Windows 10 使用 VirtualBox 创建的 Monterey 12.6.7 macOS 虚拟机不能识别到 iPhone 7 手机。
iPhone 7 已经连接到电脑主机 (win 10) 的 USB 3.0 口子,手机已经信任电脑。
在 win 10,我看到了 “此电脑\Apple iPhone”,就是说,宿主机识别到了 手机。
现在,开启macOS 虚拟机,虚拟机右下角的 usb 图标,显示并且勾选到了 "Apple Inc. iPhone [0901]",但虚拟机还是没看到手机设备,导致 Xcode 也看不到手机设备。
虚拟机运行后,插拔 iPhone 7 手机,通过
sudo log show --predicate 'eventMessage contains "usbmuxd"' --info
看到了报错信息:
2025-02-13 10:31:06.541201+0800 0xa3c Error 0x0 0 0 kernel: (Sandbox) 1 duplicate report for System Policy: usbmuxd(22583) deny(1) file-write-mode /private/var/db/lockdown
2025-02-13 10:31:07.090321+0800 0xf807 Error 0x0 140 0 sandboxd: [com.apple.sandbox.reporting:violation] System Policy: usbmuxd(22583) deny(1) file-write-mode /private/var/db/lockdown
Violation: deny(1) file-write-mode /private/var/db/lockdown
Process: usbmuxd [22583]
Path: /usr/local/sbin/usbmuxd
Load Address: 0x10564b000
Identifier: usbmuxd
Version: ??? (???)
Code Type: x86_64 (Native)
Parent Process: sudo [22582]
Responsible: /System/Applications/Utilities/Terminal.app/Contents/MacOS/Terminal
User ID: 0
Date/Time: 2025-02-13 10:31:06.793 GMT+8
OS Version: macOS 12.6.7 (21G651)
Release Type: User
Report Version: 8
MetaData: {"vnode-type":"DIRECTORY","hardlinked":false,"pid":22583,"process":"usbmuxd","primary-filter-value":"/private/var/db/lockdown","platform-policy":true,"binary-in-trust-cache":false,"path":"/private/var/db/lockdown","primary-filter":"path","action":"deny","matched-extension":false,"process-path":"/usr/local/sbin/usbmuxd","file-flags":0,"responsible-process-path":"/System/Applications/Utilities/Terminal.app/Contents/MacOS/Terminal","flags":21,"platform-binary":false,"rdev":0,"summary":"deny(1) file-write-mode /private/var/db/lockdown","target":"/private/var/db/lockdown","mount-flags":76582912,"profile":"platform","matched-user-intent-extension":false,"apple-internal":false,"storage-class":"Lockdown","platform_binary":"no","operation":"file-write-mode","profile-flags":0,"normalized_target":["private","var","db","lockdown"],"file-mode":448,"errno":1,"build":"macOS 12.6.7 (21G651)","policy-description":"System Policy","responsible-process-signing-id":"com.apple.Terminal","hardware":"Mac","uid":0,"release-type":"User"}
Thread 0 (id: 63477):
0 libsystem_kernel.dylib 0x00007ff80d8368ae __chmod + 10
1 usbmuxd 0x000000010565584e main + 3582 (main.c:816)
2 dyld 0x0000000114e3f52e start + 462
Binary Images:
0x10564b000 - 0x10565afff usbmuxd (0) <0fc9b657-d311-38b5-bf02-e294b175a615> /usr/local/sbin/usbmuxd
0x114e3a000 - 0x114ea3567 dyld (960) <2517e9fe-884a-3855-8532-92bffba3f81c> /usr/lib/dyld
0x7ff80d832000 - 0x7ff80d869fff libsystem_kernel.dylib (8020.240.18.701.6) /usr/lib/system/libsystem_kernel.dylib
2025-02-13 10:35:39.751714+0800 0x27f Default 0x0 0 0 kernel: (Sandbox) Sandbox: usbmuxd(119) allow iokit-get-properties kCDCDoNotMatchThisDevice
2025-02-13 10:35:45.025063+0800 0x27f Default 0x0 0 0 kernel: (Sandbox) Sandbox: usbmuxd(119) allow iokit-get-properties kCDCDoNotMatchThisDevice
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iphone 15 pro max
ios 26
Stuck at the developer mode startup interface and unable to swipe up.
Crash dump:
`Crashed Thread: 0 tid_103 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_ACCESS (SIGILL)
Exception Codes: KERN_PROTECTION_FAILURE at 0x000000016d3bfea0
Exception Codes: 0x0000000000000002, 0x000000016d3bfea0
Termination Reason: Namespace SIGNAL, Code 4 Illegal instruction: 4
Terminating Process: Unity [7873]
VM Region Info: 0x16d3bfea0 is in 0x169bbc000-0x16d3c0000; bytes after start: 58736288 bytes before end: 351
REGION TYPE START - END [ VSIZE] PRT/MAX SHRMOD REGION DETAIL
mapped file 169b00000-169ba8000 [ 672K] rw-/rwx SM=PRV Object_id=4d22156e
GAP OF 0x14000 BYTES
---> STACK GUARD 169bbc000-16d3c0000 [ 56.0M] ---/rwx SM=NUL stack guard for thread 0
Stack 16d3c0000-16dbbc000 [ 8176K] rw-/rwx SM=SHM thread 0
Thread 0 Crashed:: tid_103 Dispatch queue: com.apple.main-thread
0 libsystem_platform.dylib 0x1932ee7ac _platform_memset + 108
1 libmonobdwgc-2.0.dylib 0x33977abdc GC_clear_stack_inner + 60
2 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
3 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
4 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
5 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
6 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
7 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
8 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
9 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
10 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
11 libmonobdwgc-2.0.dylib 0x33977abf8 GC_clear_stack_inner + 88
12 libmonobdwgc-2.0.dylib 0x33976b518 GC_clear_stack + 76
13 libmonobdwgc-2.0.dylib 0x33973c074 mono_gc_alloc_obj + 112
14 libmonobdwgc-2.0.dylib 0x3396e0db4 mono_object_new_specific_checked + 72
15 libmonobdwgc-2.0.dylib 0x3396e116c ves_icall_object_new_specific + 28`
Hello,
There seems to be a regression with macOS SDK 15 and dynamically loading libraries if Address Sanitizer is turned on. Seems to only affect Debug builds, and .frameworks. I've also reported this via the Feedback Assistant: FB16513866
Here's a minimal repro, if anyone is interested: https://gist.github.com/peter-esik/6b00432e411be85333e14ae7d953966e
I thought I'd post this here, as according to my web searches, this isn't a very well-known bug at this point.
I work at a well-established university with a business journal that is over 25 years old. We have been waiting now for almost four months to have our Apple News account reviewed. In what world is this OK? No ability to communicate with anyone or have any updates except to log in once a month to see the 'under review' message still there. Seriously?
Hello!
I am trying to automate iOS builds for my Unreal Engine game using Unreal Automation Tool, but I cannot produce a functionnal build with it, while packaging from XCode works perfectly.
I have tracked down the issue to a missing file. I'm using the Firebase SDK that requires a GoogleService-Info.plist file. I have copied this file at the root of my project, as the Firebase documentation suggests. I have not taken any manual action to specify that this file needs to be included in the packaged app.
The Firebase code checks the existence of this file using
NSString* Path = [[NSBundle mainBundle] pathForResource: @“GoogleService-Info” ofType: @“plist”];
return Path != nil;
If I package my app from XCode using Product -> Archive, this test returns true and the SDK is properly initialized. If I package my app using Unreal Engine's RunUAT.sh BuildCookRun, this test returns false and the SDK fails to initialize (and actually crashes upon trying).
I have tried several Unreal Engine tricks to include my file, like setting it as a RuntimeDependecies in my projects Build.cs file. Which enables Unreal Engine code to find it, but not this direct call to NSBundle.
I would like to know either how to tell Unreal Engine to include files at the root of the app bundle, or what XCode does to automatically include this file and is there a way to script it? I can provide both versions .xcarchive if needed.
Thanks!
@MainActor class AddCarViewModel: ObservableObject {
@Published var photoUrls : [String] = []
func uploadImages(images: [Image], customerId: String) async throws {
let subFolderId = UUID().uuidString
let pictureFolderRef = Storage.storage().reference().child("CarPhotos").child(customerId).child("\(subFolderId)")
images.enumerated().forEach { index, image in
guard let imageData = image.asUIImage().jpegData(compressionQuality: 0.5) else {
return
}
let pictureReference = pictureFolderRef.child("image_\(index).jpeg")
pictureReference.putData(imageData, metadata: nil) {
metadata, error in
if let error = error {
print("failed to put data")
}
pictureReference.downloadURL { url, error in
if let error = error {
print("error while downloading url ")
}
guard let urlString = url?.absoluteString else {
return
}
self.photoUrls.append(urlString)
}
}
}
}
func addCar(carInfo: Car) async throws {
try await Firestore.firestore().collection("cars").document().setData(from: carInfo)
}
}
VStack {
Button {
Task {
do {
try await viewModel.uploadImages(images: selectedImages, customerId: viewModel.user!.uid)
try await viewModel.addCar(carInfo: Car(photoUrls: viewModel.photoUrls))
} catch {
print(error)
}
}
dismiss()
} label: {
Text("Post")
}
}
Topic:
Developer Tools & Services
SubTopic:
General
I'm running the latest iOS 26 beta 5 on my iPad and iPhone. Whenever I run these betas, I always get the message below telling me an update is available (whenever I plug in my devices). I'm assuming this is because the update check is detecting that I have something other than the latest production release. Obviously, it makes no sense to ask me to update to a prod build when I'm running the dev beta. Is there a way to turn this message off? Or maybe Apple could handle this situation better? Or maybe it's just a bug and I'm the only one getting this message?
Topic:
Developer Tools & Services
SubTopic:
General
Hello,
My app often crashes when I use simulators. I would like some help with reading the crash report that is generated. Especially with the part below Thread 0 Crashed. Based on other posts I understand that the 0x8BADF00D in the crash report is a WatchDog crash that basically says that WatchDog terminated the app because the main thread was blocked for a significant time. Many processes can block the main thread so it's hard to find out what it is in our specific case. Can someone help me reading through the crash report?
Short_crash_report.txt
Background information
The application is Xamarin Native and I use Rider as an IDE. When I use Visual Studio, the simulators run just fine. No crash occurs while using my app on a device.
The crash happens on multiple simulators with different OS versions. I already deleted XCode cache, erased content and settings of several simulators and deleted iOS DeviceSupport files.
Hi,
I’m trying to free up space on my computer and have uninstalled Xcode. However, I noticed that many large files remain on the filesystem even after uninstalling it.
The largest remaining files (~33 GB) are iOS Simulator images located at:
/System/Volumes/Data/Library/Developer/CoreSimulator/Volumes
I attempted to delete them using root privileges, but it seems that these system files are mounted as read-only.
I’m reaching out to ask for guidance to ensure that these files do not contain anything important for macOS, and that it’s safe to remove them before getting in recovery mode.
Thank you very much for your advice!
Hello everyone, my iPhone keep on showing multiple "Trust this Computer" alert simultaneously which I cannot tap on it to Trust. As a result, I cannot run my XCode project on my device. Does anyone has any ideas or solutions to fix this ?
Solution I have tried:
Reset Location & Privacy
Reset Network Settings
Enable Developer Mode
Restart Device
My devices specs:
iPhone 15 Pro: iOS 18.2.1
Macbook Pro M3 Max: Sequoia 15.1.1
Topic:
Developer Tools & Services
SubTopic:
General
Hi everyone.
I’m working on an iOS app that uses Firebase Cloud Messaging (FCM) to send push notifications. I’m encountering an issue when trying to send notifications either from Firebase Functions or directly using the FCM token with the Firebase Admin SDK and REST API.
Error Message:
FirebaseMessagingError: Auth error from APNS or Web Push Service
code: 'messaging/third-party-auth-error'
message: 'Auth error from APNS or Web Push Service'
What I’ve Set Up:
iOS App Registered in Firebase
Bundle ID: Kilovative-Designs.ParkAware
APNs Key downloaded from Apple Developer Portal
Team ID and Key ID correctly entered in Firebase Console
Firebase Admin SDK Service Account setup and used for sending
Device is successfully receiving FCM tokens
Subscribed to topics and calling Messaging.messaging().subscribe(toTopic:) works
Using firebase-admin to send FCM messages via sendToDevice or sendToTopic
What I’ve Tried:
Tested push via firebase-admin in Node.js (got same APNs auth error)
Tested with both topic-based and direct token-based push
Confirmed the .p8 key is uploaded in Firebase, with correct Key ID and Team ID
Tried generating a new APNs Auth Key
Firebase Admin SDK is initialized with the correct service account
Using Node.js firebase-admin with a known good FCM token, and sending this payload:
{
notification: {
title: "Test Notification",
body: "This is a direct FCM test"
},
token: "cxleOwi73EhFh9C5_V4hED:APA91bE3W..."
}
Returns: FirebaseMessagingError: Auth error from APNS or Web Push Service
Questions:
Are there known conditions under which Firebase throws this error even if the APNs Auth Key is present?
Does the Bundle ID need to start with com. in the Apple Developer Portal and Firebase for APNs authentication to work?
Could this be a certificate or provisioning profile mismatch issue (even when using a .p8 key)?
Is there a way to manually validate APNs authentication from Firebase outside of actual push delivery?
Any insight or guidance would be incredibly helpful. I’m new to developing and have tried repeated efforts to fix this issue but still haven’t resolved it.
Thanks in advance!
Topic:
Developer Tools & Services
SubTopic:
General
Hello Everyone, (and I hope folks at Apple are listening)
So around a year ago, I decided to take on the challenge of creating my own Iphone App from scratch. I am an engineer by trade, and thought it would be a fun interesting experience, and maybe make some money on the side. So I bought a macbook, and focused on learning Swift for the next few months.
Lots of really great developer folks helped me along the way. And I could not have been successful without so much help. It is very much appreciated. So I finished the app, created my own company. And deployed it to the Istore. Unfortunately, just no interest, I think I sold like 4 copies. No problem, still got to learn a lot along the way. So when it came time to renew my developer licence, I let it expire. Just did not make any sense to drop another $100 into it, since only 4 copies had sold in a year.
And then..... this happened!!!! I attempted to use the App that was installed on my own Iphone.... and got the message "My Apps Name" is no longer Available. and it stops... The code is on my phone. I am fully aware that I can no longer use xcode to put anything else on my iphone without a developer licence. But for Apple to reach into my own Iphone, and deny my access to something that I already created, (and in theory already paid for) is just infuriating!!! I checked, and even though it no longer exists in the IStore, purchased copies still seem to function. (one person that bought a copy was a friend of mine). So do I really need to drop another $100, puchase an actual copy of MY OWN APP from the app store, just to have it on my own phone again???!!! So much money and time went into this, that I am considering just smashing every apple product I own, and go with Android instead. I am a single person developer. Almost no one does this sort of thing anymore. Apple used to be the place where innovators could come to try to make something cool and fun to use. I guess not any more.
Dan
Topic:
Developer Tools & Services
SubTopic:
General
I’m using Developer iOS app to watch WWDC session videos. i notice it doesn’t record a video as watched after I watched it and even manual marking it using Mark as Watch has no effect.
I remember the issue started several years ago because some old WWDC videos were marked watches.
Topic:
Developer Tools & Services
SubTopic:
General
This posts collects together a bunch of information about the symbols found in a Mach-O file.
It assumes the terminology defined in An Apple Library Primer. If you’re unfamiliar with a term used here, look there for the definition.
If you have any questions or comments about this, start a new thread in the Developer Tools & Services > General topic area and tag it with Linker.
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
Understanding Mach-O Symbols
Every Mach-O file has a symbol table. This symbol table has many different uses:
During development, it’s written by the compiler.
And both read and written by the linker.
And various other tools.
During execution, it’s read by the dynamic linker.
And also by various APIs, most notably dlsym.
The symbol table is an array of entries. The format of each entry is very simple, but they have been used and combined in various creative ways to achieve a wide range of goals. For example:
In a Mach-O object file, there’s an entry for each symbol exported to the linker.
In a Mach-O image, there’s an entry for each symbol exported to the dynamic linker.
And an entry for each symbol imported from dynamic libraries.
Some entries hold information used by the debugger. See Debug Symbols, below.
Examining the Symbol Table
There are numerous tools to view and manipulate the symbol table, including nm, dyld_info, symbols, strip, and nmedit. Each of these has its own man page.
A good place to start is nm:
% nm Products/Debug/TestSymTab
U ___stdoutp
0000000100000000 T __mh_execute_header
U _fprintf
U _getpid
0000000100003f44 T _main
0000000100008000 d _tDefault
0000000100003ecc T _test
0000000100003f04 t _testHelper
Note In the examples in this post, TestSymTab is a Mach-O executable that’s formed by linking two Mach-O object files, main.o and TestCore.o.
There are three columns here, and the second is the most important. It’s a single letter indicating the type of the entry. For example, T is a code symbol (in Unix parlance, code is in the text segment), D is a data symbol, and so on. An uppercase letter indicates that the symbol is visible to the linker; a lowercase letter indicates that it’s internal.
An undefined (U) symbol has two potential meanings:
In a Mach-O image, the symbol is typically imported from a specific dynamic library. The dynamic linker connects this import to the corresponding exported symbol of the dynamic library at load time.
In a Mach-O object file, the symbol is undefined. In most cases the linker will try to resolve this symbol at link time.
Note The above is a bit vague because there are numerous edge cases in how the system handles undefined symbols. For more on this, see Undefined Symbols, below.
The first column in the nm output is the address associated with the entry, or blank if an address is not relevant for this type of entry. For a Mach-O image, this address is based on the load address, so the actual address at runtime is offset by the slide. See An Apple Library Primer for more about those concepts.
The third column is the name for this entry. These names have a leading underscore because that’s the standard name mangling for C. See An Apple Library Primer for more about name mangling.
The nm tool has a lot of formatting options. The ones I use the most are:
-m — This prints more information about each symbol table entry. For example, if a symbol is imported from a dynamic library, this prints the library name. For a concrete example, see A Deeper Examination below.
-a — This prints all the entries, including debug symbols. We’ll come back to that in the Debug Symbols section, below.
-p — By default nm sorts entries by their address. This disables that sort, causing nm to print the entries in the order in which they occur in the symbol table.
-x — This outputs entries in a raw format, which is great when you’re trying to understand what’s really going on. See Raw Symbol Information, below, for an example of this.
A Deeper Examination
To get more information about each symbol table, run nm with the -m option:
% nm -m Products/Debug/TestSymTab
(undefined) external ___stdoutp (from libSystem)
0000000100000000 (__TEXT,__text) [referenced dynamically] external __mh_execute_header
(undefined) external _fprintf (from libSystem)
(undefined) external _getpid (from libSystem)
0000000100003f44 (__TEXT,__text) external _main
0000000100008000 (__DATA,__data) non-external _tDefault
0000000100003ecc (__TEXT,__text) external _test
0000000100003f04 (__TEXT,__text) non-external _testHelper
This contains a world of extra information about each entry. For example:
You no longer have to remember cryptic single letter codes. Instead of U, you get undefined.
If the symbol is imported from a dynamic library, it gives the name of that dynamic library. Here we see that _fprintf is imported from the libSystem library.
It surfaces additional, more obscure information. For example, the referenced dynamically flag is a flag used by the linker to indicate that a symbol is… well… referenced dynamically, and thus shouldn’t be dead stripped.
Undefined Symbols
Mach-O’s handling of undefined symbols is quite complex. To start, you need to draw a distinction between the linker (aka the static linker) and the dynamic linker.
Undefined Symbols at Link Time
The linker takes a set of files as its input and produces a single file as its output. The input files can be Mach-O images or dynamic libraries [1]. The output file is typically a Mach-O image [2]. The goal of the linker is to merge the object files, resolving any undefined symbols used by those object files, and create the Mach-O image.
There are two standard ways to resolve an undefined symbol:
To a symbol exported by another Mach-O object file
To a symbol exported by a dynamic library
In the first case, the undefined symbol disappears in a puff of linker magic. In the second case, it records that the generated Mach-O image depends on that dynamic library [3] and adds a symbol table entry for that specific symbol. That entry is also shown as undefined, but it now indicates the library that the symbol is being imported from.
This is the core of the two-level namespace. A Mach-O image that imports a symbol records both the symbol name and the library that exports the symbol.
The above describes the standard ways used by the linker to resolve symbols. However, there are many subtleties here. The most radical is the flat namespace. That’s out of scope for this post, because it’s a really bad option for the vast majority of products. However, if you’re curious, the ld man page has some info about how symbol resolution works in that case.
A more interesting case is the -undefined dynamic_lookup option. This represents a halfway house between the two-level namespace and the flat namespace. When you link a Mach-O image with this option, the linker resolves any undefined symbols by adding a dynamic lookup undefined entry to the symbol table. At load time, the dynamic linker attempts to resolve that symbol by searching all loaded images. This is useful if your software works on other Unix-y platforms, where a flat namespace is the norm. It can simplify your build system without going all the way to the flat namespace.
Of course, if you use this facility and there are multiple libraries that export that symbol, you might be in for a surprise!
[1] These days it’s more common for the build system to pass a stub library (.tbd) to the linker. The effect is much the same as passing in a dynamic library. In this discussion I’m sticking with the old mechanism, so just assume that I mean dynamic library or stub library.
If you’re unfamiliar with the concept of a stub library, see An Apple Library Primer.
[2] The linker can also merge the object files together into a single object file, but that’s relatively uncommon operation. For more on that, see the discussion of the -r option in the ld man page.
[3] It adds an LC_LOAD_DYLIB load command with the install name from the dynamic library. See Dynamic Library Identification for more on that.
Undefined Symbols at Load Time
When you load a Mach-O image the dynamic linker is responsible for finding all the libraries it depends on, loading them, and connecting your imports to their exports. In the typical case the undefined entry in your symbol table records the symbol name and the library that exports the symbol. This allows the dynamic linker to quickly and unambiguously find the correct symbol. However, if the entry is marked as dynamic lookup [1], the dynamic linker will search all loaded images for the symbol and connect your library to the first one it finds.
If the dynamic linker is unable to find a symbol, its default behaviour is to fail the load of the Mach-O image. This changes if the symbol is a weak reference. In that case, the dynamic linking continues to load the image but sets the address of the symbol to NULL. See Weak vs Weak vs Weak, below, for more about this.
[1] In this case nm shows the library name as dynamically looked up.
Weak vs Weak vs Weak
Mach-O supports two different types of weak symbols:
Weak references (aka weak imports)
Weak definitions
IMPORTANT If you use the term weak without qualification, the meaning depends on your audience. App developers tend to assume that you mean a weak reference whereas folks with a C++ background tend to assume that you mean a weak definition. It’s best to be specific.
Weak References
Weak references support the availability mechanism on Apple platforms. Most developers build their apps with the latest SDK and specify a deployment target, that is, the oldest OS version on which their app runs. Within the SDK, each declaration is annotated with the OS version that introduced that symbol [1]. If the app uses a symbol introduced later than its deployment target, the compiler flags that import as a weak reference. The app is then responsible for not using the symbol if it’s run on an OS release where it’s not available.
For example, consider this snippet:
#include <xpc/xpc.h>
void testWeakReference(void) {
printf("%p\n", xpc_listener_set_peer_code_signing_requirement);
}
The xpc_listener_set_peer_code_signing_requirement function is declared like so:
API_AVAILABLE(macos(14.4))
…
int
xpc_listener_set_peer_code_signing_requirement(…);
The API_AVAILABLE macro indicates that the symbol was introduced in macOS 14.4. If you build this code with the deployment target set to macOS 13, the symbol is marked as a weak reference:
% nm -m Products/Debug/TestWeakRefC
…
(undefined) weak external _xpc_listener_set_peer_code_signing_requirement (from libSystem)
If you run the above program on macOS 13, it’ll print NULL (actually 0x0).
Without support for weak references, the dynamic linker on macOS 13 would fail to load the program because the _xpc_listener_set_peer_code_signing_requirement symbol is unavailable.
[1] In practice most of the SDK’s declarations don’t have availability annotations because they were introduced before the minimum deployment target supported by that SDK.
Weak definitions
Weak references are about imports. Weak definitions are about exports. A weak definition allows you to export a symbol from multiple images. The dynamic linker coalesces these symbol definitions. Specifically:
The first time it loads a library with a given weak definition, the dynamic linker makes it the primary.
It registers that definition such that all references to the symbol resolve to it. This registration occurs in a namespace dedicated to weak definitions. That namespace is flat.
Any subsequent definitions of that symbol are ignored.
Weak definitions are weird, but they’re necessary to support C++’s One Definition Rule in a dynamically linked environment.
IMPORTANT Weak definitions are not just weird, but also inefficient. Avoid them where you can. To flush out any unexpected weak definitions, pass the -warn_weak_exports option to the static linker.
The easiest way to create a weak definition is with the weak attribute:
__attribute__((weak))
void testWeakDefinition(void) {
}
IMPORTANT The C++ compiler can generate weak definitions without weak ever appearing in your code.
This shows up in nm like so:
% nm -m Products/Debug/TestWeakDefC
…
0000000100003f40 (__TEXT,__text) weak external _testWeakDefinition
…
The output is quite subtle. A symbol flagged as weak external is either a weak reference or a weak definition depending on whether it’s undefined or not. For clarity, use dyld_info instead:
% dyld_info -imports -exports Products/Debug/TestWeakRefC
Products/Debug/TestWeakDefC [arm64]:
…
-imports:
…
0x0001 _xpc_listener_set_peer_code_signing_requirement [weak-import] (from libSystem)
% dyld_info -imports -exports Products/Debug/TestWeakDefC
Products/Debug/TestWeakDefC [arm64]:
-exports:
offset symbol
…
0x00003F40 _testWeakDefinition [weak-def]
…
…
Here, weak-import indicates a weak reference and weak-def a weak definition.
Weak Library
There’s one final confusing use of the term weak, that is, weak libraries. A Mach-O image includes a list of imported libraries and a list of symbols along with the libraries they’re imported from. If an image references a library that’s not present, the dynamic linker will fail to load the library even if all the symbols it references in that library are weak references.
To get around this you need to mark the library itself as weak. If you’re using Xcode it will often do this for your automatically. If it doesn’t, mark the library as optional in the Link Binary with Libraries build phase.
Use otool to see whether a library is required or optional. For example, this shows an optional library:
% otool -L Products/Debug/TestWeakRefC
Products/Debug/TestWeakRefC:
/usr/lib/libEndpointSecurity.dylib (… 511.60.5, weak)
…
In the non-optional case, there’s no weak indicator:
% otool -L Products/Debug/TestWeakRefC
Products/Debug/TestWeakRefC:
/usr/lib/libEndpointSecurity.dylib (… 511.60.5)
…
Debug Symbols
or Why the DWARF still stabs. (-:
Historically, all debug information was stored in symbol table entries, using a format knows as stabs. This format is now obsolete, having been largely replaced by DWARF. However, stabs symbols are still used for some specific roles.
Note See <mach-o/stab.h> and the stab man page for more about stabs on Apple platforms. See stabs and DWARF for general information about these formats.
In DWARF, debug symbols aren’t stored in the symbol table. Rather, debug information is stored in various __DWARF sections. For example:
% otool -l Intermediates.noindex/TestSymTab.build/Debug/TestSymTab.build/Objects-normal/arm64/TestCore.o | grep __DWARF -B 1
sectname __debug_abbrev
segname __DWARF
…
The compiler inserts this debug information into the Mach-O object file that it creates. Eventually this Mach-O object file is linked into a Mach-O image. At that point one of two things happens, depending on the Debug Information Format build setting.
During day-to-day development, set Debug Information Format to DWARF. When the linker creates a Mach-O image from a bunch of Mach-O object files, it doesn’t do anything with the DWARF information in those objects. Rather, it records references to the source objects files into the final image. This is super quick.
When you debug that Mach-O image, the debugger finds those references and uses them to locate the DWARF information in the original Mach-O object files.
Each reference is stored in a stabs OSO symbol table entry. To see them, run nm with the -a option:
% nm -a Products/Debug/TestSymTab
…
0000000000000000 - 00 0001 OSO …/Intermediates.noindex/TestSymTab.build/Debug/TestSymTab.build/Objects-normal/arm64/TestCore.o
0000000000000000 - 00 0001 OSO …/Intermediates.noindex/TestSymTab.build/Debug/TestSymTab.build/Objects-normal/arm64/main.o
…
Given the above, the debugger knows to look for DWARF information in TestCore.o and main.o. And notably, the executable does not contain any DWARF sections:
% otool -l Products/Debug/TestSymTab | grep __DWARF -B 1
%
When you build your app for distribution, set Debug Information Format to DWARF with dSYM File. The executable now contains no DWARF information:
% otool -l Products/Release/TestSymTab | grep __DWARF -B 1
%
Xcode runs dsymutil tool to collect the DWARF information, organise it, and export a .dSYM file. This is actually a document package, within which is a Mach-O dSYM companion file:
% find Products/Release/TestSymTab.dSYM
Products/Release/TestSymTab.dSYM
Products/Release/TestSymTab.dSYM/Contents
…
Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF
Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab
…
% file Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab
Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab: Mach-O 64-bit dSYM companion file arm64
That file contains a copy of the the DWARF information from all the original Mach-O object files, optimised for use by the debugger:
% otool -l Products/Release/TestSymTab.dSYM/Contents/Resources/DWARF/TestSymTab | grep __DWARF -B 1
…
sectname __debug_line
segname __DWARF
…
Raw Symbol Information
As described above, each Mach-O file has a symbol table that’s an array of symbol table entries. The structure of each entry is defined by the declarations in <mach-o/nlist.h> [1]. While there is an nlist man page, the best documentation for this format is the the comments in the header itself.
Note The terms nlist stands for name list and dates back to truly ancient versions of Unix.
Each entry is represented by an nlist_64 structure (nlist for 32-bit Mach-O files) with five fields:
n_strx ‘points’ to the string for this entry.
n_type encodes the entry type. This is actually split up into four subfields, as discussed below.
n_sect is the section number for this entry.
n_desc is additional information.
n_value is the address of the symbol.
The four fields within n_type are N_STAB (3 bits), N_PEXT (1 bit), N_TYPE (3 bits), and N_EXT (1 bit).
To see these raw values, run nm with the -x option:
% nm -a -x Products/Debug/TestSymTab
…
0000000000000000 01 00 0300 00000036 _getpid
0000000100003f44 24 01 0000 00000016 _main
0000000100003f44 0f 01 0000 00000016 _main
…
This prints a column for n_value, n_type, n_sect, n_desc, and n_strx. The last column is the string you get when you follow the ‘pointer’ in n_strx.
The mechanism used to encode all the necessary info into these fields is both complex and arcane. For the details, see the comments in <mach-o/nlist.h> and <mach-o/stab.h>. However, just to give you a taste:
The entry for getpid has an n_type field with just the N_EXT flag set, indicating that this is an external symbol. The n_sect field is 0, indicating a text symbol. And n_desc is 0x0300, with the top byte indicating that the symbol is imported from the third dynamic library.
The first entry for _main has an n_type field set to N_FUN, indicating a stabs function symbol. The n_desc field is the line number, that is, line 22.
The second entry for _main has an n_type field with N_TYPE set to N_SECT and the N_EXT flag set, indicating a symbol exported from a section. In this case the section number is 1, that is, the text section.
[1] There is also an <nlist.h> header that defines an API that returns the symbol table. The difference between <nlist.h> and <mach-o/nlist.h> is that the former defines an API whereas the latter defines the Mach-O on-disk format. Don’t include both; that won’t end well!
In Simulator Korean character system has not working well.
I want to type "", however, if I type the same thing on the simulator's virtual keyboard (Korean), it comes out as ''.
I think this is caused by IME system in ios simulator bug. I think this has been happening since IOS 17.
Hi!
Do the consoles in the App Store Connect differ by country?
In particular, there are mentions on the Internet that in China the publisher can make refunds to users, but there is no such function in the American account.
Topic:
Developer Tools & Services
SubTopic:
General
iPhone does not show Xcode app when plugged to MacBook. Anybody know something about viewing your app on your iPhone? Thanks
Hello,
PrivacyInfo.xcprivacy Is primordial and without it the app is rejected from the Store I believe.
All 5 ressources I had found related to it, mention XCODE, or explain how to add the code to langages that I don't use (Switf i think?) etc.
I am building the app thought CI/CD, so prior to building it the app does not have privacy manifest and there is not way to generate it automatically without xcode it seems.
My app is written in Flutter prior to becoming an iOS app.
I am seeking for a method to do that. Thanks.
I have developed a Swift macro called @CodableInit in the SwiftCodableMacro module, and I’m able to use it successfully in my main project.
Here’s an example usage:
import SwiftCodableMacro
@CodableInit // This is for Codable macros
public class ErrorMonitoringWebPlugin {
public var identifier: UUID = UUID()
// MARK: - Codable
required public init(from decoder:Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
identifier = try values.decode(UUID.self, forKey: .identifier)
}
}
However, when I try to write a unit test for the ErrorMonitoringWebPlugin class, I encounter an issue. Here's the test case:
func testCodableSubjectIdentifierShouldEqualDecodedSubjectIdentifier() {
self.measure {
let encoder = JSONEncoder()
let data = try? encoder.encode(subject)
//Here I am getting this error
Class 'JSONEncoder' requires that 'ErrorMonitoringWebPlugin' conform to 'Encodable'
let decoder = JSONDecoder()
let decodedSubject = try? decoder.decode(ErrorMonitoringWebPlugin.self, from: data!)
XCTAssertEqual(subject.identifier, decodedSubject?.identifier)
}
}
The compiler throws an error saying:
Class 'JSONEncoder' requires that 'ErrorMonitoringWebPlugin' conform to 'Encodable'
Even though the @CodableInit macro is supposed to generate conformance, it seems that this macro-generated code is not visible or active inside the test target.
How can I ensure that the @CodableInit macro (from SwiftCodableMacro) is correctly applied and recognized within the XCTest target of my main project?