Skip adding value lines for accidental matches.

If the value_line regex matches, and the symbol file happens to exist
as a directory, we'd call addr2line and crash. Fix this so that calling
addr2line on a directory doesn't happen.

There isn't an easy way to test this, but I added a single new unit test. The
real test was to use a tombstone file that used to crash, but no longer crashes.

Test: Wrote new unit test, ran over a tombstone file that used to crash.
Change-Id: I4331e3b032cee8d697d1b7f409638750c61971d6

scripts/stack_core.py

@@ -409,6 +409,8 @@ class TraceConverter:
       else:
         info = symbol.SymbolInformation(area, value)
         (source_symbol, source_location, object_symbol_with_offset) = info.pop()
+        # If there is no information, skip this.
+        if source_symbol or source_location or object_symbol_with_offset:
           if not source_symbol:
             if symbol_present:
               source_symbol = symbol.CallCppFilt(symbol_name)
@@ -499,5 +501,13 @@ class LongASANStackTests(unittest.TestCase):
     self.assertGreater(trace_line_count, 10)
     tc.PrintOutput(tc.trace_lines, tc.value_lines)
 
+class ValueLinesTest(unittest.TestCase):
+  def test_value_line_skipped(self):
+    tc = TraceConverter()
+    symbol.SetAbi(["ABI: 'arm'"])
+    tc.UpdateAbiRegexes()
+    tc.ProcessLine("    12345678  00001000  .")
+    self.assertEqual([], tc.value_lines)
+
 if __name__ == '__main__':
     unittest.main()

scripts/symbol.py

@@ -189,6 +189,10 @@ def CallAddr2LineForSet(lib, unique_addrs):
     if not os.path.exists(symbols):
       return None
 
+  # Make sure the symbols path is not a directory.
+  if os.path.isdir(symbols):
+    return None
+
   cmd = [ToolPath("addr2line"), "--functions", "--inlines",
       "--demangle", "--exe=" + symbols]
   child = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE)