[asan] Display ASan history threads in reverse chronological order

[kubamracek]

Summary

For use-after-free bugs caught by ASan, we show an allocation and a deallocation stack trace. Let's display them in a "most recent event first" order, this patch does that.

[granata.enrico]

I am ok with this is Jason is

[jasonmolenda]

Makes sense to me, please apply.

lldb/trunk/source/Plugins/MemoryHistory/asan/MemoryHistoryASan.cpp

MemoryHistoryASan::GetHistoryThreads(lldb::addr_t address)
     }
     if (!return_value_sp)
     {
         return HistoryThreads();
     }
     
     HistoryThreads result;
 
-    CreateHistoryThreadFromValueObject(process_sp, return_value_sp, "alloc", "Memory allocated at", result);
     CreateHistoryThreadFromValueObject(process_sp, return_value_sp, "free", "Memory deallocated at", result);
+    CreateHistoryThreadFromValueObject(process_sp, return_value_sp, "alloc", "Memory allocated at", result);
     
     return result;
 }

lldb/trunk/test/functionalities/asan/TestMemoryHistory.py

def asan_tests (self):
         val = process.GetSelectedThread().GetSelectedFrame().EvaluateExpression("pointer")
         addr = val.GetValueAsUnsigned()
         threads = process.GetHistoryThreads(addr);
         self.assertEqual(threads.GetSize(), 2)
         
         history_thread = threads.GetThreadAtIndex(0)
         self.assertTrue(history_thread.num_frames >= 2)
         self.assertEqual(history_thread.frames[1].GetLineEntry().GetFileSpec().GetFilename(), "main.c")
-        self.assertEqual(history_thread.frames[1].GetLineEntry().GetLine(), self.line_malloc)
+        self.assertEqual(history_thread.frames[1].GetLineEntry().GetLine(), self.line_free)
         
         history_thread = threads.GetThreadAtIndex(1)
         self.assertTrue(history_thread.num_frames >= 2)
         self.assertEqual(history_thread.frames[1].GetLineEntry().GetFileSpec().GetFilename(), "main.c")
-        self.assertEqual(history_thread.frames[1].GetLineEntry().GetLine(), self.line_free)
+        self.assertEqual(history_thread.frames[1].GetLineEntry().GetLine(), self.line_malloc)
 
         # let's free the container (SBThreadCollection) and see if the SBThreads still live
         threads = None
         self.assertTrue(history_thread.num_frames >= 2)
         self.assertEqual(history_thread.frames[1].GetLineEntry().GetFileSpec().GetFilename(), "main.c")
-        self.assertEqual(history_thread.frames[1].GetLineEntry().GetLine(), self.line_free)
+        self.assertEqual(history_thread.frames[1].GetLineEntry().GetLine(), self.line_malloc)
 
         # now let's break when an ASan report occurs and try the API then
         self.runCmd("breakpoint set -n __asan_report_error")
 
         self.runCmd("continue")
 
         # the stop reason of the thread should be breakpoint.
         self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,