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[net11.0] CoreCLR-flavor iOS apps abort in xamarin_vm_initialize ("Failed to initialize the VM") on iPhone 17 / iOS 26.0 with Microsoft.iOS.Sdk.net11.0_26.5 26.5.11527-net11-p5 #25542
Description
Summary
iOS apps published with Microsoft.iOS.Sdk.net11.0_26.5 = 26.5.11527-net11-p5 and RuntimeFlavor=coreclr (/p:UseMonoRuntime=false) abort during native startup on iPhone 17 / iOS 26.0 — before any managed code runs. Apps published with UseMonoRuntime=true from the same template / same SDK / same device run fine, so this is specific to the CoreCLR path through the macios native shim.
The abort is EXC_CRASH / SIGABRT ("Abort trap: 6"), asi: libsystem_c.dylib: ["abort() called"], process lifetime ~100 ms. The crash reproduces 100 % of the time, on both Release (R2R) and Debug, on three different iOS app templates (plain dotnet new ios, dotnet new maui, dotnet new maui --sample-content).
Symbolicated stack — CoreCLR Release
Thread 0 Crashed (EXC_CRASH / SIGABRT — "Abort trap: 6")
asi: libsystem_c.dylib: ["abort() called"]
#0 libsystem_kernel.dylib __pthread_kill +8
#1 libsystem_pthread.dylib pthread_kill +268
#2 libsystem_c.dylib __abort +132
#3 libsystem_c.dylib abort +136
#4 NetiOSDefault xamarin_register_monoassembly (runtime/runtime.m:850)
#5 NetiOSDefault xamarin_pinvoke_override [inlined into (runtime/runtime.m:2593)
xamarin_vm_initialize +0x1f8]
#6 NetiOSDefault xamarin_main + 0x4b0 (runtime/monotouch-main.m:379)
#7 NetiOSDefault main + 0x40 (main.arm64.mm:62)
#8 dyld start + 7116
Raw frames as recorded in the .ips (NetiOSDefault binary UUID 0477fda9-0f54-3913-8fbf-21f5d7ddcff5, image base 0x100e78000, size 0x20000):
imageOffset symbol+symbolLocation imageIndex image
45260 __pthread_kill +8 8 libsystem_kernel.dylib
30736 pthread_kill +268 9 libsystem_pthread.dylib
491436 __abort +132 10 libsystem_c.dylib
491304 abort +136 10 libsystem_c.dylib
33204 (0x81b4) 0 NetiOSDefault
43668 (0xaa94) 0 NetiOSDefault
74524 (0x1231c) 0 NetiOSDefault
78948 (0x13464) 0 NetiOSDefault
20008 start +7116 11 dyld
Symbolicated stack — CoreCLR Debug
Thread 0 Crashed (EXC_CRASH / SIGABRT — "Abort trap: 6")
#0-3 same libsystem frames (__pthread_kill / pthread_kill / __abort / abort)
#4 NetiOSDefault xamarin_register_assembly (runtime/delegates.inc:225)
#5 NetiOSDefault xamarin_vm_initialize + 0x174 (runtime/runtime.m:2532)
#6 NetiOSDefault xamarin_main + 0x63c (runtime/monotouch-main.m:412)
#7 NetiOSDefault main + 0x40 (main.arm64.mm:62)
#8 dyld start + 7116
Raw frames as recorded in the .ips:
imageOffset imageIndex image
18384 0 NetiOSDefault (0x47d0)
55664 0 NetiOSDefault (0xd970)
120348 0 NetiOSDefault (0x1d61c)
126884 0 NetiOSDefault (0x1efa4)
Symbolication was done locally with atos against a Debug build of dotnet new ios (Microsoft.iOS.Sdk.net11.0_26.5 26.5.11527-net11-p5, preserving dSYM); the dSYM file paths embedded by the build (/Users/builder/azdo/_work/1/s/macios/runtime/runtime.m, etc.) match the macios source tree.
Source of the abort
runtime/runtime.m:2532, inside xamarin_vm_initialize:
bool rv = xamarin_bridge_vm_initialize (propertyCount, propertyKeys, propertyValues);
...
if (!rv)
xamarin_assertion_message ("Failed to initialize the VM");runtime/runtime.m:850 (Release frame 4) is the entry of xamarin_register_monoassembly.
Reproduction (minimal)
# Need Xcode 26.5 (beta 2 or final) and .NET SDK 11.0.100-preview.5 or later
dotnet new ios -o app --name NetiOSDefault
dotnet publish app/NetiOSDefault.csproj \
-c Release -f net11.0-ios -r ios-arm64 --self-contained \
-p:UseMonoRuntime=false \
-p:PublishReadyToRunStripDebugInfo=false \
-p:PublishReadyToRunStripInliningInfo=false \
-p:EnableCodeSigning=falseInstall the resulting .ipa on an iPhone 17 running iOS 26.0 (build 23A330). The app SIGABRTs ~100 ms after launch.
Switching to -p:UseMonoRuntime=true (Mono runtime) on the same template, same device, same SDK runs to completion.
Environment
| Component | Version |
|---|---|
| iOS device | iPhone 17 (iPhone18,3) — iPhone OS 26.0 build 23A330 |
| Xcode (CI) | 26.5 beta 2 |
| Xcode (local repro) | 26.5 (final, 17F42) |
| .NET SDK | 11.0.100-preview.5.26276.101 (CI) / 11.0.100-preview.6.26276.119 (local repro) |
| Microsoft.iOS.Sdk.net11.0_26.5 | 26.5.11527-net11-p5 |
| Microsoft.iOS.Sdk.net10.0_26.5 | 26.5.10280 |
| Microsoft.NETCore.App.Runtime.* | 11.0.0-preview.5.26276.101 |
| RuntimeFlavor that crashes | coreclr |
| RuntimeFlavor that works | mono |
Repro matrix (all reproduce)
| Publish config | App template | Iter 0 result |
|---|---|---|
| CoreCLR Release (R2R) | dotnet new ios |
crash |
| CoreCLR Release (R2R) | dotnet new maui |
crash |
| CoreCLR Release (R2R) | dotnet new maui --sample-content |
crash |
| CoreCLR Debug | dotnet new ios |
crash |
| CoreCLR Debug | dotnet new maui |
crash |
| CoreCLR Debug | dotnet new maui --sample-content |
crash |
| Mono Release | dotnet new ios |
✅ passes |
| Mono Release | dotnet new maui |
✅ passes |
| Mono Debug | dotnet new ios |
✅ passes |
| Mono Debug | dotnet new maui |
✅ passes |
(Mono MauiSampleContent has an unrelated cleanup-kill timing issue, not the same SIGABRT.)
Activity
davidnguyen-tech commentedon May 27, 2026
Have been working on this issue as well for the past few hours. My copilot is leading me to this PR: dotnet/runtime#128278
I'll keep looking into it. I'm getting familiar with the area.
rolfbjarne commentedon May 27, 2026
I'm currently trying to track down some regressions in our last maestro bump (#25379), which bumps from
11.0.100-preview.5.26256.105to11.0.100-preview.5.26276.113, so this might be the same issue I've been looking at (although I haven't gotten far yet).This looks like it could cause problems.
Looking at the list of expected locations for System.Private.CoreLib.dll:
https://github.com/dotnet/runtime/blob/0d92fad6223bed592e244d66eeb09aa854c34fbd/src/coreclr/binder/assemblybindercommon.cpp#L270-L273
none of those actually work for us, and because of that we use TPA to tell corlib where to find SPC.dll
davidnguyen-tech commentedon May 28, 2026
Update - I've verified experimentally that dotnet/runtime#128278 is the cause.
Microsoft.NETCore.App.Runtime.ios-arm64/11.0.0-preview.5.26269.105Microsoft.NETCore.App.Runtime.ios-arm64/11.0.0-preview.5.26269.108[net11.0] [runtime] Register host_runtime_contract callbacks so CoreC…
[net11.0] [runtime] Register host_runtime_contract callbacks so CoreC…
kotlarmilos commentedon Jun 30, 2026
Fixed in #25562