Fix object hooks in optimized device builds

.github/workflows/xcodebuild.yml

@@ -8,15 +8,19 @@ on:
       - 'InterposeKit.xcodeproj/**'
       - 'Sources/**/*.[ch]'
       - 'Sources/**/*.swift'
+      - 'Example/**'
       - 'Tests/**/*.swift'
+      - 'Tests/verify_release_linking.sh'
       - '!Tests/LinuxMain.swift'
   pull_request:
     paths:
       - '.github/workflows/xcodebuild.yml'
       - 'InterposeKit.xcodeproj/**'
       - 'Sources/**/*.[ch]'
       - 'Sources/**/*.swift'
+      - 'Example/**'
       - 'Tests/**/*.swift'
+      - 'Tests/verify_release_linking.sh'
       - '!Tests/LinuxMain.swift'
   workflow_dispatch:
 
@@ -32,6 +36,8 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - run: xcodebuild -version
+      - name: Release device app preserves object-hook helper
+        run: bash Tests/verify_release_linking.sh
       - name: macOS with UTF16
         if: always()
         run: YAMS_DEFAULT_ENCODING=UTF16 xcodebuild ${{ matrix.xcode_flags }} ${{ matrix.flags_for_test }} -destination "platform=macOS,arch=$(uname -m)" test | xcpretty

CHANGELOG.md

@@ -11,6 +11,7 @@
 ##### Bug Fixes
 
 * Preserve trampoline argument registers in code-coverage builds.
+* Preserve object-hook super trampolines in optimized Release builds, fixing https://github.com/steipete/InterposeKit/issues/29. Thanks to [@Thomvis](https://github.com/Thomvis).
 
 ## 0.01
 

Sources/SuperBuilder/src/ITKSuperBuilder.m

@@ -36,7 +36,8 @@ static IMP ITKGetTrampolineForTypeEncoding(__unused const char *typeEncoding) {
     return requiresStructDispatch ? (IMP)msgSendSuperStretTrampoline : (IMP)msgSendSuperTrampoline;
 }
 
-// Helper for binding with Swift
+// Keep the helper available for Swift's runtime lookup in optimized application binaries.
+__attribute__((__used__))
 BOOL IKTAddSuperImplementationToClass(Class originalClass, SEL selector, NSError **error);
 BOOL IKTAddSuperImplementationToClass(Class originalClass, SEL selector, NSError **error) {
     return [SuperBuilder addSuperInstanceMethodToClass:originalClass selector:selector error:error];

Tests/verify_release_linking.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+set -euo pipefail
+
+derived_data="$(mktemp -d "${TMPDIR:-/tmp}/InterposeKitReleaseLinking.XXXXXX")"
+
+xcodebuild \
+    -project Example/InterposeExample.xcodeproj \
+    -scheme InterposeExample \
+    -configuration Release \
+    -sdk iphoneos \
+    -destination "generic/platform=iOS" \
+    -derivedDataPath "$derived_data" \
+    CODE_SIGNING_ALLOWED=NO \
+    build \
+    -quiet
+
+binary="$derived_data/Build/Products/Release-iphoneos/InterposeExample.app/InterposeExample"
+
+if ! xcrun nm -a "$binary" | grep -E '[[:space:]]T[[:space:]]_IKTAddSuperImplementationToClass$' >/dev/null; then
+    echo "IKTAddSuperImplementationToClass was stripped from the optimized app binary." >&2
+    exit 1
+fi
+
+echo "Verified IKTAddSuperImplementationToClass in the optimized app binary."