[lldb/Plugins] Fix ScriptedThread IndexID reporting

When listing all the Scripted Threads of a ScriptedProcess, we can see that all
have the thread index set to 1. This is caused by the lldb_private::Thread
constructor, which sets the m_index_id member using the provided thread id `tid`.

Because the call to the super constructor is done before instantiating
the `ScriptedThreadInterface`, lldb can't fetch the thread id from the
script instance, so it uses `LLDB_INVALID_THREAD_ID` instead.

To mitigate this, this patch takes advantage of the `ScriptedThread::Create`
fallible constructor idiom to defer calling the `ScriptedThread` constructor
(and the `Thread` super constructor with it), until we can fetch a valid
thread id `tid` from the `ScriptedThreadInterface`.

rdar://87432065

Differential Revision: https://reviews.llvm.org/D117076

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp b/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
index e28658e33cda..e71a0fdf8de9 100644
--- a/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
+++ b/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
@@ -328,12 +328,14 @@ bool ScriptedProcess::DoUpdateThreadList(ThreadList &old_thread_list,
       return true;
     }
 
-    lldb::ThreadSP thread_sp =
-        std::make_shared<ScriptedThread>(*this, error, val->GetAsGeneric());
+    auto thread_or_error = ScriptedThread::Create(*this, val->GetAsGeneric());
 
-    if (!thread_sp || error.Fail())
-      return GetInterface().ErrorWithMessage<bool>(LLVM_PRETTY_FUNCTION,
-                                                   error.AsCString(), error);
+    if (!thread_or_error)
+      return GetInterface().ErrorWithMessage<bool>(
+          LLVM_PRETTY_FUNCTION, toString(thread_or_error.takeError()), error);
+
+    ThreadSP thread_sp = thread_or_error.get();
+    lldbassert(thread_sp && "Couldn't initialize scripted thread.");
 
     RegisterContextSP reg_ctx_sp = thread_sp->GetRegisterContext();
     if (!reg_ctx_sp)