[3.15] gh-156060: Do not scan every process four times in remote_debugging.get_child_pids() on macOS (GH-156061) (#156069)

Author: miss-islington

Modules/_remote_debugging/subprocess.c

@@ -307,6 +307,7 @@ get_child_pids_platform(pid_t target_pid, int recursive, pid_array_t *result)
         PyErr_SetString(PyExc_OSError, "Failed to get process count");
         goto done;
     }
+    n_pids /= sizeof(pid_t);
 
     /* Allocate buffer for PIDs (add some slack for new processes) */
     int buffer_size = n_pids + 64;
@@ -322,6 +323,7 @@ get_child_pids_platform(pid_t target_pid, int recursive, pid_array_t *result)
         PyErr_SetString(PyExc_OSError, "Failed to list PIDs");
         goto done;
     }
+    actual /= sizeof(pid_t);
 
     /* Build pid -> ppid mapping */
     ppids = (pid_t *)PyMem_Malloc(actual * sizeof(pid_t));