9 ms·

Writing Linux Modules in Ada (2016)

134 points by slondr 3y ago

gscho 3y ago
Back in university I took a course in legacy programming. We did a project in each of Fortran, COBOL and Ada. I enjoyed Ada very much. The module system made a lot of sense to me and the compiler found a lot of mistakes (compared to C). Thanks for sharing this article. It brought me back and makes me want to give Ada another go now that I have 10 years of real world experience.
- dilawar 3y ago
  I had a digital design course. The instructor hated verilog and preferred VHDL for reason that didn't make much sense to me those days. There was only one VHDL compiler available that time called ghdl which worked fine for course. There was modelsim as well but one had to go to the lab. Later I learnt that VHDL is related to ADA. I've been itching to try it for a long while. Might give it a try this week. Currently I am in my Rust phase and loving it (thanks cargo). My Haskell fever is gone though.
  - robinsonb5 3y ago
    I've been meaning to explore ADA as well, since learning that GHDL is itself written in ADA.
  - goku12 3y ago
    I haven't tried Ada yet, but do have experience with VHDL. It's the most modular language I've encountered. It's easy to work with big teams in VHDL. Choose everyone's responsibility, design the interfaces (entities) and have a brief discussion on it. Then go separate ways and implement your parts (architecture). They all finally fit together like magic without needing too much coordination or interaction between the team members. I'm pretty sure that's what's great about Ada too. However, I still don't understand what it is about the language's design that makes this possible.
- chasil 3y ago
  One place where you can easily use ADA syntax is any database that implements ANSI SQL/PSM, and there are many. "SQL/PSM is derived, seemingly directly, from Oracle's PL/SQL. Oracle developed PL/SQL and released it in 1991, basing the language on the US Department of Defense's Ada programming language." https://en.m.wikipedia.org/wiki/SQL/PSM https://en.m.wikipedia.org/wiki/SQL/PSM
- agumonkey 3y ago
  Ada module made me make sense of java oo somehow. I'd love to get a gig in ada.
ChrisArchitect 3y ago
(2016)
- dang 3y ago
  Added. Thanks!
inamberclad 3y ago
Hah, my perfect niche! I think that an ada-like language could make a real resurgence in embedded programming. Ada gets all the things about bare-metal right that C got wrong. However, it's held up by legacy tooling, clunky syntax, and obtuse compiler errors. Adacore has gone a long way towards alleviating those issues over the last few years, with alire and the ada_language_server. Time will see where this language takes us.
- ajxs 3y ago
  I completely agree. 'Design-by-committee' gets a bad rap, but Ada's designers got a lot of things right when it came to bare-metal programming. The ability to specify the in-memory representation of a type is one of my personal favourites. I don't think Ada's syntax has aged well. I wish it would get a 21st-century overhaul. I don't think that's likely though, but we can all dream. AdaCore do great work, and contribute a lot back to the open-source community.
  - nrr 3y ago
    It's unclear exactly what you mean by your remark that Ada's syntax hasn't aged well, let alone what a 21st-century overhaul would look like. Is there any chance you'd expand on that? I'm curious to know your thoughts.
    - inamberclad 3y ago
      I think it's evident to most people that write Ada that the language is too English-heavy. This gets in the way of actually representing the computations. This was a design decision when the language was created, since the emphasis was put on maintainable code
      - thrawa8387336 3y ago
        Is this meant as a joke, too English-heavy?
        3y ago
musicale 3y ago
Memory safety might not be a bad idea for Linux in general.
- erik_seaberg 3y ago
  Ada’s take on memory safety is pretty limited. Heap allocation is explicit; there’s a procedure literally named Unchecked_Deallocation to free a pointer. It does have thread-scoped locals and arenas, but nothing like declared lifetimes or borrowing. The spec allows for GC but I believe it’s rarely offered. It’s safer than C, but I’m not quite sure where recent specs line up against C++.
  - pjmlp 3y ago
    Only true for those stuck in Ada83. People keep repeating this nonsense without updating themselves beforehand. EDIT: To simply education on Ada, Yes there was an optional GC, no one ever implemented it, so in Ada2012 got removed from the standard. Almost everything can be allocated on the stack, so a strategy is to catch exceptions of not enough stack space and retry the same function with a smaller size for the data structure. Ada95 introduced controlled types, which is basically Ada's version of RAII, no need to call Unchecked_Deallocation outside implementation details. Hardly any different from Rust code that uses unsafe underneath. Ada/SPARK, now part of regular Ada specification, provides theorem proving capabilities, and contracts, allowing another safety level still not available in Rust. Additionally Ada Core is contributing improving lifetime rules for access types, to have a kind of borrow checker light, when needed. Finally, there are still 7 Ada vendors in business, with 40 years of experience deploying Ada into safety critical scenarios.
    - tomcam 3y ago
      What’s your sense of the size of the Ada job market? High hundreds? Close to 10,000? Is it static or growing or shrinking? Is there a preferred online community for Ada devs?
      - BirAdam 3y ago
tombert 3y ago
I've never used Ada, and I also don't really do systems stuff, but it does seem like it's a pretty neat language, at least compared to C. From what I have seen, it looks like it has better memory guarantees while still being fast and low-level. With be the popularity of Rust, it makes me kind of wonder why Ada isn't more popular. I should give the language a go.
- demizer 3y ago
  There wasn't an open source compiler from the beginning, and thus a lot of the compilers where expensive. You could only use the language in an awful legacy setting behind a wall of NDAs and security clearances. Not my experience, just a bunch comments on HN of actual retired Ada devs on why the language didn't take when I was researching the language. Adacore in the last few years have been investing heavily in modernizing the tool chain, but now it seems they are also investing in Rust.
  - hbossy 3y ago
    This is true, I've worked on a actively maintained Ada codebase in aerospace industry and we had to use a proprietary Ada Xd compiler that was being sold for hundreds of thousands of dollars per installation by company not interested in doing any updates, that came with a phonebook-size paper errata of known bugs.
  - thesuperbigfrog 3y ago
    >> Adacore in the last few years have been investing heavily in modernizing the tool chain, but now it seems they are also investing in Rust. Adacore is working with Ferrous Systems on Ferrocene (https://ferrous-systems.com/ferrocene/ https://ferrous-systems.com/ferrocene/), a Rust toolchain for use on safety critical applications: https://blog.adacore.com/announcing-publication-of-the-draft-ferrocene-language-specification https://blog.adacore.com/announcing-publication-of-the-draft... https://ferrous-systems.com/blog/ferrous-systems-adacore-joining-forces/ https://ferrous-systems.com/blog/ferrous-systems-adacore-joi... I am hoping that Ferrocene's work will help the drive the standardization of Rust over the next few years: https://github.com/rust-lang/rust/issues/113527 https://github.com/rust-lang/rust/issues/113527
zeroCalories 3y ago
Cool project for a proof of concept. That said, the kernel has so many unsafe features that making real world modules that are safe requires a lot of boilerplate to get around those features. Sometimes it's impossible. Rust is only barely useable now after tons of work to make it viable.
ggm 3y ago
A very long time ago The University of York (UK) secured the contract from the UK Science and Engineering Council (SERC) to write a unix Ada compiler. It was a multi pass, 5-10 stage process (or more. I want to say 13 but time plays tricks) Very costly language to compile, in those days. (Vax 11/780 running Unix 32V, a precursor to BSD and Ultrix by some years) The story was it emitted an error/warning code along the lines of "Congratulations you have used the most abstruse feature of the ADA language" -which the approval people made them take out before it got certified. Wirth had a sabbatical residency in York around the time of the Ada language selection process, his choices didn't make it through the strawman/steelman process, I think they resurfaced in Modula-II. It was a pascal teaching department like many others in the UK of the time, so it made sense for him to spend time there. Modula-II is said to be a systems programming language too. Ada was very hard to teach. The ideas of asynchronous, and exception handling didn't sit very well on young minds. Maybe now they're well enough understood to teach in Rust. At the time, the absence of a rationale around "why" was very strong. York had a miniature 2-lift engine model which it used as a proving ground for Ada programs and undergraduate projects. Lift sequencing is a bit of a black art in itself but if you put that optimality of "which lift, which direction, which floor" to one side, the mixture of real-time controls and sensors were probably a good fit. (lift == elevator for the other side of the Atlantic) I remember some concern in the department the only logical endpoint for Ada was to code military flight control/weapons/radar systems, and people felt uncomfortable about the implicit participation in the UK War economy. This was during the time of the Greenham common protests against US nuclear forces on UK soil. During the Alvey 5th Generation funding debacle ("Catch up with Japan at all costs") there was another round of this using GEC400 computers, again very directly related to Uk MOD needs for weapons control systems and what I think became the Nimrod airborne radar. Probably signals processing is a very good fit for Ada. (I didn't work on that project, or the compiler) People said that the consistency of mapping data structures to devices, chip signal lines, real things, and the abstractions around that in types worked well in Ada. I found it horrendously complicated to understand. People might say C is a hack but the literal directness of C structs on a PDP11 or Vax to the underlying architecture worked pretty well to me. I guess the problem is that C was always too close to Assembler for some people. Bliss/32 was the systems programming language of choice in Digital, and I think continued to be used to write VMS, although I read now it was almost entirely written in DEC Macro assembler.
MarcusE1W 3y ago
Here is a really good ada tutorial for low level and systems programming. https://learn.adacore.com/courses/intro-to-embedded-sys-prog/index.html https://learn.adacore.com/courses/intro-to-embedded-sys-prog... Here the bit fiddling in Ada data structures is explained https://learn.adacore.com/courses/intro-to-embedded-sys-prog/chapters/low_level_programming.html#specifying-representation https://learn.adacore.com/courses/intro-to-embedded-sys-prog... Quite cool
mkovach 3y ago
Ahh, Lovely Ada. When I was a wee lad, toiling as an Email consultant, having my mind slowly destroyed by Sendmail configurations, the constant fear induced by anything related to Microsoft and Email, and, well, let's not mention Lotus Notes, some wounds never heal, I had the grand idea of writing a secure collection of Email tools. This included SMTP, IMAP, POP3 daemons, and various other tools. I was going to write them all in Ada. I had a basic SMTP daemon that would accept mail and deliver it. But then, one of the various Outlook worms generated a ton of revenue at the expense of sleep, hygiene, and dignity, and I decided to get out of the Email business ASAP. Still wish I would have kept working with Ada. I really liked it, and one could write tight code with it.
- touisteur 3y ago
  Look up Ada Web Server :-) no IMAP though. And no QUIC yet, sadly. I hope someone is going to write a whole HTTPS stack using RecordFlux. One can dream.
  - mkovach 3y ago
    I have actually looked at it, in my endless quest to stop having Naviserver/AOLserver be my favorite web server. ;-> I'm going to be giving it another go here in a bit, I got a small little personal project where I'm going to make a serious attempt to curse at it for a bit.
    - touisteur 3y ago
      I'm actually curious whether someone has formalized message formats/grammar, protocol specs (state management, timing specs,...) for QUIC or IMAP, in some parseable form other than free-form text.
binary132 3y ago
I’ve always been attracted to the idea of Ada (particularly SPARK) as a “really safe C-like”. I guess my main concern versus C is portability and ease of integrating libraries or exporting a usable C API, and secondarily the quality of the optimizer.
- thesuperbigfrog 3y ago
  >> I guess my main concern versus C is portability and ease of integrating libraries or exporting a usable C API, and secondarily the quality of the optimizer. Interfacing with C APIs / libraries is really easy and portable across Ada implementations: https://learn.adacore.com/courses/intro-to-ada/chapters/interfacing_with_c.html https://learn.adacore.com/courses/intro-to-ada/chapters/inte... http://www.ada-auth.org/standards/22rm/html/RM-B-3.html http://www.ada-auth.org/standards/22rm/html/RM-B-3.html The quality of the optimizer depends on the Ada implementation. GNAT, the free software Ada implementation, uses the GCC backend so it is pretty good: https://www.getadanow.com/ https://www.getadanow.com/ https://www.adacore.com/gnatpro https://www.adacore.com/gnatpro
  - glacia01 3y ago
    >GNAT, the free software Ada implementation, uses the GCC backend so it is pretty good: GNAT also has LLVM Backend: https://github.com/AdaCore/gnat-llvm https://github.com/AdaCore/gnat-llvm It's stable and Adacore plans to ship it in GNAT Pro 24, i.e. next release. Note that it's the same front-end, so you get best of both worlds basically.
  - binary132 3y ago
    Thanks for showing me that, I agree it looks pretty convenient.
butterisgood 3y ago
I want to like Ada, but the lack of support for Mac OS on anything Apple Silicon related is a huge reason to skip it and do something else (for me). One thing I still haven't wrapped my head around is how "dynamic" memory allocation and cleanup works in Ada. It doesn't seem as important to mention that early in any documentation anywhere. And, maybe it's the C/C++ programmer in me, but that strikes me as a bit odd. Or, perhaps I just can't see past the tip of my nose and it's there. I kind of need to know how dynamic memory works in any programming language before I plan to invest deeply in learning it. And it needs to work on my hardware.
- docandrew 3y ago
  There’s a GNAT release for M1 now. The FSF Ada compiler is based on GCC so it has worked for RISC-V and other ARM CPUs for a little while now as well. Ada’s dynamic memory principles are definitely unique. For heap allocation its based around memory pools, at least in GNAT. For the most part it’s RTTI but you can do manual new/free style too (though discouraged). Ada uses a secondary stack as well for variable-length function returns, so in practice you don’t need to do heap allocation very much. There are also equivalents of some STL containers like vector that can handle heap allocations for you safely.
  - butterisgood 3y ago
    Thanks for this... I'll take a look at how to get started on Mac OS with GNAT. I went down a bit of a rabbit hole recently looking to see if there was a LLVM way to do this. It looked like it was being worked, but I'm not sure it's the best way to get started with Mac OS and Ada on Apple Silicon. I'll check out homebrew and macports too... again, just in case! Thanks again!
    - MarcusE1W 3y ago
      Not sure how well it works (I don’t have a Mac), but there is this repository that describes how to compile the whole gcc/gnat ada system in MacOS. https://github.com/simonjwright/building-gcc-macos-arm-eabi https://github.com/simonjwright/building-gcc-macos-arm-eabi Bonus point is that you get the compiler for ARM bare metal
cmrdporcupine 3y ago
It's interesting to see the positive talk about Ada in here. I think that's good, but also indicative of perhaps a change in perspective. I feel like if the topic of Ada had come up here 10 years ago (probably did), the responses would have been quite different and more along the lines of "that annoying stuffy/overly-verbose/old/obsolete/design-by-committee language" . I think there's a good growing consciousness of the fairly terrifying unsafety of C/C++, and the relative success of Rust is some evidence of that, at least. Many moons ago I bought an Ada 95 manual, and learned a bit of the language with intent to fiddle with it but never finished. I like the idea but not sure I'd be wanting to give up various... modern conveniences... I get from Rust in order to work in that world.
eggy 3y ago
I always recommend this book, "Building High Integrity Applications with SPARK" as an introduction to how SPARK can be used for high-integrity, safe programs for mission-critical applications. SPARK has a legacy of large, high-integrity applications over the past two decades. This puts it ahead of Rust in real-world usage for such applications. SPARK2014 the latest, is a formally verified PL along with verification tools/ecosystem made for these type of uses. I am trying to write show control software in SPARK2014 at the moment. Show control are critical since it is used to power lifts and stage machinery as well as performer flying systems where safety and high-integrity software is critical. I like Rust, but I feel it is not quite there yet especially in terms of the number of real-world systems in this niche. I also find SPARK2014 easier to write and read. I have been programming since 1978, and although I gravitate towards terse, functional languages like Haskell, APL/BQN/J, I experience a lot of friction whenever I dive back into Rust. SPARK2014 is very verbose and Pascal-like, but this is tedium vs. confusion or confidence in what I am writing. I know AdaCore is working with Ferrous Systems to bring Rust more up to the features of Ada/SPARK2014, but for now I needed to make a pragmatic choice based on real-world usage and ease of use and understanding.
- jk4930 3y ago
  Just want to add that I prefer Ada over C++ despite it having less mind share, tools, and libraries because its productivity is so high. (Not saying that I dislike C++.) And, speculating here, with the encroachment of AI into programming/software engineering, I assume that it's convenient to use languages that are declarative (e.g. Haskell) and/or designed for verification/formal methods (e.g. Ada/SPARK) to integrate AIs of various kinds.

134 points by slondr 3y ago

Back in university I took a course in legacy programming. We did a project in each of Fortran, COBOL and Ada. I enjoyed Ada very much. The module system made a lot of sense to me and the compiler found a lot of mistakes (compared to C). Thanks for sharing this article. It brought me back and makes me want to give Ada another go now that I have 10 years of real world experience.

dilawar 3y ago
I had a digital design course. The instructor hated verilog and preferred VHDL for reason that didn't make much sense to me those days. There was only one VHDL compiler available that time called ghdl which worked fine for course. There was modelsim as well but one had to go to the lab. Later I learnt that VHDL is related to ADA. I've been itching to try it for a long while. Might give it a try this week. Currently I am in my Rust phase and loving it (thanks cargo). My Haskell fever is gone though.
- robinsonb5 3y ago
  I've been meaning to explore ADA as well, since learning that GHDL is itself written in ADA.
- goku12 3y ago
  I haven't tried Ada yet, but do have experience with VHDL. It's the most modular language I've encountered. It's easy to work with big teams in VHDL. Choose everyone's responsibility, design the interfaces (entities) and have a brief discussion on it. Then go separate ways and implement your parts (architecture). They all finally fit together like magic without needing too much coordination or interaction between the team members. I'm pretty sure that's what's great about Ada too. However, I still don't understand what it is about the language's design that makes this possible.
chasil 3y ago
One place where you can easily use ADA syntax is any database that implements ANSI SQL/PSM, and there are many. "SQL/PSM is derived, seemingly directly, from Oracle's PL/SQL. Oracle developed PL/SQL and released it in 1991, basing the language on the US Department of Defense's Ada programming language." https://en.m.wikipedia.org/wiki/SQL/PSM https://en.m.wikipedia.org/wiki/SQL/PSM
agumonkey 3y ago
Ada module made me make sense of java oo somehow. I'd love to get a gig in ada.

ChrisArchitect 3y ago

(2016)

dang 3y ago
Added. Thanks!

inamberclad 3y ago

Hah, my perfect niche! I think that an ada-like language could make a real resurgence in embedded programming. Ada gets all the things about bare-metal right that C got wrong. However, it's held up by legacy tooling, clunky syntax, and obtuse compiler errors. Adacore has gone a long way towards alleviating those issues over the last few years, with alire and the ada_language_server. Time will see where this language takes us.

ajxs 3y ago
I completely agree. 'Design-by-committee' gets a bad rap, but Ada's designers got a lot of things right when it came to bare-metal programming. The ability to specify the in-memory representation of a type is one of my personal favourites. I don't think Ada's syntax has aged well. I wish it would get a 21st-century overhaul. I don't think that's likely though, but we can all dream. AdaCore do great work, and contribute a lot back to the open-source community.
- nrr 3y ago
  It's unclear exactly what you mean by your remark that Ada's syntax hasn't aged well, let alone what a 21st-century overhaul would look like. Is there any chance you'd expand on that? I'm curious to know your thoughts.
  - inamberclad 3y ago
    I think it's evident to most people that write Ada that the language is too English-heavy. This gets in the way of actually representing the computations. This was a design decision when the language was created, since the emphasis was put on maintainable code
    - thrawa8387336 3y ago
      Is this meant as a joke, too English-heavy?
      - 3y ago

musicale 3y ago

Memory safety might not be a bad idea for Linux in general.

erik_seaberg 3y ago
Ada’s take on memory safety is pretty limited. Heap allocation is explicit; there’s a procedure literally named Unchecked_Deallocation to free a pointer. It does have thread-scoped locals and arenas, but nothing like declared lifetimes or borrowing. The spec allows for GC but I believe it’s rarely offered. It’s safer than C, but I’m not quite sure where recent specs line up against C++.
- pjmlp 3y ago
  Only true for those stuck in Ada83. People keep repeating this nonsense without updating themselves beforehand. EDIT: To simply education on Ada, Yes there was an optional GC, no one ever implemented it, so in Ada2012 got removed from the standard. Almost everything can be allocated on the stack, so a strategy is to catch exceptions of not enough stack space and retry the same function with a smaller size for the data structure. Ada95 introduced controlled types, which is basically Ada's version of RAII, no need to call Unchecked_Deallocation outside implementation details. Hardly any different from Rust code that uses unsafe underneath. Ada/SPARK, now part of regular Ada specification, provides theorem proving capabilities, and contracts, allowing another safety level still not available in Rust. Additionally Ada Core is contributing improving lifetime rules for access types, to have a kind of borrow checker light, when needed. Finally, there are still 7 Ada vendors in business, with 40 years of experience deploying Ada into safety critical scenarios.
  - tomcam 3y ago
    What’s your sense of the size of the Ada job market? High hundreds? Close to 10,000? Is it static or growing or shrinking? Is there a preferred online community for Ada devs?
    - BirAdam 3y ago

tombert 3y ago

I've never used Ada, and I also don't really do systems stuff, but it does seem like it's a pretty neat language, at least compared to C. From what I have seen, it looks like it has better memory guarantees while still being fast and low-level. With be the popularity of Rust, it makes me kind of wonder why Ada isn't more popular. I should give the language a go.

demizer 3y ago
There wasn't an open source compiler from the beginning, and thus a lot of the compilers where expensive. You could only use the language in an awful legacy setting behind a wall of NDAs and security clearances. Not my experience, just a bunch comments on HN of actual retired Ada devs on why the language didn't take when I was researching the language. Adacore in the last few years have been investing heavily in modernizing the tool chain, but now it seems they are also investing in Rust.
- hbossy 3y ago
  This is true, I've worked on a actively maintained Ada codebase in aerospace industry and we had to use a proprietary Ada Xd compiler that was being sold for hundreds of thousands of dollars per installation by company not interested in doing any updates, that came with a phonebook-size paper errata of known bugs.
- thesuperbigfrog 3y ago
  >> Adacore in the last few years have been investing heavily in modernizing the tool chain, but now it seems they are also investing in Rust. Adacore is working with Ferrous Systems on Ferrocene (https://ferrous-systems.com/ferrocene/ https://ferrous-systems.com/ferrocene/), a Rust toolchain for use on safety critical applications: https://blog.adacore.com/announcing-publication-of-the-draft-ferrocene-language-specification https://blog.adacore.com/announcing-publication-of-the-draft... https://ferrous-systems.com/blog/ferrous-systems-adacore-joining-forces/ https://ferrous-systems.com/blog/ferrous-systems-adacore-joi... I am hoping that Ferrocene's work will help the drive the standardization of Rust over the next few years: https://github.com/rust-lang/rust/issues/113527 https://github.com/rust-lang/rust/issues/113527

zeroCalories 3y ago

Cool project for a proof of concept. That said, the kernel has so many unsafe features that making real world modules that are safe requires a lot of boilerplate to get around those features. Sometimes it's impossible. Rust is only barely useable now after tons of work to make it viable.

ggm 3y ago

A very long time ago The University of York (UK) secured the contract from the UK Science and Engineering Council (SERC) to write a unix Ada compiler. It was a multi pass, 5-10 stage process (or more. I want to say 13 but time plays tricks) Very costly language to compile, in those days. (Vax 11/780 running Unix 32V, a precursor to BSD and Ultrix by some years) The story was it emitted an error/warning code along the lines of "Congratulations you have used the most abstruse feature of the ADA language" -which the approval people made them take out before it got certified. Wirth had a sabbatical residency in York around the time of the Ada language selection process, his choices didn't make it through the strawman/steelman process, I think they resurfaced in Modula-II. It was a pascal teaching department like many others in the UK of the time, so it made sense for him to spend time there. Modula-II is said to be a systems programming language too. Ada was very hard to teach. The ideas of asynchronous, and exception handling didn't sit very well on young minds. Maybe now they're well enough understood to teach in Rust. At the time, the absence of a rationale around "why" was very strong. York had a miniature 2-lift engine model which it used as a proving ground for Ada programs and undergraduate projects. Lift sequencing is a bit of a black art in itself but if you put that optimality of "which lift, which direction, which floor" to one side, the mixture of real-time controls and sensors were probably a good fit. (lift == elevator for the other side of the Atlantic) I remember some concern in the department the only logical endpoint for Ada was to code military flight control/weapons/radar systems, and people felt uncomfortable about the implicit participation in the UK War economy. This was during the time of the Greenham common protests against US nuclear forces on UK soil. During the Alvey 5th Generation funding debacle ("Catch up with Japan at all costs") there was another round of this using GEC400 computers, again very directly related to Uk MOD needs for weapons control systems and what I think became the Nimrod airborne radar. Probably signals processing is a very good fit for Ada. (I didn't work on that project, or the compiler) People said that the consistency of mapping data structures to devices, chip signal lines, real things, and the abstractions around that in types worked well in Ada. I found it horrendously complicated to understand. People might say C is a hack but the literal directness of C structs on a PDP11 or Vax to the underlying architecture worked pretty well to me. I guess the problem is that C was always too close to Assembler for some people. Bliss/32 was the systems programming language of choice in Digital, and I think continued to be used to write VMS, although I read now it was almost entirely written in DEC Macro assembler.

MarcusE1W 3y ago

Here is a really good ada tutorial for low level and systems programming. https://learn.adacore.com/courses/intro-to-embedded-sys-prog/index.html https://learn.adacore.com/courses/intro-to-embedded-sys-prog... Here the bit fiddling in Ada data structures is explained https://learn.adacore.com/courses/intro-to-embedded-sys-prog/chapters/low_level_programming.html#specifying-representation https://learn.adacore.com/courses/intro-to-embedded-sys-prog... Quite cool

mkovach 3y ago

Ahh, Lovely Ada. When I was a wee lad, toiling as an Email consultant, having my mind slowly destroyed by Sendmail configurations, the constant fear induced by anything related to Microsoft and Email, and, well, let's not mention Lotus Notes, some wounds never heal, I had the grand idea of writing a secure collection of Email tools. This included SMTP, IMAP, POP3 daemons, and various other tools. I was going to write them all in Ada. I had a basic SMTP daemon that would accept mail and deliver it. But then, one of the various Outlook worms generated a ton of revenue at the expense of sleep, hygiene, and dignity, and I decided to get out of the Email business ASAP. Still wish I would have kept working with Ada. I really liked it, and one could write tight code with it.

touisteur 3y ago
Look up Ada Web Server :-) no IMAP though. And no QUIC yet, sadly. I hope someone is going to write a whole HTTPS stack using RecordFlux. One can dream.
- mkovach 3y ago
  I have actually looked at it, in my endless quest to stop having Naviserver/AOLserver be my favorite web server. ;-> I'm going to be giving it another go here in a bit, I got a small little personal project where I'm going to make a serious attempt to curse at it for a bit.
  - touisteur 3y ago
    I'm actually curious whether someone has formalized message formats/grammar, protocol specs (state management, timing specs,...) for QUIC or IMAP, in some parseable form other than free-form text.

binary132 3y ago

I’ve always been attracted to the idea of Ada (particularly SPARK) as a “really safe C-like”. I guess my main concern versus C is portability and ease of integrating libraries or exporting a usable C API, and secondarily the quality of the optimizer.

thesuperbigfrog 3y ago
>> I guess my main concern versus C is portability and ease of integrating libraries or exporting a usable C API, and secondarily the quality of the optimizer. Interfacing with C APIs / libraries is really easy and portable across Ada implementations: https://learn.adacore.com/courses/intro-to-ada/chapters/interfacing_with_c.html https://learn.adacore.com/courses/intro-to-ada/chapters/inte... http://www.ada-auth.org/standards/22rm/html/RM-B-3.html http://www.ada-auth.org/standards/22rm/html/RM-B-3.html The quality of the optimizer depends on the Ada implementation. GNAT, the free software Ada implementation, uses the GCC backend so it is pretty good: https://www.getadanow.com/ https://www.getadanow.com/ https://www.adacore.com/gnatpro https://www.adacore.com/gnatpro
- glacia01 3y ago
  >GNAT, the free software Ada implementation, uses the GCC backend so it is pretty good: GNAT also has LLVM Backend: https://github.com/AdaCore/gnat-llvm https://github.com/AdaCore/gnat-llvm It's stable and Adacore plans to ship it in GNAT Pro 24, i.e. next release. Note that it's the same front-end, so you get best of both worlds basically.
- binary132 3y ago
  Thanks for showing me that, I agree it looks pretty convenient.

butterisgood 3y ago

I want to like Ada, but the lack of support for Mac OS on anything Apple Silicon related is a huge reason to skip it and do something else (for me). One thing I still haven't wrapped my head around is how "dynamic" memory allocation and cleanup works in Ada. It doesn't seem as important to mention that early in any documentation anywhere. And, maybe it's the C/C++ programmer in me, but that strikes me as a bit odd. Or, perhaps I just can't see past the tip of my nose and it's there. I kind of need to know how dynamic memory works in any programming language before I plan to invest deeply in learning it. And it needs to work on my hardware.

docandrew 3y ago
There’s a GNAT release for M1 now. The FSF Ada compiler is based on GCC so it has worked for RISC-V and other ARM CPUs for a little while now as well. Ada’s dynamic memory principles are definitely unique. For heap allocation its based around memory pools, at least in GNAT. For the most part it’s RTTI but you can do manual new/free style too (though discouraged). Ada uses a secondary stack as well for variable-length function returns, so in practice you don’t need to do heap allocation very much. There are also equivalents of some STL containers like vector that can handle heap allocations for you safely.
- butterisgood 3y ago
  Thanks for this... I'll take a look at how to get started on Mac OS with GNAT. I went down a bit of a rabbit hole recently looking to see if there was a LLVM way to do this. It looked like it was being worked, but I'm not sure it's the best way to get started with Mac OS and Ada on Apple Silicon. I'll check out homebrew and macports too... again, just in case! Thanks again!
  - MarcusE1W 3y ago
    Not sure how well it works (I don’t have a Mac), but there is this repository that describes how to compile the whole gcc/gnat ada system in MacOS. https://github.com/simonjwright/building-gcc-macos-arm-eabi https://github.com/simonjwright/building-gcc-macos-arm-eabi Bonus point is that you get the compiler for ARM bare metal

cmrdporcupine 3y ago

It's interesting to see the positive talk about Ada in here. I think that's good, but also indicative of perhaps a change in perspective. I feel like if the topic of Ada had come up here 10 years ago (probably did), the responses would have been quite different and more along the lines of "that annoying stuffy/overly-verbose/old/obsolete/design-by-committee language" . I think there's a good growing consciousness of the fairly terrifying unsafety of C/C++, and the relative success of Rust is some evidence of that, at least. Many moons ago I bought an Ada 95 manual, and learned a bit of the language with intent to fiddle with it but never finished. I like the idea but not sure I'd be wanting to give up various... modern conveniences... I get from Rust in order to work in that world.

eggy 3y ago

I always recommend this book, "Building High Integrity Applications with SPARK" as an introduction to how SPARK can be used for high-integrity, safe programs for mission-critical applications. SPARK has a legacy of large, high-integrity applications over the past two decades. This puts it ahead of Rust in real-world usage for such applications. SPARK2014 the latest, is a formally verified PL along with verification tools/ecosystem made for these type of uses. I am trying to write show control software in SPARK2014 at the moment. Show control are critical since it is used to power lifts and stage machinery as well as performer flying systems where safety and high-integrity software is critical. I like Rust, but I feel it is not quite there yet especially in terms of the number of real-world systems in this niche. I also find SPARK2014 easier to write and read. I have been programming since 1978, and although I gravitate towards terse, functional languages like Haskell, APL/BQN/J, I experience a lot of friction whenever I dive back into Rust. SPARK2014 is very verbose and Pascal-like, but this is tedium vs. confusion or confidence in what I am writing. I know AdaCore is working with Ferrous Systems to bring Rust more up to the features of Ada/SPARK2014, but for now I needed to make a pragmatic choice based on real-world usage and ease of use and understanding.

jk4930 3y ago
Just want to add that I prefer Ada over C++ despite it having less mind share, tools, and libraries because its productivity is so high. (Not saying that I dislike C++.) And, speculating here, with the encroachment of AI into programming/software engineering, I assume that it's convenient to use languages that are declarative (e.g. Haskell) and/or designed for verification/formal methods (e.g. Ada/SPARK) to integrate AIs of various kinds.