Add logic to muxer to invoke AOT-ed SDK by elinor-fung · Pull Request #126596 · dotnet/runtime

elinor-fung · 2026-04-07T02:18:20Z

Updates the muxer to look for and natively invoke a \dotnet-aot\ shared library when it exists in the resolved SDK directory. When present, the muxer loads the library, resolves the \dotnet_execute\ entry point, and calls it with the host path, dotnet root, SDK directory, hostfxr path, and user arguments. If the AOT library is not available or doesn't have the expected entry point, the muxer falls back to the existing managed SDK path.

Changes

Native host

Add try_invoke_aot_sdk helper in fx_muxer_t::handle_cli that attempts to load dotnet-aot from the resolved SDK directory
Fall through to the existing dotnet.dll path if the AOT library is absent

Tests

Add mockaotsdk native test library that implements the dotnet_execute entry point and prints received arguments
Add DispatchToAotSdk test in SDKLookup.cs validating the muxer dispatches to the AOT SDK with the correct arguments

cc @JeremyKuhne @dotnet/appmodel @AaronRobinsonMSFT

When the dotnet muxer resolves an SDK, it now checks for a dotnet-aot native library in the SDK directory before falling back to the managed dotnet.dll path. If the library exists and exports a dotnet_execute entry point, the muxer loads it and calls it with the host path, dotnet root, SDK directory, hostfxr path, and user arguments. The AOT library handles its own fallback to the managed runtime path when needed. If the library cannot be loaded or the entry point is missing, the muxer gracefully falls back to the existing managed SDK path. Fixes dotnet#126171 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add DispatchToAotSdk test to verify the muxer correctly loads and invokes the dotnet-aot library from the resolved SDK directory. The test uses a mock AOT SDK shared library that prints the received arguments for validation. - Add mockaotsdk native test library with dotnet_execute entry point - Add DotNetAot entry to Binaries.cs for test discovery - Add DispatchToAotSdk test in SDKLookup.cs - Move 'Using AOT-ed SDK' trace to just before invocation and remove redundant failure trace on load_library Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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dotnet-policy-service · 2026-04-07T02:19:28Z

Tagging subscribers to this area: @agocke, @jeffschwMSFT, @elinor-fung
See info in area-owners.md if you want to be subscribed.

agocke

LGTM, few nits

agocke · 2026-04-07T21:16:58Z

+        if (!pal::load_library(&sdk_aot_path, &aot_dll))
+            return false;
+
+        typedef int (*dotnet_execute_fn)(


Do we have docs somewhere on this signature?

Updated one of the docs in runtime.
@JeremyKuhne Are there any sdk docs that would make sense to link to here?

@elinor-fung I don't have any links for you yet. The signature in the issue was copied directly from my wip. I'll be putting a PR up next week and I can add a link/links here after I commit. Copied again from my local changes:

[UnmanagedCallersOnly(EntryPoint = "dotnet_execute")] static int Execute( nint hostPathPtr, // const char_t* host_path nint dotnetRootPtr, // const char_t* dotnet_root nint sdkDirPtr, // const char_t* sdk_dir nint hostfxrPathPtr, // const char_t* hostfxr_path int argc, // int argc (user args, no dotnet exe) nint argvPtr) // const char_t** argv

JeremyKuhne

Looks good to me.

Copilot

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Copilot · 2026-04-17T22:27:32Z

+        pal::dll_t aot_dll = nullptr;
+        if (!pal::load_library(&sdk_aot_path, &aot_dll))
+            return false;
+
+        // See docs/design/features/sharedfx-lookup.md#sdk-search
+        typedef int (__cdecl *dotnet_execute_fn)(
+            const pal::char_t* host_path,
+            const pal::char_t* dotnet_root,
+            const pal::char_t* sdk_dir,
+            const pal::char_t* hostfxr_path,
+            int argc,
+            const pal::char_t** argv);
+
+        auto dotnet_execute = reinterpret_cast<dotnet_execute_fn>(pal::get_symbol(aot_dll, "dotnet_execute"));
+        if (dotnet_execute == nullptr)
+        {
+            trace::info(_X("AOT-ed SDK [%s] does not contain 'dotnet_execute' entry point."), sdk_aot_path.c_str());
+            pal::unload_library(aot_dll);
+            return false;
+        }
+
+        pal::string_t hostfxr_path;
+        if (!pal::get_own_module_path(&hostfxr_path))
+        {
+            trace::info(_X("Failed to determine hostfxr path."));
+            pal::unload_library(aot_dll);
+            return false;
+        }
+
+        const pal::char_t* dotnet_root = sdk_root.empty()
+            ? host_info.dotnet_root.c_str()
+            : sdk_root.c_str();
+
+        trace::info(_X("Using AOT-ed SDK=[%s]"), sdk_aot_path.c_str());
+
+        *exit_code = dotnet_execute(
+            host_info.host_path.c_str(),
+            dotnet_root,
+            sdk_dir.c_str(),
+            hostfxr_path.c_str(),
+            argc - 1, // skip 'dotnet' (first argument)
+            argv + 1);
+
+        return true;
+    }


try_invoke_aot_sdk unloads the library on the failure paths, but on the success path it returns without calling pal::unload_library(aot_dll). In long-lived hosts that call hostfxr_main multiple times, this can accumulate loaded modules / memory and can keep the SDK’s dotnet-aot file in use. Consider ensuring the handle is released on the success path too (ideally via a small RAII wrapper so all early-returns are covered).

elinor-fung and others added 2 commits April 1, 2026 18:14

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elinor-fung closed this Apr 7, 2026

elinor-fung reopened this Apr 7, 2026

agocke approved these changes Apr 7, 2026

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build-analysis bot mentioned this pull request Apr 8, 2026

Known Build Error: MultiClientHostedBuildAndPublish publish fails with duplicate HotReload DLL identity #126439

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JeremyKuhne approved these changes Apr 16, 2026

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Specify calling convention

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Comment thread src/native/corehost/fxr/fx_muxer.cpp

Comment thread docs/design/features/sharedfx-lookup.md Outdated

Update docs/design/features/sharedfx-lookup.md

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Add logic to muxer to invoke AOT-ed SDK#126596

Add logic to muxer to invoke AOT-ed SDK#126596
elinor-fung wants to merge 5 commits intodotnet:mainfrom
elinor-fung:launch-aot-sdk

elinor-fung commented Apr 7, 2026 •

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elinor-fung commented Apr 7, 2026 •

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