The requirements concluded that preventing programmers from making mistakes is the first and most essential line of defense. By removing opportunities to make subtle mistakes such as those made through implicit type casting and other dangerous constructs, the code becomes automatically safer and easier to maintain. The outcome of that selection process was that while no existing programming languages was suited to be the sole language for DoD projects, it was definitely feasible to create a new language which could fit all of those requirements.
Thus four constructors were paid to do exactly this. Take for example this bit of C code:. This is valid code that will compile, run and produce the expected result with bar printing the answer to life, the universe and everything. Not so for Ada:. The major benefit of this is that if one were to change the type definition later on, it would not suddenly make a thousand implicit conversions explode throughout the codebase.
Anyone who has wrestled through the morass of mixing standard C, Linux, and Win32 type definitions can probably appreciate not having to dig through countless pages of documentation and poorly formatted source code to figure out which typedef or macro contains the actual type definition of something that just exploded half-way through a compile or during a debug session. Ada adds further layers of defense through compile-time checks and run-time checks.
In Ada, the programmer is required to explicitly name closing statements for blocks and state the range that a variable can take on. This is also the case for strings, where aside from unbounded strings all strings have a fixed length. At run-time, errors such as illegal memory accesses, buffer overflows, range violations, off-by-one errors, and array access can be tested.
These errors can then be handled safely instead of leading to an application crash or worse. Ada implements an access-types model rather than providing low-level generic pointers. Each access type is handled by a storage pool, either the default one or a custom one to allow more exotic system memory implementations like NUMA.
An Ada programmer never accesses heap memory directly, but has to use this storage pool manager. Finally, the compiler or runtime decides how data is passed in or out of a function or procedure call. This prevents overflow issues where stack space is not sufficient. Over time features from these subsets have been absorbed into the main language specification.
It was the dawn of home computers, but it was also the awkward transition of the s into the s, when microcontrollers were becoming more popular. There are two versions of the GCC-based Ada toolchain. The AdaCore version enjoys commercial support, but comes with some strings attached.
An example of a small, yet non-trivial, Ada project written by yours truly in the form of a command line argument parser can be found at its project page. Unlike C, Ada does not have a preprocessor and does not merge source and header files to create compile units. Instead, the name of the package specified in the specification is referenced, along with its interface.
Here the name of the. This provides a lot of flexibility and prevents the all too common issues in C where one can get circular dependencies or need to include header files in a particular order. While still quite a bit of a rarity in hobbyist circles, Ada is a fully open language with solid, commercially supported toolchains that are used to write software for anything from ICBM and F avionics to firmware for medical devices.
Although a fairly sprawling language beyond the core features, it should definitely be on the list of languages you have used in a project, if only because of how cool it looks on your resume. Unless you want to become a lavatory hygene technican at your local fast food joint you just have to deal with it, write nasty, buggy code and get the job done in time.
In the end all that matters is CPU crunching instructions. Works like a charm for your first project. Then when it comes time to make version 2, 3, etc.
I hate that this attitude is so prevalent amongst embedded engineers. The main reason is that developer is often unwilling or unable to defend Waterfall process, and engineering generally. You live in some sort of fantasy world. Here in the real world we have actual customers who rely on working product, they will not pay for the product without proper documentation, and they will not adopt it if they find bugs and we cannot fix them and turn around new builds in a timely manner.
Sorry but here in Poland it is real world. If boss or project manager wants code quick then you develop it quick because in the end of day its what gets food on your table.
Bugs happen to everyone, such is life. I know its shocking but for US customers its better to pay cheap poland company than develop code themselves and still I have a good enough wage that I bought a very nice BMW when most of my friends baerly make it month-to-month with payments.
I agree with you. The trick a good developer needs to learn is producing good work quickly, without leaving a mess lying around.
Just so we understand each other here: Doing embedded using Ada is arguably cleaner than C and … in turn takes probably less time and gives better results. Real world? Not sure what planet you live on but everything they stated is exact. It certainly does work his way. The mere fact there is a market for it, proves it. Not everyone has JPL time and budgets. In the business world, there is a saying — perfect is the enemy of good enough. Too bad no one in govt.
How is linkedin doing now? Are they broadly considered a successful site that developers should emulate? Or are they a mostly-failed site that was purchased by a big company for backroom reasons? If only they programmed with ADA or in your world…. Are there any statistics for average bugs per 1, LOC by language? Certainly we had bugs back in my Ada days; a mate of main had a doozy that was found in a simulator.
When the aircraft crossed the international date line, it flipped by degrees so it was flying upside down…. Spark Ada. Like if you are having a heart attack and at takes an extra few attempts for anyone nearby to get a dial tone on their mobile phone and phone a hospital, that would not be a big deal at all. Or if the number was miss routed to the wrong destination. Software runs everywhere, the telephone exchange system runs software.
And to generate a dial tone, software runs to generate that tone. When software has bugs, either design or logic, people have died. Part of problem is that people have become so accustomed to anything that runs software being buggy. And if I would point a finger at anyone it would be the vendors with the largest number of CVE Common Vulnerabilities and Exposures databases Vulnerabilities. Microsoft and Adobe instantly pop into my mind. And these must be backwards-compatible, which means tons and tons of legacy code written in past 30 years by hundreds of people.
And one of the often repeated fallacies of FOSS is that open source makes easier to find and patch vulnerabilities. So why closed-source products have less vulnerabilities per product than open source ones? Right now Debian comprises software packages.
Not to mention 10 architectures. That 13 Microsoft vulns comes from how many products and architectures? When a fatal bug is found in Windows, mysterious fog appears. Can we see the source code?
Those issues should be prorated against the number of installations. More installations uncovers more bugs, given the identical programming practices and skills. On average, the industry, especially large corporations, are on par with each other. The code they produce is no better than the others. Good testing is critical, but super expensive. So that meant back in when I encountered it you use a different compiler for , , , , etc.
Note that this was not a compiler switch, it was a separate compiler! Admittedly, back then, compiler testing was less effective than it should have been. So, why I learn a new language that I did not have enough time to become fluent in and then end up being just another lousy programmer?
I ended up getting a copy of the Ada code from the FAA, since we no longer maintained it locally, which required special approval that took about 2 months to get. This was apparently true for both reading and writing. So, when I traced the Ada code to its temp stack variable to hold that value when making changes to it, changing ANY bit would come up with seeming random values for the reserved bits.
It still took two weeks to convince the FAA to pull out their debug tools as I said, we no longer supported it and had no resident Ada programmers to verify my theory. Once they did, I was exonerated. So why did that bit get set to ONE? Talk about esoteric bugs!
GNAT has never generated C as an intermediate language, it has always been a front end gnat1 which generated assembly, just like cc1, cc1obj, cc1objplus, cc1plus, etc. When I left the industry, the company I was at was in the middle of a MAJOR effort to rewrite half of the software running on the aircraft we were the prime contractor for.
Now try that with an Ada repo, it will be the other way around. I know because I do try this kind of stuff. In this video. They even said something like to write whole libraries in Ada. Unfortunately i do not remember in regard to which department they were talking about, as nvidia is not just GPU manufacturer. Here is the video. I really appreciate your opinion.
If your boss gives you unrealistic deadline, he is an idiot and you should run away. Other warning sign — pointy hair…. What if you are working on something like a medical device and one of bugs caused by your nasty, bad code causes someone to die? For example faulty software interlocks fail causing someone to get very high dose of X-rays?
And another thing: you wrote your code in two days, fueled by almost lethal doses of caffeine. Would you be able to read and modify that spaghetti code written under influence? Fuck It Near Enough. That simplified the compiler so that it only needed to do one pass since no forward references existed. Ideally your customer requirements include testing, safety audits, and multiple release milestones. If not then many get away with throwing any old junk over the wall the first time it seems to run in the lab.
Well possibly it could. Back in the early 90s, a project I worked on in Ada had to have parts recoded in C because it was too slow. Also the Ada that was used in avionics is not the full Ada but a reduced subset which had all the possible iffy bits generics for example removed.
It was effectively a slightly stricter Pascal. After that the Defence industry stipulation that everything had to be Ada was relaxed.
While the language is designed to prevent error, the Ariane rocket is a testament to the fact that reliable software can still cause objects to fall from the sky; reliably.
You mean like reading and comprehending the whopping two Ariane-related sentences Tricon and I wrote, before flying off the handle? Emphasis on comprehending.
If you specify the wrong actions to a condition in your requirement, no languages are going to help you. Iirc, this fall from the sky was due to badly ported code between two architectures coupled to lack of integration tests. It worked before porting so it will run after, no? The attempted assignment of an out-of-range value causes a run-time error. The ability to specify range contraints makes programmer intent explicit and makes it easier to detect a major source of coding and user input errors.
A key to reusable components is a mechanism for parameterizing modules with respect to data types and other program entities, for example a stack package for an arbitrary element type. Ada 83 was object-based, allowing the partitioning of a system into modules corresponding to abstract data types or abstract objects.
However, large real-time systems often have components such as GUIs that do not have real-time constraints and that could be most effectively developed using OOP features. Ada provided additional OOP features including Java-like interfaces and traditional operation invocation notation.
Ada supplies a structured, high-level facility for concurrency. Asynchronous task interactions are also supported, specifically timeouts and task termination. Such asynchronous behavior is deferred during certain operations, to prevent the possibility of leaving shared data in an inconsistent state. The newest versions of Ada include lightweight mechanisms to take advantage of multicore architectures, allowing for highly efficient parallel computing, while preserving portability and remaining within the safe and well-defined Ada concurrency model.
For example, you can specify the bit layout for fields in a record, define the alignment and size, place data at specific machine addresses, and express specialized or time-critical code sequences in assembly language. You can also write interrupt handlers in Ada, using the protected type facility. A protected object locking policy is defined that uses priority ceilings; this has an especially efficient implementation in Ada mutexes are not required since protected operations are not allowed to block.
Ada 95 defined a task dispatching policy that basically requires tasks to run until blocked or preempted, and Ada introduced several others including Earliest Deadline First. Why use Ada? In short, because you want to write reliable and efficient code, with confidence that it works, and not waste time and effort in the process.
Ada is unique among languages in how it helps you detect and eliminate bugs early in the software life cycle, when they are least expensive to correct. And as evidenced by the many successfully fielded applications that need to meet hard time or space constraints, Ada helps you build software that is reliable, safe and secure without sacrificing performance.
Ada also offers specialized support for systems programming and real-time systems. And the most recent version of the language includes contract-based programming pre- and postconditions , which in effect makes functional requirements part of the source code where they can be verified by dynamic checks or static analysis.
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