> What if we want to be able to store more than integers in our dynamic array ? [...] The array_push_back function also needs to be refactored in order to account for the size and type of what we store in the data buffer. A possible approach is to use a macro, instead of the original function:
This is a situation where C++ really shines: you can use C++ with templates and not only have much cleaner code, but also avoid forcing the compiler to inline every single call to array_push_back. And you don't even need to use anything more than structs and functions, you don't need to go "full OO".
I wish C programmers would be more open to C++ but it seems like they're for the most part pretty closed. That's probably the C++ community's fault, but I'm not sure how to make amends.
In that regards, I also think C++ programmers should be more open to C programmers that just needs a few new language constructs.
It is not an all or nothing approach. It's fine to write code that looks and feels mostly like C, but still takes advantage of a few nice C++ features.
That's pretty much how I use C++. Granted, my knowledge of it is very minimal. I was forced into C++ because of my Broker's api so...
One of my largest gripes making the switch, is the OO paradigm. I get it, I understand it, and I really want to love it. But the theory of it vs. the implementations that I've seen, ugh. And the number of ways you can initialize variables etc... just makes no sense to me. It's like they just keep adding new ways to do things, for no other reason than because they can. What's wrong with only have one way to do simple things like that?
I don't know, maybe it's just me but I strive to keep my code as simple, concise as I possibly can. I have enough complexity to deal with solving problems than having to wrestle with my language on top of it. Just to note, I'm strictly talking about having to use other people's code merged with my own. If it was solely me writing, I'd just use C++ for some of the nice things built in and toss classes and all that into the fire. YMMV.
Out of curiosity, what methods of initialisation are you confused with?
We have default constructors, copy construction, move construction, braced initialisation and std::initializer_list.
For my part I am working at work on a C++2003 codebase and although I can initialise my C-style array with braced initialisers, I would love to be able to initialise my vector in the same way, but I cannot as it is C++2003.
eg.
int myArray[] = { 0, 1, 2, 3};
vector<int> myVector = {0, 1, 2, 3}; // This is impossible in C++03
It may be that the OO implementations you have seen are bad because they don't understand encapsulation or haven't designed their classes from the outside in (i.e., design them interfaces first so that they are expressed from the simple point of view from the vocabulary of the user, not from you who designed the class).
I have worked with horrible C++ that had a hierarchy of inheritance yet failed to understand the point of virtual functions so would cast to child elements from a base class to decide which function to call on the child object, or would have functions in the base class that would dynamic_cast to every possible type of possible child to work out what to do. This was truly horrible. (The correct solution is to use a virtual or pure virtual function on the base and implement this in the children so that the right function gets called). This was within an apparently "object-oriented" system, so if this is your sort of experience I can understand why you would detest it.
The other horrible thing is writing C++ like it is C - pointers everywhere, no understanding or use of RAII, C-style casts everywhere (do you really know better than the compiler what a type is???), writing a million functions to do the same thing instead of a single template function etc. etc. And no const correctness, no use of STL algorithms, putting everything in a C array instead of using the correct STL container for the job, etc. etc. the list is endless
I think people are starting to get annoyed at how how these are all equivalent, and the switch in a lot of books seems to be towards the third version with braces.
int x = 0; // makes sense
int x(0); // sure
int x{0}; // braces?
> the first creates a new variable with a default value and then copies 0 into it.
No, no default constructor is invoked. In this specific example, until C++17, a temporary int object is created then x is copy constructed from it [1]. The compiler is explicitly allowed to omit the temporary+copy and directly construct from the parameter as per int x(0), but the constructor must be non-explicit.
From c++-17 on this is actually required and additionally a copy constructor is not required to exist. In practice is equivalent to #2 except for the non-explicit requirement.
Pedantic, I know, but as long as we are trying to clarify the rules is better to be clear.
[1] note: is different from default initialize then assign.
> One of my largest gripes making the switch, is the OO paradigm.
C++ supports object-oriented programming, but OO is not intrinsic to the language. OO is just one of the many tools. You can write good functional and procedural C++. If you try to shoehorn every problem into the OO model, you're probably doing it wrong.
"C++ supports OOP and other programming styles, but is deliberately not limited to any narrow view of “Object Oriented.” It supports a synthesis of programming techniques including object-oriented and generic programming."
Classes get useful once you're tired of adding "this" pointers to all your "methods" and all the "this->" inside them...
Once a C program gets large enough, it seems to become rather "OO" naturally: there's going to be data grouped into structures, and code that operates on that data. That's what classes and methods are useful for. But you don't have to obsess over "forcing" your design to be OO, i.e. things like debating between A.foo(B) or B.foo(A), because sometimes foo(A,B) or even foo(A,B,C) is the answer.
I agree completely with the complexity argument --- and I'll add that hidden ("encapsulated", "abstracted", whatever you want to call it) complexity is still complexity that can get in the way of debugging and efficiency both in terms of machine and programmer time. The latter point is something that a lot of "modern C++" seems to miss, finding more complex ways to do simple things, which look simpler on the surface but are actually far more complex in total.
> Once a C program gets large enough, it seems to become rather "OO" naturally
Very well put. One of my current projects started in plain C but gradually evolved to the point that it just "became" a C++ project. Once you write the same code a few times in a few different places, it's blindingly obvious what would be would be less painful if represented as objects. And so on with other language constructs (inheritance, templates, etc.).
The main point I'm trying to get across is to let it happen naturally, instead of trying to force everything to become objects and methods. There will still be parts that are "not OO", but they are not OO because they don't need to be; and that's perfectly fine.
> It's like they just keep adding new ways to do things, for no other reason than because they can. What's wrong with only have one way to do simple things like that?
Precise control over those things is a feature in C(++).
If you weren't unfortunately forced to use C++, a principle of Python is to (try to) have one obvious way of doing things. https://www.python.org/dev/peps/pep-0020/
We need a book with modern best practices like what happened in the Javascript world with "JavaScript: The Good Parts" from which we can glean a clean effective dialect, leading to a new C++ uptake and renaissance similar to what happened in the Javascript world in 2008
"JavaScript: The Good Parts" is outdated and should be no longer recommended. Even when I was first reading this book I had issues with some parts (adding methods to global classes, module pattern)
2008 revival in JS is not because of this book but from node.js, npm, jQuery and browsers becoming more capable. There where other factors like that fact that there is no alternative to JS on client side and HTML was lagging behind before HTML5. Both Java Applets an Flash become abandomware leaving no alternatives.
There is Rust, there should be stronger push towards this language. C++ is like PHP even with heroic efforts cannot be fully fixed. There is too much cruft, arcane syntax, platforms compatibility issues and finally lack module system.
They're not really equivalent, but Scott Meyers' series of books on C++ are some of my favorite technical writing ever, and his most recent book "Effective Modern C++" should be on the shelf of every working C++ programmer.
I agree with this - I finished reading this just before last year and I cannot recommend this book enough. It really is excellent (including topics like reference collapsing, type deduction in different scenarios, idiosyncrasies of async tasks). A great book and essential.
I don't think it will ever happen, at least in the enterprise space.
Companies are quite happy to use more productive, safer, languages like the ones on top of JVM and CLR, with C++'s role being left to infrastructure code.
The OSes and tooling from Apple, Google and Microsoft are good examples of it.
C++ is there on the lower levels, for hardware support, low level graphics, language runtimes but everything else ends up in Objective-C, Swift, Java, VB.NET, C# and F#.
From all those OSes, UWP is the only one where C++ enjoys parity with the remaining languages and apparently isn't that much used.
Even Microsoft does most of their UWP presentations in C# and despite in ongoing work in C++/WinRT as C++/CX, I doubt it will change the situation that much.
"However, no new edition of The C Programming Language has been issued to cover the more recent standards."
The book should be read by every C programmer, but it is really outdated and has many bad practices including buffer overflows etc. in examples. For learning "good parts" it certainly isn't the right thing.
There are perfectly legitimate use-cases for such a "C+" style. The disadvantage is that it won't be considered "good C++ style" and would limit the attractiveness of the project to C++ programmers that enjoy modern C++.
If one would include vector, string, array, smart pointers and maybe simple template code in C+ it would already have a big safety advantage over plain C.
Sounds like a bitter old fossil. My first look at Linux, there were 200 sound-card drivers in the source base. Mostly identical except for the layout of bits in the control register. Any change to the api or conventions, 200 files had to be edited. An ideal place to refactor as a 'sound card' base class and derive classes to handle the (miniscule) differences.
"Keeping new ideas away" is a good working definition of an old coot.
How would that be a good idea? I don't understand how I could write effective software without polymorphism or inheritance, other than in tiny tiny applications.
I've written entire components for networked and multiplayer modes for games, and an algorithmic trading system that uses ML in C++ using just structs, unions, templates, functions and composition (no polymorphism or inheritance).
I agree, which is why I mentioned that you can do what this article suggests without using anything except functions and structs. No classes or class features required.
The thing is, we get dispointed when the code just looks like "C compiled with C++ compiler", with all security exploits that entails.
A good example is how Turbo Vision, Object Windows Library, Visual Components Library, Qt look like and the concessions Microsoft had to make to Afx so that it got rebranded into MFC and appealed to the Windows C developers.
I was first talking about the set of frameworks that dared to embrace the then C++ best practices. All of them are older than C++98, or even before STL was being considered.
Then I mentioned the fact that when Microsoft presented their Afx framework to their beta testers, mostly Windows C developers, it was considered too high level and it was rebuilt as MFC.
Yes, despite all the problems in C++ it's just a much better language than C for defining new types that are on par with "native types". std::vector has so many benefits over any possible C implementation that there is no real comparison. Genericity is one, no need to remember to free after use is another.
By the way, why is this C implementation something that requires C99 or C11 features? It looked just like standard old-fashioned ANSI C to me.
I like my C alternative better. I pass growth factors/increments as parameters to the vector macros so that I can affect how it grows on capacity exhaustion during each call and I have macros for creating and closing uninitialized gaps. C++ loses on many potential optimizations by insisting that its types always be in fully well-defined states except inside methods. Moreover the particular GNU implementation of the STL on Linux completely fails to turn certain vectors methods into memsets, memcpies and memmoves where it could, which pesimizes those particular ops by like two decimal orders of magnitude. The insistence on using new/delete based allocators instead of reallocs is a significant pessimization too. Reallocs perform, on average, several tens of percents better than new allocs followed by copies. An even more noticable pessimization is in the compilation times. Including `<vector>` adds good chunks of a second to the build time of an average-length translation unit. In comparison, working with C, even with all my generics included, on top of a good build system makes me feel as if I was working with a scripting language. No lags.
These are fair points and issues like these are why many larger projects have their own custom vector-like classes. One thing I did want to call attention to is your point that C++ best practices require that objects be in well-defined states except inside methods. That's true, although it's not a language requirement, but in many cases you can get the best of both worlds through the use of lambdas. A simple example to give the flavor:
template <typename Function>
void my_vector::munge(Function initialize_gap) {
create_uninitialized_gap();
// Some of our elements now contain uninitialized memory.
// We don't want to expose this to arbitrary code, but
// it's OK to expose this to the function the user
// provided specifically to handle this.
initialize_gap(gap_begin(), gap_end());
// The gap is now initialized, so when we return from
// this method, we'll be in a well-defined state.
}
This is the standard pattern you use for such things in functional languages, and it works very well. The idea is to ensure that intermediate states are only seen by code that explicitly expects to handle them.
Your criticisms of vector are well put, but if anything they're all really problems with a particular implementation of the standard library, not the C++ language. If you make your own libraries you're free to do whatever you want, and template metaprogramming can help you gain even more performance by easily using optimized implementations for specific types, etc.
> you can use C++ with templates and not only have much cleaner code, but also avoid forcing the compiler to inline every single call to array_push_back
Actually, you really, really, really want to inline every call to push_back for std::vector. Here is a relevant presentation by Chandler Carruth https://www.youtube.com/watch?v=s4wnuiCwTGU . But, hey, you don't want to make the compiler work for you :).
It's goofy, but one of the reasons I'll pick C for a quick program is that both Windows and Linux will give better error messages for standard functions that fail and set errno than for equivalent C++ code that throws an exception.
This isn't a question about the language, it's definitely a quality-of-implementation issue for standard exceptions to have what() give a useful message.
Just to clarify perror will generally give a better error message in:
FILE* fh = fopen("foo.txt", "w+");
if (!fh) {
perror("unable to open foo.txt");
return 1;
}
Having comprehensible error messages is related to being a simple language, IMO. C++ compile-time errors are notorious for being unreadable. I'm not familiar with the output of what(), but I'd wager that the problem is a consequence of all the abstraction.
In my codebase, I use expression macros (with a little bit of __typeof__-based type checks) to do it fully generically. Much of what you think you need C++ for can be done almost just as succinctly on top of plain C (I'm talking automated scope cleanups, semi-automated error handling, many generic things) and the compile times fly. I agree C++ has had some good ideas. In fact, I originally wanted to use it. But I came to the conclusion that it's too bloated, and more importantly, fundamentally broken in certain ways (RAII, exceptions, even templates and namespaces), and I ended up emulating what I think the good parts of C++ are on top of plain C. When C++ programmers think C, they usually think lack of generics and lots of explicit manual, micromanagement and pointer arithmetic, but it can be a lot more than that.
What is fundamentally broken about RAII? To me that is one of the killer features of C++ over C, which requires manual goto statements to achieve something approaching RAII.
Yes I cannot fathom how you could write successful and maintainable C++ code without using RAII. How can you guarantee safe deterministic lifetimes of objects without using RAII?
If you are writing high-reliability C (think military, aerospace, industrial control systems), early return is usually prohibited by coding standards. Then again, dynamic memory allocation usually is too.
Personally, I think early return is lazy programming because not cleaning up non-RAII objects is only one class of bugs that it can introduce. Things like vector renormalization, update notification and even later sections of algorithms can all be missed by early return. Not having early return means you need to explicitly skip later code if you don't want it, rather than essentially turning on "skip-all".
* (Classic): use goto so that instead of returning directly, all branches jump to a cleanup label. This is tricky to do well, but possible.
* (Nonstandard): GCC offers a nonstandard function attribute to register a function as a destructor for this kind of thing. I'm sure they claim it was inspired by Scheme's dynamic-wind/dynamic-wind concept.
* (Memory pooling): Apache APR relies heavily on memory pools. One feature of APR's memory pools is the ability to register functions to run (in, I believe, non-deterministic order) on data when the pool is eventually destroyed.
Aargh! I should look at nonstandard features that I don't use before I say they solve problems. GCC's construcotrs and destructors (outside of C++ code) are limited to globals and statics. Marking a function a constructor guarantees it's automatically called before main(), and marking a function a destructor guarantees it's automatically called after main() completes.
The difficulty I have with them is they are open, not closed. Any piece of code can crack open a namespace and insert more names into it. Thus, you can have problems with "hijacking", where foo(int) is inserted, while unknown to you someone else inserted foo(unsigned) that does something completely different, and the compiler decides the latter is a better overload match.
Complicating things further, the names visible in a namespace are dependent on where the compiler is lexically in the code - more names can be inserted further down.
As a counterpoint, many have suggested to me that this openness is a critical capability they need for their code. My answer is that using namespaces in that manner offers little improvement over just using a prefix on the identifiers.
Well yes, it is a prefix, but it is a prefix that doesn't need to be used when you are already inside the namespace or if you explicity 'using namespace' it. If I had to type the full namespace of functions and enums all the time I'd go insane.
well yes they are open by design. If you want closed namespaces just put your functions (as statics) inside a struct.
Btw, visibility rules in a namespace (but not in a struct/class) are the same as for the global namespace, so no, a function in a namespace won't see another declared after it.
I'm not familiar with this approach, but I think it would entail code size increase for each use of the macros, and a runtime overhead for the typeof checks, correct?
If so, C++ has a nice advantage in that all the type checks are at compile-time so you don't pay any more for those, and also you don't duplicate binary code with macros.
__typeof_ is a compile-time feature. It's like C++'s decltype. (You can make C++'s auto out of it too.) There's is a potential for code size increases with this approach, that's true. But the potential also exists with inlinable vector methods.
True. However, I think in the case of the dynamic array, this effect is minor. The macros are small, and most of the time, they end up wrapped in a function anyway. But, admittedly,it doesn't scale well to very big generics, which should be always wrapped in a function. (Eventually I plan to shove a simple transpiler in front of all my C code and do this, along with namespacing, how I think it should be done.)
Unfortunately __typeof__ is non-standard. Despite its usefulness it always gets left out of the standard (and with weird excuses, I think last time it was lack of implementations - despite the fact that eg. both GCC and LLVM implement it).
Interestingly, C11 defines _Generic selection, a kind of a switch for types, but its usefulness is hindered by the fact that it cannot be used in conjunction with sizeof.
Expression macros `({, })` aren't standard either. But I sort of go with, if all gcc/clang/tinycc support it and it's a highly useful feature, then it's part of C as far as I'm concerned. It would certainly be nice if ({,}),__typeof__, and __label__ became part of the C standard, though.
My Google skills are failing me here. Is `({,})` a special construct, or are the '{' and '}' metacharacters and you're just referring to variadic macros, which are standard as of C11?
It's a common (gcc/clang/tcc) compiler extension (chapter 6.1 of the gcc manual) that allows you to use parentheses around a compound statement to turn the compound statement into an expression whose value is the last statement in the compound statement. For example `({ int _r; if((_r=foo())) bar(); _r })` behaves like an inline function that returns `_r`. If you want to do generic vector ops purely with macros and you want to do it robustly, you effectively need for the macros to "return" a value signalling whether the potential realloc that might have happened inside the macro succeeded or not. It's a very powerful feature because it allows you to have macros that behave like ducktyped, value-returning inline functions. (Sometimes you'll need to tone down the ducktyping a little, like it's probably a good idea to use some __typeof__-based typechecks (http://stackoverflow.com/questions/41250083/typechecking-in-...) to make the compiler warn you if you attempt to memcpy doubles into an int vector from your vector__insert method.)
A solution might be a minimal subset of C++, so with STL containers, some syntactic sugar, easier and faster to compile (modules), etc.
Basically what go and rust have achieved, except you keep most of the C/C++ syntax "taste", and you remove too high level stuff like templates and inheritance. Honestly I don't think templates are so useful, since most programmers already re-use STL containers, which are templates, but nobody really write relevant template classes.
> That's probably the C++ community's fault
The problem with C++ is backward compatibility with C and big corporations trying to not break their codebase. It makes it very hard to make the language evolve. For example D is a very good language, but it can't gain momentum as long as it doesn't have a real way to gain presence. We just have to wait that corporation clean their codebase to make room for C++ compilers to adapt, and then things should improve.
You can't have the STL containers without templates though. If you want to special-case them in the compiler, then what about the algorithms library? If you want to keep the algorithms library, then what about your own code that implements a higher-level algorithm using the lower-level ones in the algorithms library? Without templates you have to write your algorithm once for every type of container, or else use indirect function calls which would not be good. So this won't really work well I think.
For me, the only selling point of C++ is templates, and I've never written a nontrivial program that didn't use them (and I like to think that I don't just use them frivolously).
I'd rather say templates are a hack to get generics in C++, because C++ lacks real generics contrary to eg. Java, C#, Haskell or Scala. Templates used as generics are limited in a way that the typechecker can't reason about generic types, only concrete types, which leads to horrendeous error messages and makes it impossible to prove generic library code type-safety. Type templates are templates, not types.
On the other hand templates used as a metaprogramming tool fall behind any modern macro system.
Rust is getting there but still lacks type-level integers, and macros are waiting for macros 2.0. It would also be neat to have the ability to run any function at compile time, but I don't think that's in the cards.
I gave up on C++ right after I learned it. At the time, this was before the STL was part of the standard, it looked really cool but I could tell that it was easy to get into trouble and it would take years and years to be really good at it. When Java became popular, it looked like it solved a lot of the problems that I was afraid of with C++. But it was slow and really verbose compared to C++ and C. Recently, I heard someone say that today's C++ is not your grandfather's C++ and the speaker made some interesting comments about how much better it was. So I'm intrigued by it and definitely open to looking into the new C++.
std::vector is a container in a c++ standard library. C++ is a language. You're mixing apples and oranges.
What I'm saying is that you can use C++ without having to use STL and you can use C++ just fine to implement your own exceptionless container if you want (and many such implementations exist already).
And you can also compile with exceptions disabled. Should your code throw it will terminate the process.
So, garbage like "And you can also compile with exceptions disabled. Should your code throw it will terminate the process." is in the plus, and the parent comment is downvoted.
You can use any part of C++ without having to use the rest of it. For example, you don't have to write your own std::allocator to use std::vector, nor do you have to use exceptions.
You can use which bits of C++ that you want - that's its great strength, permitting low-level behaviour whilst supporting high level abstractions (and as simple or as complex as you like).
While technically you don't need exceptions and can disable it, the reality is the design of the STL is such that exceptions are required. It makes no affordance to signal errors in any other way. You can get farther if you decide OOM is a crash - but otherwise much of the STL is out of bounds.
I haven't seen it in practice, but OOM is conceivably recoverable in certain cases (e.g., exponential vector growth with large capacities fails on a 32 bit system, but switching to linear growth as a recovery strategy succeeds in allocating sufficient additional memory). But OOM errors aren't the only type of errors that you can get in ctors. Disabling exceptions makes all those errors either fatal or your class invariants become silently broken, which makes exceptions and RAII kind of a package deal in robust software.
The point was that STL is unusable without exception because of OOM. If you're not using exception anywhere in your codebase and you don't plan to recover from OOM, is this still an issue?
(I don't have much experience with exception handling in large codebase, I've mostly worked on codebase that disabled exceptions)
Realistically even our operating systems aren't OOM safe. Linux will happily over commit swap but kill you when you try to use it.
Windows actually provides a stronger gurantee here. But if any of your dependencies are not OOM safe then neither are you. And much of windows userland is not OOM safe.
It will help you either use std::vector with a custom allocator that does not throw exceptions, or else write your own non-throwing vector class with templates, which would, I hope, be more maintainable and easier to use correctly than an equivalent written in C.
This is a situation where C++ really shines: you can use C++ with templates and not only have much cleaner code, but also avoid forcing the compiler to inline every single call to array_push_back. And you don't even need to use anything more than structs and functions, you don't need to go "full OO".
I wish C programmers would be more open to C++ but it seems like they're for the most part pretty closed. That's probably the C++ community's fault, but I'm not sure how to make amends.