README.fuchsia

Name: ICU (Fuchsia fork of Chromium fork)
License: MIT
License File: LICENSE
Upstream Git: https://chromium.googlesource.com/chromium/deps/icu/
Description:

This directory contains the source code of ICU4C for C/C++, following
Chromium's changes.

This is a slight fork of Chromium's ICU, which itself is a fork of the upstream
ICU project.  See the section "LOCAL MODIFICATIONS" for the details of the local
changes.

Note that although Chromium and Chromium ICU's GN files have an `is_fuchsia`
constant that is set to `true` for binaries that target Fuchsia OS, building
_Chromium ICU_ with `is_fuchsia = true` is _not_ the same as building
_Fuchsia ICU_. This is because of the other differences in build rules between
the two.

(Fuchsia ICU can also be built with `is_fuchsia = false`, e.g. for Fuchsia host
targets.)

LOCAL MODIFICATIONS

The local changes made specifically for Fuchsia with respect to the Chromium
ICU original are fenced off like this in the respective files:

    # <fuchsia-icu>
    ... local additions ...
    # </fuchsia-icu>

- version.gni contains a config variable which has the major version of the
  ICU library.

UPDATE PROCEDURE

To ensure that Fuchsia's ICU repo properly tracks Chromium's version, do the
following when catching up:

1. Add the Chromium upstream remote (first-time only):

   Run the following command to add the upstream Chromium copy of the ICU
   repository. This is only needed if you have not previously added the
   Chromium remote:
   $ git remote add chromium https://chromium.googlesource.com/chromium/deps/icu.git

2. Merge from Chromium ToT:

   From $FUCHSIA_DIR/third_party/icu on the origin/master branch, run:
   $ git merge chromium/master

   Fix all the merge conflicts, paying special attention to not override
   Fuchsia-specific changes. In particular, make sure the Mac host build does
   not break as this configuration is not tested in CQ. If you do not have a
   Mac, ask someone who does to test your changes before submitting.

   Ensure that the version number in `//version.gni` matches the major version
   of the ICU library that is being used.  The file `//README.chromium` usually
   has the major version number listed in the `Description:` section.

   See an example here:
   https://fuchsia-review.googlesource.com/c/third_party/icu/+/403454