[SourceKit] Do not hardcode the XPC service name

Write the service name into a resource file rather than have it
hardcoded, allowing it to be updated post-build if necessary.

Author: bnbarham

tools/SourceKit/cmake/modules/AddSwiftSourceKit.cmake

@@ -445,6 +445,9 @@ macro(add_sourcekit_framework name)
       "${framework_location}/Versions/A" "${SOURCEKIT_LIBRARY_OUTPUT_INTDIR}")
     list(APPEND RPATH_LIST "@loader_path/${relative_lib_path}")
 
+    file(GENERATE OUTPUT "xpc_service_name.txt" CONTENT "com.apple.SourceKitService.${SOURCEKIT_VERSION_STRING}_${SOURCEKIT_TOOLCHAIN_NAME}")
+    target_sources(${name} PUBLIC "${CMAKE_CURRENT_BINARY_DIR}/xpc_service_name.txt")
+
     set_target_properties(${name} PROPERTIES
                           BUILD_WITH_INSTALL_RPATH TRUE
                           FOLDER "SourceKit frameworks"
@@ -455,7 +458,8 @@ macro(add_sourcekit_framework name)
                           MACOSX_FRAMEWORK_IDENTIFIER "com.apple.${name}"
                           MACOSX_FRAMEWORK_SHORT_VERSION_STRING "1.0"
                           MACOSX_FRAMEWORK_BUNDLE_VERSION "${SOURCEKIT_VERSION_STRING}"
-                          PUBLIC_HEADER "${headers}")
+                          PUBLIC_HEADER "${headers}"
+                          RESOURCE "${service_name_file}")
     add_dependencies(${SOURCEKITFW_INSTALL_IN_COMPONENT} ${name})
     swift_install_in_component(TARGETS ${name}
                                FRAMEWORK

tools/SourceKit/tools/sourcekitd/bin/XPC/Client/CMakeLists.txt

@@ -16,8 +16,6 @@ add_sourcekit_framework(sourcekitd
 )
 target_link_libraries(sourcekitd PRIVATE sourcekitdAPI)
 
-add_definitions(-DSOURCEKIT_XPCSERVICE_IDENTIFIER="com.apple.SourceKitService.${SOURCEKIT_VERSION_STRING}_${SOURCEKIT_TOOLCHAIN_NAME}")
-
 if (SOURCEKIT_BUILT_STANDALONE)
   # Create the symlink necessary to find the swift stdlib.
   swift_create_post_build_symlink(sourcekitd

tools/SourceKit/tools/sourcekitd/bin/XPC/Client/sourcekitd.cpp

@@ -15,12 +15,15 @@
 #include "SourceKit/Support/UIdent.h"
 
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Mutex.h"
+#include "llvm/Support/Path.h"
+
+#include <Block.h>
 #include <chrono>
 #include <xpc/xpc.h>
 #include <dispatch/dispatch.h>
-
-#include <Block.h>
+#include <dlfcn.h>
 
 using namespace SourceKit;
 using namespace sourcekitd;
@@ -285,9 +288,27 @@ static void handleInternalUIDRequest(xpc_object_t XVal,
 
 static void handleInterruptedConnection(xpc_object_t event, xpc_connection_t conn);
 
+extern "C" const char __dso_handle[];
+
 static void initializeXPCClient() {
   assert(!GlobalConn);
-  GlobalConn = xpc_connection_create(SOURCEKIT_XPCSERVICE_IDENTIFIER, nullptr);
+
+  Dl_info dlinfo;
+  dladdr(__dso_handle, &dlinfo);
+
+  // '.../usr/lib/sourcekitd.framework/sourcekitd'
+  llvm::SmallString<128> serviceNamePath(dlinfo.dli_fname);
+  llvm::sys::path::remove_filename(serviceNamePath);
+  // '.../usr/lib/sourcekitd.framework/Resources/xpc_service_name.txt'
+  llvm::sys::path::append(serviceNamePath, "Resources", "xpc_service_name.txt");
+
+  auto bufferOrErr = llvm::MemoryBuffer::getFile(serviceNamePath);
+  if (!bufferOrErr) {
+    llvm::report_fatal_error("Unable to find service name");
+  }
+
+  StringRef serviceName = (*bufferOrErr)->getBuffer();
+  GlobalConn = xpc_connection_create(serviceName.data(), nullptr);
 
   xpc_connection_set_event_handler(GlobalConn, ^(xpc_object_t event) {
     xpc_type_t type = xpc_get_type(event);