4241f29e2f
The ICU entry was inherited from the original package-name check (libicu-dev
on apt, libicu on dnf) and translated to a library probe without verifying
which library that should be. Three things were wrong with it.
libicui18n was never checked. The strings in libSystem.Globalization.Native.so
are exactly libicuuc and libicui18n, so probe both; libicudata arrives as a
dependency of libicuuc and the remaining ICU libraries are never referenced.
The probe accepted any SONAME down to .so.0, but the runtime's floor is
MinICUVersion 60. A host carrying only an older ICU passed the check and then
FailFast'd at startup. RHEL/CentOS 7 ships ICU 50 and is affected.
The ldconfig fast path bypassed the version range entirely, since a cache line
for libicuuc.so.50 still matches the "libicuuc.so" prefix, and it trusted a
stale cache: removing a library without refreshing the cache reported it
present. Drop it and ask the loader directly. dlopen consults the same cache
but answers the question we are actually asking, so this also removes the musl
special-case, where ldconfig exits 0 while producing nothing usable.
Add tzdata. It is data rather than a library, so no loader probe finds it, but
the event scheduler resolves configured zone IDs through TimeZoneInfo and
without /usr/share/zoneinfo every lookup except UTC throws. Slim containers
routinely omit it.
Move the rationale to dev-docs/platform-prerequisites.md so it is discoverable
without reading the build tool, covering what each dependency is for, why
InvariantGlobalization stays false, and the tzdata-legacy split on Debian 12
and Ubuntu 24.04 that hides aliases such as US/Eastern.
README no longer asks for libicu-dev. Matching the runtime package by pattern
('^libicu[0-9]+$') is version-independent without pulling in headers, so no
-dev package is required on any supported distribution.
Verified on Debian and Alpine: all present, each dependency removed
individually, a stale ldconfig cache, and ICU downgraded to .so.50.
159 lines
6.7 KiB
Markdown
159 lines
6.7 KiB
Markdown
# Platform Prerequisites
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OS-level dependencies ModernUO needs at runtime, why each one is required, and what breaks without
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it. This page is about software packages, not hardware sizing.
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Run `./build-tool --check-prereqs` from the repository root to check the current machine. It prints
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the exact install command for the detected distribution.
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## What is required
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| Dependency | Platform | Why |
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| .NET 10 Runtime | all | — |
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| ICU (`libicuuc`, `libicui18n`) | Linux, macOS | The runtime refuses to start without it; see below |
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| tzdata | Linux | Time zone lookups; see below |
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| `libdeflate` | all | `LibDeflate.Bindings` |
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| `libargon2` | all | `Argon2.Bindings` (password hashing) |
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| VC++ Redistributable v14 | Windows | Native bindings |
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Not required, despite appearances:
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- **zstd** — `ZstdNet` bundles `libzstd` for every RID.
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- **liburing** — `IORingGroup` issues `io_uring` syscalls directly. It imports only `libc`,
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`libSystem.dylib`, `kernel32.dll`, `kernelbase.dll` and `ws2_32.dll`.
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- **`-dev` / `-devel` packages** — see "Runtime packages only" below.
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## Install
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```sh
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# Debian / Ubuntu (ICU has no stable package alias, so match it by pattern)
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sudo apt-get install -y '^libicu[0-9]+$' libdeflate0 libargon2-1 tzdata
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# Fedora / RHEL
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sudo dnf install -y libdeflate libargon2 libicu tzdata
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# Alpine
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apk add --no-cache libdeflate argon2-libs icu-libs tzdata
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# macOS
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brew install icu4c libdeflate argon2
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```
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CentOS additionally needs EPEL and CRB:
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```sh
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sudo dnf install -y epel-release epel-next-release && sudo dnf config-manager --set-enabled crb
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```
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## Runtime packages only
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Only the runtime packages are needed. The `-dev`/`-devel` packages are **not** required.
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They used to be, because .NET's `DllImport` probing looks for the unversioned `libfoo.so`, and on
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Linux that bare symlink ships only in the development package. The runtime package ships the
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versioned SONAME (`libdeflate.so.0`, `libargon2.so.1`). The binding packages now probe the versioned
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names as well, so the runtime package is sufficient.
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Anything still documenting `libicu-dev` or `libdeflate-dev` as a requirement is out of date.
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## ICU
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`Directory.Build.props` sets `InvariantGlobalization=false`, so ICU is mandatory. Without it the
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runtime does **not** throw — it `FailFast`s:
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```
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Couldn't find a valid ICU package installed on the system. Please install libicu (or icu-libs)
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using your package manager and try again.
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```
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That is `SIGABRT` (exit 134) and it cannot be caught. Note the process **starts cleanly and aborts
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later**, at whatever line first touches a culture, so the crash rarely points at the cause.
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### Why invariant mode is not an option
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`InvariantGlobalization=true` would remove the ICU dependency, but it changes behaviour in ways that
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corrupt data silently. Measured on .NET 10 with the repository's settings:
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| Behaviour | With ICU | Invariant mode |
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| `new CultureInfo("de-DE")` | real culture | succeeds, returns invariant data |
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| de-DE decimal separator | `,` | `.` |
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| `1234.5` as de-DE | `1.234,5` | `1,234.5` |
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| `string.Compare("a", "B", InvariantCulture)` | `-1` (linguistic) | `31` (ordinal) |
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| sort `[b, A, a, B]` | `a, A, b, B` | `A, B, a, b` |
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| `FindSystemTimeZoneById("Eastern Standard Time")` on Linux | resolves | `TimeZoneNotFoundException` |
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| UTF-8 round-trip of non-ASCII | unaffected | unaffected |
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The dangerous row is the first. Because `Directory.Build.props` also sets
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`PredefinedCulturesOnly=false`, constructing a culture in invariant mode **succeeds** instead of
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throwing `CultureNotFoundException`, and hands back an object populated with invariant data. Number
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parsing and formatting then produce wrong values with no error, and culture-sensitive sort order
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silently becomes ordinal.
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Encoding is not affected — UTF-8 round-trips correctly in both modes.
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### Version floor
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The runtime accepts `libicuuc.so.60` and above (`MinICUVersion` in `pal_icushim.c`). The prerequisite
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checker enforces the same floor, so a host carrying only an older ICU is reported missing rather than
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passing and then aborting at startup. RHEL/CentOS 7 ships ICU 50 and is affected.
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ICU tracks its own release train, so the SONAME digit varies widely by distribution — `.so.74` on
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Ubuntu 24.04, `.so.76` on Alpine, `.so.77` on Fedora, `.so.78` on openSUSE. There is no stable
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package alias on Debian and Ubuntu, which is why the checker resolves the name via `apt-cache`
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instead of hardcoding one.
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Only `libicuuc` and `libicui18n` are used; those are the two names
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`libSystem.Globalization.Native.so` loads. `libicudata` arrives as a dependency of `libicuuc`, and
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`libicuio`/`libicutu`/`libicutest` are never referenced. Every distribution ships all of them in a
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single package, so installing ICU at all satisfies both.
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## tzdata
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The event scheduler resolves configured zone IDs through `TimeZoneInfo`, which reads
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`/usr/share/zoneinfo` on Linux. This is separate from ICU: it is data, not a library, so no loader
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probe finds it, and slim container images routinely omit it.
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Without tzdata every lookup except `UTC` throws:
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```
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TimeZoneNotFoundException: The time zone ID 'America/New_York' was not found on the local computer.
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```
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`TimeZoneInfo.GetSystemTimeZones()` returns 1 entry instead of ~419, and `TimeZoneInfo.Local` falls
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back to UTC.
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### There is no per-zone subset
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Distributions do not package individual zones — it is one `tzdata` package, about 2 MB installed for
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the full set. Subsetting is not worth pursuing.
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The one split that does exist is **`tzdata-legacy`** on Debian 12 and Ubuntu 24.04, which carries the
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deprecated aliases. With plain `tzdata` alone:
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| Zone ID | `tzdata` | `tzdata-legacy` |
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| `America/New_York` | present | — |
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| `Europe/Kyiv` | present | — |
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| `EST5EDT` | present | — |
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| `US/Eastern` | **missing** | present |
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| `Asia/Calcutta` | **missing** | present |
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So a shard configured with a legacy alias such as `US/Eastern` throws on a current Debian or Ubuntu
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even though tzdata is installed. Either install `tzdata-legacy` or switch the configured value to the
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canonical ID (`America/New_York`, `Asia/Kolkata`).
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`TZDIR` is honoured if the data lives somewhere non-standard.
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## How the check works
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`--check-prereqs` asks the loader directly — `NativeLibrary.TryLoad` on the unversioned name, then
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`libfoo.so.N` descending through the accepted range.
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It deliberately does not consult a package database or `ldconfig -p`. Both answer a different
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question than "will `dlopen` succeed":
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- Package queries need a hardcoded name, which does not exist for ICU.
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- `ldconfig`'s cache can be stale, omits `LD_LIBRARY_PATH`, and carries no version information to
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enforce the ICU floor against. On musl it exits successfully while producing nothing usable.
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