Question

I have made a project in xcode4.2 and when i opened it with xcode4.5 ,iOS 6 SDK it gives error 255 and the reason seems to be absence of libxml2.2.7.3.dylib.

What are my options is there any other substitute provided?

thanks

Answer 1

Xcode 4.5, or more precisely the iOS6 SDK (because the libraries available are dependent of the SDK, not the Xcode version) still has libxml2.2.dylib.

It is just probably not the version 2.2.7.3 but a newer, up-to-date 2.2.x.y version that is embedded in the SDK now.

You should generally not link your application with a specific version of libraries like that, but better with a generic version like libxml2.dylib or libxml2.2.dylib.

Generally libraries respect the semantic versionning, meaning that:

• their major version change only when the API is not backward compatible with the previous major version,
• the minor version change only when new methods are introduced in the API, but are still compatible with the previous API,
• patch version means that some bug fixes have been made, but the API hasn’t changed.

So if libxml respect this semantic versioning (and I guess is does, like quite every standard library), every version 2.2.x.y of libxml is API-compatible with any other 2.2.x.y version and will continue to work with your program. A hypothetic new version libxml2.2.x.z will simply fix bugs, but won’t introduce any change in its API. And when a version of libxml2.3.x.y will arise, it will still be backward compatible with 2.1 and 2.2 too (just adding new features but not dropping the existing ones).

Thus, you can safely link your application with the generic library version libxml2.dylib, which will automatically point to the latest 2.x.y.z version available in the current SDK. Or link with libxml2.2.dylib which will point to the latest 2.2.x.y version (these are symbolic links to the latest versions, as all UNIX-like OSes use to do)