[WIP] Enable std module import tests on Darwin

[aprantl]

Summary

Note that this does not fully work yet, but gets further than before. Where it previously failed with

AssertionError: False is not True : Command 'expr std::abs(-42)
Error output:
error: 'ctype.h' file not found
error: could not build module 'std'
error: while importing modules:

it now fails with

error: module 'std' is needed but has not been provided, and implicit use of module files is disabled
error: while importing modules:
'__config' file not found with <angled> include; use "quotes" instead
'__config' file not found with <angled> include; use "quotes" instead
'__config' file not found with <angled> include; use "quotes" instead
'__config' file not found with <angled> include; use "quotes" instead
'__config' file not found with <angled> include; use "quotes" instead
'__config' file not found with <angled> include; use "quotes" instead

Raphael, am I on the right track or is this a bad idea?

[teemperor]

Adding the SDK sysroot there would affect all paths (even user paths that are not in the sysroot) from what I can tell, not just /usr/include. I think the way we implemented this on Linux is via GetSystemIncludeDirectories, see D61240.

Also thanks for looking into this!

[teemperor]

This doesn't seem necessary anymore :)

lldb/packages/Python/lldbsuite/test/expression_command/import-std-module/basic/TestImportStdModule.py

 class ImportStdModule(TestBase):
 
     mydir = TestBase.compute_mydir(__file__)
 
     # FIXME: This should work on more setups, so remove these
     # skipIf's in the future.
     @add_test_categories(["libc++"])
     @skipIf(compiler=no_match("clang"))
-    @skipIf(oslist=no_match(["linux"]))
-    @skipIf(debug_info=no_match(["dwarf"]))
     def test(self):
         self.build()
 
         lldbutil.run_to_source_breakpoint(self,
             "// Set break point at this line.", lldb.SBFileSpec("main.cpp"))
 
         # Activate importing of std module.
         self.runCmd("settings set target.import-std-module true")

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

 private:
   DiagnosticManager *m_manager = nullptr;
   std::shared_ptr<clang::TextDiagnosticBuffer> m_passthrough;
 };
 
 static void
 SetupModuleHeaderPaths(CompilerInstance *compiler,
                        std::vector<ConstString> include_directories,
-                       lldb::TargetSP target_sp) {
+                       lldb_private::Target &target) {
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
   HeaderSearchOptions &search_opts = compiler->getHeaderSearchOpts();
+  search_opts.Sysroot =
+      target.GetPlatform()->GetSDKDirectory(target).GetStringRef().str();
 
   for (ConstString dir : include_directories) {
     search_opts.AddPath(dir.AsCString(), frontend::System, false, true);
     LLDB_LOG(log, "Added user include dir: {0}", dir);
   }
 
   llvm::SmallString<128> module_cache;
   auto props = ModuleList::GetGlobalModuleListProperties();
if (FileSystem::Instance().IsDirectory(resource_dir)) {
     search_opts.AddPath(resource_include, frontend::System, false, true);
 
     LLDB_LOG(log, "Added resource include dir: {0}", resource_include);
   }
 
   search_opts.ImplicitModuleMaps = true;
 
   std::vector<std::string> system_include_directories =
-      target_sp->GetPlatform()->GetSystemIncludeDirectories(
+      target.GetPlatform()->GetSystemIncludeDirectories(
           lldb::eLanguageTypeC_plus_plus);
 
   for (const std::string &include_dir : system_include_directories) {
     search_opts.AddPath(include_dir, frontend::System, false, true);
 
     LLDB_LOG(log, "Added system include dir: {0}", include_dir);
   }
 }
if (clang_expr && clang_expr->DidImportCxxModules()) {
 
     // Options we need to parse libc++ code successfully.
     // FIXME: We should ask the driver for the appropriate default flags.
     lang_opts.GNUMode = true;
     lang_opts.GNUKeywords = true;
     lang_opts.DoubleSquareBracketAttributes = true;
     lang_opts.CPlusPlus11 = true;
 
-    SetupModuleHeaderPaths(m_compiler.get(), m_include_directories,
-                           target_sp);
+    SetupModuleHeaderPaths(m_compiler.get(), m_include_directories, *target_sp);
   }
 
   if (process_sp && lang_opts.ObjC) {
     if (process_sp->GetObjCLanguageRuntime()) {
       if (process_sp->GetObjCLanguageRuntime()->GetRuntimeVersion() ==
           ObjCLanguageRuntime::ObjCRuntimeVersions::eAppleObjC_V2)
         lang_opts.ObjCRuntime.set(ObjCRuntime::MacOSX, VersionTuple(10, 7));
       else