Emscripten

It should be possible to build packages for Emscripten (asm.js) via the following conan profile:

include(default)
[settings]
os=Emscripten
arch=asm.js
compiler=clang
compiler.version=6.0
compiler.libcxx=libc++
[options]
[build_requires]
emsdk_installer/1.38.29@bincrafters/stable
[env]

And the following conan profile is required for the WASM (Web Assembly):

include(default)
[settings]
os=Emscripten
arch=wasm
compiler=clang
compiler.version=6.0
compiler.libcxx=libc++
[options]
[build_requires]
emsdk_installer/1.38.29@bincrafters/stable
[env]

These profile above are using the emsdk_installer/1.38.29@bincrafters/stable conan package. It will automatically download the Emscripten SDK and set up required environment variables (like CC, CXX, etc.).

Note

In order to use emsdk_installer package, you need to add it to the remotes:

$ conan remote add bincrafters https://api.bintray.com/conan/bincrafters/public-conan

Note

Alternatively, it’s always possible to use an existing emsdk installation and manually specify required environment variables within the [env] section of the conan profile.

Note

In addition to the above, Windows users may need to specify CONAN_MAKE_PROGRAM, for instance from the existing MinGW installation (e.g. C:\MinGW\bin\mingw32-make.exe), or use make from the mingw_installer/1.0@conan/stable.

Note

In addition to the above, Windows users may need to specify CONAN_CMAKE_GENERATOR, e.g. to MinGW Makefiles, because default one is Visual Studio. Other options (e.g. Ninja) work as well.

As specified, os has been set to the Emscripten, and arch has been set to either asm.js or wasm (only these two are currently supported). And compiler setting has been set to match the one used by Emscripten - Clang 6.0 with libc++ standard library.

Running the code inside the browser

Note

Emscripten requires Python 2.7.12 or above, make sure that you have an up-to-date Python version installed.

Note

Running demo on Windows may require pywin32 module. Install it by running pip install pywin32.

In order to demonstrate how to use conan with Emscripten, let’s check out the example project:

$ git clone --depth 1 git@github.com:conan-io/examples.git

Change the directory to the Emscripten demo:

$ cd features
$ cd emscripten

This is an extremely simple demo, which just imports the famous zlib library and outputs its version into the browser.

In order to build it for the Emscripten run:

$ ./build.sh

or (on Windows):

$ ./build.cmd

Please note that running the above command may take a while to download and build required dependencies. This script will execute several conan commands:

$ conan remove conan-hello-emscripten/* -f
$ conan create . conan/testing  -k -p emscripten.profile --build missing
$ conan install conanfile.txt  -pr emscripten.profile

First one removes any traces of previous demo installations, just to ensure that environment is clean. Then, it builds the simple demo (it uses CMakeLists.txt and main.cpp files from the current directory). The following local profile is used (file emscripten.profile within the current directory):

include(default)
[settings]
os=Emscripten
arch=wasm
compiler=clang
compiler.version=6.0
compiler.libcxx=libc++
[options]
[build_requires]
emsdk_installer/1.38.29@bincrafters/stable
ninja/1.9.0
[env]

Finally, it installs the demo importing ithe required files (.html, .js and .wasm) into the bin subdirectory.

Then we can run the code inside the browser via emrun helper:

$ ./run.sh

or (on Windows):

$ ./run.cmd

The command above uses virtualenv generator generator in order to get emrun command available in the PATH. And as the result, Web Browser should be opened (or new tab in Web Browser will be opened, if it was already run), and the following output should be displayed:

$ Using zlib version: 1.2.11

It confirms the fact we have just built zlib into JavaScript and run it inside the Web Browser.