Why would anybody use C over C++?

Question

Although people seem to like to complain about C++, I haven't been able to find much evidence as to why you would want to choose C over C++. C doesn't seem to get nearly as much flak and if C++ has all these problems why can't you just restrict yourself to the C subset? What are your thoughts/experience?

Answer 1

Joel's answer is good for reasons you might have to use C, though there are a few others:

• You must meet industry guidelines, which are easier to prove and test for in C
• You have tools to work with C, but not C++ (think not just about the compiler, but all the support tools, coverage, analysis, etc)
• Your target developers are C gurus
• You're writing drivers, kernels, or other low-level code
• You know the C++ compiler isn't good at optimizing the kind of code you need to write
• Your app not only doesn't lend itself to be object-oriented but would be harder to write in that form

In some cases, though, you might want to use C rather than C++:

• You want the performance of assembler without the trouble of coding in assembler (C++ is, in theory, capable of 'perfect' performance, but the compilers aren't as good at seeing optimizations a good C programmer will see)

• The software you're writing is trivial, or nearly so - whip out the tiny C compiler, write a few lines of code, compile and you're all set - no need to open a huge editor with helpers, no need to write practically empty and useless classes, deal with namespaces, etc. You can do nearly the same thing with a C++ compiler and simply use the C subset, but the C++ compiler is slower, even for tiny programs.

• You need extreme performance or small code size and know the C++ compiler will actually make it harder to accomplish due to the size and performance of the libraries.

You contend that you could just use the C subset and compile with a C++ compiler, but you'll find that if you do that you'll get slightly different results depending on the compiler.

Regardless, if you're doing that, you're using C. Is your question really "Why don't C programmers use C++ compilers?" If it is, then you either don't understand the language differences, or you don't understand the compiler theory.

Answer 2

I like minimalism & simplicity.

Answer 3

• Because they already know C
• Because they're building an embedded app for a platform that only has a C compiler
• Because they're maintaining legacy software written in C
• You're writing something on the level of an operating system, a relational database engine, or a retail 3D video game engine.

Answer 4

Fears of performance or bloat are not good reason to forgo C++. Every language has its potential pitfalls and trade offs - good programmers learn about these and where necessary develop coping strategies, poor programmers will fall foul and blame the language.

Interpreted Python is in many ways considered to be a "slow" language, but for non-trivial tasks a skilled Python programmer can easily produce code that executes faster than that of an inexperienced C developer.

In my industry, video games, we write high performance code in C++ by avoiding things such as RTTI, exceptions, or virtual-functions in inner loops. These can be extremely useful but have performance or bloat problems that it's desirable to avoid. If we were to go a step further and switch entirely to C we would gain little and lose the most useful constructs of C++.

The biggest practical reason for preferring C is that support is more widespread than C++. There are many platforms, particularly embedded ones, that do not even have C++ compilers.

There is also the matter of compatibility for vendors. While C has a stable and well-defined ABI (Application Binary Interface) C++ does not. The ABI in C++ is more complicated due to such things as vtables and constructurs/destructors so is implemented differently with every vendor, and even versions of a vendors toolchain.

In real-terms this means you cannot take a library generated by one compiler and link it with code or a library from another which creates a nightmare for distributed projects or middleware providers of binary libraries.

Answer 5

I take the other view: why use C++ instead of C?

The book The C Programming Language (aka: K&R) tells you clearly how to do everything the language can do in under 300 pages. It's a masterpiece of minimalism. No C++ book even comes close.

The obvious counterargument is that the same could be said of most, if not all, modern languages -- they also can't tell you how to do everything in only a few hundred pages. True. So why use C++ instead? Feature richness? Power? If you need something more feature rich or powerful then go with C#, Objective C, Java, or something else like that. Why burden yourself with the complexities of C++? If you need the degree of control C++ grants then I argue to use C. C can do anything and can do it well.

Answer 6

I choose to write in C because I enjoy working with a small, tight language. I like having access to a standard which can be read in a reasonable amount of time (for me -- I'm a very slow reader). Moreover, I use it to write software for embedded systems for which few desirable C++ compilers exist (like some PIC micro-controllers).

Answer 7

In addition to several other points mentioned already:

Less surprise

that is, it is much easier to see what a piece of code will do do exactly . In C++ you need to approach guru level to be able to know exactly what code the compiler generates (try a combination of templates, multiple inheritance, auto generated constructors, virtual functions and mix in a bit of namespace magic and argument dependent lookup).

In many cases this magic is nice, but for example in real-time systems it can really screw up your day.

Answer 8

I'm used to use C++ for my projects. Then I got a job where plain C is used (a 20 year old evolving codebase of an AV software with poor documentation...).

The 3 things I like in C are:

• Nothing is implicit: you see what your program exactly does or not does. This makes debugging easier.

• The lack of namespaces and overloads can be an advantage: if you want to know where a certain function is called, just grep through the source code directory and it will tell you. No other special tools needed.

• I rediscovered the power of the function pointers. Basically they allow you to do all polymorphic stuff you do in C++, but they are even more flexible.

Answer 9

Linus' answer to your question is "Because C++ is a horrible language"

His evidence is anecdotal at best, but he has a point..

Being more of a low level language, you would prefer it to C++..C++ is C with added libraries and compiler support for extra features (both languages have features the other language doesn't, and implement things differently), but if you have the time and experience with C, you can benefit from extra added low level related powers...[Edited](because you get used to doing more work manually rather than benefit from some powers coming from the language/compiler itself)

Adding links:

Why C++ for embedded

Why are you still using C? PDF

I would google for this.. because there are plenty of commentaries on the web already

Answer 10

Long compile times can be annoying. With C++ you can have very long compile times (which means, of course, more time for Stack Overflow!).

Answer 11

Because they're writing a plugin and C++ has no standard ABI.

Answer 12

If you want your code to be understood by virtually any programmer write in C.

Answer 13

I'm surprised no one's mentioned libraries. Lots of languages can link against C libs and call C functions (including C++ with extern "C"). C++ is pretty much the only thing that can use a C++ lib (defined as 'a lib that uses features in C++ that are not in C [such as overloaded functions, virtual methods, overloaded operators, ...], and does not export everything through C compatible interfaces via extern "C"').

Answer 14

Because they want to use features in C99 that don't have equivalents in C++.

---

However, there aren't as many C99 features that are useful to C++ as people think at first glance. Variable-length arrays? C++ has std::vectors. Support for complex/imaginary numbers? C++ has a templated complex type. Type-generic math functions? C++ overloaded the standard math functions, causing the same result.

Named initializers? Not in C++, but there's a workaround:

struct My_class_params {
    int i;
    long j;
    std::string name;

    My_class_params& set_i(int ii)
    {
        i = ii;
        return *this;
    }

    My_class_params& set_j(long jj)
    {
        j = jj;
        return *this;
    }


    template <typename STRING>
    My_class_params& set_name(STRING&& n)
    {
        name = std::forward<STRING>(n);
        return *this;
    }

    My_class_params()
    {
        // set defaults
    }
};

class My_class {
    My_class_params params;
  public:
    My_class(const My_class_params& p) : params(p) { }
    ...
};

This allows you to write things like:

My_class mc(My_class_params().set_i(5).set_name("Me"));

Answer 15

This is pretty shallow but as a busy student I chose C because I thought C++ would take too long to learn. Many professors at my university won't accept assignments in Python and I needed to pick up something quickly.

Answer 16

Because for many programming tasks C is simpler, and good enough. When I'm programming lightweight utilities especially, I can feel like C++ wants me to build in an elegant supersructure for its own sake, rather than simply write the code.

OTOH, for more complex projects, the elegance provides more good solid structural rigor than would naturally flow out of my keyboard.

Answer 17

Most of the significant features of c++ somehow involve classes or templates. These are wonderful features except for the way the compiler transforms these into object code. Most compilers use name mangling, and the ones that don't do something at least as messy.

If your system lives on its own, as is the case with many applications, then C++ is a fine choice.

If your system needs to interact with software not neccesarily written in C++ (most frequently in assembler, or Fortran Libraries) then you are in a tight spot. To interact with those kinds of cases, you'll need to disable name mangling for those symbols. this is usually done by declaring those objects extern "C", but then they can't be templates, overloaded functions, or classes. If those are likely to be your applications API, then you'll have to wrap them with helper functions, and keep those functions in sync with the actual implementations.

And in reality, the C++ language provides a standard syntax for features that can be easily implemented in pure C.

In short, the overhead of interoperable C++ is too high for most folks to justify.

Answer 18

Oh my, C vs C++, a great way to start a flame war. :)

I think C is better for driver and embedded code.

C++ has some great features that C doesn't have, but many of the object oriented features of C++ can cause monumental coding messes when people write code with non-obvious side-effects that occur behinds the scenes. Crazy code can be hidden in constructors, destructors, virtual functions, ... The beauty of C code is the language does nothing non-obvious behind your back, thus you can read the code and not have to look up at every constructor and destructor and so on. A lot of the problem is bad coding practices by SOME people.

My perfect language would be a combination of C99 plus a minimal subset of safer C++ capabilities that adds ZERO (or near zero) compiler overhead to the binary output. Perfect additions would be class encapsulation and naming concepts of data and functions.

Answer 19

One remark about "just use the subset of C++ you want to use": the problem with this idea is that it has a cost to enforce that everybody in the project uses the same subset. My own opinion is that those costs are quite high for loosely coupled projects (e.g. open source ones), and also that C++ totally failed at being a better C, in the sense that you cannot use C++ wherever you used C.

Answer 20

I haven't been able to find much evidence as to why you would want to choose C over C++.

You can hardly call what I'm about to say evidence; it's just my opinion.

People like C because it fits nicely inside the mind of the prgrammer.

There are many complex rules of C++ [when do you need virtual destructors, when can you call virtual methods in a constructor, how does overloading and overriding interact, ...], and to master them all takes a lot of effort. Also, between references, operator overloading and function overloading, understanding a piece of code can require you to understand other code that may or may not be easy to find.

A different question in why organizations would prefer C over C++. I don't know that, I'm just a people ;-)

In the defense of C++, it does bring valuable features to the table; the one I value most is probably parametric('ish) polymorphism, though: operations and types that takes one or more types as arguments.

Answer 21

I would say that C gives you better control over optimization and efficiency than C++ and hence would be useful in situations where memory and other resources are limited and every optimization helps. It also has a smaller footprint of course.

Answer 22

There's also the approach some shops take of using some of C++'s features in a C-like way, but avoiding ones that are objectionable. For example, using classes and class methods and function overloading (which are usually easy for even C diehards to cope with), but not the STL, stream operators, and Boost (which are harder to learn and can have bad memory characteristics).

Answer 23

Because you're writing for a system where resources are tight (such as an embedded system, or some kind real bare metal code like a kernel) and you want as little overhead as possible.

There's a reason why most embedded systems don't have a C++ compiler - it's not that people don't want one, it's that cramming C++ code into that small a space is task that approaches impossible.

Answer 24

• Until some years ago the existing C++ compilers were missing important features, or the support was poor and the supported features vary wildly among them, and so it was hard to write portable applications.
• Because of the no standard naming of symbols it is difficult for other languages/applications to support C++ classes directly.

Answer 25

What C needed was a better preprocessor. cfront was one and thus born c++

I'ld use C, where the 'c++ as preprocessor' would not be okay.

I'm pretty sure, at the bottom of any well written c++ library/framework/toolkit, you would find dirty-old-c ( or static casts, which is same )