Special-case OpenBSD in Versions.cpp instead of in Package.swift in case it gets a clang update in the future

Author: grynspan

Package.swift

@@ -466,9 +466,6 @@ extension Array where Element == PackageDescription.CXXSetting {
 
       .define("SWT_NO_LEGACY_TEST_DISCOVERY", .whenEmbedded()),
       .define("SWT_NO_LIBDISPATCH", .whenEmbedded()),
-
-      // OpenBSD's version of clang doesn't support __has_embed.
-      .define("SWT_TESTING_LIBRARY_VERSION", to: "0", .when(platforms: [.openbsd]))
     ]
 
     // Capture the testing library's commit info as C++ constants.

Sources/_TestingInternals/Versions.cpp

@@ -18,6 +18,7 @@
 const char *swt_getTestingLibraryVersion(void) {
 #if defined(SWT_TESTING_LIBRARY_VERSION)
   // The current environment explicitly specifies a version string to return.
+  // All CMake builds should take this path (see CompilerSettings.cmake.)
   return SWT_TESTING_LIBRARY_VERSION;
 #elif __clang_major__ >= 17 && defined(__has_embed)
 #if __has_embed("../../VERSION.txt")
@@ -43,6 +44,9 @@ const char *swt_getTestingLibraryVersion(void) {
 #warning SWT_TESTING_LIBRARY_VERSION not defined and VERSION.txt not found: testing library version is unavailable
   return nullptr;
 #endif
+#elif defined(__OpenBSD__)
+  // OpenBSD's version of clang doesn't support __has_embed or #embed.
+  return nullptr;
 #else
 #warning SWT_TESTING_LIBRARY_VERSION not defined and could not read from VERSION.txt at compile time: testing library version is unavailable
   return nullptr;

cmake/modules/shared/CompilerSettings.cmake

@@ -43,7 +43,5 @@ if(CMAKE_SYSTEM_NAME STREQUAL "WASI")
   add_compile_definitions("SWT_NO_PIPES")
 endif()
 
-# Avoid using C23's #embed when building with CMake as OpenBSD and Amazon Linux
-# 2 are both using older clang versions that don't support it.
 file(STRINGS "../VERSION.txt" SWT_TESTING_LIBRARY_VERSION LIMIT_COUNT 1)
 add_compile_definitions("$<$<COMPILE_LANGUAGE:CXX>:SWT_TESTING_LIBRARY_VERSION=\"${SWT_TESTING_LIBRARY_VERSION}\">")