[lldb][SymbolFileDWARF] Fall back to using parent DW_AT_LLVM_include_path for submodules

[Michael137]

Inferred submodule declarations are emitted in DWARF as DW_TAG_modules without DW_AT_LLVM_include_paths. 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 #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

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Michael Buch (Michael137)

Changes

Inferred submodule declarations are emitted in DWARF as DW_TAG_modules without DW_AT_LLVM_include_paths. 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 #141220.

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

---

Full diff: https://github.com/llvm/llvm-project/pull/142044.diff

7 Files Affected:

• (modified) lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp (+10-2)
• (added) lldb/test/API/lang/cpp/decl-from-submodule/Makefile (+4)
• (added) lldb/test/API/lang/cpp/decl-from-submodule/TestDeclFromSubmodule.py (+25)
• (added) lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module1.h (+2)
• (added) lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module2.h (+2)
• (added) lldb/test/API/lang/cpp/decl-from-submodule/main.cpp (+9)
• (added) lldb/test/API/lang/cpp/decl-from-submodule/module.modulemap (+6)

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index d2049161fb5ad..24f905a023317 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -1188,6 +1188,8 @@ 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)
@@ -1195,10 +1197,16 @@ bool SymbolFileDWARF::ParseImportedModules(
         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());
diff --git a/lldb/test/API/lang/cpp/decl-from-submodule/Makefile b/lldb/test/API/lang/cpp/decl-from-submodule/Makefile
new file mode 100644
index 0000000000000..e1e28fa0efebb
--- /dev/null
+++ b/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
diff --git a/lldb/test/API/lang/cpp/decl-from-submodule/TestDeclFromSubmodule.py b/lldb/test/API/lang/cpp/decl-from-submodule/TestDeclFromSubmodule.py
new file mode 100644
index 0000000000000..2819e59b1a1e5
--- /dev/null
+++ b/lldb/test/API/lang/cpp/decl-from-submodule/TestDeclFromSubmodule.py
@@ -0,0 +1,25 @@
+"""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):
+    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",
+        )
diff --git a/lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module1.h b/lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module1.h
new file mode 100644
index 0000000000000..38d9d120847c9
--- /dev/null
+++ b/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; }
diff --git a/lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module2.h b/lldb/test/API/lang/cpp/decl-from-submodule/TopLevel/module2.h
new file mode 100644
index 0000000000000..440c76dd50c77
--- /dev/null
+++ b/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; }
diff --git a/lldb/test/API/lang/cpp/decl-from-submodule/main.cpp b/lldb/test/API/lang/cpp/decl-from-submodule/main.cpp
new file mode 100644
index 0000000000000..5e05b6980169a
--- /dev/null
+++ b/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;
+}
diff --git a/lldb/test/API/lang/cpp/decl-from-submodule/module.modulemap b/lldb/test/API/lang/cpp/decl-from-submodule/module.modulemap
new file mode 100644
index 0000000000000..b00659f7efb67
--- /dev/null
+++ b/lldb/test/API/lang/cpp/decl-from-submodule/module.modulemap
@@ -0,0 +1,6 @@
+module TopLevel {
+  umbrella "TopLevel"
+  explicit module * {
+    export *
+  }
+}

[adrian-prantl]

Looks good!

[DavidSpickett]

This test was failing on Windows I think because like many others, we're not making DWARF or we're not retaining it when linking with link.exe. I've skipped it there - 7a66b28.

[Michael137]

This test was failing on Windows I think because like many others, we're not making DWARF or we're not retaining it when linking with link.exe. I've skipped it there - 7a66b28.

Thanks!