Scilla: A Smart Contract Intermediate Level Language
Introduction
Scilla short for Smart Contract Intermediate-Level LAnguage is an intermediate-level smart contract language being developed for Zilliqa. Scilla has been designed as a principled language with smart contract safety in mind.
Scilla imposes a structure on smart contracts that will make applications less vulnerable to attacks by eliminating certain known vulnerabilities directly at the language-level. Furthermore, the principled structure of Scilla will make applications inherently more secure and amenable to formal verification.
Zilliqa - the underlying blockchain platform on which Scilla contracts are run, has been designed to be scalable. It employs the idea of sharding to validate transactions in parallel. Zilliqa has an intrinsic token named Zilling, ZIL for short that are required to run smart contracts on Zilliqa.
Language Reference
A comprehensive documentation on Scilla, its features and constructs can be found here
Building and Running
Source code
We suggest users to use the latest release of Scilla available here.
Build requirements
Platform specific instructions for setting up your system for building Scilla can be found in INSTALL.md.
Compiling and Running
To build the project, run make clean; make from the root folder.
Once the project is built you can try the following things:
Evaluating a standalone closed expression:
From the project root, execute
./bin/eval-runner -gaslimit 10000 -libdir src/stdlib tests/eval/exp/good/let.scilexp
Instead of let.scilla you might want to try any different file in
tests/eval/exp. The second argument, which is a path to the Scilla
standard library can alternatively be specified in the environment
variable SCILLA_STDLIB_PATH. This must be an absolute path (or a
list of paths separated with : (or ; on Windows).
Type-checking a contract
From the project root, execute
./bin/scilla-checker -gaslimit 10000 -libdir src/stdlib tests/contracts/auction.scilla
Instead of auction.scilla you might want to try any different file in
tests/contracts with a complete implementation of a contract, or your
own contract code. The second argument, which is a path to the Scilla
standard library can alternatively be specified in the environment
variable SCILLA_STDLIB_PATH. As above, this must be an absolute
path(s).
If the checker only returns the contract structure in JSON format, it means that the contract has no type errors. Otherwise, a type error trace is provided.
The checker can be run with the following optional flags:
-cfto enable the cashflow checker and print its results.
Executing a simple transition
From the project root, execute
./bin/scilla-runner -init tests/runner/crowdfunding/init.json -istate tests/runner/crowdfunding/state_4.json -iblockchain tests/runner/crowdfunding/blockchain_4.json -imessage tests/runner/crowdfunding/message_4.json -o tests/runner/crowdfunding/output_4.json -i tests/contracts/crowdfunding.scilla -libdir src/stdlib -gaslimit 8000
or
./bin/scilla-runner -init tests/runner/zil-game/init.json -istate tests/runner/zil-game/state_5.json -iblockchain tests/runner/zil-game/blockchain_5.json -imessage tests/runner/zil-game/message_5.json -o tests/runner/zil-game/output_5.json -i tests/contracts/zil-game.scilla -libdir src/stdlib -gaslimit 8000
If you'd like to see the output produced by the aforementioned commands,
check the file specified by -o path/to/file.json argument.
Alternatively, use the easyrun script as below:
./easyrun.sh crowdfunding 1
where n is a number 0-5 for the number of "steps" to execute the
protocol (the messages and blockchain states are provided for only so
many steps in the simulation).
Where to find binaries
- The runnables are put into the folder
$PROJECT_DIR/bin
Running the testsuite
The testsuite is based on the OUnit2 framework and is driven by the
main module in tests/Testsuite.ml. Currently there are two types of
tests run in the testsuite. contracts tests run a full transition on
a contract with all input data provided. eval tests only test
expression evaluation. To add more tests of either of these kinds,
look for the corresponding .ml files in their tests/directory and add
accordingly.
To run the testsuite:
make test(this makes the Dune build system invoke testsuite executable with -print-diff true option to print colored diffs between error messages).
To run the testsuite executable manually using dune exec tests/testsuite.exe,
you have to provide the parameters -bin-dir and -tests-dir, which must be absolute paths to
the directory containing eval-runner, type-checker, scilla-runner, scilla-checker and
the tests/ directory containing the tests.
Relative paths may not work.
Parameters to testsuite executable can be passed like so:
dune exec tests/testsuite.exe -- <space-separate-parameters>To obtain a list of tests available:
dune exec tests/testsuite.exe -- -list-testTo run an individual test(s), for example
all_tests:1:exptests:14:let.scilla
(one of the tests from the list obtained via ./bin/testsuite -list-test):
dune exec tests/testsuite.exe -- -only-test all_tests:1:exptests:14:let.scilla -print-cli true The optional -print-cli true argument is to produce the command line
that has been used to run the test.
Developer Tools
Emacs mode
An emacs major mode for editing Scilla contracts is provided.
Add the following line to your .emacs file to load this mode for files ending with .scilla and .scillib.
For enabling flycheck mode for Scilla (see INSTALL.md).
;; For enabling flycheck mode for Scilla.
(setq scilla-root "/path/to/scilla/root")
;; Scilla mode
(load-file "/path/to/scilla-mode.el")
Vim plugin
A vim plugin for editing Scilla contracts is provided.
You can install the vim config files through Pathogen by:
git clone https://github.com/edisonljh/vim-scilla.git ~/.vim/bundle/vim-scilla
Or through Vundle by adding the following line to your ~/.vimrc:
Plugin 'edisonljh/vim-scilla'
Repo: vim-scilla.
VSCode Plugin
Visual Studio Code support for Scilla is avaiable. Github Source You can install it through:https://marketplace.visualstudio.com/items?itemName=as1ndu.scilla
Credits: as1ndu