[PATCH 4/4] trace2: emit cmd_ancestry data for Windows

From: Matthew John Cheetham via GitGitGadget <gitgitgadget@gmail.com>
Date: Feb 5, 2026, 16:05 UTC
Message-ID: <a06344dc753698ece37f8d066b0a51931b7fa16f.1770307510.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.2040.git.1770307510.gitgitgadget@gmail.com>

From: Matthew John Cheetham <mjcheetham@outlook.com>

Since 2f732bf1 (tr2: log parent process name) it is now possible to emit a specific process ancestry event in TRACE2. We should emit the Windows process ancestry data with the correct event type.

To not break existing consumers of the data_json "windows/ancestry" event, we continue to emit the ancestry data as a JSON event.

Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com>
---
 compat/win32/trace2_win32_process_info.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/compat/win32/trace2_win32_process_info.c b/compat/win32/trace2_win32_process_info.c
index aceea05430..6a6a396078 100644
--- a/compat/win32/trace2_win32_process_info.c
+++ b/compat/win32/trace2_win32_process_info.c
@@ -172,6 +172,11 @@ void trace2_collect_process_info(enum trace2_process_info_reason reason)
 		get_is_being_debugged();
 		get_ancestry(&names);
 		if (names.nr) {
+			/*
+			  Emit the ancestry data as a data_json event to
+			  maintain compatibility for consumers of the older
+			  "windows/ancestry" event.
+			 */
 			struct json_writer jw = JSON_WRITER_INIT;
 			jw_array_begin(&jw, 0);
 			for (size_t i = 0; i < names.nr; i++)
@@ -180,6 +185,9 @@ void trace2_collect_process_info(enum trace2_process_info_reason reason)
 			trace2_data_json("process", the_repository,
 					 "windows/ancestry", &jw);
 			jw_release(&jw);
+
+			/* Emit the ancestry data with the new event. */
+			trace2_cmd_ancestry(names.v);
 		}
 
 		strvec_clear(&names);

-- 
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