.. index:: ! installing

.. _installing-solidity:

################################
Installing the Solidity Compiler
################################

Versioning
==========

Solidity versions follow `semantic versioning <https://semver.org>`_ and in addition to
releases, **nightly development builds** are also made available.  The nightly builds
are not guaranteed to be working and despite best efforts they might contain undocumented
and/or broken changes. We recommend using the latest release. Package installers below
will use the latest release.

Remix
=====

*We recommend Remix for small contracts and for quickly learning Solidity.*

`Access Remix online <https://remix.ethereum.org/>`_, you do not need to install anything.
If you want to use it without connection to the Internet, go to
https://github.com/ethereum/remix-live/tree/gh-pages and download the ``.zip`` file as
explained on that page. Remix is also a convenient option for testing nightly builds
without installing multiple Solidity versions.

Further options on this page detail installing commandline Solidity compiler software
on your computer. Choose a commandline compiler if you are working on a larger contract
or if you require more compilation options.

.. _solcjs:

npm / Node.js
=============

Use ``npm`` for a convenient and portable way to install ``solcjs``, a Solidity compiler. The
`solcjs` program has fewer features than the ways to access the compiler described
further down this page. The
:ref:`commandline-compiler` documentation assumes you are using
the full-featured compiler, ``solc``. The usage of ``solcjs`` is documented inside its own
`repository <https://github.com/ethereum/solc-js>`_.

Note: The solc-js project is derived from the C++
`solc` by using Emscripten which means that both use the same compiler source code.
`solc-js` can be used in JavaScript projects directly (such as Remix).
Please refer to the solc-js repository for instructions.

.. code-block:: bash

    npm install -g solc

.. note::

    The commandline executable is named ``solcjs``.

    The commandline options of ``solcjs`` are not compatible with ``solc`` and tools (such as ``geth``)
    expecting the behaviour of ``solc`` will not work with ``solcjs``.

Docker
======

Docker images of Solidity builds are available using the ``solc`` image from the ``ethereum`` organisation.
Use the ``stable`` tag for the latest released version, and ``nightly`` for potentially unstable changes in the develop branch.

The Docker image runs the compiler executable, so you can pass all compiler arguments to it.
For example, the command below pulls the stable version of the ``solc`` image (if you do not have it already),
and runs it in a new container, passing the ``--help`` argument.

.. code-block:: bash

    docker run ethereum/solc:stable --help

You can also specify release build versions in the tag, for example, for the 0.5.4 release.

.. code-block:: bash

    docker run ethereum/solc:0.5.4 --help

To use the Docker image to compile Solidity files on the host machine mount a
local folder for input and output, and specify the contract to compile. For example.

.. code-block:: bash

    docker run -v /local/path:/sources ethereum/solc:stable -o /sources/output --abi --bin /sources/Contract.sol

You can also use the standard JSON interface (which is recommended when using the compiler with tooling).
When using this interface it is not necessary to mount any directories as long as the JSON input is
self-contained (i.e. it does not refer to any external files that would have to be
:ref:`loaded by the import callback <initial-vfs-content-standard-json-with-import-callback>`).

.. code-block:: bash

    docker run ethereum/solc:stable --standard-json < input.json > output.json

Linux Packages
==============

Binary packages of Solidity are available at
`solidity/releases <https://github.com/ethereum/solidity/releases>`_.

We also have PPAs for Ubuntu, you can get the latest stable
version using the following commands:

.. code-block:: bash

    sudo add-apt-repository ppa:ethereum/ethereum
    sudo apt-get update
    sudo apt-get install solc

The nightly version can be installed using these commands:

.. code-block:: bash

    sudo add-apt-repository ppa:ethereum/ethereum
    sudo add-apt-repository ppa:ethereum/ethereum-dev
    sudo apt-get update
    sudo apt-get install solc

We are also releasing a `snap package <https://snapcraft.io/>`_, which is
installable in all the `supported Linux distros <https://snapcraft.io/docs/core/install>`_. To
install the latest stable version of solc:

.. code-block:: bash

    sudo snap install solc

If you want to help testing the latest development version of Solidity
with the most recent changes, please use the following:

.. code-block:: bash

    sudo snap install solc --edge

.. note::

    The ``solc`` snap uses strict confinement. This is the most secure mode for snap packages
    but it comes with limitations, like accessing only the files in your ``/home`` and ``/media`` directories.
    For more information, go to `Demystifying Snap Confinement <https://snapcraft.io/blog/demystifying-snap-confinement>`_.

Arch Linux also has packages, albeit limited to the latest development version:

.. code-block:: bash

    pacman -S solidity

Gentoo Linux has an `Ethereum overlay <https://overlays.gentoo.org/#ethereum>`_ that contains a Solidity package.
After the overlay is setup, ``solc`` can be installed in x86_64 architectures by:

.. code-block:: bash

    emerge dev-lang/solidity

macOS Packages
==============

We distribute the Solidity compiler through Homebrew
as a build-from-source version. Pre-built bottles are
currently not supported.

.. code-block:: bash

    brew update
    brew upgrade
    brew tap ethereum/ethereum
    brew install solidity

To install the most recent 0.4.x / 0.5.x version of Solidity you can also use ``brew install solidity@4``
and ``brew install solidity@5``, respectively.

If you need a specific version of Solidity you can install a
Homebrew formula directly from Github.

View
`solidity.rb commits on Github <https://github.com/ethereum/homebrew-ethereum/commits/master/solidity.rb>`_.

Copy the commit hash of the version you want and check it out on your machine.

.. code-block:: bash

    git clone https://github.com/ethereum/homebrew-ethereum.git
    cd homebrew-ethereum
    git checkout <your-hash-goes-here>

Install it using ``brew``:

.. code-block:: bash

    brew unlink solidity
    # eg. Install 0.4.8
    brew install solidity.rb

Static Binaries
===============

We maintain a repository containing static builds of past and current compiler versions for all
supported platforms at `solc-bin`_. This is also the location where you can find the nightly builds.

The repository is not only a quick and easy way for end users to get binaries ready to be used
out-of-the-box but it is also meant to be friendly to third-party tools:

- The content is mirrored to https://binaries.soliditylang.org where it can be easily downloaded over
  HTTPS without any authentication, rate limiting or the need to use git.
- Content is served with correct `Content-Type` headers and lenient CORS configuration so that it
  can be directly loaded by tools running in the browser.
- Binaries do not require installation or unpacking (with the exception of older Windows builds
  bundled with necessary DLLs).
- We strive for a high level of backwards-compatibility. Files, once added, are not removed or moved
  without providing a symlink/redirect at the old location. They are also never modified
  in place and should always match the original checksum. The only exception would be broken or
  unusable files with a potential to cause more harm than good if left as is.
- Files are served over both HTTP and HTTPS. As long as you obtain the file list in a secure way
  (via git, HTTPS, IPFS or just have it cached locally) and verify hashes of the binaries
  after downloading them, you do not have to use HTTPS for the binaries themselves.

The same binaries are in most cases available on the `Solidity release page on Github`_. The
difference is that we do not generally update old releases on the Github release page. This means
that we do not rename them if the naming convention changes and we do not add builds for platforms
that were not supported at the time of release. This only happens in ``solc-bin``.

The ``solc-bin`` repository contains several top-level directories, each representing a single platform.
Each one contains a ``list.json`` file listing the available binaries. For example in
``emscripten-wasm32/list.json`` you will find the following information about version 0.7.4:

.. code-block:: json

    {
      "path": "solc-emscripten-wasm32-v0.7.4+commit.3f05b770.js",
      "version": "0.7.4",
      "build": "commit.3f05b770",
      "longVersion": "0.7.4+commit.3f05b770",
      "keccak256": "0x300330ecd127756b824aa13e843cb1f43c473cb22eaf3750d5fb9c99279af8c3",
      "sha256": "0x2b55ed5fec4d9625b6c7b3ab1abd2b7fb7dd2a9c68543bf0323db2c7e2d55af2",
      "urls": [
        "bzzr://16c5f09109c793db99fe35f037c6092b061bd39260ee7a677c8a97f18c955ab1",
        "dweb:/ipfs/QmTLs5MuLEWXQkths41HiACoXDiH8zxyqBHGFDRSzVE5CS"
      ]
    }

This means that:

- You can find the binary in the same directory under the name
  `solc-emscripten-wasm32-v0.7.4+commit.3f05b770.js <https://github.com/ethereum/solc-bin/blob/gh-pages/emscripten-wasm32/solc-emscripten-wasm32-v0.7.4+commit.3f05b770.js>`_.
  Note that the file might be a symlink, and you will need to resolve it yourself if you are not using
  git to download it or your file system does not support symlinks.
- The binary is also mirrored at https://binaries.soliditylang.org/emscripten-wasm32/solc-emscripten-wasm32-v0.7.4+commit.3f05b770.js.
  In this case git is not necessary and symlinks are resolved transparently, either by serving a copy
  of the file or returning a HTTP redirect.
- The file is also available on IPFS at `QmTLs5MuLEWXQkths41HiACoXDiH8zxyqBHGFDRSzVE5CS`_.
- The file might in future be available on Swarm at `16c5f09109c793db99fe35f037c6092b061bd39260ee7a677c8a97f18c955ab1`_.
- You can verify the integrity of the binary by comparing its keccak256 hash to
  ``0x300330ecd127756b824aa13e843cb1f43c473cb22eaf3750d5fb9c99279af8c3``.  The hash can be computed
  on the command line using ``keccak256sum`` utility provided by `sha3sum`_ or `keccak256() function
  from ethereumjs-util`_ in JavaScript.
- You can also verify the integrity of the binary by comparing its sha256 hash to
  ``0x2b55ed5fec4d9625b6c7b3ab1abd2b7fb7dd2a9c68543bf0323db2c7e2d55af2``.

.. warning::

   Due to the strong backwards compatibility requirement the repository contains some legacy elements
   but you should avoid using them when writing new tools:

   - Use ``emscripten-wasm32/`` (with a fallback to ``emscripten-asmjs/``) instead of ``bin/`` if
     you want the best performance. Until version 0.6.1 we only provided asm.js binaries.
     Starting with 0.6.2 we switched to `WebAssembly builds`_ with much better performance. We have
     rebuilt the older versions for wasm but the original asm.js files remain in ``bin/``.
     The new ones had to be placed in a separate directory to avoid name clashes.
   - Use ``emscripten-asmjs/`` and ``emscripten-wasm32/`` instead of ``bin/`` and ``wasm/`` directories
     if you want to be sure whether you are downloading a wasm or an asm.js binary.
   - Use ``list.json`` instead of ``list.js`` and ``list.txt``. The JSON list format contains all
     the information from the old ones and more.
   - Use https://binaries.soliditylang.org instead of https://solc-bin.ethereum.org. To keep things
     simple we moved almost everything related to the compiler under the new ``soliditylang.org``
     domain and this applies to ``solc-bin`` too. While the new domain is recommended, the old one
     is still fully supported and guaranteed to point at the same location.

.. warning::

    The binaries are also available at https://ethereum.github.io/solc-bin/ but this page
    stopped being updated just after the release of version 0.7.2, will not receive any new releases
    or nightly builds for any platform and does not serve the new directory structure, including
    non-emscripten builds.

    If you are using it, please switch to https://binaries.soliditylang.org, which is a drop-in
    replacement. This allows us to make changes to the underlying hosting in a transparent way and
    minimize disruption. Unlike the ``ethereum.github.io`` domain, which we do not have any control
    over, ``binaries.soliditylang.org`` is guaranteed to work and maintain the same URL structure
    in the long-term.

.. _IPFS: https://ipfs.io
.. _Swarm: https://swarm-gateways.net/bzz:/swarm.eth
.. _solc-bin: https://github.com/ethereum/solc-bin/
.. _Solidity release page on github: https://github.com/ethereum/solidity/releases
.. _sha3sum: https://github.com/maandree/sha3sum
.. _keccak256() function from ethereumjs-util: https://github.com/ethereumjs/ethereumjs-util/blob/master/docs/modules/_hash_.md#const-keccak256
.. _WebAssembly builds: https://emscripten.org/docs/compiling/WebAssembly.html
.. _QmTLs5MuLEWXQkths41HiACoXDiH8zxyqBHGFDRSzVE5CS: https://gateway.ipfs.io/ipfs/QmTLs5MuLEWXQkths41HiACoXDiH8zxyqBHGFDRSzVE5CS
.. _16c5f09109c793db99fe35f037c6092b061bd39260ee7a677c8a97f18c955ab1: https://swarm-gateways.net/bzz:/16c5f09109c793db99fe35f037c6092b061bd39260ee7a677c8a97f18c955ab1/

.. _building-from-source:

Building from Source
====================

Prerequisites - All Operating Systems
-------------------------------------

The following are dependencies for all builds of Solidity:

+-----------------------------------+-------------------------------------------------------+
| Software                          | Notes                                                 |
+===================================+=======================================================+
| `CMake`_ (version 3.13+)          | Cross-platform build file generator.                  |
+-----------------------------------+-------------------------------------------------------+
| `Boost`_  (version 1.65+)         | C++ libraries.                                        |
+-----------------------------------+-------------------------------------------------------+
| `Git`_                            | Command-line tool for retrieving source code.         |
+-----------------------------------+-------------------------------------------------------+
| `z3`_ (version 4.8+, Optional)    | For use with SMT checker.                             |
+-----------------------------------+-------------------------------------------------------+
| `cvc4`_ (Optional)                | For use with SMT checker.                             |
+-----------------------------------+-------------------------------------------------------+

.. _cvc4: https://cvc4.cs.stanford.edu/web/
.. _Git: https://git-scm.com/download
.. _Boost: https://www.boost.org
.. _CMake: https://cmake.org/download/
.. _z3: https://github.com/Z3Prover/z3

.. note::
    Solidity versions prior to 0.5.10 can fail to correctly link against Boost versions 1.70+.
    A possible workaround is to temporarily rename ``<Boost install path>/lib/cmake/Boost-1.70.0``
    prior to running the cmake command to configure solidity.

    Starting from 0.5.10 linking against Boost 1.70+ should work without manual intervention.

Minimum Compiler Versions
^^^^^^^^^^^^^^^^^^^^^^^^^

The following C++ compilers and their minimum versions can build the Solidity codebase:

- `GCC <https://gcc.gnu.org>`_, version 8+
- `Clang <https://clang.llvm.org/>`_, version 7+
- `MSVC <https://visualstudio.microsoft.com/vs/>`_, version 2019+

Prerequisites - macOS
---------------------

For macOS builds, ensure that you have the latest version of
`Xcode installed <https://developer.apple.com/xcode/download/>`_.
This contains the `Clang C++ compiler <https://en.wikipedia.org/wiki/Clang>`_, the
`Xcode IDE <https://en.wikipedia.org/wiki/Xcode>`_ and other Apple development
tools that are required for building C++ applications on OS X.
If you are installing Xcode for the first time, or have just installed a new
version then you will need to agree to the license before you can do
command-line builds:

.. code-block:: bash

    sudo xcodebuild -license accept

Our OS X build script uses `the Homebrew <https://brew.sh>`_
package manager for installing external dependencies.
Here's how to `uninstall Homebrew
<https://docs.brew.sh/FAQ#how-do-i-uninstall-homebrew>`_,
if you ever want to start again from scratch.

Prerequisites - Windows
-----------------------

You need to install the following dependencies for Windows builds of Solidity:

+-----------------------------------+-------------------------------------------------------+
| Software                          | Notes                                                 |
+===================================+=======================================================+
| `Visual Studio 2019 Build Tools`_ | C++ compiler                                          |
+-----------------------------------+-------------------------------------------------------+
| `Visual Studio 2019`_  (Optional) | C++ compiler and dev environment.                     |
+-----------------------------------+-------------------------------------------------------+

If you already have one IDE and only need the compiler and libraries,
you could install Visual Studio 2019 Build Tools.

Visual Studio 2019 provides both IDE and necessary compiler and libraries.
So if you have not got an IDE and prefer to develop Solidity, Visual Studio 2019
may be a choice for you to get everything setup easily.

Here is the list of components that should be installed
in Visual Studio 2019 Build Tools or Visual Studio 2019:

* Visual Studio C++ core features
* VC++ 2019 v141 toolset (x86,x64)
* Windows Universal CRT SDK
* Windows 8.1 SDK
* C++/CLI support

.. _Visual Studio 2019: https://www.visualstudio.com/vs/
.. _Visual Studio 2019 Build Tools: https://www.visualstudio.com/downloads/#build-tools-for-visual-studio-2019

Dependencies Helper Script
--------------------------

We have a helper script which you can use to install all required external dependencies
on macOS, Windows and on numerous Linux distros.

.. code-block:: bash

    ./scripts/install_deps.sh

Or, on Windows:

.. code-block:: bat

    scripts\install_deps.ps1

Note that the latter command will install ``boost`` and ``cmake`` to the ``deps`` subdirectory, while the former command
will attempt to install the dependencies globally.

Clone the Repository
--------------------

To clone the source code, execute the following command:

.. code-block:: bash

    git clone --recursive https://github.com/ethereum/solidity.git
    cd solidity

If you want to help developing Solidity,
you should fork Solidity and add your personal fork as a second remote:

.. code-block:: bash

    git remote add personal git@github.com:[username]/solidity.git

.. note::
    This method will result in a prerelease build leading to e.g. a flag
    being set in each bytecode produced by such a compiler.
    If you want to re-build a released Solidity compiler, then
    please use the source tarball on the github release page:

    https://github.com/ethereum/solidity/releases/download/v0.X.Y/solidity_0.X.Y.tar.gz

    (not the "Source code" provided by github).

Command-Line Build
------------------

**Be sure to install External Dependencies (see above) before build.**

Solidity project uses CMake to configure the build.
You might want to install `ccache`_ to speed up repeated builds.
CMake will pick it up automatically.
Building Solidity is quite similar on Linux, macOS and other Unices:

.. _ccache: https://ccache.dev/

.. code-block:: bash

    mkdir build
    cd build
    cmake .. && make

or even easier on Linux and macOS, you can run:

.. code-block:: bash

    #note: this will install binaries solc and soltest at usr/local/bin
    ./scripts/build.sh

.. warning::

    BSD builds should work, but are untested by the Solidity team.

And for Windows:

.. code-block:: bash

    mkdir build
    cd build
    cmake -G "Visual Studio 16 2019" ..

In case you want to use the version of boost installed by ``scripts\install_deps.ps1``, you will
additionally need to pass ``-DBoost_DIR="deps\boost\lib\cmake\Boost-*"`` and ``-DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded``
as arguments to the call to ``cmake``.

This should result in the creation of **solidity.sln** in that build directory.
Double-clicking on that file should result in Visual Studio firing up.  We suggest building
**Release** configuration, but all others work.

Alternatively, you can build for Windows on the command-line, like so:

.. code-block:: bash

    cmake --build . --config Release

CMake Options
=============

If you are interested what CMake options are available run ``cmake .. -LH``.

.. _smt_solvers_build:

SMT Solvers
-----------
Solidity can be built against SMT solvers and will do so by default if
they are found in the system. Each solver can be disabled by a `cmake` option.

*Note: In some cases, this can also be a potential workaround for build failures.*


Inside the build folder you can disable them, since they are enabled by default:

.. code-block:: bash

    # disables only Z3 SMT Solver.
    cmake .. -DUSE_Z3=OFF

    # disables only CVC4 SMT Solver.
    cmake .. -DUSE_CVC4=OFF

    # disables both Z3 and CVC4
    cmake .. -DUSE_CVC4=OFF -DUSE_Z3=OFF

The Version String in Detail
============================

The Solidity version string contains four parts:

- the version number
- pre-release tag, usually set to ``develop.YYYY.MM.DD`` or ``nightly.YYYY.MM.DD``
- commit in the format of ``commit.GITHASH``
- platform, which has an arbitrary number of items, containing details about the platform and compiler

If there are local modifications, the commit will be postfixed with ``.mod``.

These parts are combined as required by Semver, where the Solidity pre-release tag equals to the Semver pre-release
and the Solidity commit and platform combined make up the Semver build metadata.

A release example: ``0.4.8+commit.60cc1668.Emscripten.clang``.

A pre-release example: ``0.4.9-nightly.2017.1.17+commit.6ecb4aa3.Emscripten.clang``

Important Information About Versioning
======================================

After a release is made, the patch version level is bumped, because we assume that only
patch level changes follow. When changes are merged, the version should be bumped according
to semver and the severity of the change. Finally, a release is always made with the version
of the current nightly build, but without the ``prerelease`` specifier.

Example:

0. The 0.4.0 release is made.
1. The nightly build has a version of 0.4.1 from now on.
2. Non-breaking changes are introduced --> no change in version.
3. A breaking change is introduced --> version is bumped to 0.5.0.
4. The 0.5.0 release is made.

This behaviour works well with the  :ref:`version pragma <version_pragma>`.
