlib/public/Platform/Platform.swift b/stdlib/public/Platform/Platform.swift
index ca7417c53574b..0c2d63a0cffdb 100644
--- a/stdlib/public/Platform/Platform.swift
+++ b/stdlib/public/Platform/Platform.swift
@@ -84,11 +84,6 @@ func _convertDarwinBooleanToBool(_ x: DarwinBoolean) -> Bool {
 
 #endif
 
-// wasi-libc defines `errno` in a way ClangImporter can understand, so we don't
-// need to define shims for it. On the contrary, if we define the shim, we will
-// get an ambiguity error when importing WASILibc module and SwiftWASILibc Clang
-// module (or a Clang module that re-exports SwiftWASILibc).
-#if !os(WASI)
 //===----------------------------------------------------------------------===//
 // sys/errno.h
 //===----------------------------------------------------------------------===//
@@ -101,7 +96,6 @@ public var errno : Int32 {
     return _swift_stdlib_setErrno(val)
   }
 }
-#endif
 
 
 //===----------------------------------------------------------------------===//

From be08ebb12a99636832f055e94956cb500af1a86d Mon Sep 17 00:00:00 2001
From: Yuta Saito <kateinoigakukun@gmail.com>
Date: Sat, 10 Aug 2024 13:50:57 +0000
Subject: [PATCH 2/2] [wasm] Annotate errno as SwiftPrivate by apinotes

This patch adds an apinotes file for SwiftWASILibc clang module to mark
`errno` macro hidden from Swift code. This resolves ambiguity between
the C macro definition and the Swift wrapper in WASILibc overlay module.

This change installs the apinotes file to the resource directories for
both lib/swift/apinotes and lib/swift_static/apinotes.
---
 stdlib/public/Platform/CMakeLists.txt         | 28 +++++++++++++++++++
 stdlib/public/Platform/SwiftWASILibc.apinotes |  5 ++++
 test/stdlib/WASILibcAPI.swift                 | 19 +++++++++++++
 3 files changed, 52 insertions(+)
 create mode 100644 stdlib/public/Platform/SwiftWASILibc.apinotes
 create mode 100644 test/stdlib/WASILibcAPI.swift

diff --git a/stdlib/public/Platform/CMakeLists.txt b/stdlib/public/Platform/CMakeLists.txt
index 928b5d9cb6302..7a7cab3da6d59 100644
--- a/stdlib/public/Platform/CMakeLists.txt
+++ b/stdlib/public/Platform/CMakeLists.txt
@@ -527,6 +527,34 @@ if("WASI" IN_LIST SWIFT_SDKS)
                                  DESTINATION "lib/swift_static/${arch_subdir}"
                                  COMPONENT sdk-overlay)
     endif()
+
+    set(wasilibc_apinotes_source "SwiftWASILibc.apinotes")
+    add_custom_command_target(
+      copy_wasilibc_apinotes_resource
+      COMMAND
+        "${CMAKE_COMMAND}" "-E" "make_directory" ${SWIFTLIB_DIR}/apinotes ${SWIFTSTATICLIB_DIR}/apinotes
+      COMMAND
+        "${CMAKE_COMMAND}" "-E" "copy_if_different"
+          "${CMAKE_CURRENT_SOURCE_DIR}/${wasilibc_apinotes_source}" ${SWIFTLIB_DIR}/apinotes
+      COMMAND
+        "${CMAKE_COMMAND}" "-E" "copy_if_different"
+          "${CMAKE_CURRENT_SOURCE_DIR}/${wasilibc_apinotes_source}" ${SWIFTSTATICLIB_DIR}/apinotes
+      OUTPUT
+        ${SWIFTLIB_DIR}/apinotes/${wasilibc_apinotes_source}
+        ${SWIFTSTATICLIB_DIR}/apinotes/${wasilibc_apinotes_source}
+      COMMENT "Copying WASILibc API notes to resource directories")
+
+    list(APPEND wasilibc_modulemap_target_list ${copy_wasilibc_apinotes_resource})
+    add_dependencies(sdk-overlay ${copy_wasilibc_apinotes_resource})
+    swift_install_in_component(FILES "${wasilibc_apinotes_source}"
+                               DESTINATION "lib/swift/apinotes"
+                               COMPONENT sdk-overlay)
+    if(SWIFT_BUILD_STATIC_STDLIB)
+      swift_install_in_component(FILES "${wasilibc_apinotes_source}"
+                                 DESTINATION "lib/swift_static/apinotes"
+                                 COMPONENT sdk-overlay)
+    endif()
+
   endforeach()
 endif()
 add_custom_target(wasilibc_modulemap DEPENDS ${wasilibc_modulemap_target_list})
diff --git a/stdlib/public/Platform/SwiftWASILibc.apinotes b/stdlib/public/Platform/SwiftWASILibc.apinotes
new file mode 100644
index 0000000000000..001acc7ebb596
--- /dev/null
+++ b/stdlib/public/Platform/SwiftWASILibc.apinotes
@@ -0,0 +1,5 @@
+Name: SwiftWASILibc
+Globals:
+  # errno macro is importable but we provide explicit Swift wrapper
+  - Name: errno
+    SwiftPrivate: true
diff --git a/test/stdlib/WASILibcAPI.swift b/test/stdlib/WASILibcAPI.swift
new file mode 100644
index 0000000000000..fe599bb9f3878
--- /dev/null
+++ b/test/stdlib/WASILibcAPI.swift
@@ -0,0 +1,19 @@
+// RUN: %target-swift-frontend -typecheck -swift-version 6 %s -verify
+// REQUIRES: executable_test
+// REQUIRES: OS=wasi
+
+import WASILibc
+
+// errno is a global thread-local variable, so it should be accessible
+// from any context.
+
+enum TestErrno {
+  static func testSyncContext() {
+    _ = errno
+    errno = 0
+  }
+  static func testAsyncContext() async {
+    _ = errno
+    errno = 0
+  }
+}