[lldb][tests][gmodules] Test for expression evaluator crash for types referencing the same template

The problem here is that the ASTImporter adds
the template class member FieldDecl to
the DeclContext twice. This happens because
we don't construct a `LookupPtr` for decls
that originate from modules and thus the
ASTImporter never realizes that the FieldDecl
has already been imported. These duplicate
decls then break the assumption of the LayoutBuilder
which expects only a single member decl to
exist.

The test will be fixed by a follow-up revision
and is thus skipped for now.

Differential Revision: https://reviews.llvm.org/D133944

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/Makefile

@@ -0,0 +1,3 @@
+CXX_SOURCES   := main.cpp module1.cpp module2.cpp base_module.cpp
+
+include Makefile.rules

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/TestTemplateWithSameArg.py

@@ -0,0 +1,72 @@
+"""
+Tests the scenario where we evaluate expressions
+of two types in different modules that reference
+a class template instantiated with the same
+template argument.
+
+Note that,
+1. Since the decls originate from modules, LLDB
+   marks them as such and Clang doesn't create
+   a LookupPtr map on the corresponding DeclContext.
+   This prevents regular DeclContext::lookup from
+   succeeding.
+2. Because we reference the same class template
+   from two different modules we get a redeclaration
+   chain for the class's ClassTemplateSpecializationDecl.
+   The importer will import all FieldDecls into the
+   same DeclContext on the redeclaration chain. If
+   we don't do the bookkeeping correctly we end up
+   with duplicate decls on the same DeclContext leading
+   to crashes down the line.
+"""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestTemplateWithSameArg(TestBase):
+
+    def setUp(self):
+        TestBase.setUp(self)
+        self.build()
+        self.main_source_file = lldb.SBFileSpec("main.cpp")
+
+    @add_test_categories(["gmodules"])
+    @skipIf(bugnumber='rdar://96581048')
+    def test_same_template_arg(self):
+        lldbutil.run_to_source_breakpoint(self, "Break here", self.main_source_file)
+
+        self.expect_expr("FromMod1", result_type="ClassInMod1", result_children=[
+                ValueCheck(name="VecInMod1", children=[
+                            ValueCheck(name="Member", value="137")
+                    ])
+            ])
+
+        self.expect_expr("FromMod2", result_type="ClassInMod2", result_children=[
+                ValueCheck(name="VecInMod2", children=[
+                            ValueCheck(name="Member", value="42")
+                    ])
+            ])
+
+    @add_test_categories(["gmodules"])
+    @skipIf(bugnumber='rdar://96581048')
+    def test_duplicate_decls(self):
+        lldbutil.run_to_source_breakpoint(self, "Break here", self.main_source_file)
+
+        self.expect_expr("(intptr_t)&FromMod1 + (intptr_t)&FromMod2")
+
+        # Make sure we only have a single 'Member' decl on the AST
+        self.filecheck("target module dump ast", __file__)
+# CHECK:      ClassTemplateSpecializationDecl {{.*}} imported in Module2 struct ClassInMod3 definition
+# CHECK-NEXT: |-DefinitionData pass_in_registers aggregate standard_layout trivially_copyable pod trivial
+# CHECK-NEXT: | |-DefaultConstructor exists trivial needs_implicit
+# CHECK-NEXT: | |-CopyConstructor simple trivial has_const_param needs_implicit implicit_has_const_param
+# CHECK-NEXT: | |-MoveConstructor exists simple trivial needs_implicit
+# CHECK-NEXT: | |-CopyAssignment simple trivial has_const_param needs_implicit implicit_has_const_param
+# CHECK-NEXT: | |-MoveAssignment exists simple trivial needs_implicit
+# CHECK-NEXT: | `-Destructor simple irrelevant trivial needs_implicit
+# CHECK-NEXT: |-TemplateArgument type 'int'
+# CHECK-NEXT: | `-BuiltinType {{.*}} 'int'
+# CHECK-NEXT: `-FieldDecl {{.*}} imported in Module2 Member 'int'

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/base_module.cpp

@@ -0,0 +1,3 @@
+#include "base_module.h"
+
+namespace crash {} // namespace crash

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/base_module.h

@@ -0,0 +1,6 @@
+#ifndef MOD3_H_IN
+#define MOD3_H_IN
+
+template <typename SIZE_T> struct ClassInMod3 { int Member = 0; };
+
+#endif // _H_IN

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/main.cpp

@@ -0,0 +1,15 @@
+#include "module1.h"
+#include "module2.h"
+
+#include <cstdio>
+
+int main() {
+  ClassInMod1 FromMod1;
+  ClassInMod2 FromMod2;
+
+  FromMod1.VecInMod1.Member = 137;
+  FromMod2.VecInMod2.Member = 42;
+
+  std::puts("Break here");
+  return 0;
+}

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/module.modulemap

@@ -0,0 +1,14 @@
+module Module1 {
+  header "module1.h"
+  export *
+}
+
+module Module2 {
+  header "module2.h"
+  export *
+}
+
+module BaseModule {
+  header "base_module.h"
+  export *
+}

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/module1.cpp

@@ -0,0 +1,3 @@
+#include "module1.h"
+
+namespace crash {} // namespace crash

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/module1.h

@@ -0,0 +1,10 @@
+#ifndef MOD1_H_IN
+#define MOD1_H_IN
+
+#include "base_module.h"
+
+struct ClassInMod1 {
+  ClassInMod3<int> VecInMod1;
+};
+
+#endif // _H_IN

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/module2.cpp

@@ -0,0 +1,3 @@
+#include "module2.h"
+
+namespace crash {} // namespace crash

lldb/test/API/lang/cpp/gmodules/template-with-same-arg/module2.h

@@ -0,0 +1,10 @@
+#ifndef MOD2_H_IN
+#define MOD2_H_IN
+
+#include "base_module.h"
+
+struct ClassInMod2 {
+  ClassInMod3<int> VecInMod2;
+};
+
+#endif