Write a blog post about the -ObjC flag

priv/posts/2024-06-04-why-you-need-objc.md

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+---
+title: "Why you need the -ObjC flag"
+description: "In this blog post, I explain why you might need to set the -ObjC flag in the OTHER_LDFLAGS build setting of your Xcode project."
+tags: ["Swift", "Xcode"]
+---
+
+Tuist provides a [method](https://docs.tuist.io/guide/project/dependencies.html#tuist-s-xcodeproj-based-integration) for integrating Swift Packages, previously resolved by SPM, into Xcode projects using XcodeProj primitives such as targets, build settings and phases.
+This feature uncovered a need that some packages in the ecosystem have,
+and that's the need for upstream targets to pass `-force_load` or `-ObjC` through the build setting `OTHER_LDFLAGS`.
+Why is that needed?
+Thanks to [David](https://github.com/thedavidharris), who put together some [troubleshooting](https://docs.tuist.io/guide/project/dependencies.html#troubleshooting) guidance and provided [some references](https://github.com/tuist/tuist/issues/6320#issuecomment-2146534862) to discussions, I could better understand what the problem was.
+This post is my attempt to write down my understanding of the problem, to help other developers in the future come across the same issue. 
+
+
+In simple words,
+the problem is that the linker **overoptimizes the binary removing symbols that are needed at runtime.**
+The linker's dead-stripping logic can't delete dynamically referenced symbols.
+And this is something that happens not only when referencing Objective-C symbols, but [Swift too](https://forums.swift.org/t/linker-flag-objc-force-loads-swift-libraries/47466/3).
+For example, when integrating Composable Architecture,
+which [uses](https://github.com/pointfreeco/swift-composable-architecture/blob/7cbde3b07f193f732e256429e1351ff53cd31641/Sources/ComposableArchitecture/UIKit/NSObject%2BObservation.swift#L172) Objective-C runtime capabilities,
+developers might need to add explicit references to those symbols or add the aforementioned flags to the build settings.
+
+What's the solution? There are a few options:
+
+- The package maintainer can add static references to those symbols to prevent the dead-stripping logic from removing them  (e.g., [Promises](https://github.com/google/promises/pull/221), [IGListKit](https://github.com/Instagram/IGListKit/pull/957))
+- You set the `-force_load` or `-ObjC` flag in the `OTHER_LDFLAGS` build setting of the target that links those packages statically. Note that this has some effects, like potentially increasing the binary size.
+- You turn those dependencies into dynamic targets, which as a caveat might end up increasing the launch time of your app.
+
+This is a bit unfortunate because it requires developers to go a bit deeper in understanding their dependencies
+, but hopefully this write-up helps you understand the problem and the potential solutions.