False positive: This expression has no effect (because _function with multiple implementations_ has no external side effects [in incorrectly selected version]).

**Description of the false positive**

https://github.com/PowerDNS/pdns/pull/16363#discussion_r2455671092

> This expression has no effect (because sendUDPResponse has no external side effects).

codeql appears to have found https://github.com/PowerDNS/pdns/blob/dec9583d885713a0d0ecb55a74ef83cde5f8a235/pdns/dnsdistdist/test-dnsdist_cc.cc#L83 (which is indeed side effect free) instead of https://github.com/PowerDNS/pdns/blob/dec9583d885713a0d0ecb55a74ef83cde5f8a235/pdns/dnsdistdist/dnsdist.cc#L637 (which shouldn't be)

**Code samples or links to source code**

https://github.com/pieterlexis/pdns/blob/064c4c9f2ea60c59d4b0c1a95daad4e17cbe2ce4/pdns/dnsdistdist/dnsdist-udp.cc#L131

https://github.com/PowerDNS/pdns/blob/dec9583d885713a0d0ecb55a74ef83cde5f8a235/pdns/dnsdistdist/test-dnsdist_cc.cc#L83
https://github.com/PowerDNS/pdns/blob/dec9583d885713a0d0ecb55a74ef83cde5f8a235/pdns/dnsdistdist/dnsdist.cc#L637

**URL to the alert on GitHub code scanning (optional)**

I don't have access to this, but I'll see if I can get someone to provide it.

Start by comparing the linked call in pdns/dnsdistdist/dnsdist-udp.cc with the implementations in test-dnsdist_cc.cc and dnsdist.cc. Review the related CodeQL alert and the linked discussion to determine why the incorrect implementation is selected. Done means the cited false positive is resolved for the reported call and verified against those source locations.

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