GCC 4.8 Has Automatic Return Type Deduction

http://yapb-soc.blogspot.ru/2012/12/gcc-48-has-automatic-return-type.html

by AndreyKarpov • 14 years ago

41 46 14 years ago

yapb-soc.blogspot.ru

kombine• 14 years ago

It'll take years before it becomes part of the spec and all other implementations will catch up. D had it for ages.

indeyets3• 14 years ago

I used to be c++ "guru" some years ago, but right now code like this scares me as hell. The language is getting less-used and it's a good thing http://www.tiobe.com/index.php/paperinfo/tpci/C__.html

How many years would you give it to stay ubiquitous? I bet on 15 years

udp• 14 years ago

I was just about to make a similar comment. There isn't much about C++98 I don't know, but having ignored C++11 for too long I feel utterly lost looking at stuff like this now.

What concerns me even more is that it must be pretty much impossible for a beginner to pick up C++ today.

pjmlp7• 14 years ago

Anyone can pick it up if they really care.

They don't need to know the complete language on day 1.

fafner4• 14 years ago

> What concerns me even more is that it must be pretty much impossible for a beginner to pick up C++ today.

There certainly are issues when learning C++. But I don't think it's impossible. A major concern is the fact that there was never a centralised website collecting good information and filtering out the crap. There never was a central Tutorial or Reference.

All the knowledge is hidden in very expensive books and worst of all there are many publishers simply spitting out piles of bad C++ books.

http://isocpp.org/ and http://en.cppreference.com/w/ are a huge improvement.

Stroustrup's book is a great introduction: http://www.stroustrup.com/Programming/ I wish he'd made it freely available. A lot of programming beginners aren't happy to pay $50-$70 for a book when they can go to other languages offering great beginner tutorials for free.

And C++11 is pretty new. So of course there is a transition period with books, articles, references catching on.

pjmlp7• 14 years ago

I am still waiting to see a language that can fully replace it.

indeyets3• 14 years ago

I'm not sure that's needed. It would be much better if parts of it are replaced by different languages (and that's exactly what's happening)

haskell, python, erlang, clojure, scala, d, go, lua… take the tasks one by one. the glue is C (but something like llvm-assembly might take it's place eventually)

ebassi2• 14 years ago

a three lines program generates 95 lines of error messages; let's throw a template into it, so that it goes up to 112 lines, but look: at the beginning you'll see the error we added!

coupled with the: "To be fair, this doesn't entirely replace decltype. auto doesn't perfect forward. But it seems to work as expected, most of the time" it goes a great way to instil me a sense of safety.

not.

that post should be taken as an example of why C++ has become a liability, and the day won't come too soon when this joke on the whole industry finally gets dumped like COBOL in the nearest ditch, along with the corpses of all the projects that made the mistake of actually using it.

if it were a living thing, I'd shoot C++ in the face to put it out of its misery.

stingraycharles2• 14 years ago

The issue you describe is more a compiler-specific issue than a language specific issue. Yes, the language allows a lot of flexibility and therefor in some situations it's hard to nail down an error to a nice, specific error message (mostly when templates are involved), but it's not impossible, as clang++ shows.

Believe it or not, there are people (like me) who actually enjoy coding in C++.

fafner4• 14 years ago

It's a language specific issue. Sure clang++ has improved error reporting and GCC is actually quickly catching up. But the problem is a language issue because an error in a template confronts you with implementation details of the template. There is nothing the compiler can do about it.

gurkendoktor• 14 years ago

> a three lines program generates 95 lines of error messages; let's throw a template into it, so that it goes up to 112 lines, but look: at the beginning you'll see the error we added!

95 lines of error messages sounds terrible, no doubt. But which language is better in the real world? I am currently consuming a JSON web service written in Java, and I get no less than 30kb of stack trace back when something blows up. Rails' stack traces are filtered by default, but sometimes you still have to jump in there.

And C++ has the advantage that much of this can happen at compile-time.

I agree that almost everything about C++ is broken, but the verbosity of error messages is the smallest of it IMHO.

raverbashing• 14 years ago

I'm thinking most of the "C++ school" is affected by excesses, still, Java and C# are slightly better

" but the verbosity of error messages is the smallest of it IMHO"

It's merely a consequence of the verbosity/complexity of the language itself

shin_lao• 14 years ago

Or you can use Clang.

Feel free to shoot C++ in the face. Don't forget to rewrite most of compilers and operating systems in use in the process.

bhaak• 14 years ago

Linux doesn't use C++ and AFAIK the BSDs also don't.

So go ahead, I won't have a problem with a dead C++. :-)

abrahamsen• 14 years ago

What would the clang error message be?

microtonal• 14 years ago

Except that clang++ is only marginally better. E.g. trying to copy a std::copy a string vector in a size_t vector will give you this beauty:

http://pastebin.com/H68j6E50

Cascade a bunch of errors, end you'll soon be writing a script to analyse error output ;).

fafner4• 14 years ago

Clang is not the solution. Yes it has some better error messages. Although GCC is quickly catching up.

But it can't solve the core problem. It's simply the language. The lack of Concepts (or something similar) means that error messages simply refer to implementation internals of the Template you are using. Easily giving you a long cascade of error messages when it's in some Template that is used by the Template.

All of the sudden you have to look at implementation details of your standard library or something even worse such as boost. Just to figure out what the mistake was.

And there is nothing Clang or GCC can do about it.

wladimir• 14 years ago

I read that blog a bit and it seems to have the following pattern overall: elegant 5-line Haskell program. Then follows 100-line unreadable C++ implementation. My conclusion is that C++ is a very bad language to try to do Haskell :-)

This doesn't mean that C++ doesn't have its uses, but for your sanity's sake don't use it for high-level metaprogramming.

verroq3• 14 years ago

I don't get all this C++ hate from people that has never even used it.

Personally I want a better C and C++ satisfies most of what I want.

    1. Type level polymorphism (generics/templates/etc)
    2. Easier ways to manage memory (constructors/destructors, auto/shared pointers)
    3. A modules system (namespaces)
    4. Lambdas, etc to make life easier (C++11)
    5. A standard library with useful data structures
    6. Fast

It seems all to me all these haters still think that C++ is just C with classes, but C++ is a fairly vast language and OOP is just a small part.

C++ is blazing fast, it has an elegant standard library and templates do make sense if you know what you are doing.

You are trying to use cutting edge features that aren't properly standardised yet and complain that the error message is a bit long? Granted, template error messages aren't always the one liner you are expecting, but they are readable.

ebassi2• 14 years ago

> I don't get all this C++ hate from people that has never even used it.

wrong. I use it every day, on a fairly large code base.

obviously, for portability reasons, nobody working on the project is allowed to even think about C++11, as well as other headache-inducing features - and that includes a fair chunk of the standard library.

neumann_alfred• 14 years ago

projects that made the mistake of actually using it

You mean stuff like Unreal Engine... ?

rbanffy• 14 years ago

I'm curious: how popular is it to use syntax that's not available in other compilers and how often do programmers regret the decision?

stingraycharles2• 14 years ago

It depends on your environment. If you completely control all the environments your application is deployed in (for example, when you provide a SaaS), it's fairly common.

mdonohue• 14 years ago

Coverity, maker of c++ static analysis software, and where I used to work, has published a paper about their experience trying to parse customer code. It turns out that 'The language people code in? The strings their compiler accepts'

So yes, it is quite common to use syntax not available in other compilers. Most code is vetted against only one compiler to begin with.

http://www.stanford.edu/~engler/BLOC-coverity.pdf

fafner4• 14 years ago

Do you use EDG or another frontend? I can only assume that parsing C++ is quite problematic especially with all those compiler extensions and the current transition to C++11.

splinterofchaos• 14 years ago

This particular feature isn't offered by anyone else, so I would not write a program with it and force anyone else who wanted to compile the code to use an unsupported, bleeding edge version of GCC. But I /will/ create a branch of a project or two, using this auto deduction, and send bug reports back if necessary.

I, and many others, have been writing code in Clang and GCC for years that could not be compiled in MSVC. But that code was standard c++11. This is experimental and people should be aware of that while using it.

dagw• 14 years ago

I wonder how many times programmers are even aware that they're using syntax not available in other compilers. I remember the first time I used a non-gcc C compiler and was greatly surprised that things I'd taken for granted and simply assumed was 'C' didn't work.

Someone• 14 years ago

In my (limited) experience, it is not that popular, compared to the use of semantics not available elsewhere (is char signed? Can you cast a void* to int and back without data loss? What happens when you right shift a signed int? etc) and to the extreme use of third party libraries (why the #%$! do I need that GUI library in this json parser? Half an hour later: oh, so it is only for these three typedefs, a few macros, and this convenience debugging function), but it surely does happen.

I also think programmers do regret the decision. Unfortunately, that is unlikely to change, as the programmers regretting the decision almost always are not the ones who wrote the software. It is way rarer for a code base to move compilers within a project/team than for a team wanting to incorporate a third party library into their codebase/compiler.

nicholassmith• 14 years ago

You know when you get in a really fancy sports car and sit down and look at the console and go "What the fuck?" as your brain tries to parse the myriad of options relating to everything that are usually highly non-intuitive and often buried under many layers of cruft and you need to sit and read the manual that's as thick as a phone book? That's kind of what C++ is getting towards.

There's a simple solution, don't touch all the fancy and extreme language features, use the core, keep your sanity. I code in C++ professionally using Qt, the last time I wrote any code using anything overly fancy was probably when I was in University. It's often not needed, it's guaranteed to make your code base a nightmare, and it's usually horrid to read back over. If you're sensible and put some constraints on what you're doing C++ is a great language choice, but often people stray into using all these areas of C++ that basically make the code an unmaintainable mess.

(note, defining core as the things guaranteed to work on 95%+ of current compilers, if it's non-standard I would really, really thing twice about using it)

coliveira• 14 years ago

What many people don't understand is that C++ has at least two target audiences: (1) people writing low level libraries using templates and other esoteric stuff; and (2) people writing application code. (1) is needed because C++ is a language that can target multiple environments and operating systems. The template craziness is necessary to make the system fast and easy to use for application developers. If you are writing applications, however, you should try to use only bread and butter features, along with standard libraries such as STL and semi-standard stuff like Qt. Once you understand this, your life will be much easier with C++.

GCC 4.8 Has Automatic Return Type Deduction

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