192 entries tagged with #GNAT
by Paul Jarrett
Ada Crate of the Year: Interactive code search
A retrospective on learning Ada and developing a tool with it in 2021 from 2021 Ada Crate of the Year Winner Paul Jarrett.by Claire Dross
Handling Aliasing through Pointers in SPARK
As I explained in a blog post a couple of years ago, pointers are subjected to a strict ownership policy in SPARK. It prevents aliasing and allows for an efficient formal verification model. Of course, it comes at the cost of restrictions which might not be applicable to all usage. In particular, while ownership makes it possible to represent certain recursive data-structures, those involving cycles or sharing are de-facto forbidden. This is a choice, and not every proof tool did the same. For example, the WP plug-in of Frama-C supports pointers with arbitrary aliasing. If some information about the separation of memory cells is necessary to verify a program, then the user shall give the annotation explicitly. I have investigated modeling pointers with aliasing in SPARK as indices in a big memory array. I will present the results of my experiments in this blog post. We will see that, while such a representation is indeed possible modulo some hiding in SPARK, it can quickly become rather heavy in practice.
by Manuel Hatzl
SPARK Crate of the Year: Unbounded containers in SPARK
Manuel Hatzl is the winner of the 2021 SPARK Crate of the year! In this blog post he shares his experience using Ada/SPARK and how he created the spark_unbound libraryby Yannick Moy , Claire Dross

Proving the Correctness of GNAT Light Runtime Library
The GNAT light runtime library is a version of the runtime library targeted at embedded platforms and certification, which has been certified for use at the highest levels of criticality in several industrial domains. It contains around 180 units focused mostly on I/O, numerics, text manipulation, memory operations. We have used SPARK to prove the correctness of 40 of them: that the code is free of runtime errors, and that it satisfies its functional specifications.by Fabien Chouteau
AdaCore at FOSDEM 2022
Like previous years, AdaCore will participate in FOSDEM. Once again the event will be online only, but this won’t prevent us from celebrating Open Source software and it is an opportunity for even more people to participate around the world.
by Fabien Chouteau
Ada/SPARK Crate Of The Year 2021 Winners Announced!
In June of 2021 we announced the launch of a new programming competition called Ada/SPARK Crate Of The Year Awards. We believe the Alire source package manager is a game changer for Ada/SPARK, so we want to use this competition to reward the people contributing to the ecosystem. Today we are pleased to announce the results. But first, we want to congratulate all the participants, and the Alire community at large, for reaching 200 crates in the ecosystem in January of this year. We truly believe in a bright future for the Ada/SPARK open-source ecosystem with Alire at the forefront. Reaching this milestone is a great sign, inside and outside the Ada/SPARK community, of the evolution and the energy of the ecosystem.
by Yannick Moy
SPARKNaCl - Two Years of Optimizing Crypto Code in SPARK (and counting)
SPARKNaCl is a SPARK version of the TweetNaCl cryptographic library, developed by formal methods and security expert Rod Chapman. For two years now, Rod has been developing and optimizing this open-source cryptographic library while preserving the automatic type-safety proof across code changes and tool updates. He has recently given a talk about this experience that I highly recommend.
by Paul Butcher

Fuzz Testing in International Aerospace Guidelines
Through the HICLASS UK research group, AdaCore has been developing security-focused software development tools that are aligned with the objectives stated within the avionics security standards. In addition, they have been developing further guidelines that describe how vulnerability identification and security assurance activities can be described within a Plan for Security Aspects of Certification.by Fabien Chouteau
Starting micro-controller Ada drivers in the Alire ecosystem
A few days ago, someone asked on the Ada Drivers Library repository how to add support for the SAMD21 micro-controller. Nowadays, I would rather recommend people to contribute this kind of micro-controller support project to the Alire ecosystem. I started to write a few instructions on how to get started, but it quickly became a blog-worthy piece of text.by Pat Rogers
Task Suspension with a Timeout in Ravenscar/Jorvik
This blog entry shows how to define an abstract data type that allows tasks to block on objects of the type, waiting for resumption signals from other components, for at most a specified amount of time per object. This "timeout" capability has been available in Ada from the beginning, via select statements containing timed entry calls. But what about developers working within the Ravenscar and Jorvik tasking subsets? Select statements and timed calls are not included within either profile. This new abstraction will provide some of the functionality of timed entry calls, with an implementation consistent with the Ravenscar and Jorvik subsets.by Fabien Chouteau
A design pattern for OOP in Ada
When I do Object Oriented Programming with Ada, I tend to follow a design pattern that makes it easier for me and hopefully also for people reading my code.by Yannick Moy
When the RISC-V ISA is the Weakest Link
NVIDIA has been using SPARK for some time now to develop safety- and security-critical firmware applications. At the recent DEF CON 29, hackers Zabrocki and Matrosov presented how they went about attacking NVIDIA firmware written in SPARK but ended up attacking the RISC-V ISA instead!Zabrocki starts by explaining the context for their red teaming exercise at NVIDIA, followed by a description of SPARK and their evaluation of the language from a security attack perspective. He shows how they used an extension of Ghidra to decompile the binary code generated by GNAT and describes the vulnerability they identified in the RISC-V ISA thanks to that decompilation. Matrosov goes on to explain how they glitched the NVIDIA chip to exploit this vulnerability. Finally, Zabrocki talks about projects used to harden RISC-V platforms.
by Kyriakos Georgiou
Security-Hardening Software Libraries with Ada and SPARK
Part of AdaCore's ongoing efforts under the HICLASS project is to demonstrate how the SPARK technology can play an integral part in the security-hardening of existing software libraries written in other non-security-oriented programming languages such as C. This blog post presents the first white paper under this work-stream, “Security-Hardening Software Libraries with Ada and SPARK”.
by Fabien Chouteau

Announcing The First Ada/SPARK Crate Of The Year Award
We're happy to announce our new programming competition, the Ada/SPARK Crate Of The Year Award! We believe the Alire package manager is a game changer for Ada/SPARK, so we want to use this competition to reward the people contributing to the ecosystem.by Roderick Chapman
SPARKNaCl with GNAT and SPARK Community 2021: Port, Proof and Performance
This post continues our adventures with SPARKNaCl - our verified SPARK version of the TweetNaCl cryptographic library. This time, we'll be looking at yet more performance improvement via proof-driven "operator narrowing", porting the library to GNAT Community 2021, and the effect that has on proof and performance of the code.by Arnaud Charlet
Going beyond Ada 2022
As we've seen previously in Ada 2022 support in GNAT, the support for Ada 2022 is now mostly there for everyone to take advantage of. We're now crossing fingers for this new revision to be officially stamped by ISO in 2022.
by Fabien Chouteau , Nicolas Setton

GNAT Community 2021 is here!
We are happy to announce that the GNAT Community 2021 release is now available via https://www.adacore.com/download. Here are some release highlights:
by Pat Rogers
An Introduction to Jorvik, the New Tasking Profile in Ada 2022
The Ada 2022 draft defines a new tasking profile named Jorvik (pronounced “Yourvick”), based directly on the standard Ravenscar profile. Jorvik relaxes certain restrictions in order to increase expressive power for real-time/embedded Ada and SPARK applications. We will explore the details in this blog entry.by Fabien Chouteau

From Rust to SPARK: Formally Proven Bip-Buffers
I am following the evolution of the embedded Rust community and in particular the work of James Munns from Ferrous-Systems. One of the projects that caught my attention is bbqueue, a single producer, single consumer, lockless, thread safe queue, based on BipBuffers.by Pat Rogers
On the Benefits of Families ... (Entry Families)
Ada has a concurrency construct known as “entry families” that, in some cases, is just what we need to express a concise, clear solution.
by Simon Buist

Showing Global contracts with GNAT Studio
In the integrated development environment, GNAT Studio, there is now a plugin that inserts the generated Global contracts inline with the code.by Roderick Chapman
Doubling the Performance of SPARKNaCl (again...)
Following my last blog entry, further experiments show how the performance of SPARKNaCl can be doubled (again), plus analysis of worst-case stack usage and code size at all optimization levels.by Roderick Chapman
Performance analysis and tuning of SPARKNaCl
This blog goes into the details of both measuring and improving the runtime performance of SPARKNaCl on a real "bare metal" embedded target, and comparing results with those for the original "TweetNaCl" C implementation.by Fabien Chouteau
AdaCore at FOSDEM 2021
Like previous years, AdaCore will participate in FOSDEM. This time the event will be online only, but this won’t prevent us from celebrating Open Source software. AdaCore engineers will give two talks in the Safety and Open Source devroom, a topic at the heart of AdaCore since its inception.by Fabien Chouteau

Mini SAM M4 Ada BSP
Beyond the great look, the Mini SAM M4 provide a powerful 120 Mhz Microchip SAMD51 Cortex-M microcontroller, a couple of LEDs and a user button. Let's program it with Ada.by Léo Germond
How To: GNAT Pro with Docker
Using GNAT Pro with containerization technologies, such as Docker, is so easy, a whale could do it!
by Fabien Chouteau
Ada on any ARM Cortex-M device, in just a couple minutes
In this blog post I want to present a new tool that allows one to very quickly and easily start Ada programming on any ARM Cortex-M or RISC-V microcontroller.by Paul Butcher
Finding Vulnerabilities using Advanced Fuzz testing and AFLplusplus v3.0
Some of you may recall an AdaCore blog post written in 2017 by Thales engineer Lionel Matias titled "Leveraging Ada Run-Time Checks with Fuzz Testing in AFL". This insightful post took us on a journey of discovery as Lionel demonstrated how Ada programs, compiled using GNAT Pro and an adapted assembler pass can be subjected to advanced fuzz testing. In order to achieve this Lionel demonstrated how instrumentation of the generated assembly code around jump and label instructions, could be subjected to grey-box (path aware) fuzz testing (using the original AFL v2.52b as the fuzz engine). Lionel explained how applying the comprehensive spectrum of Ada runtime checks, in conjunction with Ada's strong typing and contract based programming, enhanced the capabilities of fuzz testing beyond the abilities of other languages. Ada's advanced runtime checking, for exceptions like overflows, and the scrutiny of Ada's design by contract assertions allow corner case bugs to be found whilst also utilising fuzz testing to verify functional correctness.
by Juliana Silva

Make with Ada 2020: Ada Robot Car With Neural Network
Guillermo Perez's project won a finalist prize in the Make with Ada 2019/20 competition. This project was originally posted on Hackster.io here. For those interested in participating in the 2020/21 competition, registration is now open and project submissions will be accepted until Jan 31st 2021, register here.by Arnaud Charlet
Ada 202x support in GNAT
News from the Ada front The next revision of the Ada standard is now almost ready, so it's time for a status update on where GNAT and AdaCore stand on this front!
by Juliana Silva

Make With Ada 2020: High Integrity Sumobot
Blaine Osepchuk's project won a finalist prize in the Make with Ada 2019/20 competition. This project was originally posted on Hackster.io here. For those interested in participating in the 2020/21 competition, registration is now open and project submissions will be accepted until Jan 31st 2021, register here.
by Michael Frank

Code Obfuscator for Ada using Libadalang and SPARK
A code obfuscator is a method of sharing coding discussions of real-world examples without giving away proprietary or classified information. This article shows an example of an Ada obfuscator, written in the SPARK language and using the Libadalang library to intelligently hide names and text within the source.by Fabien Chouteau

Ada for micro:bit Part 1: Getting Started
Welcome to the Ada for micro:bit series where we look at simple examples to learn how to program the BBC micro:bit with Ada.
by Pierre-Marie de Rodat
GNATcoverage: getting started with instrumentation
This is the second post of a series about GNATcoverage and source code instrumentation. The previous post introduced how GNATcoverage worked originally and why we extended it to support source instrumentation-based code coverage computation. Let’s now see it in action in the most simple case: a basic program running on the host machine, i.e. the Linux/Windows machine that runs GNATcoverage itself.
by Pierre-Marie de Rodat
Introducing source code instrumentation in GNATcoverage
This is the first post of a series about GNATcoverage and source code instrumentation.In order to make GNATcoverage viable in more contexts, we planned several years ago to add instrumentation support in GNATcoverage for Ada sources. This feature reached maturation recently and is available in the last Continuous Release, so it is a good time to present it with a blog series!by Emma Adby

Make with Ada 2020: LoRaDa := Ada + LoRa;
Hedley Rainnie's project combines 6 different SoCs all programmed in Ada performing as a LoRa network. He also showcases a BLE bridge to a LoRa server. His project came about when him and his wife were musing about how to detect and deter unwanted garden visitors. This ongoing project won a finalist prize in the 2019/20 Make with Ada competition.by Emma Adby

Make with Ada 2020: Disaster Management with Smart Circuit Breaker
Shahariar's project ensures safety against electrical fire or shock during an earthquake, flood, gas leakage or fire breakout by disconnecting the mains with a smart circuit breaker. Additionally, this project won a finalist prize in the 2019/20 Make with Ada competition.by Emma Adby

Make with Ada 2020: CryptAda - (Nuclear) Crypto on Embedded Device
Team CryptAda's project collects entropy, manages an entropy pool, implements a homemade PRNG, and generates RSA keys directly on the board with an accent on security. Additionally, this project won a finalist prize in the 2019/20 Make with Ada competition.by Emma Adby

Make with Ada 2020: The SmartBase - IoT Adjustable Bed
John Singleton's The SmartBase makes your existing adjustable bed safer and easier to use by adding voice control and safe (and fun!) LED underbed lighting! Additionally, this project won first place prize in the 2019/20 Make with Ada competition.by Jon Andrew
CuBit: A General-Purpose Operating System in SPARK/Ada
Last year, I started evaluating programming languages for a formally-verified operating system. I've been developing software for a while, but only recently began work in high integrity software development and formal methods. There are several operating system projects, like the SeL4 microkernel and the Muen separation kernel, that make use of formal verification. But I was interested in using a formally-verified language to write a general-purpose OS - an environment for abstracting the underlying hardware while acting as an arbiter for running the normal applications we're used to.by Nicolas Setton

GNAT Community 2020 is here!
We are happy to announce that the GNAT Community 2020 release is now available! Read the post for access to download and to find out about this year's release highlights.by Pat Rogers
From Ada to Platinum SPARK: A Case Study for Reusable Bounded Stacks
This blog entry describes the transformation of an Ada stack ADT into a completely proven SPARK implementation that relies on static verification instead of run-time enforcement of the abstraction’s semantics. We will prove that there are no reads of unassigned variables, no array indexing errors, no range errors, no numeric overflow errors, no attempts to push onto a full stack, no attempts to pop from an empty stack, that subprogram bodies implement their functional requirements, and so on. As a result, we get a maximally robust implementation of a reusable stack abstraction providing all the facilities required for production use.by Johannes Kliemann
Ada on the ESP8266
Not long ago, AdaCore published its LLVM frontend for GNAT. Also quite recently Espressif updated their LLVM backend to LLVM 9 which also happens to be the LLVM version of GNAT. This gave me to the idea to try out if LLVMs promise of providing modular and reusable toolchain technologies is true.by Martyn Pike
A Trivial File Transfer Protocol Server written in Ada
For an upcoming project, I needed a simple way of transferring binary files over an Ethernet connection with minimal (if any at all) user interaction. A protocol that's particularly appropriate for this kind of usage is the Trivial File Transfer Protocol (TFTP).by Roderick Chapman
Proving properties of constant-time crypto code in SPARKNaCl
Over the last few months, I developed a SPARK version of the TweetNaCl cryptographic library. This was made public on GitHub in February 2020, under the 2-clause BSD licence. This blog entry goes into a bit more technical detail on one particular aspect of the project: the challenge of re-writing and verifying "constant time" algorithms using SPARK.by Ghjuvan Lacambre

Time travel debugging in GNAT Studio with GDB and RR
Learn how to use GDB and RR's advanced time traveling features in GNAT Studio.by Pierre-Marie de Rodat
A Further Expedition into Libadalang: Save Time with Libadalang.Helpers.App
Martyn’s recent blog post showed small programs based on Libadalang to find uses of access types in Ada sources. Albeit short, these programs need to take care of all the tedious logistics around processing Ada sources: find the files to work on, create a Libadalang analysis context, use it to read the source files, etc. Besides, they are not very convenient to run:
by Vadim Godunko
Using GNAT-LLVM to target Ada to WebAssembly
The GNAT-LLVM project provides an opportunity to port Ada to new platforms, one of which is WebAssembly. We conducted an experiment to evaluate the porting of Ada and the development of bindings to use Web API provided by the browser directly from Ada applications.
by Fabien Chouteau

Ada on a Feather
I was quite happy to see AdaFruit release their first Feather format board including a micro-controller with plenty of Ada support, the STM32F4. I bought a board right away and implemented some support code for it.by Quentin Ochem
Witnessing the Emergence of a New Ada Era
For nearly four decades the Ada language (in all versions of the standard) has been helping developers meet the most stringent reliability, safety and security requirements in the embedded market. As such, Ada has become an entrenched player in its historic A&D niche, where its technical advantages are recognized and well understood. Ada has also seen usage in other domains (such as medical and transportation) but its penetration has progressed at a somewhat slower pace. In these other markets Ada stands in particular contrast with the C language, which, although suffering from extremely well known and documented flaws, remains a strong and seldom questioned default choice. Or at least, when it’s not the choice, C is still the starting point (a gateway drug?) for alternatives such as C++ or Java, which in the end still lack the software engineering benefits that Ada embodies..
by Martyn Pike
An Expedition into Libadalang
I’ve been telling Ada developers for a while now that Libadalang will open up the possibility of more-easily writing Ada source code analysis tools. (You can read more about Libadalang here and here and can also access the project on Github.)
by Alexander Senier
RecordFlux: From Message Specifications to SPARK Code
Handling binary data is hard. Errors in parsers routinely lead to critical security vulnerabilities. In this post we show how the RecordFlux toolset eases the creation of formally verified binary parsers in SPARK.by Arnaud Charlet
The Power of Technology Integration and Open Source
Part of our core expertise at AdaCore is to integrate multiple technologies as smoothly as possible and make it a product. This started at the very beginning of our company by integrating a code generator (GCC) with an Ada front-end (GNAT) which was then followed by integrating a debugger engine (GDB) and led to today's rich GNAT Pro offering.
by Claire Dross
Pointer Based Data-Structures in SPARK
As seen in a previous post, it is possible to use pointers (or access types) in SPARK provided the program abides by a strict memory ownership policy designed to prevent aliasing. We will show in this post how to define pointer-based data-structures in SPARK and how to traverse them without breaking the ownership policy.by Arnaud Charlet
Combining GNAT with LLVM
Presenting the GNAT LLVM projectAt AdaCore labs, we have been working for some time now on combining the GNAT Ada front-end with a different code generator than GCC.
by Emma Adby

The Make with Ada competition is back!
AdaCore’s fourth annual Make with Ada competition launched this week with over $8K in cash and prizes to be awarded for the most innovative embedded systems projects developed using Ada and/or SPARK.
by Isabelle Vialard
Secure Use of Cryptographic Libraries: SPARK Binding for Libsodium
The challenge faced by cryptography APIs is to make building functional and secure programs easy for the user. In this blog post I will present you how I created a SPARK binding for Libsodium, using strong typing and preconditions/postconditions to enforce a safe and functional use of basic cryptographic primitives.by Joffrey Huguet , Johannes Kanig
Proving a simple program doing I/O ... with SPARK
The functionality of many security-critical programs is directly related to Input/Output (I/O). This includes command-line utilities such as gzip, which might process untrusted data downloaded from the internet, but also any servers that are directly connected to the internet, such as webservers, DNS servers and so on. In this blog post we show an approach that deals with error handling and reasoning about content, and demonstrate the approach using the cat command line utility.by Juan Zamorano
Using Ada for a Spanish Satellite Project
I am an Associate Professor at Polytechnic University of Madrid’s (Universidad Politécnica de Madrid / UPM) in the Department of Architecture and Technology of Computer Systems. For the past several years I have been directing a team of colleagues and students in the development of a UPMSat-2 microsatellite. The project originally started in 2013 as a follow-to the UPM-SAT 1, launched by an Ariane-4 in 1995.
by Claire Dross
Using Pointers in SPARK
In this blog post, I will present one of the most interesting additions to the community 2019 version of SPARK: pointer support. One of the core assumption in SPARK has always been the absence of aliasing, so adding pointers without breaking this assumption was quite a challenge. I will explain how this was achieved using an ownership model for pointers (like is done in Rust) through small examples.by Nicolas Setton

GNAT Community 2019 is here!
We are pleased to announce that GNAT Community 2019 has been released! See https://www.adacore.com/download.
by Boran Car

Bringing Ada To MultiZone
C is the dominant language of the embedded world, almost to the point of exclusivity. Due to its age, and its goal of being a “portable assembler”, it deliberately lacks type-safety, opening up exploit vectors. Proposed solutions are partitioning the application into smaller intercommunicating blocks, designed with the principle of least privilege in mind; and rewriting the application in a type-safe language. We believe that both approaches are complementary and want to show you how to combine separation and isolation provided by MultiZone together with iteratively rewriting parts in Ada. We will take the MultiZone SDK demo and rewrite one of the zones in Ada.by Allan Ascanius , Per Dalgas Jakobsen
Winning DTU RoboCup with Ada and SPARK
The Danish Technical University has a yearly RoboCup where autonomous vehicles solve a number of challenges. We participated with RoadRunner, a 3D printed robot with wheel suspension, based on the BeagleBone Blue ARM-based board and the Pixy 1 camera with custom firmware enabling real-time line detection. Code is written in Ada and formally proved correct with SPARK at Silver level.by Pamela Trevino
Public Ada Training Paris June 3-7, 2019
This course is geared to software professionals looking for a practical introduction to the Ada language with a focus on embedded systems, including real-time features as well as critical features introduced in Ada 2012. By attending this course you will understand and know how to use Ada for both sequential and concurrent applications, through a combination of live lectures from AdaCore's expert instructors and hands-on workshops using AdaCore's latest GNAT technology. AdaCore will provide an Ada 2012 tool-chain and ARM-based target boards for embedded workshops. No previous experience with Ada is required.
by Arnaud Charlet
How Do We Use CodePeer at AdaCore
A question that our users sometimes ask us is "do you use CodePeer at AdaCore and if so, how?". The answer is yes! and this blog post will hopefully give you some insights into how we are doing it for our own needs.
by Rob Tice
AdaFractal Part1: Ada with a Portable GUI
The is the first part of a multiple part post that covers the development of the AdaFractal project. The idea was to create fractals in Ada. Here we will cover how to use AWS to create a flexible and portable way to display the generated fractals without using bulky graphics libraries.by Quentin Ochem
Proving Memory Operations - A SPARK Journey
The promise behind the SPARK language is the ability to formally demonstrate properties in your code regardless of the input values that are supplied - as long as those values satisfy specified constraints. As such, this is quite different from static analysis tools such as our CodePeer or the typical offering available for e.g. the C language, which trade completeness for efficiency in the name of pragmatism. Indeed, the problem they’re trying to solve - finding bugs in existing applications - makes it impossible to be complete. Or, if completeness is achieved, then it is at the cost of massive amount of uncertainties (“false alarms”). SPARK takes a different approach. It requires the programmer to stay within the boundaries of a (relatively large) Ada language subset and to annotate the source code with additional information - at the benefit of being able to be complete (or sound) in the verification of certain properties, and without inundating the programmer with false alarms.
by Pamela Trevino
Public Ada Training Paris, France Dec 3 - 7, 2018
This course is geared to software professionals looking for a practical introduction to the Ada language with a focus on embedded systems, including real-time features as well as critical features introduced in Ada 2012. By attending this course you will understand and know how to use Ada for both sequential and concurrent applications, through a combination of live lectures from AdaCore's expert instructors and hands-on workshops using AdaCore's latest GNAT technology. AdaCore will provide an Ada 2012 tool-chain and ARM-based target boards for embedded workshops. No previous experience with Ada is required.
by Fabien Chouteau

Ada on FPGAs with PicoRV32
When I bought the TinyFPGA-BX board, I thought it would be an opportunity to play a little bit with FPGA, learn some Verilog or VHDL. But when I discovered that it was possible to have a RISC-V CPU on it, I knew I had to run Ada code on it.by Emma Adby , Fabien Chouteau

GNAT Community 2018 is here!
Calling all members of the Ada and SPARK community, we are pleased to announce that GNAT Community 2018 is here! adacore.com/download
by Thomas Quinot
PolyORB now lives on Github
PolyORB, AdaCore's versatile distribution middleware, now lives on Github. Its new home is https://github.com/AdaCore/polyorb
by Rob Tice

SPARKZumo Part 2: Integrating the Arduino Build Environment Into GPS
This is part #2 of the SPARKZumo series of blog posts. This post covers the build system that was used to build the SPARKZumo project and how to automate the process in GPS.by Rob Tice
SPARKZumo Part 1: Ada and SPARK on Any Platform
So you want to use SPARK for your next microcontroller project? Great choice! All you need is an Ada 2012 ready compiler and the SPARK tools. But what happens when an Ada 2012 compiler isn’t available for your architecture?
by Fabien Chouteau
Ada on the micro:bit
Updated July 2018
by Yannick Moy
Tokeneer Fully Verified with SPARK 2014
Tokeneer is a software for controlling physical access to a secure enclave by means of a fingerprint sensor. This software was created by Altran (Praxis at the time) in 2003 using the previous generation of SPARK language and tools, as part of a project commissioned by the NSA to investigate the rigorous development of critical software using formal methods. The project artefacts, including the source code, were released as open source in 2008. Tokeneer was widely recognized as a milestone in industrial formal verification. We recently transitioned this software to SPARK 2014, and it allowed us to go beyond what was possible with the previous SPARK technology. We have also shown how security vulnerabilities introduced in the code can be detected by formal verification.by Felix Krause
The Road to a Thick OpenGL Binding for Ada: Part 2
This blog post is part two of a tutorial based on the OpenGLAda project and will cover implementation details such as a type system for interfacing with C, error handling, memory management, and loading functions.by Johannes Kanig

Bitcoin blockchain in Ada: Lady Ada meets Satoshi Nakamoto
Bitcoin is getting a lot of press recently, but let's be honest, that's mostly because a single bitcoin worth 800 USD in January 2017 was worth almost 20,000 USD in December 2017. However, bitcoin and its underlying blockchain are beautiful technologies that are worth a closer look. Let’s take that look with our Ada hat on!
by Felix Krause

The Road to a Thick OpenGL Binding for Ada: Part 1
This blog post is part one of a tutorial based on the OpenGLAda project and will cover some the background of the OpenGL API and the basic steps involved in importing platform-dependent C functions.
by Lionel Matias
Leveraging Ada Run-Time Checks with Fuzz Testing in AFL
Fuzzing is a very popular bug finding method. The concept, very simple, is to continuously inject random (garbage) data as input of a software component, and wait for it to crash. If, like me, you find writing robustness test tedious and not very efficient in finding bugs, you might want to try fuzzing your Ada code.Here's a recipe to fuzz-test your Ada code, using American Fuzzy Lop and all the runtime checks your favorite Ada compiler can provide.Let's see (quickly) how AFL works, then jump right into fuzzing 3 open-source Ada libraries: ZipAda, AdaYaml, and GNATCOLL.JSON.by Pierre-Marie de Rodat , Raphaël Amiard
Cross-referencing Ada with Libadalang
Libadalang has come a long way since the last time we blogged about it. In the past 6 months, we have been working tirelessly on name resolution, a pretty complicated topic in Ada, and it is finally ready enough that we feel ready to blog about it, and encourage people to try it out.
by Manuel Iglesias Abbatermarco
Make with Ada 2017- Ada Based IoT Framework
SummaryThe Ada IoT Stack consists of an lwIp (“lightweight IP”) stack implementation written in Ada, with an associated high-level protocol to support embedded device connectivity nodes for today’s IoT world. The project was developed for the Make With Ada 2017 competition based on existing libraries and ported to embedded STM32 devices.
by Jamie Ayre
Welcoming New Members to the GNAT Pro Family
As we see the importance of software grow in applications, the quality of that software has become more and more important. Even outside the mission- and safety-critical arena customers are no longer accepting software failures (the famous blue screens of death, and there are many...). Ada has a very strong answer here and we are seeing more and more interest in using the language from a range of industries. It is for this reason that we have completed our product line by including an entry-level offer for C/C++ developers wanting to switch to Ada and reinforced our existing offer with GNAT Pro Assurance for programmers building the most robust software platforms with life cycles spanning decades.
by Fabien Chouteau
There's a mini-RTOS in my language
The first thing that struck me when I started to learn about the Ada programing language was the tasking support. In Ada, creating tasks, synchronizing them, sharing access to resources, are part of the language
by J. German Rivera

Make with Ada 2017- A "Swiss Army Knife" Watch
SummaryThe Hexiwear is an IoT wearable development board that has two NXP Kinetis microcontrollers. One is a K64F (Cortex-M4 core) for running the main embedded application software. The other one is a KW40 (Cortex M0+ core) for running a wireless connectivity stack (e.g., Bluetooth BLE or Thread). The Hexiwear board also has a rich set of peripherals, including OLED display, accelerometer, magnetometer, gryroscope, pressure sensor, temperature sensor and heart-rate sensor. This blog article describes the development of a "Swiss Army Knife" watch on the Hexiwear platform. It is a bare-metal embedded application developed 100% in Ada 2012, from the lowest level device drivers all the way up to the application-specific code, for the Hexiwear's K64F microcontroller. I developed Ada drivers for Hexiwear-specific peripherals from scratch, as they were not supported by AdaCore's Ada drivers library. Also, since I wanted to use the GNAT GPL 2017 Ada compiler but the GNAT GPL distribution did not include a port of the Ada Runtime for the Hexiwear board, I also had to port the GNAT GPL 2017 Ada runtime to the Hexiwear. All this application-independent code can be leveraged by anyone interested in developing Ada applications for the Hexiwear wearable device.
by Yannick Moy , Martin Becker , Emanuel Regnath
Physical Units Pass the Generic Test
The support for physical units in programming languages is a long-standing issue, which very few languages have even attempted to solve. This issue has been mostly solved for Ada in 2012 by our colleagues Ed Schonberg and Vincent Pucci who introduced special aspects for specifying physical dimensions on types. This dimension system did not attempt to deal with generics though. As was noted by others, handling generics in a dimensional analysis that is, like in GNAT, a compile-time analysis with no impact on the executable size or running time, is the source of the problem of dimension handling. Together with our partners from Technical Universitat München, we have finally solved this remaining difficulty.by Yannick Moy
Prove in the Cloud
We have put together a byte (8 bits) of examples of SPARK code on a server in the cloud. The benefit with this webpage is that anyone can now experiment live with SPARK without installing first the toolset. Something particularly interesting for academics is that all the code for this widget is open source. So you can setup your own proof server for hands-on sessions, with your own exercises, in a matter of minutes.by Pierre-Marie de Rodat

Highlighting Ada with Libadalang
While we are working very hard on semantic analysis in Libadalang, it is already possible to leverage its lexical and syntactic analyzers. A useful example for this is a syntax highlighter.
by Pierre-Marie de Rodat
Pretty-Printing Ada Containers with GDB Scripts
When things don’t work as expected, developers usually do one of two things: either add debug prints to their programs, or run their programs under a debugger. Today we’ll focus on the latter activity.
by Yannick Moy
Proving Loops Without Loop Invariants
For all the power that comes with proof technology, one sometimes has to pay the price of writing a loop invariant. Along the years, we've strived to facilitate writing loop invariants by improving the documentation and the technology in different ways, but writing loops invariants remains difficult sometimes, in particular for beginners. To completely remove the need for loop invariants in simple cases, we have implemented loop unrolling in GNATprove. It turns out it is quite powerful when applicable.by Yannick Moy
Research Corner - Focused Certification of SPARK in Coq
The SPARK toolset aims at giving guarantees to its users about the properties of the software analyzed, be it absence of runtime errors or more complex properties. But the SPARK toolset being itself a complex tool, it is not free of errors. To get confidence in its results, we have worked with academic partners to establish mathematical evidence of the correctness of a critical part of the SPARK toolset. The part on which we focused is the tagging of nodes requiring run-time checks by the frontend of the SPARK technology. This work has been accepted at SEFM 2017 conference.by Yannick Moy

Applied Formal Logic: Searching in Strings
A friend pointed me to recent posts by Tommy M. McGuire, in which he describes how Frama-C can be used to functionally prove a brute force version of string search, and to find a previously unknown bug in a faster version of string search called quick search. Frama-C and SPARK share similar history, techniques and goals. So it was tempting to redo the same proofs on equivalent code in SPARK, and completing them with a functional proof of the fixed version of quick search. This is what I'll present in this post.by Rob Tice
The Adaroombot Project
The Adaroombot project consists of an iRobot CreateⓇ 2 and Ada running on a Raspberry Pi with a Linux OS. This is a great Intro-to-Ada project as it focuses on a control algorithm and a simple serial communications protocol. The iRobot CreateⓇ 2 platform was originally design for STEM education and has great documentation and support - making it very easy to create a control application using Ada. This blog looks at the creation of the project and some cool features of Ada that were learned along the way.by Pierre-Marie de Rodat , Nicolas Setton

GNAT GPL 2017 is out!
For those users of the GNAT GPL edition, we are pleased to announce the availability of the 2017 release of GNAT GPL and SPARK GPL.
by Fabien Chouteau

Ada on the first RISC-V microcontroller
Updated July 2018
by Yannick Moy
Research Corner - FLOSS Glider Software in SPARK
Two years ago, we redeveloped the code of a small quadcopter called Crazyflie in SPARK, as a proof-of-concept to show it was possible to prove absence of run-time errors (no buffer overflows, not division by zero, etc.) on such code. The researchers Martin Becker and Emanuel Regnath have raised the bar by developing the code for the autopilot of a small glider in SPARK in three months only. Their paper and slides are available, and they have released their code as FLOSS for others to use/modify/enhance!by Yannick Moy
(Many) More Low Hanging Bugs
We reported in a previous post our initial experiments to create lightweight checkers for Ada source code, based on the new Libadalang technology. The two checkers we described discovered 12 issues in the codebase of the tools we develop at AdaCore. In this post, we are reporting on 6 more lightweight checkers, which have discovered 114 new issues in our codebase. This is definitely showing that these kind of checkers are worth integrating in static analysis tools, and we look forward to integrating these and more in our static analyzer CodePeer for Ada programs.by Yannick Moy , Nicolas Roche
A Usable Copy-Paste Detector in A Few Lines of Python
After we created lightweight checkers based on the recent Libadalang technology developed at AdaCore, a colleague gave us the challenge of creating a copy-paste detector based on Libadalang. It turned out to be both easier than anticipated, and much more efficient and effective than we could have hoped for. In the end, we hope to use this new detector to refactor the codebase of some of our tools, and we expect to integrate it in our IDEs.by Yannick Moy
VerifyThis Challenge in SPARK
This year again, the VerifyThis competition took place as part of ETAPS conferences. This is the occasion for builders and users of formal program verification platforms to use their favorite tools on common challenges. The first challenge this year was a good fit for SPARK, as it revolves around proving properties of an imperative sorting procedure. In this post, I am using this challenge to show how one can reach different levels of software assurance with SPARK.by Emmanuel Briot
User-friendly strings API
User friendly strings APIIn a previous post, we described the design of a new strings package, with improved performance compared to the standard Ada unbounded strings implementation. That post focused on various programming techniques used to make that package as fast as possible.
by Yannick Moy
GNATprove Tips and Tricks: Proving the Ghost Common Divisor (GCD)
Euclid's algorithm for computing the greatest common divisor of two numbers is one of the first ones we learn in school, and also one of the first algorithms that humans devised. So it's quite appealing to try to prove it with an automatic proving toolset like SPARK. It turns out that proving it automatically is not so easy, just like understanding why it works is not so easy. In this post, I am using ghost code to prove correct implementations of the GCD, starting from a naive linear search algorithm and ending with Euclid's algorithm.by Emmanuel Briot
New strings package in GNATCOLL
This post describes the new GNATCOLL.Strings package, and the various optimizations it performs to provide improved performance.by Jerome Guitton , Jérôme Lambourg , Joel Brobecker
Simics helps run 60 000 GNAT Pro tests in 24 hours
This post has been updated in March 2017 and was originally posted in March 2016.
by Yannick Moy
Two Projects to Compute Stats on Analysis Results
Two projects by Daniel King and Martin Becker facilitate the analysis of GNATprove results by exporting the results (either from the log or from the generated JSON files) to either Excel or JSON/text.by Pierre-Marie de Rodat
GNATcoverage moves to GitHub
Following the current trend, the GNATcoverage project moves to GitHub! Our new address is: https://github.com/AdaCore/gnatcoverage
by Jorge Real

Writing on Air
While searching for motivating projects for students of the Real-Time Systems course here at Universitat Politècnica de València, we found a curious device that produces a fascinating effect. It holds a 12 cm bar from its bottom and makes it swing, like an upside-down pendulum, at a frequency of nearly 9 Hz. The free end of the bar holds a row of eight LEDs. With careful and timely switching of those LEDs, and due to visual persistence, it creates the illusion of text... floating in the air!
by Fabien Chouteau , Arnaud Charlet , Yannick Moy
SPARK Tetris on the Arduboy
One of us got hooked on the promise of a credit-card-size programmable pocket game under the name of Arduboy and participated in its kickstarter in 2015. The kickstarter was successful (but late) and delivered the expected working board in mid 2016. Of course, the idea from the start was to program it in Ada , but this is an 8-bits AVR microcontroller (the ATmega32u4 by Atmel) not supported anymore by GNAT Pro. One solution would have been to rebuild our own GNAT compiler for 8-bit AVR from the GNAT FSF repository and use the AVR-Ada project. Another solution, which we explore in this blog post, is to use the SPARK-to-C compiler that we developed at AdaCore to turn our Ada code into C and then use the Arduino toolchain to compile for the Arduboy board.
by Claire Dross
Research Corner - Auto-active Verification in SPARK
GNATprove performs auto-active verification, that is, verification is done automatically, but usually requires annotations by the user to succeed. In SPARK, annotations are most often given in the form of contracts (pre and postconditions). But some language features, in particular ghost code, allow proof guidance to be much more involved. In a paper we are presenting at NASA Formal Methods symposium 2017, we describe how an imperative red black tree implementation in SPARK was verified using intensive auto-active verification.by Pat Rogers
Getting started with the Ada Drivers Library device drivers
The Ada Drivers Library (ADL) is a collection of Ada device drivers and examples for ARM-based embedded targets. The library is maintained by AdaCore, with development originally (and predominantly) by AdaCore personnel but also by the Ada community at large. It is available on GitHub and is licensed for both proprietary and non-proprietary use.
by Raphaël Amiard , Yannick Moy , Pierre-Marie de Rodat
Going After the Low Hanging Bug
At AdaCore, we have a strong expertise in deep static analysis tools (CodePeer and SPARK), and we have been relying on the compiler GNAT and our coding standard checker GNATcheck to deal with more syntactic or weakly-semantic checks. The recent Libadalang technology, developed at AdaCore, provided us with an ideal basis to develop specialized light-weight static analyzers. As an experiment, we implemented two simple checkers using the Python binding of Libadalang. The results on our own codebase were eye-opening: we found a dozen bugs in the codebases of the tools we develop at AdaCore (including the compiler and static analyzers).by Johannes Kanig
Hash it and Cache it
A new feature of SPARK2014 allows to use a memcached server to share proof results between runs of the SPARK tools and even between developers on different machines. Check out this post to see the details.by Raphaël Amiard , Pierre-Marie de Rodat
Introducing Libadalang
AdaCore is working on a host of tools that works on Ada code. The compiler, GNAT, is the most famous and prominent one, but it is far from being the only one. At AdaCore, we already have several other tools to process Ada code: the ASIS library, GNAT2XML, the GPS IDE. A realization of the past years, however, has been that we were lacking a unified solution to process code that is potentially evolving, potentially incorrect Ada code. Hence Libadalang.by Johannes Kanig
SPARK and CodePeer, a Good Match!
It turns out that the CodePeer engine can be used as a powerful prover for SPARK programs. This feature will be available in the next version of SPARK Pro, make sure you try it out!by Sylvain Dailler
GNATprove Tips and Tricks: a Lemma for Sorted Arrays
We report on the creation of the first lemma of a new lemma library on arrays: a lemma on transitivity of the order in arrays.by Emmanuel Briot

Integrate new tools in GPS (2)
Customizing build target switchesIn the first post in this series (Integrate new tools in GPS) we saw how to create new build targets in GPS to spawn external tools via a menu or toolbar button, and then display the output of that tool in its own console, as well as show error messages in the Locations view.
by Claire Dross
Automatic Generation of Frame Conditions for Array Components
One of the most important challenges for SPARK users is to come up with adequate contracts and annotations, allowing GNATprove to verify the expected properties in a modular way. Among the annotations mandated by the SPARK toolset, the hardest to come up with are probably loop invariants. A previous post explains how GNATprove can automatically infer loop invariants for preservation of unmodified record components, and so, even if the record is itself nested inside a record or an array. Recently, this generation was improved to also support the simplest cases of partial array updates. We describe in this post in which cases GNATprove can, or cannot, infer loop invariants for preservation of unmodified array components.by Yannick Moy
GNATprove Tips and Tricks: What’s Provable for Real Now?
One year ago, we presented on this blog what was provable about fixed-point and floating-point computations (the two forms of real types in SPARK). Since then, we have integrated static analysis in SPARK, and modified completely the way floating-point numbers are seen by SMT provers. Both of these features lead to dramatic changes in provability for code doing fixed-point and floating-point computations.by Emmanuel Briot

Integrate new tools in GPS
This blog, the first in a series, explains the basic mechanisms that GPS (the GNAT Programming Studio) provides to integrate external tools. A small plugin might make your daily workflow more convenient by providing toolbar buttons and menus to spawn your tool and parse its output.by Piotr Trojanek
Verifying Tasking in Extended, Relaxed Style
Tasking was one of the big features introduced in the previous release of SPARK 2014. However, GNATprove only supported tasking-related constructs allowed by the Ravenscar profile. Now it also supports the more relaxed GNAT Extended Ravenscar profile.by Claire Dross
SPARK 2014 Rationale: Support for Type Invariants
Type invariants are used to model properties that should always hold for users of a data type but can be broken inside the data type implementation. Type invariant are part of Ada 2012 but were not supported in SPARK until SPARK Pro 17.by Emmanuel Briot
GNAT On macOS Sierra
GNAT and all the tools work great on the newly released macOS Sierra, but gdb needs some tweaking of the system.by Yannick Moy
Verified, Trustworthy Code with SPARK and Frama-C
Last week, a few of us at AdaCore have attended a one-day workshop organized at Thales Research and Technologies, around the topic of "Verified, trustworthy code - formal verification of software". Attendees from many different branches of Thales (avionics, railway, security, networks) were given an overview of the state-of-practice in formal verification of software, focused on two technologies: the SPARK technology that we develop at AdaCore for programs in Ada, and the Frama-C technology developed at CEA research labs for programs in C. The most interesting part of the day was the feedback given by three operational teams who have experimented during a few months with either SPARK (two teams) or Frama-C (one team). The lessons learned by first-time adopters of such technologies are quite valuable.by Emmanuel Briot

Debugger improvements in GPS 17
The GNAT Programming Studio support for the debugger has been enhanced. This post describes the various changes you can expect in this year's new release of GPS.by Quentin Ochem

Unity & Ada
Using Ada technologies to develop video games doesn’t sound like an an obvious choice - although it seems like there could be an argument to be made. The reverse, however, opens some more straightforward perspectives.by Emmanuel Briot

GNAT Programming Studio (GPS) on GitHub
The GPS source repository has been published on GitHub. This post briefly describes how you can access it, and hopefully contribute.by Emmanuel Briot

Bookmarks in the GNAT Programming Studio (GPS)
As we improve existing views in GPS, we discover new ways to use them. This post shows some of the improvements done recently in the Bookmarks view, and how you can now use it as a TODO list.by Claire Dross
Automatic Generation of Frame Conditions for Record Components
Formal verification tools like GNATprove rely on the user to provide loop invariants to describe the actions performed inside loops. Though the preservation of variables which are not modified in the loop need not be mentioned in the invariant, it is in general necessary to state explicitly the preservation of unmodified object parts, such as record fields or array elements. These preservation properties form the loop’s frame condition. As it may seem obvious to the user, the frame condition is unfortunately often forgotten when writing a loop invariant, leading to unprovable checks. To alleviate this problem, the GNATprove tool now generates automatically frame conditions for preserved record components. In this post, we describe this new feature on an example.by Yannick Moy
Research Corner - Proving Security of Binary Programs with SPARK
Researchers from Dependable Computing and Zephyr Software LLC have presented at the latest NASA Formal Methods conference last week their work on proving security of binary programs. In this work, they use SPARK as intermediate language and GNATprove as proof tool, which is an atypical and interesting use of the SPARK technology.by Pierre-Marie de Rodat

C library bindings: GCC plugins to the rescue
I recently started working on an Ada binding for the excellent libuv C library. This library provides a convenient API to perform asynchronous I/O under an event loop, which is a popular way to develop server stacks. A central part of this API is its enumeration type for error codes: most functions use it. Hence, one of the first things I had to do was to bind the enumeration type for error codes. Believe it or not: this is harder than it first seems!
by Yannick Moy

GNATprove Tips and Tricks: Using the Lemma Library
A well-know result of computing theory is that the theory of arithmetic is undecidable. This has practical consequences in automatic proof of programs which manipulate numbers. The provers that we use in SPARK have a good support for addition and subtraction, but much weaker support for multiplication and division. This means that as soon as the program has multiplications and divisions, it is likely that some checks won't be proved automatically. Until recently, the only way forward was either to complete the proof using an interactive prover (like Coq or Isabelle/HOL) or to justify manually the message about an unproved check. There is now a better way to prove automatically such checks, using the recent SPARK lemma library.by Claire Dross
Quantifying over Elements of a Container
Containers holding several items of the same type such as arrays, lists, or sets are a common occurrence in computer programs. Stating a property over such containers often involves quantifying over the elements they contain. The way quantified formulas over containers are translated for proof can be tuned in GNATprove using a specific annotation.by Jérôme Lambourg
Efficient use of Simics for testing
As seen in the previous blog article, AdaCore relies heavily on virtualisation to perform the testing of its GNAT Pro products for VxWorks.
by AdaCore Admin

Provably safe programming at Embedded World
AdaCore continues to build reliable and secure software for embedded software development tools. Last month, we attended Embedded World 2016, one of the largest conferences of its kind in Europe, to present our embedded solutions and our expertise for safety, and mission critical applications in a variety of domains.
by Yannick Moy
Formal Verification of Legacy Code
Just a few weeks ago, one of our partners reported a strange behavior of the well-known function Ada.Text_IO.Get_Line, which reads a line of text from an input file. When the last line of the file was of a specific length like 499 or 500 or 1000, and not terminated with a newline character, then Get_Line raised an exception End_Error instead of returning the expected string. That was puzzling for a central piece of code known to have worked for the past 10 years! But fair enough, there was indeed a bug in the interaction between subprograms in this code, in boundary cases having to do with the size of an intermediate buffer. My colleague Ed Schonberg who fixed the code of Get_Line had nonetheless the intuition that this particular event, finding such a bug in an otherwise trusted legacy piece of code, deserved a more in depth investigation to ensure no other bugs were hiding. So he challenged the SPARK team at AdaCore in checking the correctness of the patched version. He did well, as in the process we uncovered 3 more bugs.
by Fabien Chouteau

Make with Ada: Candy dispenser, with a twist...
A few months ago, my colleague Rebecca installed a candy dispenser in our kitchen here at AdaCore. I don’t remember how exactly, but I was challenged to make it more… fun.
by AdaCore Admin

Embedded Product Line Updates
Embedded products are not stand alone, this allows them to have safety, mission critical and real-time requirements that they wouldn’t necessarily have otherwise. The embedded product line provides analyzable, verifiable, and certifiable software for both static and dynamic analysis tools.
by Jérôme Lambourg

Porting the Ada Runtime to a new ARM board
A step by step tutorial to adapt the ARM runtime to new MCUs/boards.by Yannick Moy
GNATprove Tips and Tricks: What’s Provable for Real?
SPARK supports two ways of encoding reals in a program: the usual floating-point reals, following the standard IEEE 754, and the lesser known fixed-point reals, called this way because their precision is fixed (contrary to floating-points whose precision varies with the magnitude of the encoded number). This support is limited in some ways when it comes to proving properties of computations on real numbers, and these limitations depend strongly in the encoding chosen. In this post, I show the results of applying GNATprove on simple programs using either floating-point or fixed-point reals, to explain these differences.by Yannick Moy
SPARK 2014 Rationale: Support for Ravenscar
As presented in a recent post by Pavlos, the upcoming release of SPARK Pro will support concurrency features of Ada, with the restrictions defined in the Ravenscar profile of Ada. This profile restricts concurrency so that concurrent programs are deterministic and schedulable. SPARK analysis makes it possible to prove that shared data is protected against data races, that deadlocks cannot occur and that no other run-time errors related to concurrency can be encountered when running the program. In this post, I revisit the example given by Pavlos to show SPARK features and GNATprove analysis in action.by Fabien Chouteau
Make with Ada: Formal proof on my wrist
When the Pebble Time kickstarter went through the roof, I looked at the specification and noticed the watch was running on an STM32F4, an ARM cortex-M4 CPU which is supported by GNAT. So I backed the campaign, first to be part of the cool kids and also to try some Ada hacking on the device.by Emma Adby

Modernizing Adacore's Open-Source Involvement
Through the adoption of GitHub we have taken our first step on the way to having a more collaborative and dynamic interaction with, both our users and open source technologies.
by David Hauzar

SPARK 16: Generating Counterexamples for Failed Proofs
While the analysis of failed proofs is one of the most challenging aspects of formal verification, it would be much easier if a tool would automatically find values of variables showing why a proof fails. SPARK Pro 16, to be released in 2016, is going to introduce such a feature. If a proof fails, it attempts to generate a counterexample exhibiting the problem. This post introduces this new feature, developed in the scope of the ProofInUse laboratory.by Yannick Moy

GNATprove Tips and Tricks: User Profiles
One of the most difficult tasks when using proof techniques is to interact with provers, in particular to progressively increase proof power until everything that should be proved is proved. Until the last release, increasing the proof power meant operating on three separate switches. There is now a simpler solution based on a new switch --level, together with a simpler proof panel in GPS for new users.by AdaCore Admin

AdaCore Tech Days 2015
by Emmanuel Briot
Traits-Based Containers
This post describes the design of a new containers library. It highlights some of the limitations of the standard Ada containers, and proposes a new approach using generic packages as formal parameters to make these new containers highly configurable at compile time.by Jack Mellor
2015: A Space Ada‑ssey
AdaCore has a long history of providing tools and support to develop mission critical applications for Space. Check out this video we made and showed at the conference to see which ones!by Yannick Moy
SPARK 2014 Rationale: Type Predicates
Preconditions and postconditions define a very strong mechanism for specifying invariant properties over the program's control. What about similar properties for the program's data? It turns out Ada 2012 defined such a construct, type predicates, which was not supported in SPARK until now. And now it is.by Fabien Chouteau

Make with Ada: "The Eagle has landed"
July 20, 1969, 8:18 p.m. UTC, while a bunch of guys were about to turn blue on Earth, commander Neil A. Armstrong confirms the landing of his Lunar Module (LM), code name Eagle, on the moon. Will you be able to manually land Eagle on the Sea of Tranquillity?by Cyrille Comar

Farewell Robert...
It is with great sadness that I have to announce the death of Robert Dewar...
by Yannick Moy
SPARKSkein: From tour-de-force to run-of-the-mill Formal Verification
In 2010, Rod Chapman released an implementation in SPARK of the Skein cryptographic hash algorithm, and he proved that this implementation was free of run-time errors. That was a substantial effort with the previous version of the SPARK technology. We have recently translated the code of SPARKSkein from SPARK 2005 to SPARK 2014, and used GNATprove to prove absence of run-time errors in the translated program. The difference between the two technologies is striking. The heroic effort that Rod put in the formal verification of the initial version of SPARKSkein could now be duplicated with modest effort and modest knowledge of the technology, thanks to the much greater proof automation that the SPARK 2014 technology provides, as well as various features that lower the need to provide supporting specifications, most notably contracts on internal subprograms and loop invariants.by Yannick Moy
How Our Compiler Learnt From Our Analyzers
Program analyzers interpret the source code of a program to compute some information. Hopefully, the way they interpret the program is consistent with the way that the compiler interprets it to generate an executable, or the information computed is irrelevant, possibly misleading. For example, if the analyzer says that there are no possible run-time errors in a program, and you rely on this information to compile with dynamic checking off, it is crucial that no run-time error could occur as a result of a divergence of opinion between the analyzer and the compiler on the meaning of an instruction. We recently discovered such an inconsistency in how our compiler and analyzers dealt with floating-point exponentiation, which lead to a change in how GNAT now compile these operations.by Emmanuel Briot
Count them all (reference counting)
Reference countingReference counting is a way to automatically reclaim unused memory. An element is automatically deallocated as soon as there are no more references to it in the program.
by Emmanuel Briot
Larger than it looks (storage pools)
This post shows how to implement a special storage pool that allocates an extra header every time it allocates some memory. This can be used to store type specific information, outside of the type itself.by Claire Dross
A quick glimpse at the translation of Ada integer types in GNATprove
In SPARK, as in most programming languages, there are a bunch of bounded integer types. On the other hand, Why3 only has mathematical integers and a library for bitvectors. Since bitwise operations can only be done on modular types in Ada, we currently translate arithmetic operations on signed integer types as operations on mathematical integers and arithmetic operations on modular types as operation on bitvectors. The only remaining question now is, how do we encode specific bounds of the Ada types into our Why3 translation ? In this post, I will present three different ways we tried to do this and explain which one we currently use and why.by Yannick Moy
GNATprove Tips and Tricks: Minimizing Rework
As automatic proof is time consuming, it is important that rework following a change in source code is minimized. GNATprove uses a combination of techniques to ensure that, both for a single user, and when working in a team.by Clément Fumex
GNATprove Tips and Tricks: Bitwise Operations
The ProofInUse joint laboratory is currently improving the way SPARK deals with modular types and bitwise operators. Until now the SPARK tool was trying its best to translate those into equivalent operations on integers. It is now using native theory of smt-solvers when available resulting in much better support, and guaranteeing state of the art handling of bitwise operations. We present some examples in this post.by Jamie Ayre

20 years on...
20 Years of AdaCore: Company as Committed as Ever on Safety-Critical Software Solutions
by Olivier Ramonat

AdaCore Releases GNAT Pro 7.3, QGen 1.0 and GNATdashboard 1.0
February saw the annual customer release of a number of important products. This is no mean task when you consider the fact that GNAT Pro is available on over 50 platforms and supports over 150 runtime profiles (ranging from Full Ada Support to the very restricted Zero Footprint Profile suitable for safety-critical development). All in all, from the branching of the preview version to the customer release it takes us nearly 4 months to package everything up! Quality is assured through the internally developed AdaCore Factory.
by Yannick Moy
AdaCore Tech Days Prez on SPARK
Hristian Kirtchev, who leads the developments of the GNAT compiler frontend, gave a very clear presentation of SPARK at the last AdaCore Tech Days in Boston. This was recorded, here is the video.
by Yannick Moy
GNATprove Tips and Tricks: Catching Mistakes in Contracts
Contracts may be quite complex, as complex as code in fact, so it is not surprising that they contain errors sometimes. GNATprove can help by pinpointing suspicious constructs that, although legal, do not make much sense. These constructs are likely to be caused by mistakes made by the programmer when writing the contract. In this post, I show examples of incorrect constructs that are signaled by GNATprove.by Tristan Gingold
AdaCore at FOSDEM'15
I was at Bruxelles on January 31st to present the components of GNAT GPL 2015 : SPARK 2014 and GNAT GPL for ARM bare-board. This is not unrelated to a previous blog entry on Tetris in SPARK on ARM Cortex M4, in particular I presented that Tetris demo (I brought some boards with me and despite the simple package, none were broken!). The slides contain technical details on the ravenscar profile (main principles), how to build a program for the stm32f4-discovery board and how to port the runtime. There are also less technical slides such as why we choose the stm32f4 board and photos of some graphical demos. As that could be useful to anyone interested in Ravenscar or in porting the runtime to other boards or other platforms, we've made the slides available here.
by Yannick Moy
GNATprove Tips and Tricks: Keeping Justifications Up-To-Date
GNATprove supports the suppression of warnings and justification of check messages with pragmas inserted in the source code. But these justifications may become obsolete across time. To help with that, GNATprove now issues a warning on useless justifications.by Yannick Moy
SPARK 2014 Rationale: Functional Update
While attribute Old allows expressing inside postconditions the value of objects at subprogram entry, this is in general not enough to conveniently express how record and array objects are modified by a procedure. A special attribute Update is defined in SPARK to make it easy to express such properties.by Yannick Moy
SPARK 2014 Rationale: Object Oriented Programming
Object Oriented Programming is known for making it particularly difficult to analyze programs, because the subprograms called are not always known statically. The standard for civil avionics certification has recognized this specific problem, and defines a specific verification objective called Local Type Consistency that should be met with one of three strategies. SPARK allows using one of these strategies, by defining the behavior of an overridden subprogram using a special class-wide contract and checking that the behavior of the overriding subprogram is a suitable substitution, following the Liskov Substitution Principle.by Tristan Gingold , Yannick Moy

Tetris in SPARK on ARM Cortex M4
Tetris is a well-known game from the 80's, which has been ported in many versions to all game platforms since then. There are even versions of Tetris written in Ada. But there was no version of Tetris written in SPARK, so we've repaired that injustice. Also, there was no version of Tetris for the Atmel SAM4S ARM processor, another injustice we've repaired.
by Cyrille Comar
Welcome To AdaCore's Blog
I'm proud, if not a bit nervous, to be the one firing the very first post on this brand new blog. Why are we starting a corporate blog at this time? There are many reasons for this. The main one is that there are many things happening at AdaCore and around the GNAT technology and we are seeking better ways to make them widely known while offering interested recipients the possibility to react and interact with us.by Yannick Moy
SPARK 2014 Rationale: Ghost Code
A common situation when proving properties about a program is that you end up writing additional code whose only purpose is to help proving the original program. If you're careful or lucky enough, the additional code you write will not impact the program being verified, and it will be removed during compilation, so that it does not inflate binary size or waste execution cycles. SPARK provides a way to get these benefits automatically, by marking the corresponding code as ghost code, using the new Ghost aspect.by Yannick Moy

Using Coq to Verify SPARK 2014 Code
In the first release of SPARK 2014, GNATprove only provided support for automatic provers, in particular Alt-Ergo. Automatic provers are very handy when it comes to perform a big numberof simple proof. But they can fail to prove valid formulas when the proof involves some advanced reasoning. As mentioned in a previous post, one check left unproved might invalidate assumptions on which are based the proofs of multiple other checks. This is a case where manual proof may be useful for SPARK 2014 users. The development version of GNATprove now supports Coq to perform manual proof.by Johannes Kanig
SPARK 15: Errors, Warnings and Checks
The messages issued by the SPARK toolset will change a bit in the next version of both SPARK Pro and SPARK GPL. This post explains the change and the motivation behind it.by Yannick Moy

Using SPARK to Prove AoRTE in Robot Navigation Software
Correctness of robot software is a challenge. Just proving the absence of run-time errors (AoRTE) in robot software is a challenge big enough that even NASA has not solved it. Researchers have used SPARK to do precisely that for 3 well-known robot navigation algorithms. Their results will be presented at the major robotics conference IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2014) this coming September.by Claire Dross
External Axiomatizations: a Trip Into SPARK’s Internals
There are cases expressing all the specification of a package in SPARK is either impossible (for example if you need to link them to elements of the mathematical world, like trigonometry functions), cumbersome (especially if they require concepts that cannot easily be described using contracts, like transitivity, counting, summation...), or simply inefficient, for big and complex data structures like containers for example. In these cases, a user can provide directly a manually written Why3 translation for an Ada package using a feature named external axiomatizations. Coming up with this manual translation requires both a knowledge of the WhyML language and a minimal understanding of GNATprove's mechanisms and is therefore reserved to advanced users.by Claire Dross
Manual Proof with Ghost Code in SPARK 2014
Guiding automatic solvers by adding intermediate assertions is a commonly used technique. We can go further in this direction, by adding complete pieces of code doing nothing, generally called ghost code, to guide the automated reasoning. This is an advanced feature, for people willing to manually guide proofs. Still, it is all in SPARK 2014 and thus does not require the user to learn a new language. We explain here how we can achieve inductive proofs on a permutation function.by Claire Dross
Contracts of Functions in SPARK 2014
In SPARK 2014, we can write a function F and annotate it with a pre and a postcondition. In this post, we explain how the SPARK 2014 proof tool handles a call to such a function.by Florian Schanda
SPARK 2014 Rationale: Information Flow
In a previous blog post we described how aspect Global can be used to designate the specific global variables that a subprogram has to read and write. So, by reading the specification of a subprogram that has been annotated with aspect Global we can see exactly which variables, both local and global, are read and/or written each time the subprogram is called. Based purely on the Global aspect, this pretty much summarizes the full extent of our knowledge about the flow of information in a subprogram. To be more precise, at this point, we know NOTHING about the interplay between the inputs and outputs of the subprogram. For all we know, all outputs could be randomly generated and the inputs might not contribute in the calculation of any of the outputs. To improve this situation, SPARK 2014 uses aspect Depends to capture the dependencies between a subprogram's outputs and inputs. This blog post demonstrates through some examples how aspect Depends can be used to facilitate correct flow of information through a subprogram.by Yannick Moy
Contextual Analysis of Subprograms Without Contracts
We have implemented a new feature in GNATprove for analyzing local subprograms in the context of their calls. This makes it possible to benefit from the most precise analysis for local subprograms, without incurring the cost of adding contracts to these subprograms.by Johannes Kanig
Prove in Parallel with SPARK 2014
The article explains how we improved the performance of the SPARK 2014 toolset when multiple CPU cores are available for proof.by Yannick Moy
