Reject invalid values from ASan historical stack traces

[kubamracek]

Summary

The ASan fast unwinder sometimes likes to add frames like 0x0 or 0xffffffff at the very ending of the stack trace. Let's ignore these frames.

source/Plugins/MemoryHistory/asan/MemoryHistoryASan.cpp

MemoryHistoryASan::GetHistoryThreads(lldb::addr_t address)
     tid_t free_tid = return_value_sp->GetValueForExpressionPath(".free_tid")->GetValueAsUnsigned(0);
     
     if (alloc_count > 0)
     {
         std::vector<lldb::addr_t> pcs;
         ValueObjectSP trace_sp = return_value_sp->GetValueForExpressionPath(".alloc_trace");
         for (int i = 0; i < alloc_count; i++) {
             addr_t pc = trace_sp->GetChildAtIndex(i, true)->GetValueAsUnsigned(0);
+            if (pc == 0 || pc == 1 || pc == LLDB_INVALID_ADDRESS) continue;
             pcs.push_back(pc);
         }
         
         HistoryThread *history_thread = new HistoryThread(*process_sp, alloc_tid, pcs, 0, false);
         ThreadSP new_thread_sp(history_thread);
         // let's use thread name for the type of history thread, since history threads don't have names anyway
         history_thread->SetThreadName("Memory allocated at");
         result.push_back(new_thread_sp);
     }
     
     if (free_count > 0)
     {
         std::vector<lldb::addr_t> pcs;
         ValueObjectSP trace_sp = return_value_sp->GetValueForExpressionPath(".free_trace");
         for (int i = 0; i < free_count; i++) {
             addr_t pc = trace_sp->GetChildAtIndex(i, true)->GetValueAsUnsigned(0);
+            if (pc == 0 || pc == 1 || pc == LLDB_INVALID_ADDRESS) continue;
             pcs.push_back(pc);
         }
         
         HistoryThread *history_thread = new HistoryThread(*process_sp, free_tid, pcs, 0, false);
         ThreadSP new_thread_sp(history_thread);
         // let's use thread name for the type of history thread, since history threads don't have names anyway
         history_thread->SetThreadName("Memory deallocated at");
         result.push_back(new_thread_sp);
     }
     
     return result;
 }