SDK for an experimental vireo runtime engine.

vireo, webvi
npm install vireo@21.2.0



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A compact parallel execution runtime for VIs (virtual instruments) saved in VI assembly format (.via files).

The Vireo project provides a subset of LabVIEW runtime functionality for small targets. Example usages are WebVIs and the EV3 support in the LabVIEW Module for LEGO® MINDSTORMS®. The LabVIEW features supported are primarily defined by the features needed for the VIA files generated by LabVIEW NXG.

Getting VireoSDK Source

Before starting Vireo development it is recommended that you create a GitHub Fork and enable CI integration in your fork. For more information see


Prerequisites for all targets

Software requirements

  • git
  • Node.js (>8, latest LTS release recommended)
  • GNU Make and GNU core utilities (see following)

Installing GNU Make and GNU core utilities

On Windows you can get these by installing the Chocolatey package manager and then running the following commands to install GNU Make and the GNU core utilities:

choco install make
choco install gnuwin32-coreutils.portable

For other platforms, see platform documentation for installing a compatible version of GNU make and GNU core utilities.

Fetching tooling dependencies

On all platforms run the following in the VireoSDK folder to install JavaScript-based tooling needed for the test infrastructure:

npm install

vireo.js target

Software requirements

  • emsdk toolchain (see following)

Installing the emsdk toolchain

The emsdk toolchain is used to cross-compile Vireo to Vireo.js to run in Node.js and web browser environments.

  1. Create a directory outside of the VireoSDK folder to store the emsdk toolchain binaries.

  2. Do ONE of the following:

  3. If you download the zip archive you will need to run the following command inside the extracted folder to bring it up to date:

    emsdk update
  4. From either the extracted folder or the cloned emsdk repository run the following commands:

    emsdk install sdk-1.38.30-64bit
    emsdk activate sdk-1.38.30-64bit
    emcc -v # should match the sdk version

NOTE: The above commands only add emcc to the path for your current shell session. The emsdk tool provides the emsdk activate SOME_SDK_VERSION --global option but there is a known issue where using the --global flag hangs on Windows.

Instead it is recommended that in a new shell where you wish to build Vireo you run the emsdk_env.bat (Windows) or (Mac / Linux) from the emsdk folder to update your path variables for the shell session.

For more detailed information about emsdk see the juj/emsdk GitHub repository.

Building vireo.js

To create a default (release) build of vireo.js:

make js

The above default build of vireo.js is equivalent to:

make js BUILD=release

To create a debug build of vireo.js:

make js BUILD=debug

To create a profile build of vireo.js:

make js BUILD=profile

Notice that vireo.js is created in the dist folder based on the BUILD type. For example, a default vireo.js build equivalent to BUILD=release will be located at: dist/wasm32-unknown-emscripten/release/vireo.js

Vireo Windows Native target

Software requirements

  • Visual Studio 2013, Visual Studio 2015, or Visual Studio 2017 with C++ support

Building Vireo Windows Native

  1. Open the Vireo_VS/VireoCommandLine.sln solution in Visual Studio
  2. Perform a Debug build

Notice the esh executable placed in the dist folder.

Vireo Linux Native target

Software requirements

  • GCC 4.9

Building Vireo Linux Native

From the root directory run the following:

make native

Notice the esh executable placed in the dist folder.

There is a flag you can pass to make to enable AddressSanitizer:

make native ASAN=1

Vireo MacOS Native target

Software requirements

  • XCode

Building Vireo MacOS Native

Open the Vireo_Xcode/VireoEggShell.xcodeproj

If you prefer to build from the command line, the instructions for building Vireo Linux Native will work on macOS as well.

Running Tests

Running VTR Tests

The VTR (Vireo Test Result) test suite runs .via files located in the test-it/ViaTests directory, captures the standard output during the execution, and compares it to the .vtr output file located in test-it/ExpectedResults. The VTR test suite is the primary test suite for testing execution behavior for Vireo.

From the root directory

To run all the native and Node.js vtr tests:

make test

To run all the native vtr tests:

make testnative

To run all the Node.js vtr tests:

make testjs

From within the test-it directory

To run all the native and Node.js vtr tests:

node ./test.js

To run all the native vtr tests:

node ./test.js -n

To run all the Node.js vtr tests:

node ./test.js -j

To run a specific test suite:

node ./test.js -t <test suite>

To run an individual test:

node ./test.js HelloWorld.via

Listing Out VTR Tests (-l [test suite])

Since the test suites can be created recursively from other test suites in the configuration file, the -l command line argument lists all of the tests to be run for the test suite name provided. Example:

node ./test.js -l native

will list the tests that would be run against the native test suite.

VTR Test Suite Runner Help

$ node ./test.js -h
Usage: node ./test.js [options] [via test files]
 -n                  Run the tests against the native vireo target (esh)
 -j                  Run the tests against the JavaScript target (vireo.js)
 -t [test suite]     Run the tests in the given test suite
 -l [test suite]     List the tests that would be run in given test suite,
                        or list the test suite options if not provided
 -e                  Execute the test suite or tests provided and show their
                        raw output; do not compute pass/fail
 -h                  Print this usage message
 --once              Will only run the tests once (default is to run twice)

Running Karma Tests

The karma test suite is a web browser only test suite used to test the JS public API for Vireo along with the portion of Vireo features which are JS specific (i.e. the actual HTTP communication layer of the HTTP Client feature). The karma test suite also runs the VTR test suite as part of its execution.

To run the full karma test suite (you will need Firefox installed on your machine):

npm run test

To debug the karma tests, use the command below which will print a URL to the console. Open the URL on a browser and open the browser's debugging tool:

npm run test-manual

Running the HTTP test server

Vireo tests rely on a locally running instance of the httpbin server for testing the HTTP Client functionality. If the httpbin server is not running locally, the test suite will skip tests which rely on it. If you would like to run the HTTP client tests locally these instructions show you how.

Software requirements


  1. Ensure python (correct version) and pip are available on the path.
  2. From a command line in the VireoSDK directory or elsewhere do pip install tox to globally install the tox tool.

Starting the Server

  1. Open a command prompt in the VireoSDK directory.

  2. Run the npm run httpbin command. This will install dependencies of httpbin if necessary and start the httpbin server locally.

    Note: On Windows you can alternatively execute npm run httpbin-start to start the httpbin server in a new console window.

  3. With the server running in a new window you can now run the tests which rely on the HTTP client:

    • Running HTTP karma tests
    npm run test
    • Running HTTP VTR tests
    make testhttpbin

Adding Tests

Adding to the VTR test suite

Test Configuration

The .via test files to run are located in the test-it/ViaTests folder. The expected result from the stdout of running the test .via file is located in a file of the same name but with the extension .vtr inside the test-it/ExpectedResults folder. The test name exists within a test suite in the test-it/testList.json file.

The testList.json file has two required properties for each test suite name:


An array of strings that are names to other test suites. These test suite names are processed recursively to accumulate tests together into one list of tests to run (Duplicates are omitted if overlap exists between test suites).


An array of strings which contains the list of .via files the test suite should run.

Adding a Test Suite

Here is a simple example that adds the test suite rpi with the RpiTest.via file to the test manager.

  1. Put the RpiTest.via file in the test-it/ViaTests folder and put the RpiTest.vtr file in the test-it/ExpectedResults folder.

  2. Then add this example code to the testList.json file:

    "rpi": {
        "include": [ "common" ],
        "tests": [

    This will add the test suite rpi which will include the test RpiTest.via and all of the tests included in the common test suite.

  3. Try it out to verify it works and your tests pass:

node ./test.js -n -t rpi

Updating Vireo Documentation

We are using Doxygen to generate our documentation. This tool lets us annotate our source code and generate documentation from it. We are currently using version 1.8.6.

Installers can be found here. On Windows use the 64-bit version.

Once Doxygen is installed run the following command from any directory in the repo:

npm run doxygen

It will find and use the Doxyfile file in the source directory to generate documentation files in the gh-pages directory:

The main html file in the gh-pages directory is called index.html.


Features beyond the core set that can be accessed directly from VIA source written by hand should be considered experimental, and subject to change at any time. A complete list of disclaimers and terms is described in LICENSE.txt.