# Building from Source

## Installing Rustup

Building Wasmer from source requires [Rust](https://rustup.rs/) **1.45+**.

The easiest way to install Rust on your system is via Rustup. To get Rustup on Linux and macOS, you can run the following:

```bash
curl https://sh.rustup.rs -sSf | sh
```

{% hint style="info" %}
To install Rust on Windows, download and run [rustup-init.exe](https://win.rustup.rs/), then follow the onscreen instructions.
{% endhint %}

## Installing Additional Dependencies

### Windows

Windows support is fully supported. WASI is fully supported, but Emscripten support is in the works.

1. Install [Visual Studio](https://visualstudio.microsoft.com/thank-you-downloading-visual-studio/?sku=Community\&rel=15)
2. Install [Rust for Windows](https://win.rustup.rs/)
3. Install [Git for Windows](https://git-scm.com/download/win). Allow it to add `git.exe` to your PATH (default settings for the installer are fine).
4. (optional) Install [LLVM 10.0](https://prereleases.llvm.org/win-snapshots/LLVM-10.0.0-e20a1e486e1-win64.exe)

## Building the Wasmer Runtime

Wasmer is built with [Cargo](https://crates.io/), the Rust package manager.

First, let's clone Wasmer:

```
git clone https://github.com/wasmerio/wasmer.git
cd wasmer
```

Wasmer supports three different compilers at the moment:

### Singlepass Compiler

Build Wasmer:

```
make build-wasmer
```

**Note**: you should see this as the first line in the console:\
`Available compilers: singlepass`

### Cranelift Compiler

The Cranelift compiler will work if you are in a X86 or ARM machine, so you don't need to do anything in your system to enable it.

```
make build-wasmer
```

**Note**: should see this as the first line in the console:\
`Available compilers: cranelift`

### LLVM Compiler

If you want support for the Wasmer LLVM compiler, then you will also need to ensure:

* Ensure that LLVM 10.0.x > is installed on your system
  * You can also [download and use a prebuilt LLVM binary](https://releases.llvm.org/download.html)
* In case `llvm-config` is not accessible, set the correct environment variable for LLVM to access: For example, the environment variable for LLVM 10.0.x would be: `LLVM_SYS_100_PREFIX=/path/to/unpacked/llvm-10.0` 

And create a Wasmer release

```bash
make build-wasmer
```

**Note**: you should see this as the first line in the console:\
`Available compilers: llvm`

### All compilers

Once you have LLVM and Rust, you can just run:

```bash
make build-wasmer
```

**Note**: you should see this as the first line in the console:\
`Available compilers: singlepass cranelift llvm`

## Running your Wasmer binary

Once you run the `make build-wasmer` command, you will have a new binary ready to be used!

```
./target/release/wasmer quickjs.wasm
```

## Building Wasmer C-API from source

Wasmer provides a pre-compiled version for the C-API on its [release page](https://github.com/wasmerio/wasmer/releases).

However, you can also compile the shared library from source:

```
make build-capi
```

This will generate the shared library (depending on your system):

* Windows: `package/release/libwasmer_c_api.dll`
* macOS: `target/release/libwasmer_runtime_c_api.dylib`
* Linux: `target/release/libwasmer_runtime_c_api.so`

If you want to generate the library and headers for using them easily, you can execute:

```bash
make package-capi
```

This command will generate a `package` directory, that you can then use easily in the [Wasmer C API examples](https://jubianchi.gitbook.io/wasmer-docs/fix-python-summary/ecosystem/wasmer/building-from-source).

```
package/
  lib/
    libwasmer.so
  headers/
    wasm.h
    wasmer.h
    wasmer.hh
    wasmer_wasm.h
```

{% hint style="warning" %}
By default, the Wasmer C API shared library is built with Cranelift as the *default* compiler and JIT engine.\
You can generate the C-API for a specific compiler and engine with:

* **Singlepass**:
  * **JIT**: `make build-capi-singlepass-jit`
  * **Native Engine**: not yet available ⚠️
* **Cranelift**:
  * **JIT**: `make build-capi-cranelift-jit`
  * **Native Engine**: `make build-capi-cranelift-native`
* **LLVM**: `make build-capi-llvm`
  * **JIT**: `make build-capi-llvm-jit`
  * **Native Engine**: `make build-capi-llvm-native`
    {% endhint %}


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