[Mono] mini-llvm.c build failure: LLVMMono1CallConv undeclared after LLVM SDK version bump to 26159.1 #125769
Description
Build Information
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1342414&view=results
Build error leg or test failing: tvos-arm64 Release AllSubsets_Mono
Pull request: #125556
Error Message
Fill the error message using step by step known issues guidance.
{
"ErrorMessage": "error: use of undeclared identifier 'LLVMMono1CallConv'",
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}The tvOS/iOS cross-compiler build fails with use of undeclared identifier 'LLVMMono1CallConv' in mini-llvm.c after the Mono LLVM SDK package version bump to 19.1.0-alpha.1.26159.1. In the dotnet/llvm-project the macOS SDK package appears to have been built with Homebrew LLVM 18 instead of AppleClang, because llvm.proj specifies the compiler as bare clang which resolves to /usr/local/bin/clang.
Similar to #125763
Known issue validation
Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1342414
Error message validated: [error: use of undeclared identifier 'LLVMMono1CallConv']
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/19/2026 11:29:41 AM UTC
Report
| Build | Definition | Step Name | Console log | Pull Request |
|---|---|---|---|---|
| 1343113 | dotnet/runtime | Build product | Log | #125732 |
| 1343078 | dotnet/runtime | Build product | Log | #121223 |
| 1343075 | dotnet/runtime | Build product | Log | #125774 |
| 1343072 | dotnet/runtime | Build product | Log | #125768 |
| 1343011 | dotnet/runtime | Build product | Log | #125772 |
| 1342977 | dotnet/runtime | Build product | Log | #125771 |
| 1342756 | dotnet/runtime | Build product | Log | #115996 |
| 1342966 | dotnet/runtime | Build product | Log | #122950 |
| 1342934 | dotnet/runtime | Build product | Log | #125441 |
| 1342906 | dotnet/runtime | Build product | Log | #124266 |
| 1342879 | dotnet/runtime | Build product | Log | #124648 |
| 1342889 | dotnet/runtime | Build product | Log | #125439 |
| 1342882 | dotnet/runtime | Build product | Log | #123209 |
| 1342876 | dotnet/runtime | Build product | Log | #124650 |
| 1342852 | dotnet/runtime | Build product | Log | #125437 |
| 1342845 | dotnet/runtime | Build product | Log | #124544 |
| 1340985 | dotnet/runtime | Build product | Log | #125603 |
| 1342794 | dotnet/runtime | Build product | Log | #125507 |
| 1342725 | dotnet/runtime | Build product | Log | #125656 |
| 1342672 | dotnet/runtime | Build product | Log | #125703 |
| 1342414 | dotnet/runtime | Build product | Log |
Summary
| 24-Hour Hit Count | 7-Day Hit Count | 1-Month Count |
|---|---|---|
| 21 | 21 | 21 |