ctreffs · October 28, 2021 10:15 · Jan 17, 2021 · Jan 17, 2021 · Jan 17, 2021 · Jan 17, 2021
diff --git a/README.md b/README.md
@@ -7,8 +7,9 @@
 
 # Notes
 
-1. Passing `-Xfrontend -enable-implicit-dynamic` removes you from having to add `dynamic` to everything you want to be replacable
-2. Passing `-enable-private-imports` to the `main.swift` build, and then `-Xfrontend -disable-access-control` to the dylib build stops you from having to make things `public` unnecessarily. Depending on the use case if the symbols are `public` already you could remove these flags
-3. The dylib compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
+- Passing `-Xfrontend -enable-implicit-dynamic` removes you from having to add `dynamic` to everything you want to be replacable
+- Passing `-enable-private-imports` to the `main.swift` build, and then `-Xfrontend -disable-access-control` to the dylib build stops you from having to make things `public` unnecessarily. Depending on the use case if the symbols are `public` already you could remove these flags
+- The dylib compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building
+- There must be a better way than passing `-undefined suppress -flat_namespace` to the linker for the dylib compilation. You could pass `-U SYMBOL` but I think that's a bit more annoying to track down and maintain
 
 Useful reference: https://tech.guardsquare.com/posts/swift-native-method-swizzling
diff --git a/README.md b/README.md
@@ -1,14 +1,14 @@
 # Usage
 
-1. `swiftc main.swift -emit-module-path main.swiftmodule -emit-executable`
+1. `swiftc main.swift -emit-module-path main.swiftmodule -emit-executable -enable-private-imports -Xfrontend -enable-implicit-dynamic`
 2. `./main` -> prints `From original bar()`
-3. `swiftc -emit-library inject.swift -o inject.dylib -I . -Xlinker -undefined -Xlinker suppress -Xlinker -flat_namespace`
+3. `swiftc -emit-library inject.swift -o inject.dylib -I . -Xlinker -undefined -Xlinker suppress -Xlinker -flat_namespace -Xfrontend -disable-access-control`
 4. `DYLD_INSERT_LIBRARIES=inject.dylib ./main` -> prints `From replacement bar()`
 
 # Notes
 
-1. The symbols in `main.swift` have to be public even though I don't think they should. I tried using `-Xfrontend -disable-access-control` when building the dylib, which works for the build, but the symbol fails to be found at runtime because it's local not external. Besides marking the type / function as `public` I don't see any compiler or linker flags to force these external (Using `-exported_symbol '_$s4main3FooV3baryyFTx'` throws this warning: `ld: warning: cannot export hidden symbol ...`)
-2. The dylib compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
-3. You can remove the explicit `dynamic` on `Foo.bar` if you pass `-Xfrontend -enable-implicit-dynamic`
+1. Passing `-Xfrontend -enable-implicit-dynamic` removes you from having to add `dynamic` to everything you want to be replacable
+2. Passing `-enable-private-imports` to the `main.swift` build, and then `-Xfrontend -disable-access-control` to the dylib build stops you from having to make things `public` unnecessarily. Depending on the use case if the symbols are `public` already you could remove these flags
+3. The dylib compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
 
 Useful reference: https://tech.guardsquare.com/posts/swift-native-method-swizzling
diff --git a/main.swift b/main.swift
@@ -1,5 +1,5 @@
-public struct Foo {
-    public dynamic func bar() {
+struct Foo {
+    func bar() {
         print("From original bar()")
     }
 }

diff --git a/README.md b/README.md
@@ -8,4 +8,7 @@
 # Notes
 
 1. The symbols in `main.swift` have to be public even though I don't think they should. I tried using `-Xfrontend -disable-access-control` when building the dylib, which works for the build, but the symbol fails to be found at runtime because it's local not external. Besides marking the type / function as `public` I don't see any compiler or linker flags to force these external (Using `-exported_symbol '_$s4main3FooV3baryyFTx'` throws this warning: `ld: warning: cannot export hidden symbol ...`)
-2. The dylib compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
+2. The dylib compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
+3. You can remove the explicit `dynamic` on `Foo.bar` if you pass `-Xfrontend -enable-implicit-dynamic`
+
+Useful reference: https://tech.guardsquare.com/posts/swift-native-method-swizzling
diff --git a/README.md b/README.md
@@ -8,4 +8,4 @@
 # Notes
 
 1. The symbols in `main.swift` have to be public even though I don't think they should. I tried using `-Xfrontend -disable-access-control` when building the dylib, which works for the build, but the symbol fails to be found at runtime because it's local not external. Besides marking the type / function as `public` I don't see any compiler or linker flags to force these external (Using `-exported_symbol '_$s4main3FooV3baryyFTx'` throws this warning: `ld: warning: cannot export hidden symbol ...`)
-2. The dylib injection compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
+2. The dylib compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
diff --git a/README.md b/README.md
@@ -0,0 +1,11 @@
+# Usage
+
+1. `swiftc main.swift -emit-module-path main.swiftmodule -emit-executable`
+2. `./main` -> prints `From original bar()`
+3. `swiftc -emit-library inject.swift -o inject.dylib -I . -Xlinker -undefined -Xlinker suppress -Xlinker -flat_namespace`
+4. `DYLD_INSERT_LIBRARIES=inject.dylib ./main` -> prints `From replacement bar()`
+
+# Notes
+
+1. The symbols in `main.swift` have to be public even though I don't think they should. I tried using `-Xfrontend -disable-access-control` when building the dylib, which works for the build, but the symbol fails to be found at runtime because it's local not external. Besides marking the type / function as `public` I don't see any compiler or linker flags to force these external (Using `-exported_symbol '_$s4main3FooV3baryyFTx'` throws this warning: `ld: warning: cannot export hidden symbol ...`)
+2. The dylib injection compilation depends on the main module. I was hoping I could use a string or something instead and specify `main.Foo.bar` explicitly instead of having to depend `main` directly for building.
diff --git a/inject.swift b/inject.swift
@@ -0,0 +1,8 @@
+import main
+
+extension Foo {
+    @_dynamicReplacement(for: bar)
+    func replacementBar() {
+        print("From replacement bar()")
+    }
+}
diff --git a/main.swift b/main.swift
@@ -0,0 +1,7 @@
+public struct Foo {
+    public dynamic func bar() {
+        print("From original bar()")
+    }
+}
+
+Foo().bar()