lldb/test/API/functionalities/unwind/zeroth_frame/TestZerothFrame.py

   1 """
   2 Test that line information is recalculated properly for a frame when it moves
   3 from the middle of the backtrace to a zero index.
   4
   5 This is a regression test for a StackFrame bug, where whether frame is zero or
   6 not depends on an internal field. When LLDB was updating its frame list value
   7 of the field wasn't copied into existing StackFrame instances, so those
   8 StackFrame instances, would use an incorrect line entry evaluation logic in
   9 situations if it was in the middle of the stack frame list (not zeroth), and
  10 then moved to the top position. The difference in logic is that for zeroth
  11 frames line entry is returned for program counter, while for other frame
  12 (except for those that "behave like zeroth") it is for the instruction
  13 preceding PC, as PC points to the next instruction after function call. When
  14 the bug is present, when execution stops at the second breakpoint
  15 SBFrame.GetLineEntry() returns line entry for the previous line, rather than
  16 the one with a breakpoint. Note that this is specific to
  17 SBFrame.GetLineEntry(), SBFrame.GetPCAddress().GetLineEntry() would return
  18 correct entry.
  19
  20 This bug doesn't reproduce through an LLDB interpretator, however it happens
  21 when using API directly, for example in LLDB-MI.
  22 """
  23
  24 import lldb
  25 from lldbsuite.test.decorators import *
  26 from lldbsuite.test.lldbtest import *
  27 from lldbsuite.test import lldbutil
  28
  29
  30 class ZerothFrame(TestBase):
  31     def test(self):
  32         """
  33         Test that line information is recalculated properly for a frame when it moves
  34         from the middle of the backtrace to a zero index.
  35         """
  36         self.build()
  37         self.setTearDownCleanup()
  38
  39         exe = self.getBuildArtifact("a.out")
  40         target = self.dbg.CreateTarget(exe)
  41         self.assertTrue(target, VALID_TARGET)
  42
  43         bp1_line = line_number("main.c", "// Set breakpoint 1 here")
  44         bp2_line = line_number("main.c", "// Set breakpoint 2 here")
  45
  46         lldbutil.run_break_set_by_file_and_line(
  47             self, "main.c", bp1_line, num_expected_locations=1
  48         )
  49         lldbutil.run_break_set_by_file_and_line(
  50             self, "main.c", bp2_line, num_expected_locations=1
  51         )
  52
  53         process = target.LaunchSimple(None, None, self.get_process_working_directory())
  54         self.assertTrue(process, VALID_PROCESS)
  55
  56         thread = process.GetThreadAtIndex(0)
  57         if self.TraceOn():
  58             print("Backtrace at the first breakpoint:")
  59             for f in thread.frames:
  60                 print(f)
  61         # Check that we have stopped at correct breakpoint.
  62         self.assertEqual(
  63             process.GetThreadAtIndex(0).frame[0].GetLineEntry().GetLine(),
  64             bp1_line,
  65             "LLDB reported incorrect line number.",
  66         )
  67
  68         # Important to use SBProcess::Continue() instead of
  69         # self.runCmd('continue'), because the problem doesn't reproduce with
  70         # 'continue' command.
  71         process.Continue()
  72
  73         thread = process.GetThreadAtIndex(0)
  74         if self.TraceOn():
  75             print("Backtrace at the second breakpoint:")
  76             for f in thread.frames:
  77                 print(f)
  78         # Check that we have stopped at the breakpoint
  79         self.assertEqual(
  80             thread.frame[0].GetLineEntry().GetLine(),
  81             bp2_line,
  82             "LLDB reported incorrect line number.",
  83         )
  84         # Double-check with GetPCAddress()
  85         self.assertEqual(
  86             thread.frame[0].GetLineEntry().GetLine(),
  87             thread.frame[0].GetPCAddress().GetLineEntry().GetLine(),
  88             "LLDB reported incorrect line number.",
  89         )