App Crash with mxSignpost function not found

Consider this:

% swift demangle
_$s9MetricKit10mxSignpost_3dso3log4name10signpostID__ySo03os_H7_type_ta_SVSo03OS_j1_F0Cs12StaticStringV0J0010OSSignpostI0VALSays7CVarArg_pGtF
MetricKit.mxSignpost(_: __C.os_signpost_type_t, dso: Swift.UnsafeRawPointer, log: __C.OS_os_log, name: Swift.StaticString, signpostID: os.OSSignpostID, _: Swift.StaticString, _: [Swift.CVarArg]) -> ()

So, the problematic symbol is mxSignpost(…). According to the documentation, that’s available on iOS 13 and later. However, that’s clearly not the case O-:

I see two possibilities here:

• The availability annotation is just wrong.
• The symbol is available on older system, but it moved, and the corresponding .tbd file doesn’t record that move.

I suspect that it’s the latter [1] but, either way, it’s a bug in the MetricKit framework interface and you should file it as such.

Please post your bug number, just for the record.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

[1] I’ve seen stuff like that before.

  Referenced from: <BE7BFAFD-CE49-3373-9146-F342D87BF49F> /private/var/containers/Bundle/Application/FF873B01-8EA2-4C96-9DBE-D2FDE6BD6B42/MyApp.app/MyApp.debug.dylib
  Expected in:     <BD4E2A51-DF45-3674-9B18-9D6527AE18BD> /System/Library/Frameworks/MetricKit.framework/MetricKit
Symbol not found: _$s9MetricKit10mxSignpost_3dso3log4name10signpostID__ySo03os_H7_type_ta_SVSo03OS_j1_F0Cs12StaticStringV0J0010OSSignpostI0VALSays7CVarArg_pGtF
  Referenced from: <BE7BFAFD-CE49-3373-9146-F342D87BF49F> /private/var/containers/Bundle/Application/FF873B01-8EA2-4C96-9DBE-D2FDE6BD6B42/MyApp.app/MyApp.debug.dylib
  Expected in:     <BD4E2A51-DF45-3674-9B18-9D6527AE18BD> /System/Library/Frameworks/MetricKit.framework/MetricKit
dyld config: DYLD_LIBRARY_PATH=/usr/lib/system/introspection DYLD_INSERT_LIBRARIES=/usr/lib/libLogRedirect.dylib:/usr/lib/libBacktraceRecording.dylib:/usr/lib/libMainThreadChecker.dylib:/usr/lib/libRPAC.dylib:/usr/lib/libViewDebuggerSupport.dylib:/System/Library/PrivateFrameworks/GPUToolsCapture.framework/GPUToolsCapture
Symbol not found: _$s9MetricKit10mxSignpost_3dso3log4name10signpostID__ySo03os_H7_type_ta_SVSo03OS_j1_F0Cs12StaticStringV0J0010OSSignpostI0VALSays7CVarArg_pGtF
  Referenced from: <BE7BFAFD-CE49-3373-9146-F342D87BF49F> /private/var/containers/Bundle/Application/FF873B01-8EA2-4C96-9DBE-D2FDE6BD6B42/MyApp.app/MyApp.debug.dylib
  Expected in:     <BD4E2A51-DF45-3674-9B18-9D6527AE18BD> /System/Library/Frameworks/MetricKit.framework/MetricKit
dyld config: DYLD_LIBRARY_PATH=/usr/lib/system/introspection DYLD_INSERT_LIBRARIES=/usr/lib/libLogRedirect.dylib:/usr/lib/libBacktraceRecording.dylib:/usr/lib/libMainThreadChecker.dylib:/usr/lib/libRPAC.dylib:/usr/lib/libViewDebuggerSupport.dylib:/System/Library/PrivateFrameworks/GPUToolsCapture.framework/GPUToolsCapture

Same here

Hi,

App crashes on launch on iOS 26.3.1 after building with Xcode 26.4.

dyld: Symbol not found: MetricKit.mxSignpost

Works fine on iOS 26.4+.

FB: FB22384135

Anyone else seeing this or any workaround?

Thanks.

FB: FB22384135

Thanks for filing that.

I took a look at Xcode 26.5b1 and it still seems to have the problem )-:

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Just a quick update…

I’m confidant that we now have a handle on this issue (FB22384135). I can’t offer any concrete details about timelines but, as always, I encourage you to test with the latest betas as we seed them.

And in this case that means Xcode betas, because this is an Xcode issue.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Please try this again with Xcode 26.4.1. Quoting the release note:

Fixed crash for MetricKit apps built with Xcode 26.4 due to missing symbols when running on iOS, macOS, and visionOS versions below 26.4. Please rebuild your app with the updated Xcode to resolve the issue. (173827073) (FB22384135)

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"