[DWARFASTParserClang] Complete external record types before using them as a decl context.

Summary:
When in a gmodules-like debugging scenario, you can have a parent decl context
that gets imported from an external AST. When this happens, we must be careful
to complete this type before adding children to it, otherwise it sometimes
results in a crash.

Reviewers: clayborg, jingham

Subscribers: aprantl, JDevlieghere, lldb-commits

Differential Revision: https://reviews.llvm.org/D43592

llvm-svn: 327750

4 files changed, 68 insertions, 0 deletions

diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/TestWithModuleDebugging.py b/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/TestWithModuleDebugging.py
index b9f25537258..20207c54db9 100644
--- a/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/TestWithModuleDebugging.py
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/TestWithModuleDebugging.py
@@ -69,3 +69,26 @@ class TestWithGmodulesDebugInfo(TestBase):
             42,
             memberValue.GetValueAsSigned(),
             "Member value incorrect")
+
+        testValue = frame.EvaluateExpression("bar")
+        self.assertTrue(
+            testValue.GetError().Success(),
+            "Test expression value invalid: %s" %
+            (testValue.GetError().GetCString()))
+        self.assertTrue(
+            testValue.GetTypeName() == "Foo::Bar",
+            "Test expression type incorrect")
+
+        memberValue = testValue.GetChildMemberWithName("i")
+        self.assertTrue(
+            memberValue.GetError().Success(),
+            "Member value missing or invalid: %s" %
+            (testValue.GetError().GetCString()))
+        self.assertTrue(
+            memberValue.GetTypeName() == "int",
+            "Member type incorrect")
+        self.assertEqual(
+            123,
+            memberValue.GetValueAsSigned(),
+            "Member value incorrect")
+
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/main.cpp b/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/main.cpp
index aa401368517..588a3a8e01f 100644
--- a/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/main.cpp
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/main.cpp
@@ -1,5 +1,8 @@
+class Foo::Bar { int i = 123; };
+
 int main(int argc, const char * argv[])
 {
     IntContainer test(42);
+    Foo::Bar bar;
     return 0; // break here
 }
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/pch.h b/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/pch.h
index a6c59b94c89..dba4fee9a8c 100644
--- a/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/pch.h
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/gmodules/pch.h
@@ -10,3 +10,8 @@ class GenericContainer {
 };
 
 typedef GenericContainer<int> IntContainer;
+
+struct Foo {
+  class Bar;
+  Bar *bar;
+};
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index 3d13d40a687..fbf35b8be09 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -205,6 +205,33 @@ TypeSP DWARFASTParserClang::ParseTypeFromDWO(const DWARFDIE &die, Log *log) {
   return type_sp;
 }
 
+static void CompleteExternalTagDeclType(ClangASTImporter &ast_importer,
+                                        clang::DeclContext *decl_ctx,
+                                        DWARFDIE die,
+                                        const char *type_name_cstr) {
+  auto *tag_decl_ctx = clang::dyn_cast<clang::TagDecl>(decl_ctx);
+  if (!tag_decl_ctx)
+    return;
+
+  // If this type was not imported from an external AST, there's
+  // nothing to do.
+  CompilerType type = ClangASTContext::GetTypeForDecl(tag_decl_ctx);
+  if (!type || !ast_importer.CanImport(type))
+    return;
+
+  auto qual_type = ClangUtil::GetQualType(type);
+  if (!ast_importer.RequireCompleteType(qual_type)) {
+    die.GetDWARF()->GetObjectFile()->GetModule()->ReportError(
+        "Unable to complete the Decl context for DIE '%s' at offset "
+        "0x%8.8x.\nPlease file a bug report.",
+        type_name_cstr ?: "", die.GetOffset());
+    // We need to make the type look complete otherwise, we
+    // might crash in Clang when adding children.
+    if (ClangASTContext::StartTagDeclarationDefinition(type))
+      ClangASTContext::CompleteTagDeclarationDefinition(type);
+  }
+}
+
 TypeSP DWARFASTParserClang::ParseTypeFromDWARF(const SymbolContext &sc,
                                                const DWARFDIE &die, Log *log,
                                                bool *type_is_new_ptr) {
@@ -795,6 +822,16 @@ TypeSP DWARFASTParserClang::ParseTypeFromDWARF(const SymbolContext &sc,
         if (!clang_type) {
           clang::DeclContext *decl_ctx =
               GetClangDeclContextContainingDIE(die, nullptr);
+
+          // If your decl context is a record that was imported from
+          // another AST context (in the gmodules case), we need to
+          // make sure the type backing the Decl is complete before
+          // adding children to it. This is not an issue in the
+          // non-gmodules case because the debug info will always contain
+          // a full definition of parent types in that case.
+          CompleteExternalTagDeclType(GetClangASTImporter(), decl_ctx, die,
+                                      type_name_cstr);
+
           if (accessibility == eAccessNone && decl_ctx) {
             // Check the decl context that contains this class/struct/union.
             // If it is a class we must give it an accessibility.