[SR-8876] Build recent ICU on Linux

[milseman]

Previous ID	SR-8876
Radar	None
Original Reporter	@milseman
Type	Task
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	1
Component/s	Foundation, Project Infrastructure, Standard Library
Labels	Task
Assignee	@spevans
Priority	Medium

md5: 6d81b0a7f1a52a5092036698acf6929b

Issue Description:

Linux system ICU is often very old, with both performance issues and the inability to answer recent Unicode.Scalar/Character properties. Swift works best with more recent versions of ICU, so for consistency sake we should have the default Linux build also build a libICU. For further consistency across platforms, we could consider building Apple's open source fork.

[spevans]

swiftlang/swift#19860

[tkremenek]

PR merged:

swiftlang/swift@7af28e8

[ole]

@spevans Thanks so much for working on this. To clarify, does this mean that Swift binaries on Linux will use this modern ICU lib for all their Unicode needs, regardless of the ICU version that comes with the OS the program is running on?

[spevans]

Correct, the Linux snapshots now ship with a ICU library, currently 61.1 and use that for stdlib and Foundation:

$ cat hello.swift 
import Foundation

print("Hello")
$ ~/swift-DEVELOPMENT-SNAPSHOT-2018-11-25-a-ubuntu18.04/usr/bin/swiftc hello.swift && ./hello
Hello
ubuntu1804:~ $ ldd hello|grep icu
    libicuucswift.so.61 => /home/spse/swift-DEVELOPMENT-SNAPSHOT-2018-11-25-a-ubuntu18.04/usr/lib/swift/linux/libicuucswift.so.61 (0x00007f669afda000)
    libicui18nswift.so.61 => /home/spse/swift-DEVELOPMENT-SNAPSHOT-2018-11-25-a-ubuntu18.04/usr/lib/swift/linux/libicui18nswift.so.61 (0x00007f669aae4000)
    libicudataswift.so.61 => /home/spse/swift-DEVELOPMENT-SNAPSHOT-2018-11-25-a-ubuntu18.04/usr/lib/swift/linux/libicudataswift.so.61 (0x00007f669876f000)
    libicuuc.so.60 => /usr/lib/x86_64-linux-gnu/libicuuc.so.60 (0x00007f6696785000)
    libicudata.so.60 => /usr/lib/x86_64-linux-gnu/libicudata.so.60 (0x00007f6692c5a000)

Note that the version 60 in that list is used by libXML2 (used by Foundation) which is a system library so it linked to the system ICU (version 60) as part of Ubuntu18.

[ole]

Thank you!