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!

I am trying to learn Metal development on my MacBook Pro M1 Pro (Sequoia 15.3.1) on Xcode Playground, but when I write these two lines of code: import Metal let device = MTLCreateSystemDefaultDevice()! I get the error The LLDB RPC server has crashed. Any ideas as to what I can do to solve this? I have rebooted the machine and reinstalled Xcode...

My app is running Compute Shaders that use non-uniform thread groups. When I run the app in the debugger with a simulator target the app crashes on encoder.dispatchThreads and the error message is: Dispatch Threads with Non-Uniform Threadgroup Size is not supported on this device. Previously the log output states that: Metal Shader Validation is unsupported for Simulator. However: When I stop the debugger and just run the app in the simulator without the debugger attached, the app just runs fine and does not crash. The SwiftUI Preview that also triggers the Compute Shader when preparing data also just runs fine without a crash. I can run and debug on a real device no problem - I just don't have all sizes available. Is there anything I need to check in my lldb/simulator configuration? It obviously does work, just the debugger cannot really deal with it? Any input would be nice as this really slows my down as I have to be extremely careful when debugging on the simulator.

The charging port of my iPhone may be damaged due to water, and it cannot be charged and transmitted data. It can only be charged wirelessly that does not support data transmission. However, since Xcode supports wireless debugging, I can continue to test my App. However, I recently changed to a new Mac, but there is no connection record with the iPhone in the new Mac, which makes it impossible to debug wirelessly. So I want to know how to realize wireless debugging on such a device without debugging records?

Here's a simple C++ program that echoes its arguments... #include <stdio.h> int main(int argc, char* argv[]) { for (int i=0; i<argc; ++i) printf("%d %s\n", i, argv[i]); } This works as expected... > ./test arg1 #arg2 arg3 0 ./test 1 arg1 2 #arg2 3 arg3 Running under lldb gives this... > lldb ./test arg1 #arg2 arg3 (lldb) target create "./test" Current executable set to '/Users/richard/Work/test' (arm64). (lldb) settings set -- target.run-args "arg1" "#arg2" "arg3" (lldb) run Process 6138 launched: '/Users/richard/Work/test' (arm64) 0 /Users/richard/Work/test 1 arg1 Process 6138 exited with status = 0 (0x00000000) I get the same if I quote the arguments, or if I add them to the run line. Stepping into main() we see the argv and args values are as though we only had the first argument. If I quote the second argument and add an initial space " #arg1" then it works. I first saw this on an M1 running Sequoia 13.1. It am now on OS 13.3. lldb --version lldb-1600.0.39.109 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)

I'm pulling my hair out here with this new Xcode 16, it complains that my app's dSYM is empty though it's clearly not, it's about 25MB. I'm working on a project using an internal static library, everything is built inhouse using swift, we own all the source code. It worked just fine until the other week, when I updated the Xcode, and now I can't debug anything. I keep getting "type for self cannot be reconstructed" when I run "po self.some_property". Why is that? The Debug information Format is set to DWARF with dSYM File for both the executable and lib projects. I've been a Unix guy since before I knew myself and I enjoy fixing things myself, down to bare metal, but man, this bug is driving me crazy. Is it even a bug?? It's the first time in more than 15 years since I started coding on Mac and iPhone when a bug has defeated me. I was always able to fix things using just the documentation and google, but the Apple toolchain is getting worse and worse nowadays. I remember the time when Apple made the complicated things simple, now they make the simple things complicated :( I just split the static lib from the main project one year ago, because of the ridiculously long build time. Should I merge back all the code in a single project? Something seems wrong to me. So I created this account to ask the masters. How can I get back my debug info (and sanity)? Using Xcode 15 is not an option because it doesn't run on Sequoia.

All is fine in Xcode15, no LLDB errors whatsoever, but in Xcode16 I can't get any variable displayed in the console because of the following error: error: type for self cannot be reconstructed: type for typename "$......." was not found (cached) error: Couldn't realize Swift AST type of self. Hint: using `v` to directly inspect variables and fields may still work. I've checked the output of swift-healthcheck and there are several messages like this: SwiftASTContextForExpressions(module: "ROA", cu: "ROA+ViewLayer.swift")::LoadOneModule() -- Missing Swift module or Clang module found for "UIKit", "imported" via SwiftDWARFImporterDelegate. Hint: Register Swift modules with the linker using -add_ast_path. I added -add_ast_path to the OTHER_LDFLAGS in the faulty module's build settings but no luck. How can I debug my project in Xcode16?

Chrome has started crashing almost immediately after startup. I've reported the issue to the Chrome team here: https://issues.chromium.org/issues/385433270 I'm hoping to debug the issue a bit more myself. This page from the Chrome team https://chromium.googlesource.com/chromium/src/+/master/docs/mac/debugging.md#chrome-builds suggests using the follow to strip off the protections: codesign --force --sign - path/to/Google\ Chrome.app However, applying that seems to have no effect: % codesign --force --sign - /Applications/Google\ Chrome\ copy.app /Applications/Google Chrome copy.app: replacing existing signature /Applications/Google Chrome copy.app: resource fork, Finder information, or similar detritus not allowed % lldb /Applications/Google\ Chrome\ copy.app (lldb) target create "/Applications/Google Chrome copy.app" Current executable set to '/Applications/Google Chrome copy.app' (arm64). (lldb) run error: process exited with status -1 (attach failed (Not allowed to attach to process. Look in the console messages (Console.app), near the debugserver entries, when the attach failed. The subsystem that denied the attach permission will likely have logged an informative message about why it was denied.)) I have tried other variations like the following based on Stack Overflow, this forum, etc., but with the same result. (I'm still a little vague on the meaning for some flags, sorry.) Though codesign says that it's "replacing existing signature", as far as I can tell, nothing is changing: % cat <<EOF > debuggee-entitlement.xml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>com.apple.security.get-task-allow</key> <true/> </dict> </plist> EOF % codesign --verbose=4 -fs - --options library-validation --entitlements debuggee-entitlement.xml /Applications/Google\ Chrome\ copy.app /Applications/Google Chrome copy.app: replacing existing signature /Applications/Google Chrome copy.app: resource fork, Finder information, or similar detritus not allowed file with invalid attached data: Disallowed xattr com.apple.FinderInfo found on /Applications/Google Chrome copy.app lldb still fails the same way. Here's what I see after the above: % codesign -d -vvv /Applications/Google\ Chrome\ copy.app Executable=/Applications/Google Chrome copy.app/Contents/MacOS/Google Chrome Identifier=com.google.Chrome Format=app bundle with Mach-O universal (x86_64 arm64) CodeDirectory v=20500 size=1821 flags=0x12a00(kill,restrict,library-validation,runtime) hashes=46+7 location=embedded Hash type=sha256 size=32 CandidateCDHash sha256=5d7beab2b03d9892426076b24acc19815d7a3ff8 CandidateCDHashFull sha256=5d7beab2b03d9892426076b24acc19815d7a3ff8c1446966e422c3c10672626b Hash choices=sha256 CMSDigest=5d7beab2b03d9892426076b24acc19815d7a3ff8c1446966e422c3c10672626b CMSDigestType=2 CDHash=5d7beab2b03d9892426076b24acc19815d7a3ff8 Signature size=8989 Authority=Developer ID Application: Google LLC (EQHXZ8M8AV) Authority=Developer ID Certification Authority Authority=Apple Root CA Timestamp=Dec 17, 2024 at 2:47:58 PM Notarization Ticket=stapled Info.plist entries=44 TeamIdentifier=EQHXZ8M8AV Runtime Version=15.0.0 Sealed Resources version=2 rules=13 files=63 Internal requirements count=1 size=288 From what I can tell, my codesign runs have changed nothing... I see no diff as compared with what I see running codesign -d on a fresh copy. Is it possible to strip off the protections on my local instance to allow debugging with lldb? If so, could someone share a command for accomplishing that? Although I'm asking about this because of Chrome specifically, I'm hoping to learn more about codesigning in general and to be more empowered as a user to be able to debug when an app I depend on is crashing. Thanks much! Happy Holidays!

everything works fine in Xcode15, but in Xcode16 it break down. when I add breakpoint, I start po variable , the lldb shows error: type for self cannot be reconstructed: type for typename "$s8XYRouter8RegistryOXMtD" was not found (cached) error: Couldn't realize Swift AST type of self. Hint: using `v` to directly inspect variables and fields may still work. how can I fix the issues!!!. it really mattttttes, and it cause cant developing as normally. pls, save the child.

Is there a way I can use the lldb user defined commands, which I can load from a KDK, to determine how much memory my kext has consumed? Is there a way to figure out what size blocks they are? I have already run the showallclasses command and the output has assured me that I am not leaking any objects which are defined by my driver's classes. Thanks, Tim

I am building an MPI C project in Xcode. In order to do run it, I had to: Specify /path/to/mpiexec in Edit Scheme -> Run -> Info -> Executable, instead of the "default" one, say myprogram if my target is called myprogram. Specify the following arguments in Edit Scheme -> Run -> Arguments -> Arguments Passed On Launch: -np 4, ${BUILT_PRODUCTS_DIR}/${EXECUTABLE_NAME} This is clearly analogous to a mpiexec -np 4 a.out command launched on terminal. The problem is, when I want to debug my application, the execution doesn't "stop" on the breakpoints. I instantly thought that it is because of the check box Debug Executable in Edit Scheme -> Run -> Info -> Executable. Indeed (as I have just said), the Executable specified in there is mpiexec and not myprogram. Thus, is there an option or some command I could set in Xcode to attach the lldb to myprogram?

Hello! We're working on a large app with over 400 modules in both Swift and Objective-C, totaling more than 3 million lines of code. Since the release of Xcode 15 and 16 this summer, we’ve been experiencing issues with LLDB that have made debugging practically impossible. Here are some of the problems we’re facing: The first breakpoint takes a very long time to hit. When using 'po self', we encounter the following error: error: type for self cannot be reconstructed: type for typename "$s5MyModule10PlayerViewCD" was not found (cached) error: Couldn't realize Swift AST type of self. Hint: using `v` to directly inspect variables and fields may still work. We get numerous log messages like this: Debugging will be degraded due to missing types. Rebuilding the project will regenerate the needed module files.warning: (arm64) /Users/egormerkushev/Library/Developer/Xcode/DerivedData/App-enhtbwiyebmjsffoqkqhhpshsfia/Build/Products/Debug-iphoneos/MyModule.framework/MyModule(UploadConfiguration.o) 0x000000000000079d: unable to locate module needed for external types: /Users/builder/Library/Developer/Xcode/DerivedData/ModuleCache.noindex/169D1N0MIKBUI/Security-3BRN4UPIIGHME.pcm error: '/Users/builder/Library/Developer/Xcode/DerivedData/ModuleCache.noindex/169D1N0MIKBUI/Security-3BRN4UPIIGHME.pcm' does not exist In the Derived Data folder, we find files with hash-like names, such as: Security-3JM2E93YFDLZNYHWPPIMWNENB.d Security-3JM2E93YFDLZNYHWPPIMWNENB.dia Security-3JM2E93YFDLZNYHWPPIMWNENB.pcm Security-3JM2E93YFDLZNYHWPPIMWNENB.scan Security-3NAAT3MGN7XY96KVJW529HR41.d Security-3NAAT3MGN7XY96KVJW529HR41.dia Security-3NAAT3MGN7XY96KVJW529HR41.pcm Security-3NAAT3MGN7XY96KVJW529HR41.scan Security-3RJH8STJC01N1KKN7JCY1WK7F.d Security-3RJH8STJC01N1KKN7JCY1WK7F.dia Security-3RJH8STJC01N1KKN7JCY1WK7F.pcm Security-3RJH8STJC01N1KKN7JCY1WK7F.scan Security-3TILE9XTY0B8UV9VYL7Y0MJN.d Security-3TILE9XTY0B8UV9VYL7Y0MJN.dia Security-3TILE9XTY0B8UV9VYL7Y0MJN.pcm Security-3TILE9XTY0B8UV9VYL7Y0MJN.scan Security-3ZE8O6ZPHE4L52UZGL0PCBA59.d Security-3ZE8O6ZPHE4L52UZGL0PCBA59.dia ... When enabling LLDB logs with: log enable -f /tmp/lldb.log lldb all we end up with a 1.5GB log file containing hundreds of thousands of error messages. Finally, the LLDB console output in Xcode ends with errors like: error: Assertion failed: (byte_size > 0 && byte_size <= 8 && "GetMaxU64 invalid byte_size!"), function GetMaxU64, file DataExtractor.cpp, line 527 Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it): 0 LLDB 0x0000000116ccfe1c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56 1 LLDB 0x000000011682fdcc lldb_private::lldb_assert(bool, char const*, char const*, char const*, unsigned int) + 148 2 LLDB 0x000000011682944c lldb_private::DataExtractor::GetMaxU64(unsigned long long*, unsigned long) const + 72 3 LLDB 0x00000001167335a8 lldb_private::CompilerType::GetValueAsScalar(lldb_private::DataExtractor const&, unsigned long long, unsigned long, lldb_private::Scalar&, lldb_private::ExecutionContextScope*) const + 304 4 LLDB 0x000000011666f0f4 lldb_private::Value::ResolveValue(lldb_private::ExecutionContext*, lldb_private::Module*) + 388 5 LLDB 0x0000000116671e94 lldb_private::ValueObject::ResolveValue(lldb_private::Scalar&) + 104 6 LLDB 0x0000000116674d6c lldb_private::ValueObject::GetValueAsSigned(long long, bool*) + 140 7 LLDB 0x000000011650510c lldb::SBValue::GetValueAsSigned(long long) + 160 8 lldb-rpc-server 0x00000001025ebe70 rpc_server::_ZN4lldb7SBValue16GetValueAsSignedEx::HandleRPCCall(rpc_common::Connection&, rpc_common::RPCStream&, rpc_common::RPCStream&) + 92 ... 13 libsystem_pthread.dylib 0x00000001917fb2e4 _pthread_start + 136 14 libsystem_pthread.dylib 0x00000001917f60fc thread_start + 8 Please file a bug report against lldb reporting this failure log, and as many details as possibleerror: Assertion failed: (byte_size > 0 && byte_size <= 8 && "GetMaxU64 invalid byte_size!"), function GetMaxU64, file DataExtractor.cpp, line 527 Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it): 0 LLDB 0x0000000116ccfe1c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56 1 LLDB 0x000000011682fdcc lldb_private::lldb_assert(bool, char const*, char const*, char const*, unsigned int) + 148 2 LLDB 0x000000011682944c lldb_private::DataExtractor::GetMaxU64(unsigned long long*, unsigned long) const + 72 3 LLDB 0x00000001167335a8 lldb_private::CompilerType::GetValueAsScalar(lldb_private::DataExtractor const&, unsigned long long, unsigned long, lldb_private::Scalar&, lldb_private::ExecutionContextScope*) const + 304 4 LLDB 0x000000011666f0f4 lldb_private::Value::ResolveValue(lldb_private::ExecutionContext*, lldb_private::Module*) + 388 5 LLDB 0x0000000116671e94 lldb_private::ValueObject::ResolveValue(lldb_private::Scalar&) + 104 6 LLDB 0x0000000116674c44 lldb_private::ValueObject::GetValueAsUnsigned(unsigned long long, bool*) + 140 7 LLDB 0x0000000116505224 lldb::SBValue::GetValueAsUnsigned(unsigned long long) + 160 8 lldb-rpc-server 0x00000001025ebf18 rpc_server::_ZN4lldb7SBValue18GetValueAsUnsignedEy::HandleRPCCall(rpc_common::Connection&, rpc_common::RPCStream&, rpc_common::RPCStream&) + 92 9 lldb-rpc-server 0x00000001025f62b8 rpc_common::Connection::PrivateHandleRPCPacket(rpc_common::RPCPacket&, rpc_common::RPCPacket&, bool&) + 628 10 lldb-rpc-server 0x00000001025f9e8c Packets::ProcessPackets() + 564 11 lldb-rpc-server 0x00000001025f9bf4 Packets::ReadThread() + 276 12 lldb-rpc-server 0x00000001025f9ad4 Packets::RunReadThread(void*) + 12 13 libsystem_pthread.dylib 0x00000001917fb2e4 _pthread_start + 136 14 libsystem_pthread.dylib 0x00000001917f60fc thread_start + 8 Please file a bug report against lldb reporting this failure log, and as many details as possiblePrinting description of self: error: type for self cannot be reconstructed: type for typename "$s5MyModule10PlayerViewCD" was not found (cached) error: Couldn't realize Swift AST type of self. Hint: using `v` to directly inspect variables and fields may still work. In short, our debugger is completely unusable at this point, which is severely impacting our team's ability to develop effectively. Do you have any suggestions on how we can resolve these issues? We would really appreciate your help. Thank you!

The kernel sends SIGKILL to application if it handles ES_EVENT_TYPE_AUTH_OPEN and lldb is attached to this process. App: int main(int /*argc*/, char** /*argv*/) { es_client_t *pEpClient = nullptr; es_new_client_result_t result = es_new_client(&pEpClient, ^(es_client_t *pClient, const es_message_t *pMessage) { switch (pMessage->event_type) { case ES_EVENT_TYPE_AUTH_OPEN: { uint32_t authorizedFlags = pMessage->event.open.fflag; if ((authorizedFlags & FREAD) || (authorizedFlags & FWRITE)) { std::filesystem::path filePath = std::string(pMessage->event.open.file->path.data, pMessage->event.open.file->path.length); std::string fileName = filePath.filename(); if (fileName == "test.txt") { std::cout << "blocked fileName: " << filePath.filename() << std::endl; authorizedFlags &= ~FWRITE; authorizedFlags &= ~FREAD; } } if (es_respond_flags_result(pClient, pMessage, authorizedFlags, false) != ES_RESPOND_RESULT_SUCCESS) { std::cout << "es_respond_flags_result() failed with error " << std::endl; } } break; default: break; } }); if (result != ES_NEW_CLIENT_RESULT_SUCCESS) { std::cout << "es_new_client() failed." << std::endl; return 1; } es_event_type_t eventsList[] = { ES_EVENT_TYPE_AUTH_OPEN }; if (es_subscribe(pEpClient, eventsList, 1) == ES_RETURN_ERROR) { std::cout << "es_subscribe() failed." << std::endl; } // wait int i = 0; std::cin >> i; if (es_delete_client(pEpClient) == ES_RETURN_ERROR) { std::cout << "es_delete_client() failed." << std::endl; } return 0; } (lldb) process attach --pid 61127 .... (lldb) c Process 61127 resuming Process 61127 exited with status = 9 (0x00000009) Terminated due to signal 9 System log: Allowing set_exception_ports from [debugserver] on [ep_sample] for entitled process/debugger Client did not respond in appropriate amount of time (client pid: 61127), sent SIGKILL

Hi, i have met error below when i tried to po one attributes of an instance in my Xcode lldb: error: type for self cannot be reconstructed: type for typename "$xxxxx" was not found (cached) error: Couldn't realize Swift AST type of self. Hint: using `v` to directly inspect variables and fields may still work. Is there anybody met the same error before? I urgently want to know why this happen and how to fix this issue. My macOS Version is Sequoia v15.0.1, Xcode16.0. This problem showed after i upgraded my macOS and Xcode version.

When I run my app on iOS 18, the following gets logged to the XCode console. error: Error reading commands from file lldbinit - file not found. I've never heard of that file before. What is it, why is it needed, why does the app (unbeknown to me) try to read from it, and why is it missing?

I've downloaded xcode beta and from then I'm not able to see any messages in the debugger console. I only see the: "Message from debugger: killed" after stopping it. I tried downgrading it but since I'm using Sequoia Beta, "normal" xcode won't be compatible with this MacOs version. This is what I have: xcode Version 16.1 beta (16B5001e) Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4) Target: x86_64-apple-darwin24.0.0 lldb-1500.0.404.7 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4) xcode-select version 2409. package-id: com.apple.pkg.CLTools_Executables version: 15.3.0.0.1.1708646388 volume: / location: / install-time: 1725364937 It can be a mess as I tried so many ways to make this work. Thanks in advance. Regards.

i'm trying to get firefox running in 10.7 but the kernel is crashing. i have it working/running/looking great on 10.8 and higher. something is happening in 10.7 that is causing the panic. i need the right kit. someone asked a similar question for 10.11: https://forums.developer.apple.com/forums/thread/108732 but feedback assistant doesn't seem like the right answer. i need this kit to move forward. right now using either the 10.7.0 or 10.7.4 kernel debug kit causes a panic on reboot; something to do with AVX and the fpu. i am hoping APPUL had enough foresight to see this would be an issue (even one year later) for people on newer architectures debugging for older, supported (until 2014) targets: this use-case definitely falls within the parameters.

I am on M1 (Xcode Version 15.4 (15F31d), MacOS 14.5 (23F79), Simulator IOS 17.4) and as far as I remember printing common usage register was possible. I am not sure why it stopped to work rid, rsi and etc (arg1 arg2 seems like still working).

Hello, I have a test bundle in my application and one of the strong request of our project is to run ui tests from command line having just application build. How to run unit tests on .app file that has a test target? What we tried xcrun devicectl device install app --device <device-identifier> <UITestBundle-Runner.app> xcrun devicectl device process launch --device <device-identifier> --start-stopped <com.apptestbundle-Runner.xcrun> It launches and is waiting pid to be attached. In lldb: device select <device-identifier> device process list Seeing process 'UITestBundle-Runner' pid. device process --pid 'pid id' It attaches and I can see 'debugserver' in the pid list, but it does not start testing and I need tests to start and run. Thanks!

Hi 👋 I need assistance in attaching the to the pid in terminal. In lldb mode I am connecting to the pid using device process attach --pid <pid-id> which gives me an error Process 505 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP frame #0: 0x00000001d505c808 libsystem_kernel.dylib`mach_msg2_trap + 8 libsystem_kernel.dylib`mach_msg2_trap: -> 0x1d505c808 <+8>: ret Thanks