In some recent releases of macos (14.x and 15.x), we have noticed what seems to be a slower dlopen() implementation. I don't have any numbers to support this theory. I happened to notice this "slowness" when investigating something unrelated. In one part of the code we have a call of the form: const char * fooBarLib = ....; dlopen(fooBarLib, RTLD_NOW + RTLD_GLOBAL); It so happened that due to some timing related issues, the process was crashing. A slow execution of code in this part of the code would trigger an issue in some other part of the code that would then lead to a process crash. The crash itself isn't a concern, because it's an internal issue that will addressed in the application code. What was interesting is that the slowness appears to be contributed by the call to dlopen(). Specifically, whenever a slowness was observed, the crash reports showed stack frames of the form: Thread 1: 0 dyld 0x18f08b5b4 _kernelrpc_mach_vm_protect_trap + 8 1 dyld 0x18f08f540 vm_protect + 52 2 dyld 0x18f0b87e0 lsl::MemoryManager::writeProtect(bool) + 204 3 dyld 0x18f0a7fe4 invocation function for block in dyld4::Loader::findAndRunAllInitializers(dyld4::RuntimeState&) const + 932 4 dyld 0x18f0e629c invocation function for block in dyld3::MachOAnalyzer::forEachInitializer(Diagnostics&, dyld3::MachOAnalyzer::VMAddrConverter const&, void (unsigned int) block_pointer, void const*) const + 172 5 dyld 0x18f0d9c38 invocation function for block in dyld3::MachOFile::forEachSection(void (dyld3::MachOFile::SectionInfo const&, bool, bool&) block_pointer) const + 496 6 dyld 0x18f08c2dc dyld3::MachOFile::forEachLoadCommand(Diagnostics&, void (load_command const*, bool&) block_pointer) const + 300 7 dyld 0x18f0d8bcc dyld3::MachOFile::forEachSection(void (dyld3::MachOFile::SectionInfo const&, bool, bool&) block_pointer) const + 192 8 dyld 0x18f0db5a0 dyld3::MachOFile::forEachInitializerPointerSection(Diagnostics&, void (unsigned int, unsigned int, bool&) block_pointer) const + 160 9 dyld 0x18f0e5f90 dyld3::MachOAnalyzer::forEachInitializer(Diagnostics&, dyld3::MachOAnalyzer::VMAddrConverter const&, void (unsigned int) block_pointer, void const*) const + 432 10 dyld 0x18f0a7bb4 dyld4::Loader::findAndRunAllInitializers(dyld4::RuntimeState&) const + 176 11 dyld 0x18f0af190 dyld4::JustInTimeLoader::runInitializers(dyld4::RuntimeState&) const + 36 12 dyld 0x18f0a8270 dyld4::Loader::runInitializersBottomUp(dyld4::RuntimeState&, dyld3::Array<dyld4::Loader const*>&, dyld3::Array<dyld4::Loader const*>&) const + 312 13 dyld 0x18f0ac560 dyld4::Loader::runInitializersBottomUpPlusUpwardLinks(dyld4::RuntimeState&) const::$_0::operator()() const + 180 14 dyld 0x18f0a8460 dyld4::Loader::runInitializersBottomUpPlusUpwardLinks(dyld4::RuntimeState&) const + 412 15 dyld 0x18f0c089c dyld4::APIs::dlopen_from(char const*, int, void*) + 2432 16 libjli.dylib 0x1025515b4 DoFooBar + 56 17 libjli.dylib 0x10254d2c0 Hello_World_Launch + 1160 18 helloworld 0x10250bbb4 main + 404 19 libjli.dylib 0x102552148 apple_main + 88 20 libsystem_pthread.dylib 0x18f4132e4 _pthread_start + 136 21 libsystem_pthread.dylib 0x18f40e0fc thread_start + 8 So, out of curiosity, have there been any known changes in the implementation of dlopen() which might explain the slowness? Like I noted, I don't have concrete numbers, but to quantify the slowness I don't think it's slower by a noticeable amount - maybe a few milli seconds. I guess what I am trying to understand is, whether there's anything that needs attention here.

Until recently, it was possible to view the profiles of every user who posted in the forums. The profile page would then have links to posts/replies and other pages so that one could "follow" the recent comments by those users. However, it appears that it no longer is possible to view a profile of individual "DTS Engineer". What I mean is I can no longer view their profile page and as a result the recent posts/replies that a specific "DTS Engineer" makes. It's especially a loss because posts made by such engineers are very helpful and valuable and not being able to easily follow such posts on a single page makes the forum software less useful. Is there a way the previous feature can be brought back?

Around a month back, developers of the OpenJDK project, when using XCode 16 to build the JDK started noticing odd failures when executing code which was compiled using the clang++ compiler shipped in that XCode 16 release (details in https://bugs.openjdk.org/browse/JDK-8340341). Specifically, a trivial for loop in a c++ code of the form: int limit = ... // method local variable for (i=0; i<limit; i++) { ... } ends up iterating more times than the specified limit. The "i<limit" returns true even when it should have returned false. In fact, debug log messages within the for loop of the form: fprintf(stderr, "parsing %d of %d, %d < % d == %s", i, limit, i, limit, (i<limit) ? "true" : "false"); would show output of the form: parsing 0 of 2, 0 < 2 == true parsing 1 of 2, 1 < 2 == true parsing 2 of 2, 2 < 2 == true Notice, how it entered the for loop even when 2 < 2 should have prevented it from entering it. Furthermore, notice the message says 2 < 2 == true (which clearly isn't right). This happens when that code is compiled with optimization level -O2 or -O3. The issue doesn't happen with -O1. I had reported this as an issue to Apple through feedback assistance, more than a month back. The feedback id is FB15162411. There hasn't been any response to it nor any indication that the issue has been noticed and can be reproduced (the steps to reproduce have been provided in that issue). In the meantime, more and more users are now running into this failure in JDK when using XCode 16. We haven't put any workaround in place (the only workaround we know of is using -O1 for the compilation of this file) because it isn't clear what exactly is causing this issue (other than the fact that it shows up with specific optimization levels). It's also unknown if this bug has wider impact. Would it be possible to check if FB15162411 is being looked into and any technical details on what's causing this? That would help us decide if it's OK to put in place a temporary workaround in the OpenJDK build and how long to maintain that workaround. For reference, this was reproduced on: clang++ --version Apple clang version 16.0.0 (clang-1600.0.26.3) Target: arm64-apple-darwin23.6.0 Thread model: posix InstalledDir: /xcode-16/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Consider this very trivial code which accesses the operatingSystemVersion property of NSProcessInfo as documented at https://developer.apple.com/documentation/foundation/nsprocessinfo/1410906-operatingsystemversion osversion.c: #include <Foundation/Foundation.h> int main(int argc, char *argv[]) { NSOperatingSystemVersion osVersion = [[NSProcessInfo processInfo] operatingSystemVersion]; fprintf(stderr, "OS version: %ld.%ld.%ld\n", osVersion.majorVersion, osVersion.minorVersion, osVersion.patchVersion); } Compile it: /usr/bin/clang -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk -iframework /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk/System/Library/Frameworks -x objective-c -o a.out -framework Foundation osversion.c Then run it: ./a.out It works fine and prints the OS version: OS version: 14.6.1 Run it again and pass it some arbitrary program arguments: ./a.out foo bar Still continues to work fine and prints the output: OS version: 14.6.1 Now run it again and this time pass it two program arguments, the first one being - and the second one being something of the form {x=y} ./a.out - {x=y} This time notice how it prints a couple of warning logs from CFPropertyListCreateFromXMLData before printing the output: 2024-10-11 11:18:03.584 a.out[61327:32412190] CFPropertyListCreateFromXMLData(): Old-style plist parser: missing semicolon in dictionary on line 1. Parsing will be abandoned. Break on _CFPropertyListMissingSemicolon to debug. 2024-10-11 11:18:03.585 a.out[61327:32412190] CFPropertyListCreateFromXMLData(): Old-style plist parser: missing semicolon in dictionary on line 1. Parsing will be abandoned. Break on _CFPropertyListMissingSemicolon to debug. OS version: 14.6.1 As far as I can see there's nothing wrong in the code nor the user inputs to the program. Is this some issue in the internal implementation of NSProcessInfo? Should this be reported as an issue through feedback assistant (which category)? Although this example was run on 14.6.1 of macos, the issue is reproducible on older versions too.

We have been observing an issue where when binding a UDP socket to an ephemeral port (i.e. port 0), the OS ends up allocating a port which is already bound and in-use. We have been seeing this issue across all macos versions we have access to (10.x through recent released 13.x). Specifically, we (or some other process) create a udp4 socket bound to wildcard and ephemeral port. Then our program attempts a bind on a udp46 socket with ephemeral port. The OS binds this socket to an already in use port, for example you can see this netstat output when that happens: netstat -anv -p udp | grep 51630 udp46 0 0 *.51630 *.* 786896 9216 89318 0 00000 00000000 00000000001546eb 00000000 00000800 1 0 000001 udp4 0 0 *.51630 *.* 786896 9216 89318 0 00000 00000000 0000000000153d9d 00000000 00000800 1 0 000001 51630 is the (OS allocated) port here, which as you can see has been allocated to 2 sockets. The process id in this case is the same (because we ran an explicit reproducer to reproduce this), but it isn't always the case. We have a reproducer which consistenly shows this behaviour. Before filing a feedback assistant issue, I wanted to check if this indeed appears to be an issue or if we are missing something here, since this appears to be a very basic thing.

I've been investigating an issue with the SO_OOBINLINE socket option. When that option is disabled, the expectation is that out-of-band data that is sent on the socket will not be available through the use of read() or recv() calls on that socket. What we have been noticing is that when the socket is bound to a non-loopback address (and the communication is happening over that non-loopback address), then even when SO_OOBINLINE is disabled for the socket, the read()/recv() calls both return the out-of-band data. The issue however isn't reproducible with loopback address, and read()/recv() both correctly exclude the out-of-band data. This issue is only noticed on macos. I have been able to reproduce on macos M1, following version, but the original report which prompted me to look into this was reported on macos x64. My M1 OS version is: sw_vers ProductName: macOS ProductVersion: 14.3.1 BuildVersion: 23D60 Attached is a reproducer (main.c.txt - rename it to main.c after downloading) that I have been able to develop which reproduces this issue on macos. When you compile and run that: ./a.out it binds to a non-loopback address by default and you should see the failure log, resembling: ... ERROR: expected: 1234512345 but received: 12345U12345 To run the same reproducer against loopback address, run it as: ./a.out loopback and that should succeed (i.e. no out-of-band data) with logs resembling: ... SUCCESS: completed successfully, expected: 1234512345, received: 1234512345 Is this a bug in the OS? I would have reported this directly through feedback assistant, but my past few open issues (since more than a year) have not even seen an acknowledgement or a reply, so I decided to check here first. main.c.txt

We have been noticing some mysterious port binds on our macos setups, where the syslogd process binds to a ephemeral port on UDP. This socket isn't bound from the time syslogd process starts, but something/ some event triggers this bind. So we investigated further. It appears that one of the macos specific modules in syslogd is the "bsd_out" module which reads the config rules from a file called "/etc/syslog.conf". The contents of that file on my setup are: cat /etc/syslog.conf # Note that flat file logs are now configured in /etc/asl.conf install.* @127.0.0.1:32376 These contents are the default ones shipped in macos and nothing has been edited/changed. So it appears that the bsd_out module has been configured with a rule to send logs/messages in the "install" facility to be forwarded to some process which has a socket listening on loopback's 32376 port. Whenever some software gets installed/uninstalled from the machine, it looks like a log message gets generated which falls under this "install" facility and then the bsd_out module binds a socket for UDP and uses that socket to send the data to 127.0.0.1:32376. You will notice that before installing/uninstalling any software the command: sudo lsof -p &lt;syslogd-pid&gt; will not list any UDP port. As soon as you install/uninstall something that socket gets bound and is visible in the output of the above command. The (bound) socket stays around. The curious part is there's still no one/nothing that listens on that 32376 port. So it appears that this module is sending some datagrams that are just lost and not delivered? Is there a reason why the /etc/syslog.conf has this rule if there's nothing that's receiving that data? The "man syslogd" page does state that bsd_out module is only there for backward compatibility, so perhaps this config rule in /etc/syslog.conf is just a left over that is no longer relevant? I'm on macos 13.2.1: sw_vers ProductName: macOS ProductVersion: 13.2.1 BuildVersion: 22D68 but this has been noticed on older version (even 10.15.x) too. To reproduce, here are the steps: Find the pid of syslogd (ps -aef | grep syslogd) Find the resources used by this process including ports (sudo lsof -p &lt;syslog-pid&gt;) At this point, ideally, you shouldn't see any UDP ports being used by this process Install/uninstall any software (for example: move to trash and delete any installed application) Run the lsof command again (sudo lsof -p &lt;syslog-pid&gt;), you will now see that it uses a UDP port bound to INADDR_ANY address and an ephemeral port: syslogd 12345 root 11u IPv4 0xf557ad678c99264b 0t0 UDP *:56972 netstat output too will show that port (for example: netstat -anv -p UDP)

I have a setup where /bin/ksh constantly crashes. The generated crash logs available at ~/Library/Logs/DiagnosticReports aren't too helpful because the content there contains only hex references to the ksh stack backtrace. I then ran "dtruss" against the crashing /bin/ksh program and even that isn't helping narrow it down because that too uses hex digits in the stack backtrace. What would be the right way to debug this crashing ksh program? Are there debug symbols available for the /bin/ksh binary shipped in macos M1 (13.0.1 version)? I found some documentation about using XCode to "symbolicate" the crash logs, but following those instructions too wasn't helpful because even after loading the crash report in the XCode "Device Logs" window, it still only showed hex references.

Hello, I have been looking at some TCP related configurations on Linux and then checking their counterparts on macos. On macos, I see these 2 (among many others) from "sysctl -a" output: net.inet.tcp.ack_strategy: 1 ... net.inet.tcp.delayed_ack: 3 What does the ack_strategy = 1 imply and what does the value 3 for delayed_ack imply? Is there some additional documentation on what values are supported here and what each one implies? I did a basic search but couldn't find any details about these configurations.

We have some extensive tests which exercise UDP communication. Some of these tests fail fairly often due to the UDP packet being dropped by the kernel (or related reasons). These tests use loopback interface for communication. I have been looking to see if there's a way to pinpoint or narrow down exactly why a particular packet was dropped by the kernel. Looking at the kernel code, like here https://github.com/apple-opensource/xnu/blob/master/bsd/netinet/udp_usrreq.c#L1463 it appears that there are log message that get written out during some of this communication. However, looking at what KERNEL_DEBUG stands for, it appears that it's: /* * Traced only on debug kernels. */ #define KDBG_DEBUG(x, ...) KDBG_(_DEBUG, x, ## __VA_ARGS__, 4, 3, 2, 1, 0) So I don't think these logs get generated in a regular release build of the OS. Are there any other ways we can generate similar logs or any other tools that will give a clearer picture of why the packet might be drop?

In this thread https://developer.apple.com/forums/thread/705281 (which I am the original poster), I have marked my own post as the accepted answer. I did that before I got input from Quinn on how to achieve what I was after. I have posted that information in a subsequent post in that thread here https://developer.apple.com/forums/thread/705281?answerId=712746022#712746022. Can someone please mark this as the correct answer? I tried but I don't see any option to do it myself. P.S: In some forum threads, I see that things like these are sorted through direct messages sometimes. But I can't see any place in my profile where I can send a direct message from. Does that feature require some level of forum points?

The man page of "connect" states (snippet below): ".... datagram sockets may use connect() multiple times to change their association. Datagram sockets may dissolve the association by calling disconnectx(2), or by connecting to an invalid address, such as a null address ..." Up until 12.3.1 (and even 12.4 Beta1), if a connect() call was used on a datagram socket to disconnect an IPv4-mapped IPv6 address, the call used to complete and return back "EADDRNOTAVAIL". Internally it would indeed dissolve the current association of the connected datagram socket (i.e. subsequent calls to "send" would return back a "EDESTADDRREQ" errno). However, starting 12.4 Beta2, if a connect() call is made on such a datagram socket which is connected to a IPv4-mapped IPv6 address, the call now returns a "EINVAL" errno. Do note that this change in behaviour is happening in this Beta release only with IPv4-mapped IPv6 addresses. Other addresses like plain IPv6 address, continue to return "EADDRNOTAVAIL" on such connect() calls which are used to dissolve the current association. We have been able to reproduce this issue with a trivial C program that is attached to this discussion. The attached program, creates a datagram socket which then connects to a IPv4-mapped IPv6 loopback address. This connect is expected to succeed and does succeed. Once the connect is done, a next connect() is issued on the connected datagram socket, this time passing it a null address (as noted in the man page) and this call is expected to dissolve the connection association. The program expects a EADDRNOTAVAIL to be returned by this call (since that's what was being returned in all MacOS releases so far) and if some other errno gets returned then the program fails. When the attached reproducer is run against 12.3.1 (or other previous MacOS versions or even 12.4 Beta1), the program gets the expected EADDRNOTAVAIL and when it is run against 12.4 Beta2, it gets the unexpected EINVAL errno. Here's a sample output from 12.3.1 (the "successful" one): $> sw_vers ProductName: macOS ProductVersion: 12.3.1 BuildVersion: 21E258 $> clang main.c $> ./a.out created a socket, descriptor=3 trying to bind to addr ::ffff:127.0.0.1:0, addr family=30 Bound socket to ::ffff:127.0.0.1:46787, addr family=30 created another socket, descriptor=4 connecting to ::ffff:127.0.0.1:46787, addr family=30 successfully connected Disconnecting using addr :::0, addr family=30 got errno 49, which is considered OK for a connect to null address (a.k.a disconnect) Successfully disconnected Output from 12.4 Beta2 (the case where the behaviour has changed): $> sw_vers ProductName: macOS ProductVersion: 12.4 BuildVersion: 21F5058e $> clang main.c $> ./a.out created a socket, descriptor=3 trying to bind to addr ::ffff:127.0.0.1:0, addr family=30 Bound socket to ::ffff:127.0.0.1:23015, addr family=30 created another socket, descriptor=4 connecting to ::ffff:127.0.0.1:23015, addr family=30 successfully connected Disconnecting using addr :::0, addr family=30 Got unexpected errno 22 disconnect failed: Invalid argument Notice how the call to connect() to dissolve the connected association now returns errno 22 == Invalid Argument. We had a look at the release notes here https://developer.apple.com/documentation/macos-release-notes/macos-12_4-release-notes but they appear to be very high level release notes and we couldn't find anything relevant related to this change. So: Is this an intentional change? Are applications expected to account for this errno to be returned when calling connect() to dissolve a connected association of a datagram socket? If this is intentional, is there a reason why this is specific only for IPv4-mapped IPv6 address? The man connect page also talks about using disconnectx as an alternative way to dissolve the association. This appears to be specific to MacOS systems (couldn't find it in BSD man pages for example). Is disconnectx the recommended way to do the dissociation? P.S: I created a issue for this through the bug/feedback reporting tool (issue id: FB9996296), but there hasn't been any response to it since almost a week. So creating this thread in the forums hoping to get some inputs. main.c

I realize that recent versions of MacOS ship with a dynamic library cache. I am looking for inputs on how to list the dependencies of one such system library that's part of this cache. Consider the case where I have a libfoo library which when inspected through "otool -L libfoo.dylib" shows this output: otool -L libfoo.dylib /home/me/lib/libjli.dylib: @rpath/libjli.dylib (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/Cocoa.framework/Versions/A/Cocoa (compatibility version 1.0.0, current version 23.0.0) /System/Library/Frameworks/Security.framework/Versions/A/Security (compatibility version 1.0.0, current version 60157.60.19) /System/Library/Frameworks/ApplicationServices.framework/Versions/A/ApplicationServices (compatibility version 1.0.0, current version 56.0.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.0.0) /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation (compatibility version 150.0.0, current version 1856.105.0) /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation (compatibility version 300.0.0, current version 1856.105.0) /usr/lib/libobjc.A.dylib (compatibility version 1.0.0, current version 228.0.0) One of the dependencies in that library is the /usr/lib/libSystem.B.dylib. Previously, I could just do otool -L /usr/lib/libSystem.B.dylib to find the dependencies of libSystem.B.dylib, but now with the dynamic library cache in picture, if I do: otool -L /usr/lib/libSystem.B.dylib error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/otool-classic: can't open file: /usr/lib/libSystem.B.dylib (No such file or directory) So how do I get otool to show the dependencies of this cache library. Are there any other tools instead of otool which can do this in recent versions of MacOS? I'm on 12.3.1 of macOS

I see that MacOS 12.2.1 ships in its dynamic libraries cache the zlib 1.2.11 version. The zlib library has the ability to log messages (at runtime) if it was configured during compilation with the --debug/-d option[1] (which internally sets the ZLIB_DEBUG compiler flag). How does one go about finding the config options that were used to build this system library (or any system library for that matter that's shipped in MacOS)? Is the current one shipped enabled for this option? [1] https://github.com/madler/zlib/blob/v1.2.11/configure#L139 [2] https://github.com/madler/zlib/blob/v1.2.11/configure#L202