Incorrect special case for "return 204" removed. The special case in question leads to replies without body in configuration like location / { error_page 404 /zero; return 404; } location /zero { return 204; } while replies with empty body are expected per protocol specs. Correct one will look like if (status == NGX_HTTP_NO_CONTENT) { rc = ngx_http_send_header(r); if (rc == NGX_ERROR || r->header_only) { return rc; } return ngx_http_send_special(r, NGX_HTTP_LAST); } though it looks like it's better to drop this special case at all.

// stub module to test header files' C++ compatibilty

extern "C" {
  #include <ngx_config.h>
  #include <ngx_core.h>
  #include <ngx_event.h>
  #include <ngx_event_connect.h>
  #include <ngx_event_pipe.h>

  #include <ngx_http.h>

  #include <ngx_mail.h>
  #include <ngx_mail_pop3_module.h>
  #include <ngx_mail_imap_module.h>
  #include <ngx_mail_smtp_module.h>
}

// nginx header files should go before other, because they define 64-bit off_t
// #include <string>


void
ngx_cpp_test_handler(void *data)
{
    return;
}