[lldb][debugserver] Fix an off-by-one error in watchpoint identification (#134314)

lldb/test/API/functionalities/watchpoint/consecutive-watchpoints/Makefile

@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules

lldb/test/API/functionalities/watchpoint/consecutive-watchpoints/TestConsecutiveWatchpoints.py

@@ -0,0 +1,96 @@
+"""
+Watch contiguous memory regions with separate watchpoints, check that lldb
+correctly detect which watchpoint was hit for each one.
+"""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class ConsecutiveWatchpointsTestCase(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def continue_and_report_stop_reason(self, process, iter_str):
+        process.Continue()
+        self.assertIn(
+            process.GetState(), [lldb.eStateStopped, lldb.eStateExited], iter_str
+        )
+        thread = process.GetSelectedThread()
+        return thread.GetStopReason()
+
+    # debugserver only gained the ability to watch larger regions
+    # with this patch.
+    def test_consecutive_watchpoints(self):
+        """Test watchpoint that covers a large region of memory."""
+        self.build()
+        self.main_source_file = lldb.SBFileSpec("main.c")
+        (target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
+            self, "break here", self.main_source_file
+        )
+
+        frame = thread.GetFrameAtIndex(0)
+
+        field2_wp = (
+            frame.locals["var"][0]
+            .GetChildMemberWithName("field2")
+            .Watch(True, False, True)
+        )
+        field3_wp = (
+            frame.locals["var"][0]
+            .GetChildMemberWithName("field3")
+            .Watch(True, False, True)
+        )
+        field4_wp = (
+            frame.locals["var"][0]
+            .GetChildMemberWithName("field4")
+            .Watch(True, False, True)
+        )
+        field5_wp = (
+            frame.locals["var"][0]
+            .GetChildMemberWithName("field5")
+            .Watch(True, False, True)
+        )
+
+        # Require that the first two watchpoints
+        # are set -- hopefully every machine running
+        # the testsuite can support two watchpoints.
+        self.assertTrue(field2_wp.IsValid())
+        self.assertTrue(field3_wp.IsValid())
+
+        reason = self.continue_and_report_stop_reason(process, "continue to field2 wp")
+        self.assertEqual(reason, lldb.eStopReasonWatchpoint)
+        stop_reason_watchpoint_id = (
+            process.GetSelectedThread().GetStopReasonDataAtIndex(0)
+        )
+        self.assertEqual(stop_reason_watchpoint_id, field2_wp.GetID())
+
+        reason = self.continue_and_report_stop_reason(process, "continue to field3 wp")
+        self.assertEqual(reason, lldb.eStopReasonWatchpoint)
+        stop_reason_watchpoint_id = (
+            process.GetSelectedThread().GetStopReasonDataAtIndex(0)
+        )
+        self.assertEqual(stop_reason_watchpoint_id, field3_wp.GetID())
+
+        # If we were able to set the second two watchpoints,
+        # check that they are hit.  Some CI bots can only
+        # create two watchpoints.
+        if field4_wp.IsValid() and field5_wp.IsValid():
+            reason = self.continue_and_report_stop_reason(
+                process, "continue to field4 wp"
+            )
+            self.assertEqual(reason, lldb.eStopReasonWatchpoint)
+            stop_reason_watchpoint_id = (
+                process.GetSelectedThread().GetStopReasonDataAtIndex(0)
+            )
+            self.assertEqual(stop_reason_watchpoint_id, field4_wp.GetID())
+
+            reason = self.continue_and_report_stop_reason(
+                process, "continue to field5 wp"
+            )
+            self.assertEqual(reason, lldb.eStopReasonWatchpoint)
+            stop_reason_watchpoint_id = (
+                process.GetSelectedThread().GetStopReasonDataAtIndex(0)
+            )
+            self.assertEqual(stop_reason_watchpoint_id, field5_wp.GetID())

lldb/test/API/functionalities/watchpoint/consecutive-watchpoints/main.c

@@ -0,0 +1,22 @@
+#include <stdint.h>
+struct fields {
+  uint32_t field1;
+  uint32_t field2; // offset +4
+  uint16_t field3; // offset +8
+  uint16_t field4; // offset +10
+  uint16_t field5; // offset +12
+  uint16_t field6; // offset +14
+};
+
+int main() {
+  struct fields var = {0, 0, 0, 0, 0, 0};
+
+  var.field1 = 5; // break here
+  var.field2 = 6;
+  var.field3 = 7;
+  var.field4 = 8;
+  var.field5 = 9;
+  var.field6 = 10;
+
+  return var.field1 + var.field2 + var.field3;
+}

lldb/tools/debugserver/source/DNBBreakpoint.cpp

@@ -98,7 +98,7 @@ DNBBreakpointList::FindNearestWatchpoint(nub_addr_t addr) const {
     if (pos.second.IsEnabled()) {
       nub_addr_t start_addr = pos.second.Address();
       nub_addr_t end_addr = start_addr + pos.second.ByteSize();
-      if (addr >= start_addr && addr <= end_addr)
+      if (addr >= start_addr && addr < end_addr)
         return &pos.second;
     }
   }