GPS for bare-metal developers
In my previous blog article, I exposed some techniques that helped me rewrite the Crazyflie’s firmware from C into Ada and SPARK 2014, in order to improve its safety.
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Emmanuel Briot
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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.
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Yannick Moy
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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.
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Emmanuel Briot
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New strings package in GNATCOLL
This post describes the new GNATCOLL.Strings package, and the various optimizations it performs to provide improved performance.
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.
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Yannick Moy
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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.
GNATcoverage moves to GitHub
Following the current trend, the GNATcoverage project moves to GitHub! Our new address is: https://github.com/AdaCore/gnatcoverage
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!
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.
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Claire Dross
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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.
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Yannick Moy
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Rod Chapman on Software Security
Rod Chapman gave an impactful presentation at Bristech conference last year. His subject: programming Satan's computer! His way of pointing out how difficult it is to produce secure software. Of course, it would not be Rod Chapman if he did not have also a few hints at how they have done it at Altran UK over the years. And SPARK is central to this solution, although it does not get mentioned explicitly in the talk! (although Rod lifts the cover in answering a question at the end)
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Emma Adby
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AdaCore attends FOSDEM
Earlier this month AdaCore attended FOSDEM in Brussels, an event focused on the use of free and open source software. Two members of our technical team presented.
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Pat Rogers
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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.
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Yannick Moy
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Proving Tetris With SPARK in 15 Minutes
I gave last week a 15-minutes presentation at FOSDEM conference of how you can prove interesting properties of Tetris with SPARK. Here is the recording.
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).
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Johannes Kanig
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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.
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.
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Yannick Moy
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New Year's Resolution for 2017: Use SPARK, Say Goodbye to Bugs
NIST has recently published a report called "Dramatically Reducing Software Vulnerabilities" in which they single out five approaches which have the potential for creating software with 100 times fewer vulnerabilities than we do today. One of these approaches is formal methods. Among formal methods, the report highlights strong suits of SPARK, and cites SPARK projects as example of mature uses of formal methods. NIST is not the only ones to support the use of SPARK. Editor Bill Wong from Electronic Design has included SPARK in his "2016 Gifts for the Techie". So if your new year's resolutions include software without bugs, have a look at SPARK in 2017.
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Johannes Kanig
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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!
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Yannick Moy
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SPARK Cheat Sheets (en & jp)
The SPARK cheat sheet usually distributed in trainings has recently been translated to Japanese. Here they are, both in English and in Japanese. My modest Xmas present.