[lldb-dap] Allow returning multiple breakpoints in "stopped" event #149133

SLTozer · 2025-07-16T16:28:07Z

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.

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".

llvmbot · 2025-07-16T16:28:40Z

@llvm/pr-subscribers-lldb

Author: Stephen Tozer (SLTozer)

Changes

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.

Full diff: https://github.com/llvm/llvm-project/pull/149133.diff

4 Files Affected:

(modified) lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py (+23)
(modified) lldb/test/API/tools/lldb-dap/breakpoint/TestDAP_setBreakpoints.py (+20)
(modified) lldb/test/API/tools/lldb-dap/breakpoint/main.cpp (+1-1)
(modified) lldb/tools/lldb-dap/JSONUtils.cpp (+11-6)

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 d823126e3e2fd..9b227c67bb859 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 +173,29 @@ def verify_breakpoint_hit(self, breakpoint_ids, timeout=DEFAULT_TIMEOUT):
                         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 breakpoint ID strings
+        (["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(int(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 831edd6494c1e..121933c672bf7 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 +398,23 @@ def test_column_breakpoints(self):
         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", "// end of foo check"),
+            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 = 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 a84546a95af15..a9a16f240e37d 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 @@ int main(int argc, char const *argv[]) {
   if (foo == nullptr) {
     fprintf(stderr, "%s\n", dlerror());
     exit(2);
-  }
+  } // end of foo check
   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 41ca29a405ac9..30e6ea900d919 100644
--- a/lldb/tools/lldb-dap/JSONUtils.cpp
+++ b/lldb/tools/lldb-dap/JSONUtils.cpp
@@ -654,12 +654,17 @@ llvm::json::Value CreateThreadStopped(DAP &dap, lldb::SBThread &thread,
       } 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<llvm::json::Value> 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(llvm::json::Value(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;

github-actions · 2025-07-16T16:30:41Z

✅ With the latest revision this PR passed the Python code formatter.

JDevlieghere · 2025-07-16T16:42:41Z

lldb/test/API/tools/lldb-dap/breakpoint/main.cpp

@@ -33,7 +33,7 @@ int main(int argc, char const *argv[]) {
  if (foo == nullptr) {
    fprintf(stderr, "%s\n", dlerror());
    exit(2);
-  }
+  } // end of foo check


Suggested change

} // end of foo check

}

This comment is being used to set the breakpoint from here in the test - thinking about it, the only real requirement for where the second breakpoint appears is that it be on a line that is not breakpoint-able that precedes a breakpoint-able line, so I could also move the comment to an empty line before any other line.

Ah, I missed that you were using that to set the breakpoint. In that case, maybe say something like "Break here for non-breakpointable line" or something.

I can make this change, but other comments used for setting breakpoints in the same file follow this "minimal" convention, e.g.

return 12 + i; // break 12 return 14 + i; // break 14 foo(12); // before loop int x = twelve(i) + thirteen(i) + a::fourteen(i); // break loop

I'll add break as a prefix to match most of the other cases, though I'm also happy to just rewrite the string following your suggestion if you think that would be better.
Edit: Actually, "non-breakpointable" does explain better the purpose for the test, so I've used that!

JDevlieghere · 2025-07-16T16:42:52Z

lldb/packages/Python/lldbsuite/test/tools/lldb-dap/lldbdap_testcase.py

+        "breakpoint_ids" should be a list of breakpoint ID strings
+        (["1", "2"])."""


Why not numbers, to match the protocol?

I chose to have it accept the output from a setBreakpoints response as with verify_breakpoint_hit, but converting to ints in the test and passing those also makes sense.

lldb/tools/lldb-dap/JSONUtils.cpp

github-actions · 2025-07-17T20:19:54Z

✅ With the latest revision this PR passed the C/C++ code formatter.

JDevlieghere

LGTM!

…lvm#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.

SLTozer requested a review from ashgti July 16, 2025 16:28

SLTozer self-assigned this Jul 16, 2025

SLTozer requested a review from JDevlieghere as a code owner July 16, 2025 16:28

llvmbot added lldb lldb-dap labels Jul 16, 2025

JDevlieghere reviewed Jul 16, 2025

View reviewed changes

SLTozer added 2 commits July 16, 2025 17:54

Some review comments

71a817e

Address further review comments

c789b42

crush clang-format

83ad725

JDevlieghere approved these changes Jul 18, 2025

View reviewed changes

SLTozer merged commit d544005 into llvm:main Jul 22, 2025
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		"breakpoint_ids" should be a list of breakpoint ID strings
		(["1", "2"])."""

[lldb-dap] Allow returning multiple breakpoints in "stopped" event #149133

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