This article helped me fix the problem [the link][1]
### What I did ?
At the end of my Podfile i add the following snippet and i run `pod install` command through terminal.
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
post_install do |installer|
installer.pods_project.targets.each do |target|
target.build_configurations.each do |config|
config.build_settings["ONLY_ACTIVE_ARCH"] = "YES"
end
end
end
<!-- end snippet -->
[1]: https://milanpanchal24.medium.com/xcode-12-building-for-ios-simulator-but-linking-in-object-file-built-for-ios-file-for-8c0cc28ec832
TL;DR;
Set "Build Active Architecture Only (`ONLY_ACTIVE_ARCH`)" to **Yes** for your libraries/apps, even for **release** mode.
---
While trying to identify the root cause of the issue I realized some fun facts about Xcode 12.
1. Xcode 12 is actually the stepping stone for [Apple silicon][1] which unfortunately is not yet available (*when the answer was written*). But with that platform we are going to get an arm64-based macOS where simulators will also run on the arm64 architecture unlike the present Intel-based *x86_64* architecture.
2. Xcode usually depends on the "Run Destination" to build its libraries/applications. So when a simulator is chosen as the "Run Destination", it builds the app for available simulator architectures and when a device is chosen as the "Run Destination" it builds for the architecture that the device supports (`arm*`).
3. `xcodebuild`, in the Xcode 12+ build system considers `arm64` as a valid architecture for simulator to support Apple silicon. So when a simulator is chosen as the run destination, it can potentially try to compile/link your libs/apps against `arm64` based simulators, as well. So it sends `clang(++)` some -target flag like `arm64-apple-ios13.0-simulator` in <architecture>-<os>-<sdk>-<destination> format and clang tries to build/link against an arm64-based simulator that eventually fails on an Intel based Mac.
4. But `xcodebuild` tries this only for **Release** builds. Why? Because, "Build Active Architecture Only (`ONLY_ACTIVE_ARCH`)" build settings is usually set to "No" for the "Release" configuration only. And that means `xcodebuild` will try to build all architectural variants of your libs/apps for the selected run destination for release builds. And for the Simulator run destination, it will includes both `x86_64` and `arm64` now on, **since `arm64` in Xcode 12+ is also a supported architecture for simulators** to support Apple silicon.
Simply putting, Xcode will fail to build your application anytime it tries the command line, `xcodebuild`, (which defaults to release build, see the general tab of your project setting) or otherwise and **tries to build all architectural variants supported by the run destination**. So a simple workaround to this issue is to set "Build Active Architecture Only (`ONLY_ACTIVE_ARCH`)" to **Yes** in your libraries/apps, even for release mode.
[![Enter image description here][2]][2]
[![Enter image description here][3]][3]
If the libraries are included as Pods and you have access to `.podspec` you can simply set:
> spec.pod_target_xcconfig = { 'ONLY_ACTIVE_ARCH' => 'YES' }
> spec.user_target_xcconfig = { 'ONLY_ACTIVE_ARCH' => 'YES' } # not
> recommended
I personally don't like the second line since [pods shouldn't pollute the target project][4] and it could be overridden in the target settings, itself. So it should be the responsibility of the consumer project to override the setting by some means. However, **this could be necessary for successful linting of podspecs.**
However, if you don't have access to the `.podspec`, you can always update the settings during installation of the pods:
post_install do |installer|
installer.pods_project.targets.each do |target|
target.build_configurations.each do |config|
config.build_settings["ONLY_ACTIVE_ARCH"] = "YES"
end
end
end
One thing I was concerned about that what will be the impact of this when we actually archive the libraries and applications. During archiving applications usually take the "Release" configuration and since this will be creating a release build considering only the active architecture of the current run destination, with this approach, we may lose the slices for armv7, armv7s, etc. from the target build. However, I noticed the documentation says (highlighted in the attached picture) that this setting will be ignored when we choose "Generic iOS Device/Any Device" as the run destination, since it doesn't define any specific architecture. So I guess we should be good if we archive our app choosing that as a run destination.
[1]: https://en.wikipedia.org/wiki/Apple_silicon
[2]: https://i.stack.imgur.com/EwcNf.png
[3]: https://i.stack.imgur.com/ryqPU.png
[4]: https://guides.cocoapods.org/syntax/podspec.html#user_target_xcconfig
