[lldb/Reproducers] Fix API boundary tracking bug

When recording the result from the LLDB_RECORD_RESULT macro, we need to
update the boundary so we capture the copy constructor. However, when
called to record the this pointer of the (copy) constructor itself, the
boundary should not be toggled, because it is called from the
LLDB_RECORD_CONSTRUCTOR macro, which might be followed by other API
calls.

This manifested itself as an object encountered during replay that we
hadn't seen before. The index-to-object mapping would return a nullptr
and lldb would crash.

lldb/include/lldb/Utility/ReproducerInstrumentation.h

@@ -98,7 +98,7 @@ template <typename... Ts> inline std::string stringify_args(const Ts &... ts) {
     sb_recorder.Record(data.GetSerializer(), data.GetRegistry(),               \
                        &lldb_private::repro::construct<Class Signature>::doit, \
                        __VA_ARGS__);                                           \
-    sb_recorder.RecordResult(this);                                            \
+    sb_recorder.RecordResult(this, false);                                     \
   }
 
 #define LLDB_RECORD_CONSTRUCTOR_NO_ARGS(Class)                                 \
@@ -107,7 +107,7 @@ template <typename... Ts> inline std::string stringify_args(const Ts &... ts) {
           LLDB_GET_INSTRUMENTATION_DATA()) {                                   \
     sb_recorder.Record(data.GetSerializer(), data.GetRegistry(),               \
                        &lldb_private::repro::construct<Class()>::doit);        \
-    sb_recorder.RecordResult(this);                                            \
+    sb_recorder.RecordResult(this, false);                                     \
   }
 
 #define LLDB_RECORD_METHOD(Result, Class, Method, Signature, ...)              \
@@ -175,7 +175,7 @@ template <typename... Ts> inline std::string stringify_args(const Ts &... ts) {
                        static_cast<Result (*)()>(&Class::Method));             \
   }
 
-#define LLDB_RECORD_RESULT(Result) sb_recorder.RecordResult(Result);
+#define LLDB_RECORD_RESULT(Result) sb_recorder.RecordResult(Result, true);
 
 /// The LLDB_RECORD_DUMMY macro is special because it doesn't actually record
 /// anything. It's used to track API boundaries when we cannot record for
@@ -716,8 +716,16 @@ class Recorder {
   }
 
   /// Record the result of a function call.
-  template <typename Result> Result RecordResult(Result &&r) {
-    UpdateBoundary();
+  template <typename Result>
+  Result RecordResult(Result &&r, bool update_boundary) {
+    // When recording the result from the LLDB_RECORD_RESULT macro, we need to
+    // update the boundary so we capture the copy constructor. However, when
+    // called to record the this pointer of the (copy) constructor, the
+    // boundary should not be toggled, because it is called from the
+    // LLDB_RECORD_CONSTRUCTOR macro, which might be followed by other API
+    // calls.
+    if (update_boundary)
+      UpdateBoundary();
     if (m_serializer && ShouldCapture()) {
       assert(!m_result_recorded);
       m_serializer->SerializeAll(r);