# Use Executorch's Module Extension API on arm64 Mac

**URL:** <https://discuss.pytorch.org/t/use-executorchs-module-extension-api-on-arm64-mac/215068>\
**Category:** ExecuTorch\
**Created:** [January 7, 2025, 11:43am UTC](https://discuss.pytorch.org/t/use-executorchs-module-extension-api-on-arm64-mac/215068 "2025-01-07T11:43:19Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![simonsasse](https://discuss.pytorch.org/user_avatar/discuss.pytorch.org/simonsasse/32/74884_2.png) [@simonsasse](https://discuss.pytorch.org/u/simonsasse)\
**Post date:** [January 7, 2025, 11:43am UTC](https://discuss.pytorch.org/t/use-executorchs-module-extension-api-on-arm64-mac/215068/1 "2025-01-07T11:43:19Z")

</div>

I want to run a small MLP in the Executorch runtime (eventually on android, currently on arm64 Mac).  
For the start I just cloned the Executorch Repo and set everything up.  
I can build and run the `executor_runner` without problems.  
I then started to edit the `executor_runner` so that it matches my needs.  
Problem is, as soon as I start using the Module Extension API, which would ease things, I get the below error when calling Cmake.  
I added the `module.h` to the `targets.bzl` and #included it in the `executor_runner.cpp`.

```auto
Undefined symbols for architecture arm64:
  "executorch::extension::Module::Module(std:: __1::basic_string<char, std::__ 1::char_traits<char>, std:: __1::allocator<char>> const&, executorch::extension::Module::LoadMode, std::__ 1::unique_ptr<executorch::runtime::EventTracer, std::__1::default_delete<executorch::runtime::EventTracer>>)", referenced from:
      _main in executor_runner.cpp.o
ld: symbol(s) not found for architecture arm64
c++: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [executor_runner] Error 1
make[1]: *** [CMakeFiles/executor_runner.dir/all] Error 2
make: *** [all] Error 2

```

I am new to Executorch and also not a pro in c++ and Cmake.

Executorch: release/0.4  
MacBook Air M3 (arm64)

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<div class="post-metadata">

**Author:** ![lucylq](https://discuss.pytorch.org/user_avatar/discuss.pytorch.org/lucylq/32/65270_2.png) [@lucylq](https://discuss.pytorch.org/u/lucylq)\
**Post date:** [January 7, 2025, 8:09pm UTC](https://discuss.pytorch.org/t/use-executorchs-module-extension-api-on-arm64-mac/215068/2 "2025-01-07T20:09:35Z")

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Hi @simonsasse,

Thanks for trying out ExecuTorch!

The `targets.bzl` file is for building with Buck; you’ll have to edit the `CMakeLists.txt` file to build with CMake. You could take a look at the module test as an example: [executorch/extension/module/test at main · pytorch/executorch · GitHub](https://github.com/pytorch/executorch/tree/main/extension/module/test)

Could you explain more about what you’re trying to do with the Module API / `executor_runner`? `executor_runner` uses all the lower-level APIs to load and run a model, whereas Module is a higher-level API that does the same thing. So you probably want to use one or the other.

cc @shoumikhin for Module API.

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<div class="post-metadata">

**Author:** ![simonsasse](https://discuss.pytorch.org/user_avatar/discuss.pytorch.org/simonsasse/32/74884_2.png) [@simonsasse](https://discuss.pytorch.org/u/simonsasse)\
**Post date:** [January 8, 2025, 3:49pm UTC](https://discuss.pytorch.org/t/use-executorchs-module-extension-api-on-arm64-mac/215068/3 "2025-01-08T15:49:56Z")

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Hi @lucylq, thank you so much for the quick reply.

I want to use the Module API instead of the lower level APIs used in the executor\_runner.

I wrote my own run script before (outside the executorch directory) and ran into the same issue. So I thought I might just try if my Cmake build is missing some reference or so . That’s why I started to edit the executor\_runner. It’s basically taken from this tutorial:  
[https://pytorch.org/executorch/stable/extension-module.html#running-an-executorch-model-using-the-module-extension-in-c](https://pytorch.org/executorch/stable/extension-module.html#running-an-executorch-model-using-the-module-extension-in-c)

```auto
#include <executorch/extension/module/module.h>
#include <executorch/extension/tensor/tensor.h>

#include <cassert>
#include <iostream>

using namespace ::executorch::extension;

int main(int argc, char **argv)
{
    // Create a Module.
    Module module("example/path.pte");

    // Wrap the input data with a Tensor.
    float input[1 * 3];
    auto inTensor = from_blob(input, {1, 3});

    // ......

    // Perform forward
    const auto result = module.forward(inTensor);

    // Check for success or failure.
   // ......
}

```

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<div class="post-metadata">

**Author:** ![lucylq](https://discuss.pytorch.org/user_avatar/discuss.pytorch.org/lucylq/32/65270_2.png) [@lucylq](https://discuss.pytorch.org/u/lucylq)\
**Post date:** [January 8, 2025, 11:39pm UTC](https://discuss.pytorch.org/t/use-executorchs-module-extension-api-on-arm64-mac/215068/4 "2025-01-08T23:39:57Z")

</div>

Hi @simonsasse, thanks for the additional context.

So executor\_runner is built in the [root CMakeLists.txt file](https://github.com/pytorch/executorch/blob/main/CMakeLists.txt#L808-L835), set to ON by default.

And Module is built in the root CMakeLists.txt file if [`EXECUTORCH_BUILD_EXTENSION_MODULE=ON`](https://github.com/pytorch/executorch/blob/main/CMakeLists.txt#L692), it is OFF by default.

I think the missing pieces are:

1. Set `EXECUTORCH_BUILD_EXTENSION_MODULE=ON` in the root CMakeLists.txt, to build the Module library. This will build the targets [`extension_module`, `extension_module_static`](https://github.com/pytorch/executorch/blob/main/extension/module/CMakeLists.txt#L49).
2. Link `extension_module` or `extension_module_static` as a library to your target, eg., `target_link_libraries({your_target_name} extension_module)`

[See this example](https://github.com/pytorch/executorch/pull/7557). It might be better to create a separate CMakeLists.txt file rather than putting it into the root, but hopefully this helps.