<rdar://problem/15776874>

ValueObjectPrinter could enter an infinite loop while trying to display an aptly formed ValueObject: a reference, with a child of some pointer type, such that the pointees chain ended up pointing back to some part of itself - a pointer to itself being the simplest such case

Fixed here by only setting a pointer depth when needed, and ensuring that we won't overflow and wrap the pointer depth when it's zero.

llvm-svn: 200247

lldb/test/functionalities/data-formatter/refpointer-recursion/TestDataFormatterRefPtrRecursion.py

@@ -0,0 +1,56 @@
+"""
+Test that ValueObjectPrinter does not cause an infinite loop when a reference to a struct that contains a pointer to itself is printed.
+"""
+
+import os, time
+import unittest2
+import lldb
+from lldbtest import *
+import lldbutil
+
+class DataFormatterRefPtrRecursionTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @unittest2.skipUnless(sys.platform.startswith("darwin"), "requires Darwin")
+    @dsym_test
+    def test_with_dsym_and_run_command(self):
+        """Test that ValueObjectPrinter does not cause an infinite loop when a reference to a struct that contains a pointer to itself is printed."""
+        self.buildDsym()
+        self.data_formatter_commands()
+
+    @dwarf_test
+    def test_with_dwarf_and_run_command(self):
+        """Test that ValueObjectPrinter does not cause an infinite loop when a reference to a struct that contains a pointer to itself is printed."""
+        self.buildDwarf()
+        self.data_formatter_commands()
+
+    def setUp(self):
+        # Call super's setUp().
+        TestBase.setUp(self)
+        # Find the line number to break at.
+        self.line = line_number('main.cpp', '// Set break point at this line.')
+
+    def data_formatter_commands(self):
+        """Test that ValueObjectPrinter does not cause an infinite loop when a reference to a struct that contains a pointer to itself is printed."""
+        self.runCmd("file a.out", CURRENT_EXECUTABLE_SET)
+
+        lldbutil.run_break_set_by_file_and_line (self, "main.cpp", self.line, num_expected_locations=1, loc_exact=True)
+
+        self.runCmd("run", RUN_SUCCEEDED)
+
+        # The stop reason of the thread should be breakpoint.
+        self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+            substrs = ['stopped',
+                       'stop reason = breakpoint'])
+
+        self.expect("frame variable foo", substrs = []);
+        self.expect("frame variable foo --ptr-depth=1", substrs = ['ID = 1']);
+        self.expect("frame variable foo --ptr-depth=2", substrs = ['ID = 1']);
+        self.expect("frame variable foo --ptr-depth=3", substrs = ['ID = 1']);
+
+if __name__ == '__main__':
+    import atexit
+    lldb.SBDebugger.Initialize()
+    atexit.register(lambda: lldb.SBDebugger.Terminate())
+    unittest2.main()