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Hello, I am a beginner with MacOS. I am trying to compile a program that builds using Xcode. Right now I have Xcode 12.2 on Catalina 10.15.5 . My build runs up to a point where I have : 'CoreServices/CoreServices.h' file not found. From my readings, I think that this file should be in a headers package, probably macOS_SDK_headers_for_macOS_10.15.pkg or something like that. I have reinstalled Xcode 12.2 (a .xip) and also the command lines tools for Xcode 12.2 ( a .dmg ). After doing these installs, I still do not find the missing headers or even the pkg file that would contain them. Can anybody help me with installing the missing headers ? How do I get the SDK headers to complete my compilation ? Thank you Gilbert