1*8975f5c5SAndroid Build Coastguard Worker# Mac and iOS hermetic toolchain instructions 2*8975f5c5SAndroid Build Coastguard Worker 3*8975f5c5SAndroid Build Coastguard WorkerThe following is a short explanation of why we use a the hermetic toolchain 4*8975f5c5SAndroid Build Coastguard Workerand instructions on how to roll a new toolchain. This toolchain is only 5*8975f5c5SAndroid Build Coastguard Workeravailable to Googlers and infra bots. 6*8975f5c5SAndroid Build Coastguard Worker 7*8975f5c5SAndroid Build Coastguard Worker## How to roll a new hermetic toolchain. 8*8975f5c5SAndroid Build Coastguard Worker 9*8975f5c5SAndroid Build Coastguard Worker1. Download a new version of Xcode, and confirm either mac or ios builds 10*8975f5c5SAndroid Build Coastguard Worker properly with this new version. 11*8975f5c5SAndroid Build Coastguard Worker 12*8975f5c5SAndroid Build Coastguard Worker2. Create a new CIPD package by moving Xcode.app to the `build/` directory, then 13*8975f5c5SAndroid Build Coastguard Worker follow the instructions in 14*8975f5c5SAndroid Build Coastguard Worker [build/xcode_binaries.yaml](../xcode_binaries.yaml). 15*8975f5c5SAndroid Build Coastguard Worker 16*8975f5c5SAndroid Build Coastguard Worker The CIPD package creates a subset of the toolchain necessary for a build. 17*8975f5c5SAndroid Build Coastguard Worker 18*8975f5c5SAndroid Build Coastguard Worker2. Create a CL with the updated `MAC_BINARIES_TAG` in 19*8975f5c5SAndroid Build Coastguard Worker [mac_toolchain.py](../mac_toolchain.py) with the version created by the 20*8975f5c5SAndroid Build Coastguard Worker previous command. 21*8975f5c5SAndroid Build Coastguard Worker 22*8975f5c5SAndroid Build Coastguard Worker3. Run the CL through the trybots to confirm the roll works. 23*8975f5c5SAndroid Build Coastguard Worker 24*8975f5c5SAndroid Build Coastguard Worker## Why we use a hermetic toolchain. 25*8975f5c5SAndroid Build Coastguard Worker 26*8975f5c5SAndroid Build Coastguard WorkerBuilding Chrome Mac currently requires many binaries that come bundled with 27*8975f5c5SAndroid Build Coastguard WorkerXcode, as well the macOS and iphoneOS SDK (also bundled with Xcode). Note that 28*8975f5c5SAndroid Build Coastguard WorkerChrome ships its own version of clang (compiler), but is dependent on Xcode 29*8975f5c5SAndroid Build Coastguard Workerfor these other binaries. Using a hermetic toolchain has two main benefits: 30*8975f5c5SAndroid Build Coastguard Worker 31*8975f5c5SAndroid Build Coastguard Worker1. Build Chrome with a well-defined toolchain (rather than whatever happens to 32*8975f5c5SAndroid Build Coastguard Worker be installed on the machine). 33*8975f5c5SAndroid Build Coastguard Worker 34*8975f5c5SAndroid Build Coastguard Worker2. Easily roll/update the toolchain. 35