Hello Andrew and Rebecca, This issue happens on macOS when the CPATH variable is not set, headers are stored within the Xcode tools and are not included by default in the path.
export CPATH=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/ Usually fixes it, if you want to know where the header is: sudo find /Library -name Availability.h Best regards, Theo Jehl -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#90036): https://edk2.groups.io/g/devel/message/90036 Mute This Topic: https://groups.io/mt/91344827/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
