🍒[lldb][SymbolFileDWARF] Fall back to using parent DW_AT_LLVM_include_path for submodules (swiftlang#10764)

* [lldb][SymbolFileDWARF] Fall back to using parent DW_AT_LLVM_include_path for submodules (llvm#142044)

Inferred submodule declarations are emitted in DWARF as `DW_TAG_module`s
without `DW_AT_LLVM_include_path`s. Instead the parent DIE will have the
include path. This patch adds support for such setups. Without this, the
`ClangModulesDeclVendor` would fail to `AddModule` the submodules (i.e.,
compile and load the submodules). This would cause errors such as:
```
note: error: Header search couldn't locate module 'TopLevel'
```

The test added here also tests
llvm#141220. Without that patch
we'd fail with:
```
note: error: No module map file in /Users/jonas/Git/llvm-worktrees/llvm-project/lldb/test/API/lang/cpp/decl-from-submodule
```

Unfortunately the embedded clang instance doesn't allow us to use the
decls we find in the modules. But we'll try to fix that in a separate
patch.

rdar://151022173
(cherry picked from commit 7b96272)

* [lldb][test] Disable DeclFromSubmodule test on Windows

Or more precisely, when linking with link.exe, but Windows
is our closest proxy for that right now.

This test requires the DWARF info to work, on the Windows on Arm
buildbot it fails:
```
AssertionError: Ran command:
"expr func(1, 2)"

Got output:
error: <user expression 0>:1:1: use of undeclared identifier 'func'

    1 | func(1, 2)

      | ^~~~

Expecting start string: "error: <user expression 0>:1:1: 'func' has unknown return type" (was not found)
```

(cherry picked from commit 7a66b28)

---------

Co-authored-by: David Spickett <[email protected]>

Author: Michael137

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

@@ -1221,17 +1221,25 @@ bool SymbolFileDWARF::ParseImportedModules(
       SourceModule module;
       module.path.push_back(ConstString(name));
 
+      const char *include_path = module_die.GetAttributeValueAsString(
+          DW_AT_LLVM_include_path, nullptr);
       DWARFDIE parent_die = module_die;
       while ((parent_die = parent_die.GetParent())) {
         if (parent_die.Tag() != DW_TAG_module)
           break;
         if (const char *name =
                 parent_die.GetAttributeValueAsString(DW_AT_name, nullptr))
           module.path.push_back(ConstString(name));
+
+        // Inferred submodule declarations may not have a
+        // DW_AT_LLVM_include_path. Pick the parent (aka umbrella) module's
+        // include path instead.
+        if (!include_path)
+          include_path = parent_die.GetAttributeValueAsString(
+              DW_AT_LLVM_include_path, nullptr);
       }
       std::reverse(module.path.begin(), module.path.end());
-      if (const char *include_path = module_die.GetAttributeValueAsString(
-              DW_AT_LLVM_include_path, nullptr)) {
+      if (include_path) {
         FileSpec include_spec(include_path, dwarf_cu->GetPathStyle());
         MakeAbsoluteAndRemap(include_spec, *dwarf_cu,
                              m_objfile_sp->GetModule());

lldb/test/API/lang/cpp/decl-from-submodule/Makefile

@@ -0,0 +1,4 @@
+CXX_SOURCES := main.cpp
+CXXFLAGS_EXTRAS = $(MANDATORY_MODULE_BUILD_CFLAGS)
+
+include Makefile.rules

lldb/test/API/lang/cpp/decl-from-submodule/TestDeclFromSubmodule.py

@@ -0,0 +1,27 @@
+"""Test that decl lookup into submodules in C++ works as expected."""
+
+import lldb
+import shutil
+
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class DeclFromSubmoduleTestCase(TestBase):
+    # Requires DWARF debug info which is not retained when linking with link.exe.
+    @skipIfWindows
+    def test_expr(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "return 0", lldb.SBFileSpec("main.cpp"))
+
+        # FIXME: LLDB finds the decl for 'func' in the submodules correctly and hands it to Clang
+        # but Sema rejects using the decl during name lookup because it is not marked "Visible".
+        # However, this assertions still ensures that we at least don't fail to compile the
+        # submodule (which would cause other errors to appear before the expression error, hence
+        # we use "startstr").
+        self.expect(
+            "expr func(1, 2)",
+            error=True,
+            startstr="error: <user expression 0>:1:1: 'func' has unknown return type",
+        )

lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module1.h

@@ -0,0 +1,2 @@
+// nodebug to force LLDB to find the decls in modules
+[[gnu::nodebug]] inline int func(int x) { return x; }

lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module2.h

@@ -0,0 +1,2 @@
+// nodebug to force LLDB to find the decls in modules
+[[gnu::nodebug]] inline int func(int x, int y) { return x + y; }

lldb/test/API/lang/cpp/decl-from-submodule/main.cpp

@@ -0,0 +1,9 @@
+#include "TopLevel/module1.h"
+#include "TopLevel/module2.h"
+
+int main() {
+  func(1);
+  func(2, 3);
+
+  return 0;
+}

lldb/test/API/lang/cpp/decl-from-submodule/module.modulemap

@@ -0,0 +1,6 @@
+module TopLevel {
+  umbrella "TopLevel"
+  explicit module * {
+    export *
+  }
+}