Fix lldb-vscode frame id integer overflow

[yinghuitan]

Summary

This patch fixes a 32bit integer overflow in lldb-vscode.
The current implementation of frame_id does (thread_index << 19 | frame_index). Since thread_index is a 32 bit integer this leaves only 32 - 19 == 13 bits available for the thread_index. As a result, lldb-vscode can only handle 2^13 == 8192 threads. Normally, this would be sufficient, but we have seen crazy process having +12000 threads, causing the frame_id algorithm above to integer overflow during casting.

The patch fixes the overflow by up casting to 64 bit integer first before bit shifiting.

[clayborg]

We ran into this with a process that had many threads. No easy way to test this without creating a process with 8K threads.

lldb/tools/lldb-vscode/LLDBUtils.cpp

uint32_t GetLLDBThreadIndexID(uint64_t dap_frame_id) {
   return dap_frame_id >> THREAD_INDEX_SHIFT;
 }
 
 uint32_t GetLLDBFrameID(uint64_t dap_frame_id) {
   return dap_frame_id & ((1u << THREAD_INDEX_SHIFT) - 1);
 }
 
 int64_t MakeVSCodeFrameID(lldb::SBFrame &frame) {
-  return (int64_t)(frame.GetThread().GetIndexID() << THREAD_INDEX_SHIFT |
-                   frame.GetFrameID());
+  return ((int64_t)frame.GetThread().GetIndexID() << THREAD_INDEX_SHIFT) |
+         frame.GetFrameID();
 }
 
 } // namespace lldb_vscode