There are 2 functions which are used to expand log file name:
  - make_log_name(const char* log_name, const char* force_directory) in ostream.cpp
  - Arguments::copy_expand_pid(const char* src, size_t srclen,
                                char* buf, size_t buflen) in arguments.cpp
make_log_name: %p => pid{pid}
copy_expand_pid: %p => {pid}

Although it may be not feasible to share code between them (copy_expand_pid is used in VM error reporter), the format should be the unified (%p => {pid}).