Running from Native AOT app fails to build signature #2187

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1. kzu commented on Jul 22, 2026

   

   kzu

   on Jul 22, 2026

   ContributorAuthor

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   Root cause analysis

   This is not a missing native library / load failure, and it is not the same as #2160 (static linking for single-file AOT). The native git2-* binary loads correctly next to the published AOT executable.

   The failure is in config discovery under Native AOT.

   What fails

   Configuration.BuildSignature only reads user.name / user.email from the layered config:

   var name = this.GetValueOrDefault<string>("user.name");
   var email = this.GetValueOrDefault<string>("user.email");

   When opening a repository, global/system/xdg/programdata paths are resolved via:

   Proxy.git_config_find_global()
     → ConvertPath(NativeMethods.git_config_find_global)
     → libgit2 fills a git_buf, managed code reads buf.ptr
   

   Under CoreCLR (dotnet run), those finds succeed and global config is loaded (including include.path chains that often hold user.name / user.email).

   Under Native AOT (dotnet publish + run the native exe), the same APIs appear to fail: HasConfig(Global) / HasConfig(System) are false, so only local .git/config is present. If identity is not set locally, BuildSignature returns null.

   Why it fails under AOT

   GitBuf is a sequential-layout class passed by value to P/Invoke:

   [StructLayout(LayoutKind.Sequential)]
   internal class GitBuf : IDisposable
   {
       public IntPtr ptr;
       public UIntPtr asize;
       public UIntPtr size;
   }
   
   [DllImport(...)]
   internal static extern int git_config_find_global(GitBuf global_config_path);

   On CoreCLR, blittable sequential classes are typically pinned and native code writes directly into the object fields.

   On Native AOT, sequential class marshalling is effectively [In]-only: native code can fill a temporary buffer and return success, but managed ptr / size are never updated.

   ConvertPath then does:

   int result = pathRetriever(buf);          // often 0 (success) under AOT
   // ...
   return LaxFilePathMarshaler.FromNative(buf.ptr);  // ptr still IntPtr.Zero

   So discovery returns "no path", global/system config is never added, and signature building fails whenever identity lives outside the local repo config.

   Minimal probe (struct vs class vs pin)

   Calling the same git_config_find_global export after git_libgit2_init:

   Call style	CoreCLR	Native AOT
   ref blittable struct	OK (rc=0, path filled)	OK
   sequential-layout class (current style)	OK	rc=0 but ptr=0
   pinned class (GCHandle + IntPtr)	OK	OK

   That isolates the bug to marshalling of sequential classes under Native AOT, not to libgit2 path logic or environment variables (USERPROFILE / HOME are fine; setting HOME does not help).

   Why "explicit path" workarounds work

   Configuration.BuildFrom(localConfigPath, globalConfigPath)

   skips git_config_find_* and still loads includes. That confirms libgit2 config parsing is fine; only discovery via GitBuf class P/Invoke is broken under AOT.

   ---

   Proposed fix

   Introduce a blittable buffer type and use it for path-returning APIs that currently go through ConvertPath.

   1. Add a native-friendly buffer struct

   [StructLayout(LayoutKind.Sequential)]
   internal struct GitBufNative
   {
       public IntPtr ptr;
       public UIntPtr asize;
       public UIntPtr size;
   }

   Keep the existing GitBuf class for call sites that still use class marshalling (can migrate later).

   2. Change path-find P/Invokes to ref GitBufNative

   At minimum (these feed Configuration / repository discovery):

   • git_config_find_global
   • git_config_find_system
   • git_config_find_xdg
   • git_config_find_programdata
   • git_repository_discover
   • git_buf_dispose(ref GitBufNative) overload

   3. Update Proxy.ConvertPath

   private delegate int PathRetriever(ref GitBufNative buf);
   
   private static FilePath ConvertPath(PathRetriever pathRetriever)
   {
       var buf = new GitBufNative();
       try
       {
           int result = pathRetriever(ref buf);
           if (result == (int)GitErrorCode.NotFound)
               return null;
   
           Ensure.ZeroResult(result);
           return LaxFilePathMarshaler.FromNative(buf.ptr);
       }
       finally
       {
           NativeMethods.git_buf_dispose(ref buf);
       }
   }

   Method-group binding stays clean, e.g. ConvertPath(NativeMethods.git_config_find_global).

   4. Expected outcome

   After this change, Native AOT published apps should again:

   • resolve global/system config paths
   • honor include.path
   • make repo.Config.BuildSignature(DateTimeOffset.Now) match dotnet run behavior when user.name / user.email come from global config

   Follow-up (optional, larger)

   Many other APIs still pass class GitBuf for out-buffers (short ids, messages, opts getters, etc.). Those can misbehave under AOT the same way. Migrating remaining out-git_buf call sites to ref GitBufNative would make the whole surface AOT-safe; the config-find path above is the high-impact fix for this issue.

   Not in scope for this fix

   • Enable static linking of libgit2 (NativeLibrary / DirectPInvoke) for NativeAOT builds #2160 (static linking / true single-file) is orthogonal: that is about embedding libgit2, not about config discovery.
   • No change required in consumer apps once the library fix ships; workarounds like explicit Configuration.BuildFrom(...) paths are only needed on current NuGet packages.

   ---

   Happy to open a PR with the surgical GitBufNative + ConvertPath change if that approach looks good to maintainers.
2. kzu commented on Jul 22, 2026

   

   kzu

   on Jul 22, 2026

   ContributorAuthor

   More actions

   I promise the above is not just AI slop. I have this issue currently and am looking for a proper fix. I'll submit a PR that does so, but it's written by Grok 4.5.

   ❤️React with ❤️2Reacted by Javier Rojo and Ivan Balan
3. kzu

   added a commit that references this issue on Jul 22, 2026

   Fix rebase issue when run with dnx go

   ...

   cf9a58d