trace2: refactor Windows process ancestry trace2 event

In 353d3d77f4 (trace2: collect Windows-specific process information,
2019-02-22) we added process ancestry information for Windows to TRACE2
via a data_json event. It was only later in 2f732bf15e (tr2: log parent
process name, 2021-07-21) that the specific cmd_ancestry event was
added to TRACE2.

In a future commit we will emit the ancestry information with the newer
cmd_ancestry TRACE2 event. Right now, we rework this implementation of
trace2_collect_process_info to separate the calculation of ancestors
from building and emiting the JSON array via a data_json event.

Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/compat/win32/trace2_win32_process_info.c b/compat/win32/trace2_win32_process_info.c
index f147da706a240e0a39f53f717e27b0fe594fb555..aceea05430150166798912aa44b2b09fcf67a469 100644 (file)
--- a/compat/win32/trace2_win32_process_info.c
+++ b/compat/win32/trace2_win32_process_info.c
@@ -3,6 +3,7 @@
 #include "../../git-compat-util.h"
 #include "../../json-writer.h"
 #include "../../repository.h"
+#include "../../strvec.h"
 #include "../../trace2.h"
 #include "lazyload.h"
 #include <psapi.h>
@@ -32,12 +33,7 @@ static int find_pid(DWORD pid, HANDLE hSnapshot, PROCESSENTRY32 *pe32)
 }
 
 /*
- * Accumulate JSON array of our parent processes:
- *     [
- *         exe-name-parent,
- *         exe-name-grand-parent,
- *         ...
- *     ]
+ * Accumulate array of our parent process names.
  *
  * Note: we only report the filename of the process executable; the
  *       only way to get its full pathname is to use OpenProcess()
@@ -73,7 +69,7 @@ static int find_pid(DWORD pid, HANDLE hSnapshot, PROCESSENTRY32 *pe32)
  * simple and avoid the alloc/realloc overhead.  It is OK if we
  * truncate the search and return a partial answer.
  */
-static void get_processes(struct json_writer *jw, HANDLE hSnapshot)
+static void get_processes(struct strvec *names, HANDLE hSnapshot)
 {
        PROCESSENTRY32 pe32;
        DWORD pid;
@@ -82,19 +78,19 @@ static void get_processes(struct json_writer *jw, HANDLE hSnapshot)
 
        pid = GetCurrentProcessId();
        while (find_pid(pid, hSnapshot, &pe32)) {
-               /* Only report parents. Omit self from the JSON output. */
+               /* Only report parents. Omit self from the output. */
                if (nr_pids)
-                       jw_array_string(jw, pe32.szExeFile);
+                       strvec_push(names, pe32.szExeFile);
 
                /* Check for cycle in snapshot. (Yes, it happened.) */
                for (k = 0; k < nr_pids; k++)
                        if (pid == pid_list[k]) {
-                               jw_array_string(jw, "(cycle)");
+                               strvec_push(names, "(cycle)");
                                return;
                        }
 
                if (nr_pids == NR_PIDS_LIMIT) {
-                       jw_array_string(jw, "(truncated)");
+                       strvec_push(names, "(truncated)");
                        return;
                }
 
@@ -105,24 +101,14 @@ static void get_processes(struct json_writer *jw, HANDLE hSnapshot)
 }
 
 /*
- * Emit JSON data for the current and parent processes.  Individual
- * trace2 targets can decide how to actually print it.
+ * Collect the list of parent process names.
  */
-static void get_ancestry(void)
+static void get_ancestry(struct strvec *names)
 {
        HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
 
        if (hSnapshot != INVALID_HANDLE_VALUE) {
-               struct json_writer jw = JSON_WRITER_INIT;
-
-               jw_array_begin(&jw, 0);
-               get_processes(&jw, hSnapshot);
-               jw_end(&jw);
-
-               trace2_data_json("process", the_repository, "windows/ancestry",
-                                &jw);
-
-               jw_release(&jw);
+               get_processes(names, hSnapshot);
                CloseHandle(hSnapshot);
        }
 }
@@ -176,13 +162,27 @@ static void get_peak_memory_info(void)
 
 void trace2_collect_process_info(enum trace2_process_info_reason reason)
 {
+       struct strvec names = STRVEC_INIT;
+
        if (!trace2_is_enabled())
                return;
 
        switch (reason) {
        case TRACE2_PROCESS_INFO_STARTUP:
                get_is_being_debugged();
-               get_ancestry();
+               get_ancestry(&names);
+               if (names.nr) {
+                       struct json_writer jw = JSON_WRITER_INIT;
+                       jw_array_begin(&jw, 0);
+                       for (size_t i = 0; i < names.nr; i++)
+                               jw_array_string(&jw, names.v[i]);
+                       jw_end(&jw);
+                       trace2_data_json("process", the_repository,
+                                        "windows/ancestry", &jw);
+                       jw_release(&jw);
+               }
+
+               strvec_clear(&names);
                return;
 
        case TRACE2_PROCESS_INFO_EXIT: