win32: ensure PIDs are read early in procps_scan()

Recent changes to allow orphaned processes to report a parent PID
of 1 rely on the assumption that Process32First/Process32Next
return parents before children.  This isn't guaranteed by the API.

Obtain all known PIDs on the first call to procps_scan() so that
dead parents can be detected reliably.

Costs 48 bytes.

2 files changed, 16 insertions, 12 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 8d5537114..d37d4e64c 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -2148,9 +2148,8 @@ typedef struct procps_status_t {
         DIR *dir;
 #else
         HANDLE snapshot;
-        unsigned *pids;
+        DWORD *pids;
         int npids;
-        int maxpids;
 #endif
         IF_FEATURE_SHOW_THREADS(DIR *task_dir;)
         uint8_t shift_pages_to_bytes;
diff --git a/win32/process.c b/win32/process.c
index 9dd4bc1db..bbb04678f 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -605,6 +605,16 @@ UNUSED_PARAM
                         free(sp);
                         return NULL;
                 }
+                if (Process32First(sp->snapshot, &pe)) {
+                        int maxpids = 0;
+                        do {
+                                if (sp->npids == maxpids) {
+                                        maxpids += NPIDS;
+                                        sp->pids = xrealloc(sp->pids, sizeof(DWORD) * maxpids);
+                                }
+                                sp->pids[sp->npids++] = pe.th32ProcessID;
+                        } while (Process32Next(sp->snapshot, &pe));
+                }
                 ret = Process32First(sp->snapshot, &pe);
         }
         else {
@@ -665,12 +675,7 @@ UNUSED_PARAM
                         break;
                 }
         }
-
-        if (sp->npids == sp->maxpids) {
-                sp->maxpids += NPIDS;
-                sp->pids = xrealloc(sp->pids, sizeof(unsigned) * sp->maxpids);
-        }
-        sp->pids[sp->npids++] = sp->pid = pe.th32ProcessID;
+        sp->pid = pe.th32ProcessID;
 
         if (sp->pid == getpid()) {
                 comm = applet_name;
@@ -787,10 +792,10 @@ static int kill_signal(pid_t pid, int sig)
 }
 
 /**
- * If the process ID is positive invoke the callback for that process
- * only.  If negative or zero invoke the callback for all descendants
- * of the indicated process.  Zero indicates the current process; negative
- * indicates the process with process ID -pid.
+ * If the process ID is positive signal that process only.  If negative
+ * or zero signal all descendants of the indicated process.  Zero
+ * indicates the current process; negative indicates the process with
+ * process ID -pid.
  */
 static int kill_pids(pid_t pid, int sig)
 {