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If by low level you mean embedded systems programming, you will definetly need to be proficient in C. The other knowledge depends on the product that you will make. For example I work in the automotive industry, where you need to be interested in cars and how the different parts work. Knowledge of electrical engineering and control theory is also valuable. There is a good book about it if you wat to learn how cars works: Bosch Automotive Handbook.

If you go that path, bear in mind that you will not be involved in creating clever algorithm. When safety is involved, you need to program very simple and easy code. The complexity lies in how all the parts and ECUs are interacting with each other. On the upside, you do not need to constantly learn new languages and library, and you accumulate expert knowledge which is interesting for companies.






What if -and I'm sorry to hijack- by low-level OP means a position as a C/C++ developer (asking for ~a friend~ me)? I've always been insanely attracted to the C variants and messed around with them to minor extents, but what might someone _need_ to know to be competitive if they're trying to make a move to that area of SE?

Memory management is the major difference between them and most of the higher level stuff. You need a good grasp of who owns what in a program so you can free and close things when they aren't needed (and not before). Less so in C++ these days of course, but definitely in C.

It's worth picking up some basic gdb skills. Use of ddd can help with this. On windows you can use VS for most of this of course. Picking up the basics of valgrind will also help you.

Get comfortable with the preprocessor. Get comfortable with Makefiles. Get comfortable pulling in library headers and binaries as needed.

Errr....

I was (mostly) a C programmer for over a decade, but that's about all I can think of right now!

--edit--

And someone below has just triggered me - FFS use stdint.h!


> You need a good grasp of who owns what in a program so you can free and close things when they aren't needed (and not before). Less so in C++ these days of course, but definitely in C

You absolutely need to know in C++ too. Modern C++ just gives you tools to express ownership in code. Rust goes way further and gives you compile time correctness of your lifetime handling


For C:

Pointers, stacks (one in ever 23.7 bugs is a stack smashing bug), bit bashing and endianness, types and coercion at the byte level (see also: pointers, bit bashing), C strings, the stupid rules about when a variable's value is actually written to memory that need to die in a fire, memory allocation/clearing/copying/ownership/freeing, ALWAYS CHECK RETURN CODES, what the heck an lvalue is.

This book is fun:

http://shop.oreilly.com/product/0636920033677.do


Thanks! I just started reading that last night. Pretty good so far.

The german version is called "Kraftfahrtechnisches Taschenbuch" and is ~15EUR cheaper.

But it is in german, and i believe that a native will not fully understand it if he did not work in the field in germany.

I'm french and studied in the UK. I'm sometimes lost when my colleague use french technical terms, i have to ask the concept behind it to be able to identify the english term which i learnt during my studies.


From a review on amazon:

> However, as an English speaking engineer, I found many of the discussions rather clumsily written. I'm guessing that it was translated from the German by someone who doesn't thoroughly understand the subject matter.


I don't do embedded systems, but as a self-respecting software engineer, I am intending to develop proficiency in C/C++ over this next year. Does anybody have any recommended books/courses/projects?

I highly recommend Computer Systems: A Programmer's Perspective for learning C. In particular chapter 3 of that book is what made it all click for me. Understanding how C is translated down into assembly is incredibly useful for understanding pointers and reasoning about your code.

EDIT. The book also comes with a collection of excellent projects, which the authors have made freely available online at http://csapp.cs.cmu.edu/3e/labs.html


Agreed! The labs are very informative and fun. One of my favorite undergrad courses used this book/labs ~10 years ago. Glad to see it is still being used!

Aside from K&R, you might want to look at the Modern C PDF https://gustedt.wordpress.com/2016/11/25/modern-c-is-now-fea... for an opinionated but sane guide.

Also 21st Century C has been recommended, and it goes into tooling as well.


A quick word of warning: be sure to treat C and C++ as two completely separate languages that just happen to have similar syntax. Yes, you can use C++ as "C with classes" (I and many others sure have at times), but you're doing yourself a disservice most of the time if you do.

Huh. I always perceived C to be a subset of C++.

Current versions of C have some features that are not present in current versions of C++ (e.g. designated initializers).

But that's not the point. C and C++ are in practice used completely differently, so writing C++ using C concepts with some additions rarely happens in the wild.


... except in the firmware space, where important C++ mechanisms (especially RTTI and exceptions) tend to be unavailable, giving rise to a (useful, powerful, fun) hybrid of the two.

C++ is largely backwards compatible to C, but idiomatic code is very different in modern practice between the two. A somewhat dated blog post I wrote on the topic a decade ago:

https://blog.directededge.com/2009/05/21/c-and-c-are-not-the...


C enum values are convertible from int; C++ enum values aren't. This is one of the biggest differences in fairly idiomatic C code and has been the case for a very long time (i.e. not dependent on newer C features not being in C++).

    #include <stdio.h>
    
    typedef enum EFoo {
        FOO_A = 1,
        FOO_B = 2
    } TFoo;
    
    int main()
    {
        TFoo foo = FOO_A | FOO_B;
        printf("foo = %d\n", foo);
    }
This compiles in C but not C++.


That's not the same code, is it? GP's code does not seem to compile in C++: https://godbolt.org/z/5oAIYE

But it does in C: https://godbolt.org/z/zdTKiE


Try creating a foo https://godbolt.org/z/AlHDhg

I like to think what is JSON to Javascript is C to C++ (not capability wise). JSON and Javascript are completely, entirely different things even though JSON is technically a subset of Javascript (every valid JSON sentence is a valid Javascript sentence). C and C++ are extremely different languages -- mostly due to cultural reasons -- even though every valid C program is a valid C++ program (not strictly true, C and C++ diverged slightly, but you got the point). I, for example, write C-ish C++ and compile it with g++ but call it "C" because it's "nothing like C++" and "it's basically C with some extra keywords". I know this comment sounds absurd but C++, especially modern C++, is a very complicated beast with a complex ecosystem and culture attached to it. If you inherit a C program and add one C++ line and compile it with g++, even though it's "technically" C++ now, I really wouldn't call it C++. The way you solve problems in C and C++ are extremely different, and this matters.

Can I be pedantic? If I'm wrong someone will correct me and I'll learn something.

Json is not exactly a subset because it supports representation of numbers of any precision. JavaScript will convert to an IEEE 754. But it's up to a json deserializer to decide how many decimals to use. I think.


I mean sure, doesn't change my point (pedantically C isn't a subset of C++ either). That was just a metaphor.

That used to be true, but becomes less true with each new version of the respective language specs. Sometimes the differences are obvious because legal identifiers in C can be keywords in C++, sometimes the difference is subtle, like with the rules regarding type punning.

But the major point is that there are almost always safer or more ergonomic ways to do things using C++ features that are not present in C.


imho, c :: c++ == ipv4 :: ipv6 (where '::' should be read as 'is to' relation)

FWIW I think he's wrong. Basically, when writing C, you should write code the same as if you'd write it in C++, except that you're using C.

Because sometimes that's annoying, things can get less type safe, but in your head, there's a C++ program that you're representing.


Programs written in this mindset might be the number one reason why C has a bad reputation. Of course, if you just emulate what other languages automate for you, you should better write in these languages.

But in reality, why C is still the best programming language for large projects (IMO) is exactly that the programmer is allowed to choose a suitable structure, such that the program can fulfill the technical requirements. Other languages force the project into a structure that somehow never fits after a couple thousand LOC.


What.

What good programs are written in C that don't have well-structured memory management the way C++ does it with RAII?

Edit:

"But in reality, why C is still the best programming language for large projects (IMO) is exactly that the programmer is allowed to choose a suitable structure, such that the program can fulfill the technical requirements. Other languages force the project into a structure that somehow never fits after a couple thousand LOC."

Yeah, this doesn't make any sense. The reason is, C++ doesn't impose anything on your program structure that C doesn't, while C, with the limitations it has, imposes a tax on all sorts of ways of structuring your program.

For example, you can't practically write a program using a futures library (such as the Seastar framework) in C. And every program you write in sensibly written C can be translated to C++. The exception might be really really small-scale embedded stuff that doesn't allocate memory.


> What good programs are written in C that don't have well-structured memory management the way C++ does it with RAII?

MISRA C standards, popular in embedded projects especially automotive, ban the use of memory management altogether.

The whole point of RAII is that the compiler manages it for you as far as it can. This is impossible in C because you have to do it manually. You might end up writing malloc() at the top and free() at the bottom of functions but that's the opposite of RAII.


Note that they ban the use of dynamic allocation at run-time except via the stack, but that you are still allowed to allocate from the heap as long as that heap allocation is static for the life of the system. This avoids a whole host of problems related to heap exhaustion that result from allocation timing causing heap fragmentation.

It also eliminates a whole lot of uncertainty in the timing.

If you're running in an automotive environment, you're probably real time; that is, you have to finish your processing before, for example, the next cylinder comes into firing position. You have to hit that, for every cylinder of every rotation of the engine, for any rotation rate that the engine is capable of reaching. You can't be late even once.

Now in the processing you have a malloc call. How long will the call take? Depends on the state of the heap. And what is that state? Depends on the exact sequence of other calls to the heap since boot time. That's really hard to analyze.

Yes, you can get a memory allocator that has a bounded-worst-case response time, but you also need one that absolutely guaranteed always returns you a valid block. And the same on calls to free: there must be a guaranteed hard upper bound on how long it takes, and it must always leave the heap in a state where future allocations are guaranteed to work and guaranteed to have bounded time.

And, after all of that, you still have a bunch of embedded engineers scratching their heads, and asking "explain to me again how allocating memory at all is making my life easier?"

So embedded systems that care about meeting their timings often allocate the buffers they need at startup, and never after startup. Instead, the just re-use their buffers.


RAII is a disaster. Piecemeal allocation and wild jumping across the project to do all these little steps (to the point where the programmer cannot predict anymore what will happen) is not the way to go.

Then all the implications like exceptions and needing to implement copy constructors, move constructors, etc. in each little structure.

As to what C project doesn't just emulate RAII: Take any large C project and you will likely find diverse memory management strategies other than the object-oriented, scope-based one. Also, other interfacing strategies than the "each little thing carries their own vtable" approach. The linux kernel is one obvious example, of course.

But I also want to reference my own current project since it's probably written in a slightly unusual style (almost no pointers except a few global arrays. Very relational approach). https://github.com/jstimpfle/language. Show me a compiler written in RAII style C++ that can compile millions of lines of code per second and we can meet for a beer.

> The reason is, C++ doesn't impose anything on your program structure that C doesn't

Of course you can write C in C++ (minus designated initializers and maybe a few other little things). What point does this prove, though?


I guess you're the yin to my yang, because I've got a compiler written in C that doesn't use any global variables at all: https://github.com/srh/kit/tree/master/phase1

It wasn't really implemented for performance, and maybe the language is more complicated -- no doubt it's a lot slower. On the other hand, I can look at any function and see what its inputs and outputs are.


My compiler isn't optimized for performance, either! I didn't do much other than expanding a linear symbol search into a few more lines doing binary symbol search. And I've got string interning (hashing).

I've mostly optimized for clean "mathematical" data structures - basically a bunch of global arrays. This approach is grounded on the realization that arrays are just materialized functions, and in fact they are often the better, clearer, and more maintainable functions. If you can represent the domain as consecutive integer values, of course. So I've designed my datastructures around that. It's great for modularity as well, since you can use multiple parallel arrays to associate diverse types of data.

But anyway, your language looks impressive I must say.


What are your thoughts on D or Rust as they compare to C++?

Rust makes intuitive sense to anybody that knows C++ and Haskell (deeply enough to have seen the ST type constructor). There are some natural, healthy memory management decisions you might make in C++ that you can't do in Rust, but that's life. The obvious example would be if you want one struct member to point into another. I like Rust traits or Go style interfaces over classes. cppreference is far far better than any Rust documentation, which aside from Rust by Example, is an unnavigable mess. Oh, and it would be nice if C++ had discriminated unions.

I don't know enough about D to really comment on it (I read the black book on it 9 years ago, and the examples crashed the compiler), but... it has better compile times, right? There's a module system? I'd have to look at the D-with-no-GC story, figure out how hard it is to interop with C++ API's. I think I'd have better feelings about D (or C++) if it didn't have class-based OOP.


This seems like the wrong direction; C++ style projects are either more heavily indirected or make heavier use of compile-time reasoning with the type system. While you can pretend that a structure full of function pointers is a vtable (and the Linux kernel does a lot of this), it's not really the same thing.

Treating C as a sort of "portable assembler" is a lot better, although it runs into UB problems (see DJB on this subject).


The view of C programming that I'm describing is mostly compatible with the concept of treating C as a portable assembler.

I think there is a world of wild and crazy C++ (like, boost::spirit-grade, or std::allocator-using) that you're imagining, that is not what I am thinking of. If you took C, and added vector<T> and hash_table<K, V>, added constructors and destructors so you don't have to call cleanup functions, you'd get a language which most sensible non-embedded C programs would map to, which then maps upward to C++.

Maybe some templated functions like std::min<T> and std::max<T> and add_checking_overflow<T> would be nice to have too.

Edit:

An example of where I think properly written C diverges from portable assembler is things like here: https://github.com/Tarsnap/tarsnap/blob/master/libcperciva/d...

It depends on whether you think ELASTICARRAY_DECL is within the scope of portable assembler. (It gives you type safety!) (And I don't know what advanced assembly languages can offer in terms of that -- maybe they do too.)


Do C first. Achieve a small functioning project of your own, like the calculator in the back of Kernighan and Pike. This will give you a good understanding of pointer orientated programming and the C tooling and debug strategies.

Then pick whether you want to start from the "front" or "back" of C++; i.e. learning the language in chronological order or in reverse. C++17 idiomatic style is very different from the 99 style that most existing C++ is written in.

I would suggest picking a codebase to work on and learning its style and subset of C++ first.


For the language, K&R is good, and Expert C Programming: Deep C Secrets by Peter van der Linden is a great second book.

But all the fun stuff happens when you start talking with your OS, so get a book about that too. If you are planning to develop on Linux, Michael Kerrisk's The Linux Programming Interface is excellent. Much of it will be familiar to someone used to shells and the terminal, but there will be plenty of new ideas too, and even the stuff you know will get a much deeper perspective.


The Linux Programming Interface is an excellent book. Beyond that, if you're looking to go deeper into the libc in Linux I would recommend taking a look at the man pages. They're very comprehensive, especially the pages in sections 7 and 8 which explain the operating system and administration tasks.

The prevailing opinion is that one does not simply develop proficiency in C++ in a year.

C is definitely doable though. Loads of good recommendations of you search for them. Everyone will recommend K&R. |This book also goes through a lot of the lower-level things, debugging, etc: https://nostarch.com/hacking2.htm.

I have this and K&R. Recommend both /very/ highly.

I learned it with "Advanced Programming in the UNIX Environment".

> as a self-respecting software engineer

Then you probably already know more about C than you realise: if, while, for, etc. all work the same as most other languages.

What you're probably not used to is needing to define functions in advance, pointers, and memory (de)allocation.

If you learn by doing, then with google and github, you can create a few simplified versions of unix utilities (cat, ls, grep -F).

If you're on Windows, I recommend using a Linux VM, WSL, or Cygwin - it's easier to setup than the C tooling in Windows (and you're stealth learning something else).

Once you know C, you can then move onto C++ (I stopped at C).


> I learned it with "Advanced Programming in the UNIX Environment".

Agreed. APUE is perhaps one of the best book available covering SUS, POSIX layer in detail.


APUE is good, but I believe it has now been superseded by The Linux Programming Interface.

> APUE is good, but I believe it has now been superseded by The Linux Programming Interface.

Nice. I'll check it out.


Zed Shaw's Learn C the Hard Way.


Nah, that author wrote:

>before you rewrite your C book, perhaps you should take the time to actually dig into it and learn C first (inside and out.)

which is uninformed, as Zed wrote Mongrel and Mongrel2 in C. Saying he doesn't know C is ludicrous. He might have a different approach to C, but then argue this view instead of claiming your way is the only way. The author of that blog post is saying the book is bad because it is not the way he writes C. Not because it is objectively bad.

Also, replies to that post like "Just for info K&R stands for "Kernighan" and "Ritchie", please, don't compare the bible of C with "just another book on C". It is a blasphemy." are hilarious. People are just parotting "read K&R!!" off of each other. The term Stockholm syndrome is overused but it is very appropriate for people who think C is actually good.


K&R is a remarkably good and concise introduction to C.

I think that C is actually good, and that C++ is a Scooby-Doo sandwich of fail. But this is an opinion concerning a particular domain (low-level programming) that doesn't carry over to anywhere else.


K&R,and Richard Stevens's books

Please, please, please don't suggest people use the k&r book to learn C. It is one bad practice after another and many of the suggestions in that book have given C much of its reputation for buffer overflows, stack smashing, etc.

Give me an example?



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