swift_getSingletonMetadata crashes when called via Bundle.main.classNamed()
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Description
The code somewhere in swift_getSingletonMetadata crashes with EXC_BAD_ACCESS (SIGSEGV) when trying to get an ObjC Class definition via Bundle.main.classNamed(), NSClassFromString, objc_getClass or objc_lookUpClass for a Swift class that references a class in RoomPlan or ActivityKit on an iOS version lower than the minimum required version of RoomPlan or ActivityKit.
This came up in getsentry/sentry-cocoa#3798.
Reproduction
I created a sample project on GH: https://github.com/philipphofmann/ObjCGetClassCrash, but here are the most important steps:
Create the following class in Swift
import RoomPlan
@available(iOS 17.0, *)
class RoomPlanWrapper {
private var finalResults: CapturedStructure?
}Then try to get the ObjC class definition via the following ObjC code.
void getClass(void) {
// Also crashes with objc_getClass or objc_lookUpClass
NSClassFromString(@"YourProjectName.RoomPlanWrapper");
}Run the project on an iOS simulator with iOS version 15.x or lower.
The app crashes with EXC_BAD_ACCESS (SIGSEGV).
Stack dump
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000000
Exception Codes: 0x0000000000000001, 0x0000000000000000
VM Region Info: 0 is not in any region. Bytes before following region: 4306698240
REGION TYPE START - END [ VSIZE] PRT/MAX SHRMOD REGION DETAIL
UNUSED SPACE AT START
--->
__TEXT 100b30000-100b3c000 [ 48K] r-x/r-x SM=COW ...GetClassCrash
Termination Reason: SIGNAL 11 Segmentation fault: 11
Terminating Process: exc handler [20850]
Triggered by Thread: 0
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 ??? 0x0 ???
1 ObjCGetClassCrash 0x100b33e20 type metadata completion function for RoomPlanWrapper + 28
2 libswiftCore.dylib 0x103b98930 swift::MetadataCacheEntryBase<(anonymous namespace)::SingletonMetadataCacheEntry, int>::doInitialization(swift::MetadataWaitQueue::Worker&, swift::MetadataRequest) + 392
3 libswiftCore.dylib 0x103b89cf8 swift_getSingletonMetadata + 956
4 ObjCGetClassCrash 0x100b33de4 type metadata accessor for RoomPlanWrapper + 68
5 ObjCGetClassCrash 0x100b33d98 ObjC metadata update function for RoomPlanWrapper + 16
6 libobjc.A.dylib 0x100df3938 realizeClassMaybeSwiftMaybeRelock(objc_class*, mutex_tt<false>&, bool) + 116
7 libobjc.A.dylib 0x100df9548 look_up_class + 108
8 Foundation 0x10246fcb8 NSClassFromString + 192
9 ObjCGetClassCrash 0x100b31dec getClass + 36 (GetClassCrash.m:4)
10 ObjCGetClassCrash 0x100b336d8 ObjCGetClassCrashApp.init() + 28 (ObjCGetClassCrashApp.swift:13)
11 ObjCGetClassCrash 0x100b339e8 protocol witness for App.init() in conformance ObjCGetClassCrashApp + 12
12 SwiftUI 0x10b0fa670 static App.main() + 64
13 ObjCGetClassCrash 0x100b33950 static ObjCGetClassCrashApp.$main() + 40
14 ObjCGetClassCrash 0x100b339fc main + 12 (ObjCGetClassCrashApp.swift:11)
15 dyld_sim 0x100cb9cd8 start_sim + 20
16 dyld 0x100e9a0e0 start + 2360
Thread 0 crashed with ARM Thread State (64-bit):
x0: 0x00000000000000ff x1: 0x000000016f2cd870 x2: 0x0000000000000000 x3: 0x0000000104594510
x4: 0x0000000000000000 x5: 0x0000000000000000 x6: 0x0000000000000072 x7: 0x0000000000000000
x8: 0x00000000000000ff x9: 0x0000000000000000 x10: 0x0000000000000000 x11: 0x0000000000000000
x12: 0x0000000000000000 x13: 0x0000000031070000 x14: 0x0000000031000000 x15: 0x000000000000006f
x16: 0x0000000000000000 x17: 0x000000000d400000 x18: 0x0000000000000000 x19: 0x00006000031280c0
x20: 0x000000016f2cd8f8 x21: 0x00006000031280c0 x22: 0x0000000100b40270 x23: 0x0000000000000000
x24: 0x0000000100b48938 x25: 0x0000000000000000 x26: 0x0000000000000000 x27: 0x0000000000000002
x28: 0x0000000000000000 fp: 0x000000016f2cd810 lr: 0x0000000100b33f00
sp: 0x000000016f2cd7e0 pc: 0x0000000000000000 cpsr: 0x60001400
far: 0x0000000000000000 esr: 0x82000006 (Instruction Abort) Translation fault
Expected behavior
The call to Bundle.main.classNamed(), NSClassFromString, objc_getClass or objc_lookUpClass should return the class without crashing or nil.
Environment
swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-macosx14.0
It also crashes when compiling the project with Xcode 15.1 / Swift 5.9.
Additional information
No response