PVS-Studio warning V579 for Apache

AP_DECLARE(apr_size_t) ap_regerror(int errcode,
  const ap_regex_t *preg, char *errbuf, apr_size_t errbuf_size)
{
  ...
  apr_snprintf(errbuf, sizeof errbuf,
    "%s%s%-6d", message, addmessage, (int)preg->re_erroffset);
  ...
}

This suspicious code was found in Apache project by PVS-Studio static code analyzer.
Warning message is:
V579 The apr_snprintf function receives the pointer and its size as arguments. It is possibly a mistake. Inspect the second argument. libhttpd util_pcre.c 85

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/