What are the Pros and Cons of ICU?

Question

My team is tasked with implementing Unicode in our software, which is well over a million lines of code. We support an MFC Client and a Server on Windows, AIX or Solaris with an Oracle or SQL Server database. ICU looks like a very helpful tool. What are the pros and cons of using ICU? Does ICU work as advertised without major bugs?

Answer 1

A data point: Our (yes, that's a disclaimer) list of users and bugs is all on our project site.

IMBO (biased): Pros:

• works as advertised, comprehensive.
• Mature: 10+ years now, with a good stability policy and very active development.
• Uses latest Unicode+CLDR+BCP47+other standards.
• Compiles basically everywhere. C/C++/J and called by/implements python,perl,php,…
• Open source, with an increasing diversity of contributors.
• Comes with all needed data for the above (see below, under cons), yet customizable. (can add custom data)

Cons:

• Needs better documentation (we try- anyone want to help?).
• Lots of APIs- "it's too big #1" hard to know which one to use, even if it does what you want.
• Used by lots of types of programs, from embedded devices, smartphones through major desktop apps through databases and operating systems and enterprise apps: So, there may be multiple ways to do something.
• Comes with all needed data for the above! "it's too big #2" (see above, under pros), yet customizable. (can be trimmed down to size)

Answer 2

ICU is terrible: avoid if at all possible.

• Despite its age, basic things in it are broken, for example in this question: Fixing regex to work around ICU/RegexKitLite bug

• Time handling is broken as times are underspecified: you can't distinguish a DST from a non-DST time in a reliable way in many APIs.

• It's freaking huge.

• The documentation needs a lot of work. Less-used features are often unusable because there's no way to figure out the right way to use them. I spent days trying to get transliteration to work as explained and eventually gave up.

• It likes to work in UTF-16, the worst of all possible worlds.

• Support is unresponsive to problems.

• In my experience, it's not until you're most of the way through a project that you begin to discover the insidious flaws that will take 90% of your time.

For many people, there is no alternative so you're stuck with it.