The runtime pack shipped ICU's full icudt78l.dat (33.1 MB), and every
Intl executable gets a copy beside it. scr_intl.c answers its Intl forms
with ICU's break iterators, number and date formatters, calendars and
locale IDs, which never read the charset converters or the collation,
language, region, time zone name, unit, spell-out and transliterator
trees: 21.5 MB of the file.
- The pack build writes icudt78l.dat without those items
(ICU_DATA_DROPPED in icu-inputs.mjs). filterIcuData rewrites the data
file's table of contents to the remaining items, and the result is
checked against a pinned sha256 and size (11,653,984 B).
- tests/harness/icu-data-filter.test.ts runs every @requires-icu corpus
program under 47 locales and 3 time zones with the pack's data, with
the full data and in Node, and fails when the outputs differ, so an
Intl form that reads a dropped category fails there.
- intl-word-segmenter-dictionaries.ts segments Chinese, Japanese, Thai,
Lao, Khmer and Burmese text, which ICU breaks with the dictionaries in
brkitr/.
The pack builds the ICU archive with the same Zig C++ recipe, adds
scr_intl.c as an optional unit under the intl predicate, and publishes
the archive under the id "icu". Its data file (icudt78l.dat) is not a
link input: the pack lists it in a new manifest "data" array, and every
Intl build copies it next to the executable it links (verifyArtifact
checked, atomic copy, size-checked before reuse). A pack that omits
scr_intl.c refuses an Intl program with SC3002 instead of linking
undefined scr_intl_ references.
The pack fetches both ICU inputs from the pinned release assets: the
source tarball (verified, cached, unpacked by the system tar) for the
archive, and the data zip (sha256 and size pinned twice) for the data,
unpacked by a small stored/deflate reader. Nothing is embedded in a
binary. The runtime fingerprint keeps covering the vendored trees, the
pinned ICU version keys the archive path, and the pack matrix gains the
icu archive with the intl predicate.
The isolated native host (native/compiler.ts) links outside the in-process
linker and writes its executables synchronously, so it installs the same
data artifacts itself (installNativeRuntimeData); the stored pack
selection gains a schema version so a selection cached before the data
list existed is discarded rather than trusted. Nothing selects a data
artifact for a program without the intl feature.
The sanitized lane links the pack's ICU archive as shipped. ICU is C++
and compiles with Zig's C++ driver for the packs' glibc floor, so it cannot
ride the sanitizer lane's per-TU C rebuild, and instrumenting ~600 C++ TUs
would add a multi-minute build to the first Intl program in every sanitized
lane. scr_intl.c itself still compiles instrumented with every other runtime
unit, and AddressSanitizer's interceptors cover ICU's allocations.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Chris Tate