Upgrading to Xcode 16.3, all previews across my AppKit project stopped working. The error message I'm getting is especially baffling. It says the project could not be built with incremental compilation because SWIFT_COMPILATION_MODE is set to "incremental": I tried clearing DerivedData with no effect. When I click the diagnostics button the information given is not very revealing, at least not to me. If I open the project in Xcode 16.2 everything works perfectly again. I switched over to Previews for all new code but this error situation is quite demotivating. Does anyone have any suggestions?

I've observed a significant performance regression in Apple Clang 16 (Xcode 16.0/16.2) compared to Clang 15 (Xcode 15.2) when processing flutter aot compilation. Further research shows that clang -cc1as process became extremely slow. The compilation time has increased by approximately 4x. Environment Machine: Apple M2 (8C8T) Memory: 16GB macOS Version: 14.7.2 Target: Flutter AOT compilation (snapshot_assembly.o) Performance Comparison Xcode Version iOS SDK Duration 15.2 17.2 1:08.90 15.2 18.2 1:03.98 16.2 17.2 4:11.07 16.2 18.2 4:08.43 16.0 18.2 4:29.32 Reproduction Steps The issue can be reproduced with the following command which is generated by flutter aot_assembly_release process: time ${xcode_app_path}/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc \ -arch arm64 \ -miphoneos-version-min=12.0 \ -v \ -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS18.2.sdk \ -c ${project_path}/.dart_tool/flutter_build/f9ebf46f040933de7c8d103c84d38156/arm64/snapshot_assembly.S \ -o ${project_path}/.dart_tool/flutter_build/f9ebf46f040933de7c8d103c84d38156/arm64/snapshot_assembly.o Additional Information This issue specifically affects large assembly files generated by Flutter's AOT compilation The performance regression appears to be consistent across different iOS SDK versions The same assembly file compiles significantly faster with Xcode 15.2 Same performance regression observed on M4 Mac mini, suggesting this is not hardware-specific Size of object: size -m ${project_path}/.dart_tool/flutter_build/f9ebf46f040933de7c8d103c84d38156/arm64/snapshot_assembly.o Segment : 64577616 Section (__TEXT, __text): 26603344 Section (__DATA, __bss): 48 (zerofill) Section (__TEXT, __const): 21292928 Section (__DWARF, __debug_abbrev): 61 Section (__DWARF, __debug_info): 8934534 Section (__DWARF, __debug_line): 4464443 Section (__LD, __compact_unwind): 3282208 total 64577566 total 64577616 Questions Is this a known issue with Apple Clang 16? Are there any workarounds or compiler flags we can use to improve the performance? Is this behavior expected or should it be considered a regression? Any insights or suggestions would be greatly appreciated.

I have a SwiftUI app that I've been working on in XCode 16.1. The project builds and runs in the simulators, on my mac and on my iPhone/iPad without any issues. I'm also able to build my unit test project and run them without any errors. The project has zero warnings in it. When I go to the Edit Schemes options and change the Run scheme to be a Release build with the Debug Executable unchecked I get a compiler error: Command SwiftCompile failed with a nonzero exit code I've attempted this Release Run with the following target devices in XCode: My iPhone 15 Pro Max (iOS 18.2 Beta 3) MacBook Air (M1) (15.2 Beta) iPhone 16 Simulator (iOS 18.1) Any iOS Simulator Device (arm64, x86_64) All 3 of these target have the same issue. Normally I would just debug the error from the logs but when I look at the build output I can't see any information in the log to tell me what happened. It looks like the source files are sent into the SwiftCompiler and the compiler fails without bubbling up the issue. I've provided the full error log export as a Gist HERE due to it's size. Is there anything in the log I'm missing? Is there a way for me to turn on more verbose logging during compilation of a Release Build? I created a brand new Multiplatform App in XCode and I added all of my source files to it. No project configuration settings were changed. I could build it successfully with the debug configuration. I then changed it to the Release configuration and experienced the same error. I can create another fresh project and make the same release configuration with none of my source files in it and get a successful build. I t seems there is something wrong with my source files and the release configuration but the compiler doesn't indicate what. I'm lost at this point as I can't figure out how to get a release build and can't seem to find any indication as to why.