#include <stdio.h> void test50() { unsigned int b = 0x7d40d133; unsigned int m = 0x22e5bbf; unsigned int r = 64; b += (((m) << ((int)(r))) | ((m) >> (32 - (int)(r)))); // expect b = 0x7f6f2cf2, however in opt bigger than O1, b = 0x819d88b1 printf("%#x\n", b); } int main() { test50(); return 0; } Compiling with -O0 and -O1 produces different results. There appears to be a compiler optimization bug that is triggered when r % 32 == 0，This feature works correctly in Xcode 26.0.

Is std::move_only_function or std:execution planned for an upcoming Xcode/libc++ release? The C++ compiler support page indicates that it is not currently implemented (Apple developer forums won't let me share a link to this page). Is the planned support for Xcode/libc++ published anywhere? If not, is there any particular release that I should be watching out for?

Hello, everyone! I've discovered a bug similar to libstdc++/115939 in GCC. This bug exists for a while. Did someone face it too? I'd be glad to accept any advise. Thank you in advance!

Hello, I was wondering about the timeline for C23 library features being added to libSystem, specifically the %b printf format specifier for binary output. Currently, printf("%b\n", 42) on macOS just prints b rather than the expected binary representation. This and other C23 library additions would be great to have. Are there plans to include these in an upcoming release? Thank you.

After enabling Enhanced Security for an existing iOS project (mixed Objective-C / Swift) I get the linker error: Library 'c++polyfills' not found This happens when compiling for a simulator as run destination. Device builds (debug) or archiving a release build works. However I need to be able to test on a simulator... Xcode version is 26.4.1, Simulator uses iOS 26.4.1

It didn't happen with Xcode 16.2 that I used before, but after updating to 16.3, when I build the app, the following error is output to the console and the app doesn't run. dyld[2150]: Symbol not found: ___cxa_current_primary_exception Referenced from: <6B00A4F2-B208-3FDB-BA38-B7095AF0034A> /private/var/containers/Bundle/Application/B590DB18-9C66-4C9E-8330-104943419E60/Mubeat DEV.app/Mubeat DEV.debug.dylib Expected in: <7F51CB08-A0CA-386E-BB62-4B8BFB0CED9F> /usr/lib/libc++.1.dylib Symbol not found: ___cxa_current_primary_exception Referenced from: <6B00A4F2-B208-3FDB-BA38-B7095AF0034A> /private/var/containers/Bundle/Application/B590DB18-9C66-4C9E-8330-104943419E60/Mubeat DEV.app/Mubeat DEV.debug.dylib Expected in: <7F51CB08-A0CA-386E-BB62-4B8BFB0CED9F> /usr/lib/libc++.1.dylib dyld config: DYLD_LIBRARY_PATH=/usr/lib/system/introspection DYLD_INSERT_LIBRARIES=/usr/lib/libBacktraceRecording.dylib:/usr/lib/libMainThreadChecker.dylib:/usr/lib/libRPAC.dylib:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib After looking for another solution, I found a way to remove the -Objc option in Other Linker Flags, but this method only works on iOS 18.4 and doesn't work on other versions. Is there another solution?

Hello, From what I have heard, macOS will soon phase out Rosetta. I was wondering if Rosetta will still be available to install separately (instead of being preinstalled). I don't use Rosetta to run applications, because all the applications I use are ARM. However, for my YouTube channel, I often use the -arch x86_64 flag with clang. I do this so I can show the result from objdump and teach x86_64 Assembly, while also running the program through Rosetta. This may be a very niche use case, however I was still curious. Thank you!

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 can create an ipa file with vs using the wildcard bundle identifier but this is rejected by apple when I upload with the Transporter app saying invalid identifier and no distribution profile/certificate. When I create a new distribution profile with the correct XC identifier and distribution certificate and try to archive with visual studio publish says the bundle id is not a match for the distribution profile with iOS? This is a net 10 net maui project and my first build attempt

LLVM Linker Crash on ARM64 with bfloat16 Symbols (Xcode 17.0.0) We're encountering a critical linker crash in Xcode 17.0.0 (clang-1700.4.4.1) on macOS 15.1.0 (Darwin 25.1.0) with Apple Silicon M3 Max when linking a pybind11 C++ extension against the MLX framework (v0.30.1). The linker consistently crashes with LLVM ERROR: No way to correctly truncate anything but float to bfloat during the linking phase, even though our code uses only integer types (int64, uint32) for BPE tokenization and never directly references bfloat16 types. Error Details: [100%] Linking CXX shared module _metal_trainer.cpython-312-darwin.so LLVM ERROR: No way to correctly truncate anything but float to bfloat clang++: error: unable to execute command: Abort trap: 6 clang++: error: linker command failed due to signal (use -v to see invocation) Reproduction: Install MLX framework: pip install mlx (any version with bfloat16 support) Create a minimal pybind11 extension that links against MLX: Compiler: AppleClang 17.0.0.17000404 Target: arm64-apple-darwin25.1.0 Flags: -std=c++17 -O2 -march=native Link against: libmlx.dylib (contains bfloat16 symbols) Run: cmake .. && make Linker crashes during final linking phase Root Cause: The LLVM ARM64 backend in Xcode 17.0.0 has a code generation bug when processing bfloat16 truncation operations during link-time. The crash occurs when the linker processes bfloat16 symbols from libmlx.dylib, regardless of whether the application code uses them. The error originates from LLVM's type legalization pass attempting to truncate bfloat16 values, but the ARM64 backend lacks a valid code path for this operation. Workarounds Attempted (all failed): Disabling LTO: INTERPROCEDURAL_OPTIMIZATION FALSE Linker flags: -Wl,-no_compact_unwind, -fno-lto Runtime symbol resolution: -undefined dynamic_lookup Compiler optimizations: Changed from -O3 to -O2 Impact: This blocks any C++ extension development that links against libraries containing bfloat16 symbols on Xcode 17.0.0. The issue does not occur on Xcode 16.x. Linker Crash Dump Location: /var/folders/gn/7_g6wy1j66b8z3lkywyrbsx00000gn/T/linker-crash-* Expected Behavior: Linker should successfully link the extension, or at minimum, gracefully handle bfloat16 symbols without crashing. Temporary Solution: Downgrade to Xcode 16.x or use Python-only implementations until this is fixed in a future Xcode release.

I am developing an iOS in-app SDK for collecting code coverage data. The SDK writes coverage data to a specified file by calling __llvm_profile_set_filename and __llvm_profile_write_file. This implementation worked correctly until I switched to Xcode 26.0 to build my project. Now, when __llvm_profile_write_file() is executed, it crashes with the following error stack. Can anyone provide any assistance? Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000001 Exception Codes: 0x0000000000000001, 0x0000000000000001 Termination Reason: Namespace SIGNAL, Code 11, Segmentation fault: 11 Terminating Process: exc handler [454] Thread 96 name: Dispatch queue: com.test-coverage.processing Thread 96: Crashed: 0 Demo 0x122602ea8 initializeValueProfRuntimeRecord (in Demo) (InstrProfilingValue.c:351) 1 Demo 0x00000001226064c0 writeOneValueProfData (in Demo) (InstrProfilingWriter.c:153) 2 Demo 0x0000000122606308 writeValueProfData (in Demo) (InstrProfilingWriter.c:234) 3 Demo 0x00000001226060d0 lprofWriteDataImpl (in Demo) (InstrProfilingWriter.c:401) 4 Demo 0x0000000122605d98 lprofWriteData (in Demo) (InstrProfilingWriter.c:261) 5 Demo 0x0000000122604804 writeFile (in Demo) (InstrProfilingFile.c:536) 6 Demo 0x122604664 __llvm_profile_write_file_alias + 228 7 Demo 0x000000011c6dd108 -[BDTestCoverage p_dumpMainCoverageInfoWithCustomKey:] (in Demo) (TestCoverage.m:995) 8 Demo 0x000000011c6dcef8 -[BDTestCoverage p_dumpAllCoverageProfileWithCustomKey:] (in Demo) (TestCoverage.m:970)

Failed to generate code coverage report when doing Swift Testing on iPhone device, but it's ok in UI testing or running on "My Mac(Designed for iPad)". I have enable code coverage in test plan. My app can't run on simulator due to frameworks limitations. Platform: Mac mini M2 w/ macOS15.7, iPhoneXR 18.6.2 Xcode version: 26.1 & 16.0 error msg: Failed to download profiles from paths ["/private/var/mobile/Containers/Data/Application/76A1F9BC-98C8-4349-998B-0FC030DEE3EC/tmp/3A424286-872D-40AD-B4CA-65B232B57EB4"] on device 'iPhoneXR' for application with bundle ID 'xxx.xxxx.xxxx' to directory /Users//Library/Developer/Xcode/DerivedData/-bosqsqmqiqwweldrfrtgsfpnhroht/Build/ProfileData/00008020-00042C2A3E38002E: Failed to retrieve the file node for tmp/3A424286-872D-40AD-B4CA-65B232B57EB4. (Underlying Error: Failed to retrieve the file node for tmp/3A424286-872D-40AD-B4CA-65B232B57EB4)

Hello, Is there any plan to integrate realtime sanitier (RTSan) in Apple Clang? This tool has been introduced in Clang 20.1.0 back in March 2025. This tool is incredibly useful, and having it in AppleClang (and ideally integrated in Xcode and xcodebuild) would be great. Thank you, Best, Thomas

Fails to gather code coverage and throws this error Showing All Messages Failed to merge raw profiles in directory /Users//Library/Developer/Xcode/DerivedData/Receiver-ekqrbpsaciuxmlfslviajhoecyat/Build/ProfileData/0B0C6B69-FD46-4801-B106-56B7FCD44370 to destination /Users//Library/Developer/Xcode/DerivedData/Receiver-ekqrbpsaciuxmlfslviajhoecyat/Build/ProfileData/0B0C6B69-FD46-4801-B106-56B7FCD44370/Coverage.profdata: Aggregation tool '/Users/shwethamugeraya/Downloads/Xcode 2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/llvm-profdata' failed with exit code 1: warning: /Users/shwethamugeraya/Library/Developer/Xcode/DerivedData/Receiver-ekqrbpsaciuxmlfslviajhoecyat/Build/ProfileData/0B0C6B69-FD46-4801-B106-56B7FCD44370/2F4EFBF7-1CCF-4E9E-8FD6-482EEDB98B6C-34646.profraw: raw profile version mismatch: Profile uses raw profile format version = 4; expected version = 8 PLEASE update this tool to version in the raw profile, or regenerate raw profile with expected version. error: no profile can be merged

After uprgading to new XCode version 26.0.1 my project can't be longer build. There are strange compiler errors without concrete error message. If I want to investigate the single errors they disappears on selection... I can send a recorded screen-video. I invested over 2 weeks on trying to solve the problem without success. That's not the first time that the project couldnt be build after a xcode upgrade. Thats really annoying.

After upgrading to macOS Tahoe 26.0.1, I encountered an issue where the debugger could no longer display standard C++ library types such as std::map, std::string, and other std:: containers. Instead, the debugger simply showed: Summary Unavailable 🧪 What I Tried • Switched from the default LLVM compiler to GDB to check if it was a debugger-related problem — no improvement. • Cleaned and rebuilt the project — the issue persisted. ✅ Solution Downgrading Xcode to version 16.4 immediately resolved the issue. According to Apple’s official Xcode support documentation, Xcode 16.4 is compatible with macOS Sequoia 15.6 and later, which includes macOS Tahoe 26.0.1. This suggests that the problem may be caused by a compatibility issue in the latest Command Line Tools bundled with newer versions of Xcode. 💡 Takeaway If you encounter the same problem: 1. Try downgrading to Xcode 16.4 or reinstalling the corresponding Command Line Tools. 2. Make sure your debugger (LLDB or GDB) is correctly linked to the appropriate SDK version. Hopefully this helps anyone experiencing the same issue!

After upgrading to macOS Tahoe 26.0.1, I encountered an issue where the debugger could no longer display standard C++ library types such as std::map, std::string, and other std:: containers. Instead, the debugger simply showed: Summary Unavailable 🧪 What I Tried • Switched from the default LLVM compiler to GDB to check if it was a debugger-related problem — no improvement. • Cleaned and rebuilt the project — the issue persisted. ✅ Solution Downgrading Xcode to version 16.4 immediately resolved the issue. According to Apple’s official Xcode support documentation, Xcode 16.4 is compatible with macOS Sequoia 15.6 and later, which includes macOS Tahoe 26.0.1. This suggests that the problem may be caused by a compatibility issue in the latest Command Line Tools bundled with newer versions of Xcode. 💡 Takeaway If you encounter the same problem: Try downgrading to Xcode 16.4 or reinstalling the corresponding Command Line Tools. Make sure your debugger (LLDB or GDB) is correctly linked to the appropriate SDK version. Hopefully this helps anyone experiencing the same issue!

In my app target Foo, I have a dependency on package Bar. Bar itself have a dependency on another package Other. In my test target FooTests, I have a dependency on package BarTestsHelpers. BarTestsHelpers depends on Bar. When compiling test target FooTests, I get the following unexpected warning in Xcode 26 only: 'Bar' is missing a dependency on 'Other' because dependency scan of Swift module 'Bar' discovered a dependency on 'Other' I can see this is being discussed here as well without a solution. I filled a feedback with a sample project here: FB20602885 It seems that we can remove the warning by explicitly adding the dependency Other on BarTestHelpers. But this shouldn't be needed as BarTestHelpers doesn't use nor know about Other, it only needs it as part of its dependency on Bar.

When upgrading to a new version of Xcode, normally we look in the "Toolchain version history" table of the Xcode wikipedia page. But for Xcode 16.2, it lists git tag swift-6.0.3-RELEASE, which fails to compile with a known error. There was a fix for this error way back on July 4, 2024, but for some reason this fix does not appear in swift-6.0.3-RELEASE (as confirmed with git log, even though the tag occurred on December 2, 2024). So it turns out the minimum tag is swift-6.1-RELEASE for building LLVM with Xcode 16.2 (there are no other release tags between these two). Is it possible that the wikipedia table is simply incorrect in this case? If not, is there a workaround to build swift-6.0.3-RELEASE using Xcode 16.2, as published by Apple?

Hi all, I’m running into a persistent build issue with my Swift project ORSOFINAL after migrating from Xcode stable to Xcode-beta.app 26 (June 2025 version). ⸻ 💥 Errors displayed: 1. C99 was enabled in PCH file but is currently disabled 2. module file .../ModuleCache.noindex/SwiftShims-AXUM98L131W4...pcm cannot be loaded due to a configuration mismatch with the current compilation 3. missing required module 'SwiftShims' ⸻ 🛠 What I’ve already tried: • xcode-select -s /Applications/Xcode-beta.app/Contents/Developer • Deleted ~/Library/Developer/Xcode/DerivedData, ModuleCache.noindex, Archives, and Products • Ran sudo xcodebuild -runFirstLaunch • Clean Build Folder in Xcode-beta • Verified Command Line Tools setting points to Xcode-beta ⸻ ❓Looking for guidance on: • Whether this is a known bug in Xcode-beta • If SwiftShims/PCM conflicts are expected between versions • Best practices to safely migrate from Xcode stable to beta for Swift-based projects Any advice is much appreciated. Thanks, Mathéo