3692267ca8
Watchpoints in lldb can be either 'read', 'write', or 'read/write'. This is exposing the actual behavior of hardware watchpoints. gdb has a different behavior: a "write" type watchpoint only stops when the watched memory region *changes*. A user is using a watchpoint for one of three reasons: 1. Want to find what is changing/corrupting this memory. 2. Want to find what is writing to this memory. 3. Want to find what is reading from this memory. I believe (1) is the most common use case for watchpoints, and it currently can't be done in lldb -- the user needs to continue every time the same value is written to the watched-memory manually. I think gdb's behavior is the correct one. There are some use cases where a developer wants to find every function that writes/reads to/from a memory region, regardless of value, I want to still allow that functionality. This is also a bit of groundwork for my large watchpoint support proposal https://discourse.llvm.org/t/rfc-large-watchpoint-support-in-lldb/72116 where I will be adding support for AArch64 MASK watchpoints which watch power-of-2 memory regions. A user might ask to watch 24 bytes, and a MASK watchpoint stub can do this with a 32-byte MASK watchpoint if it is properly aligned. And we need to ignore writes to the final 8 bytes of that watched region, and not show those hits to the user. This patch adds a new 'modify' watchpoint type and it is the default. rdar://108234227
40 lines
1.3 KiB
Python
40 lines
1.3 KiB
Python
"""
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Confirm that lldb modify watchpoints only stop
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when the value being watched changes.
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"""
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import lldb
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from lldbsuite.test.decorators import *
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from lldbsuite.test.lldbtest import *
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from lldbsuite.test import lldbutil
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class ModifyWatchpointTestCase(TestBase):
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NO_DEBUG_INFO_TESTCASE = True
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def test_modify_watchpoint(self):
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"""Test that a modify watchpoint only stops when the value changes."""
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self.build()
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self.main_source_file = lldb.SBFileSpec("main.c")
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(target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
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self, "break here", self.main_source_file
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)
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self.runCmd("watch set variable value")
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process.Continue()
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frame = process.GetSelectedThread().GetFrameAtIndex(0)
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self.assertEqual(frame.locals["value"][0].GetValueAsUnsigned(), 10)
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process.Continue()
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frame = process.GetSelectedThread().GetFrameAtIndex(0)
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self.assertEqual(frame.locals["value"][0].GetValueAsUnsigned(), 5)
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process.Continue()
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frame = process.GetSelectedThread().GetFrameAtIndex(0)
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self.assertEqual(frame.locals["value"][0].GetValueAsUnsigned(), 7)
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process.Continue()
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frame = process.GetSelectedThread().GetFrameAtIndex(0)
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self.assertEqual(frame.locals["value"][0].GetValueAsUnsigned(), 9)
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