dnslabeltext.rl assumes labellen is signed

[zeha]

• Program: dnsdist (affected code is shared though)
• Issue type: Bug report

Short description

dnslabeltext.rl: In function ‘DNSName::string_t segmentDNSNameRaw(const char*, size_t)’:
dnslabeltext.rl:115:38: warning: comparison is always false due to limited range of data type [-Wtype-limits]
  115 |                         if (labellen < 0 || labellen > 63) {
      |                             ~~~~~~~~~^~~
dnslabeltext.rl:115:38: warning: comparison is always false due to limited range of data type [-Wtype-limits]
  115 |                         if (labellen < 0 || labellen > 63) {
      |                             ~~~~~~~~~^~~

labeltext is defined as char, but some platforms have char as unsigned.

I cannot tell if this is harmless or not.

Environment

• Operating system: Debian bullseye (testing) arm64, ppc64el, s390x
• Software version: 1.6.0
• Software source: source tarball

Steps to reproduce

Build on arm64 / ppc64el / s390x, apparently :)

Other information

Logs:

• arm64: https://buildd.debian.org/status/fetch.php?pkg=dnsdist&arch=arm64&ver=1.6.0-1&stamp=1620903160&raw=0
• ppc64el: https://buildd.debian.org/status/fetch.php?pkg=dnsdist&arch=ppc64el&ver=1.6.0-1&stamp=1620902758&raw=0
• s390x: https://buildd.debian.org/status/fetch.php?pkg=dnsdist&arch=s390x&ver=1.6.0-1&stamp=1620904242&raw=0

[Habbie]

Some fun background at https://blog.powerdns.com/2013/10/28/on-ragel-and-char-types/