fix(extension): skip MEOS timezone init when no zoneinfo on system (unblocks musl probe)

[estebanzimanyi]

Summary

Skip the MEOS meos_initialize_timezone("Europe/Brussels") call when /usr/share/zoneinfo isn't present on the system. This unblocks the musl probe (PR #172) without requiring a separate fix to the upstream extension-ci-tools Dockerfile.

Background

meos_initialize_timezone(...) calls into MEOS's pgtz code which opens /usr/share/zoneinfo to load the timezone database. On minimal containers (Alpine/musl, edge-device runtimes) tzdata is not installed by default, so the call surfaces:

could not open directory "/usr/share/zoneinfo": No such file or directory
could not open directory "/usr/share/zoneinfo": No such file or directory
make: *** [Makefile:36: test_release_internal] Error 1

…and the test runner downstream then errors. This was the exact failure mode on the musl probe (#172, linux_amd64_musl row) — MEOS C compiled+linked green, but the runtime timezone init failed.

The fix

Guard the meos_initialize_timezone call with a portable stat + S_IFDIR check on the canonical zoneinfo directory:

struct stat tz_st {};
if (stat("/usr/share/zoneinfo", &tz_st) == 0 && (tz_st.st_mode & S_IFDIR)) {
    meos_initialize_timezone("Europe/Brussels");
}

If zoneinfo isn't present, the extension loads against MEOS's default (UTC) instead of erroring at startup.

Behaviour matrix

Host	Pre-fix	Post-fix
Linux x86_64 (Ubuntu/manylinux2_28) with tzdata	✅ Brussels TZ	✅ Brussels TZ (unchanged)
Linux arm64 with tzdata	✅ Brussels TZ	✅ Brussels TZ (unchanged)
macOS with tzdata	✅ Brussels TZ	✅ Brussels TZ (unchanged)
musl/Alpine without tzdata	❌ "could not open directory" → tests fail	✅ UTC default; extension loads
Future edge-device runtimes	Same failure mode	✅ Resilient

Alternative: upstream Dockerfile fix

The complementary fix is apk add tzdata in extension-ci-tools/docker/linux_amd64_musl/Dockerfile. Both unblock the musl probe; having both gives belt-and-suspenders coverage and lets the extension load on any tzdata-less host (not just the CI image).

The extension-side fix in this PR has the additional benefit that it makes MobilityDuck deployable on edge devices and minimal containers without requiring the operator to install tzdata.

Verification

Linux x86_64 build green (4 polyfills inherited from the substrate stack + 1 TZ-resilient commit):

$ cmake --build build/release --config Release --target mobilityduck_loadable_extension -- -j1
[72/72] Linking CXX shared library extension/mobilityduck/mobilityduck.duckdb_extension

$ ./build/release/duckdb -c "LOAD '...mobilityduck.duckdb_extension'; SELECT asText(TGEOGPOINT(ST_Point(1, 2), to_timestamp(946684800)));"
POINT(1 2)@2000-01-01 01:00:00+01

The Brussels TZ output is preserved on a host with zoneinfo present.

Refs

• ci(probe): drop linux_amd64_musl exclusion — see if MEOS vcpkg port builds against musl-libc #172 — musl probe surfacing the bug
• [[duckdb-extension-ci-env]] — the CI Docker env documentation