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Fix DllImportResolver #27397

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Merged
tianleiwu merged 2 commits into from
Feb 24, 2026
Merged

Fix DllImportResolver #27397

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956dc9e
Fix DllImportResolver
tianleiwu Feb 19, 2026
5a4191a
Add Test
tianleiwu Feb 20, 2026
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156 changes: 86 additions & 70 deletions csharp/src/Microsoft.ML.OnnxRuntime/NativeMethods.shared.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -892,99 +892,115 @@ internal class NativeLib
/// On Windows, it explicitly loads the library with a lowercase .dll extension to handle
/// case-sensitive filesystems.
/// </summary>
#if NET5_0_OR_GREATER
[System.Diagnostics.CodeAnalysis.UnconditionalSuppressMessage("SingleFile", "IL3000:Avoid accessing Assembly file path when publishing as a single file", Justification = "We also check AppContext.BaseDirectory as a fallback")]
#endif
private static IntPtr DllImportResolver(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)
{
if (libraryName == NativeLib.DllName || libraryName == OrtExtensionsNativeMethods.ExtensionsDllName)
try
{
string mappedName = null;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
// Explicitly load with .dll extension to avoid issues where the OS might try .DLL
mappedName = libraryName + ".dll";
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
if (libraryName == NativeLib.DllName || libraryName == OrtExtensionsNativeMethods.ExtensionsDllName)
{
// Explicitly load with .so extension and lib prefix
mappedName = "lib" + libraryName + ".so";
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
{
// Explicitly load with .dylib extension and lib prefix
mappedName = "lib" + libraryName + ".dylib";
}

if (mappedName != null)
{
// 1. Try default loading (name only)
if (NativeLibrary.TryLoad(mappedName, assembly, searchPath, out IntPtr handle))
string mappedName = null;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
return handle;
// Explicitly load with .dll extension to avoid issues where the OS might try .DLL
mappedName = libraryName + ".dll";
}

// 2. Try relative to assembly location (look into runtimes subfolders)
string assemblyLocation = null;
try { assemblyLocation = assembly.Location; } catch { }
if (!string.IsNullOrEmpty(assemblyLocation))
else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
{
// Explicitly load with .so extension and lib prefix
mappedName = "lib" + libraryName + ".so";
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
{
string assemblyDir = System.IO.Path.GetDirectoryName(assemblyLocation);
string rid = RuntimeInformation.RuntimeIdentifier;
// Explicitly load with .dylib extension and lib prefix
mappedName = "lib" + libraryName + ".dylib";
}

// Probe the specific RID first, then common fallbacks for the current OS
string[] ridsToTry;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
ridsToTry = new[] { rid, "win-x64", "win-arm64" };
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
{
ridsToTry = new[] { rid, "linux-x64", "linux-arm64" };
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
{
// We no longer provide osx-x64 in official package since 1.24.
// However, we keep it in the list for build-from-source users.
ridsToTry = new[] { rid, "osx-arm64", "osx-x64" };
}
else
if (mappedName != null)
{
// 1. Try default loading (name only)
if (NativeLibrary.TryLoad(mappedName, assembly, searchPath, out IntPtr handle))
{
ridsToTry = new[] { rid };
return handle;
}

foreach (var tryRid in ridsToTry)
// 2. Try relative to assembly location (look into runtimes subfolders)
string assemblyLocation = null;
try { assemblyLocation = assembly.Location; } catch { }
if (!string.IsNullOrEmpty(assemblyLocation))
{
string probePath = System.IO.Path.Combine(assemblyDir, "runtimes", tryRid, "native", mappedName);
if (System.IO.File.Exists(probePath) && NativeLibrary.TryLoad(probePath, assembly, searchPath, out handle))
string assemblyDir = System.IO.Path.GetDirectoryName(assemblyLocation);
string rid = RuntimeInformation.RuntimeIdentifier;

// Probe the specific RID first, then common fallbacks for the current OS
string[] ridsToTry;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
LogLibLoad($"[DllImportResolver] Loaded {mappedName} from: {probePath}");
return handle;
ridsToTry = new[] { rid, "win-x64", "win-arm64" };
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
{
ridsToTry = new[] { rid, "linux-x64", "linux-arm64" };
}
else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
{
// We no longer provide osx-x64 in official package since 1.24.
// However, we keep it in the list for build-from-source users.
ridsToTry = new[] { rid, "osx-arm64", "osx-x64" };
}
else
{
ridsToTry = new[] { rid };
}
}
}

// 3. Try AppContext.BaseDirectory as a fallback
string baseDir = AppContext.BaseDirectory;
if (!string.IsNullOrEmpty(baseDir))
{
string probePath = System.IO.Path.Combine(baseDir, mappedName);
if (NativeLibrary.TryLoad(probePath, assembly, searchPath, out handle))
{
LogLibLoad($"[DllImportResolver] Loaded {mappedName} from: {probePath}");
return handle;
foreach (var tryRid in ridsToTry)
{
string probePath = System.IO.Path.Combine(assemblyDir, "runtimes", tryRid, "native", mappedName);
if (System.IO.File.Exists(probePath) && NativeLibrary.TryLoad(probePath, assembly, searchPath, out handle))
{
LogLibLoad($"[DllImportResolver] Loaded {mappedName} from: {probePath}");
return handle;
}
}
}

string rid = RuntimeInformation.RuntimeIdentifier;
probePath = System.IO.Path.Combine(baseDir, "runtimes", rid, "native", mappedName);
if (NativeLibrary.TryLoad(probePath, assembly, searchPath, out handle))
// 3. Try AppContext.BaseDirectory as a fallback
try
{
LogLibLoad($"[DllImportResolver] Loaded {mappedName} from: {probePath}");
return handle;
string baseDir = AppContext.BaseDirectory;
if (!string.IsNullOrEmpty(baseDir))
{
string probePath = System.IO.Path.Combine(baseDir, mappedName);
if (NativeLibrary.TryLoad(probePath, assembly, searchPath, out handle))
{
LogLibLoad($"[DllImportResolver] Loaded {mappedName} from: {probePath}");
return handle;
}

string rid = RuntimeInformation.RuntimeIdentifier;
probePath = System.IO.Path.Combine(baseDir, "runtimes", rid, "native", mappedName);
if (NativeLibrary.TryLoad(probePath, assembly, searchPath, out handle))
{
LogLibLoad($"[DllImportResolver] Loaded {mappedName} from: {probePath}");
return handle;
}
}
}
}
catch { } // Ignore AppDomainUnloadedException or similar from AppContext.BaseDirectory

LogLibLoad($"[DllImportResolver] Failed loading {mappedName} (RID: {RuntimeInformation.RuntimeIdentifier}, Assembly: {assemblyLocation})");
LogLibLoad($"[DllImportResolver] Failed loading {mappedName} (RID: {RuntimeInformation.RuntimeIdentifier}, Assembly: {assemblyLocation})");

}
}
}
catch (Exception ex)
{
// Unhandled exceptions inside DllImportResolver can result in TypeInitializationException.
// Log and swallow the error, returning IntPtr.Zero to fall back to default CLR logic.
try { System.Diagnostics.Trace.WriteLine($"[DllImportResolver] Exception during resolution: {ex}"); } catch { }
}

// Fall back to default resolution
return IntPtr.Zero;
Expand Down
43 changes: 43 additions & 0 deletions csharp/test/Microsoft.ML.OnnxRuntime.Tests.Common/OrtEnvTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -489,4 +489,47 @@ void TestCopyTensors()
}
}
}

[Collection("Ort Inference Tests")]
public class OrtEnvDllImportResolverTest
{
[Fact(DisplayName = "TestDllImportResolverDoesNotThrow")]
public void TestDllImportResolverDoesNotThrow()
{
// The DllImportResolver is a private static method in NativeMethods.
var nativeMethodsType = typeof(OrtEnv).Assembly.GetType("Microsoft.ML.OnnxRuntime.NativeMethods");
Assert.NotNull(nativeMethodsType);

// It might not be defined on all platforms (defined when !NETSTANDARD2_0 && !__ANDROID__ && !__IOS__).
var resolverMethod = nativeMethodsType.GetMethod("DllImportResolver", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);

if (resolverMethod != null)
{
try
{
// Invoke with null assembly to force it into edge cases where assembly.Location would throw NullReferenceException.
// It should catch the exception and return IntPtr.Zero gracefully rather than throwing.
var result = resolverMethod.Invoke(null, new object[] { "onnxruntime", null, null });

// If it reaches here without throwing TargetInvocationException, the try-catch in DllImportResolver works.
Assert.True(result is IntPtr);
}
catch (System.Reflection.TargetInvocationException ex)
{
// If NativeMethods..cctor() threw because the native library is missing,
// we will get a TypeInitializationException wrapping a DllNotFoundException (or DllImportException).
// This is acceptable locally. What we want to avoid is NullReferenceException from DllImportResolver.
if (ex.InnerException is TypeInitializationException typeInitEx)
{
Assert.IsNotType<NullReferenceException>(typeInitEx.InnerException);
}
else
{
Assert.IsNotType<NullReferenceException>(ex.InnerException);
throw;
}
}
}
}
}
}
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