[lldb-dap] Allow returning multiple breakpoints in "stopped" event (#149133) Currently, the "stopped" event returned when a breakpoint is hit will always return only the ID of first breakpoint returned from `GetStopReasonDataAtIndex`. This is slightly different from the behaviour in `lldb`, where multiple breakpoints can exist at a single instruction address and all are returned as part of the stop reason when that address is hit. This patch allows all multiple hit breakpoints to be returned in the "stopped" event, both in the hitBreakpointIds field and in the description, using the same formatting as lldb e.g. "breakpoint 1.1 2.1". I'm not aware of any effect this will have on debugger plugins; as far as I can tell, it makes no difference within the VS Code UI - this just fixes a minor issue encountered while writing an `lldb-dap` backend for Dexter.

diff --git a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py
index d823126..1567462 100644
--- a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py
+++ b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py

@@ -173,6 +173,28 @@
                         return
         self.assertTrue(False, f"breakpoint not hit, stopped_events={stopped_events}")
 
+    def verify_all_breakpoints_hit(self, breakpoint_ids, timeout=DEFAULT_TIMEOUT):
+        """Wait for the process we are debugging to stop, and verify we hit
+        all of the breakpoint locations in the "breakpoint_ids" array.
+        "breakpoint_ids" should be a list of int breakpoint IDs ([1, 2])."""
+        stopped_events = self.dap_server.wait_for_stopped(timeout)
+        for stopped_event in stopped_events:
+            if "body" in stopped_event:
+                body = stopped_event["body"]
+                if "reason" not in body:
+                    continue
+                if (
+                    body["reason"] != "breakpoint"
+                    and body["reason"] != "instruction breakpoint"
+                ):
+                    continue
+                if "hitBreakpointIds" not in body:
+                    continue
+                hit_bps = body["hitBreakpointIds"]
+                if all(breakpoint_id in hit_bps for breakpoint_id in breakpoint_ids):
+                    return
+        self.assertTrue(False, f"breakpoints not hit, stopped_events={stopped_events}")
+
     def verify_stop_exception_info(self, expected_description, timeout=DEFAULT_TIMEOUT):
         """Wait for the process we are debugging to stop, and verify the stop
         reason is 'exception' and that the description matches

diff --git a/lldb/test/API/tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.py b/lldb/test/API/tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.py
index 831edd6..2e860ff 100644
--- a/lldb/test/API/tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.py
+++ b/lldb/test/API/tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.py

@@ -398,3 +398,26 @@
         self.stepIn()
         func_name = self.get_stackFrames()[0]["name"]
         self.assertEqual(func_name, "a::fourteen(int)")
+
+    @skipIfWindows
+    def test_hit_multiple_breakpoints(self):
+        """Test that if we hit multiple breakpoints at the same address, they
+        all appear in the stop reason."""
+        breakpoint_lines = [
+            line_number("main.cpp", "// break non-breakpointable line"),
+            line_number("main.cpp", "// before loop"),
+        ]
+
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program)
+
+        # Set a pair of breakpoints that will both resolve to the same address.
+        breakpoint_ids = [
+            int(bp_id)
+            for bp_id in self.set_source_breakpoints(self.main_path, breakpoint_lines)
+        ]
+        self.assertEqual(len(breakpoint_ids), 2, "expected two breakpoints")
+        self.dap_server.request_continue()
+        print(breakpoint_ids)
+        # Verify we hit both of the breakpoints we just set
+        self.verify_all_breakpoints_hit(breakpoint_ids)

diff --git a/lldb/test/API/tools/lldb-dap/breakpoint/main.cpp b/lldb/test/API/tools/lldb-dap/breakpoint/main.cpp
index a84546a..2206b07 100644
--- a/lldb/test/API/tools/lldb-dap/breakpoint/main.cpp
+++ b/lldb/test/API/tools/lldb-dap/breakpoint/main.cpp

@@ -33,7 +33,7 @@
   if (foo == nullptr) {
     fprintf(stderr, "%s\n", dlerror());
     exit(2);
-  }
+  } // break non-breakpointable line
   foo(12); // before loop
 
   for (int i = 0; i < 10; ++i) {

diff --git a/lldb/tools/lldb-dap/JSONUtils.cpp b/lldb/tools/lldb-dap/JSONUtils.cpp
index 41ca29a..f42c502 100644
--- a/lldb/tools/lldb-dap/JSONUtils.cpp
+++ b/lldb/tools/lldb-dap/JSONUtils.cpp

@@ -654,12 +654,17 @@
       } else {
         body.try_emplace("reason", "breakpoint");
       }
-      lldb::break_id_t bp_id = thread.GetStopReasonDataAtIndex(0);
-      lldb::break_id_t bp_loc_id = thread.GetStopReasonDataAtIndex(1);
-      std::string desc_str =
-          llvm::formatv("breakpoint {0}.{1}", bp_id, bp_loc_id);
-      body.try_emplace("hitBreakpointIds",
-                       llvm::json::Array{llvm::json::Value(bp_id)});
+      std::vector<lldb::break_id_t> bp_ids;
+      std::ostringstream desc_sstream;
+      desc_sstream << "breakpoint";
+      for (size_t idx = 0; idx < thread.GetStopReasonDataCount(); idx += 2) {
+        lldb::break_id_t bp_id = thread.GetStopReasonDataAtIndex(idx);
+        lldb::break_id_t bp_loc_id = thread.GetStopReasonDataAtIndex(idx + 1);
+        bp_ids.push_back(bp_id);
+        desc_sstream << " " << bp_id << "." << bp_loc_id;
+      }
+      std::string desc_str = desc_sstream.str();
+      body.try_emplace("hitBreakpointIds", llvm::json::Array(bp_ids));
       EmplaceSafeString(body, "description", desc_str);
     }
   } break;