AvailabilityVersions

Intro

AvailabilityVersions provides functionality related to the versions numbers of various platforms. These take several forms including:

• Macros for API availability annotation (API_AVAILABLE(), etc)
• Version defines used for dyld version checks
• Mappings for aligned OSes and platforms (version sets)

Most of this is programmatically generated with data sourced in the availability_dsl. The files in the that folder are read in order.

Operation

All of the content defined in the dsl is accessed via the /usr/local/libexec/availability script. It provides several options for outputing information about versions:

• --macos, --ios, etc: Outputs a list of versions for the platform
• --sets: Outputs YAML describing all the aligned versions of each platforms as version sets
• --preprocess: Undocumented flag that parse through an input file and replaces macros in it with contnet derived from the DSL

Build:

The build system is implemented in CMake, but a Makefile is provided to support B&I builds, and make install the recommended way of invoking the build. The build process is as follows:

1. $SRCROOT/availability is invoked to preprocess itself and create $OBJROOT/availability that embeds the DSL content directly into the script
2. $OBJROOT/availability is called on all the files in templates to preprocess their macros and store the results in $OBJROOT
3. The install phase then copies all the processed files into the DSTROOT