[lldb][darwin] force BuiltinHeadersInSystemModules to be always false (#144913)

`SDKSupportsBuiltinModules` always returns true on newer versions of
Darwin based OS. The only way for this call to return `false` would be
to have a version mismatch between lldb and the SDK (recent lldb
manually installed on macOS 14 for instance).

This patch removes this check and hardcodes the value of
`BuiltinHeadersInSystemModules` to `false`.

Author: charles-zablit

lldb/include/lldb/Utility/XcodeSDK.h

@@ -93,19 +93,6 @@ class XcodeSDK {
   static bool SDKSupportsModules(Type type, llvm::VersionTuple version);
   static bool SDKSupportsModules(Type desired_type, const FileSpec &sdk_path);
 
-  /// Returns true if the SDK for the specified triple supports
-  /// builtin modules in system headers.
-  ///
-  /// NOTE: should be kept in sync with sdkSupportsBuiltinModules in
-  /// Toolchains/Darwin.cpp
-  ///
-  /// FIXME: this function will be removed once LLDB's ClangExpressionParser
-  /// constructs the compiler instance through the driver/toolchain. See \ref
-  /// SetupImportStdModuleLangOpts
-  ///
-  static bool SDKSupportsBuiltinModules(const llvm::Triple &target_triple,
-                                        llvm::VersionTuple sdk_version);
-
   /// Return the canonical SDK name, such as "macosx" for the macOS SDK.
   static std::string GetCanonicalName(Info info);
   /// Return the best-matching SDK type for a specific triple.

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

@@ -319,49 +319,6 @@ class ClangDiagnosticManagerAdapter : public clang::DiagnosticConsumer {
   StringRef m_filename;
 };
 
-/// Returns true if the SDK for the specified triple supports
-/// builtin modules in system headers. This is used to decide
-/// whether to pass -fbuiltin-headers-in-system-modules to
-/// the compiler instance when compiling the `std` module.
-static llvm::Expected<bool>
-sdkSupportsBuiltinModules(lldb_private::Target &target) {
-  auto arch_spec = target.GetArchitecture();
-  auto const &triple = arch_spec.GetTriple();
-  auto module_sp = target.GetExecutableModule();
-  if (!module_sp)
-    return llvm::createStringError("Executable module not found.");
-
-  // Get SDK path that the target was compiled against.
-  auto platform_sp = target.GetPlatform();
-  if (!platform_sp)
-    return llvm::createStringError("No Platform plugin found on target.");
-
-  auto sdk_or_err = platform_sp->GetSDKPathFromDebugInfo(*module_sp);
-  if (!sdk_or_err)
-    return sdk_or_err.takeError();
-
-  // Use the SDK path from debug-info to find a local matching SDK directory.
-  auto sdk_path_or_err =
-      HostInfo::GetSDKRoot(HostInfo::SDKOptions{std::move(sdk_or_err->first)});
-  if (!sdk_path_or_err)
-    return sdk_path_or_err.takeError();
-
-  auto VFS = FileSystem::Instance().GetVirtualFileSystem();
-  if (!VFS)
-    return llvm::createStringError("No virtual filesystem available.");
-
-  // Extract SDK version from the /path/to/some.sdk/SDKSettings.json
-  auto parsed_or_err = clang::parseDarwinSDKInfo(*VFS, *sdk_path_or_err);
-  if (!parsed_or_err)
-    return parsed_or_err.takeError();
-
-  auto maybe_sdk = *parsed_or_err;
-  if (!maybe_sdk)
-    return llvm::createStringError("Couldn't find Darwin SDK info.");
-
-  return XcodeSDK::SDKSupportsBuiltinModules(triple, maybe_sdk->getVersion());
-}
-
 static void SetupModuleHeaderPaths(CompilerInstance *compiler,
                                    std::vector<std::string> include_directories,
                                    lldb::TargetSP target_sp) {
@@ -705,7 +662,6 @@ static void SetupLangOpts(CompilerInstance &compiler,
 
 static void SetupImportStdModuleLangOpts(CompilerInstance &compiler,
                                          lldb_private::Target &target) {
-  Log *log = GetLog(LLDBLog::Expressions);
   LangOptions &lang_opts = compiler.getLangOpts();
   lang_opts.Modules = true;
   // We want to implicitly build modules.
@@ -723,12 +679,7 @@ static void SetupImportStdModuleLangOpts(CompilerInstance &compiler,
   lang_opts.GNUKeywords = true;
   lang_opts.CPlusPlus11 = true;
 
-  if (auto supported_or_err = sdkSupportsBuiltinModules(target))
-    lang_opts.BuiltinHeadersInSystemModules = !*supported_or_err;
-  else
-    LLDB_LOG_ERROR(log, supported_or_err.takeError(),
-                   "Failed to determine BuiltinHeadersInSystemModules when "
-                   "setting up import-std-module: {0}");
+  lang_opts.BuiltinHeadersInSystemModules = false;
 
   // The Darwin libc expects this macro to be set.
   lang_opts.GNUCVersion = 40201;

lldb/source/Utility/XcodeSDK.cpp

@@ -266,27 +266,6 @@ bool XcodeSDK::SupportsSwift() const {
   }
 }
 
-bool XcodeSDK::SDKSupportsBuiltinModules(const llvm::Triple &target_triple,
-                                         llvm::VersionTuple sdk_version) {
-  using namespace llvm;
-
-  switch (target_triple.getOS()) {
-  case Triple::OSType::MacOSX:
-    return sdk_version >= VersionTuple(15U);
-  case Triple::OSType::IOS:
-    return sdk_version >= VersionTuple(18U);
-  case Triple::OSType::TvOS:
-    return sdk_version >= VersionTuple(18U);
-  case Triple::OSType::WatchOS:
-    return sdk_version >= VersionTuple(11U);
-  case Triple::OSType::XROS:
-    return sdk_version >= VersionTuple(2U);
-  default:
-    // New SDKs support builtin modules from the start.
-    return true;
-  }
-}
-
 bool XcodeSDK::SDKSupportsModules(XcodeSDK::Type desired_type,
                                   const FileSpec &sdk_path) {
   ConstString last_path_component = sdk_path.GetFilename();