report error "invalidPrintfArgType_unit" with cppcheck v2.8

[DarrenSong]

it confused me.
the code is like below, the format string type is same as argument type, but still report this error.

%lu in format string (no. 3) requires 'unsigned long' but the argument type is 'std::size_t {aka unsigned long}

 snprintf((char *)ev.data, MaxLogLength, "%6d:%6d:%5lu;%5s;%-16s;%s", \
   getpid(), gettid(), mq ? mq->getnumber() : 0, level, from, msgstr.c_str());

the definition of function of getnumber() is below, my PC OS is 64 bit Debian9.

std::size_t GCEventContext_MQ::getnumber()
{
  return m_mq->get_num_msg();
}

[CHR]

The portable format specifier for size_t is %zu.

[DarrenSong]

Thank you very much