I'm new to c++ & I've this big confusion around c++ & g++ versions. I've come to understand that there are different version of g++ compiler, latest being 4.8 (i think). But then I see c++98 & c++11 mentioned at so many places. Are these two versioning systems for the same thing or is it for totally different things? And if they are different, how can I check if I'm using c++98 or c++11? Thanks!
C++98 and C++11 are standards rather than compilers. They are issued by ISO and compilers are expected to implement the features as given in the standards.
The g++ compiler is one that provides (as of 4.8 anyway) most of the features from the c++11 standard, as you can see here.
Related
First of all, C++17 changes are listed in this post. Today I downloaded clang to check if it was complete for C++17 (as gcc hasn't implemented everything yet), and here you can read:
Clang 5 and later implement all the features of the C++ 2017 Draft International Standard.
You can use Clang in C++17 mode with the -std=c++17 option (use -std=c++1z in Clang 4 and earlier).
Then, I assume that all features of C++17 have been added in clang 5.0, but checking all of them, I couldn't find the extensions for parallelism of stl algorithms and so on. I tried adding the header <execution> to test the new feature, but nothing seems to work.
I'm suspencting that this feature "maybe" won't be available, but I'm not sure because there's almost no information about it.
I think Intel implemented something in its compiler, but I'm not really into it since I use Linux.
Are extensions for parallelism going to be available for the new C++17 Standard?
Yes, extensions for parallelism have been merged into the ISO C++ Standard.
Clang 5 and later implement all the features of the C++ 2017 Draft International Standard.
This seems to refer only to core language features. You probably want to check the libc++ and/or libstdc++ conformance status instead.
https://libcxx.llvm.org/cxx1z_status.html
https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html
In the above links, P0024 is not marked as implemented.
I am currently on RHEL 5.4 with gcc 4.1 installed, but I want to use unordered_map. As I found out, this is only introduced in C++11 to the standard, and therefore not available. One alternative would be using __gnu_cxx::hash_map, but I would prefer using standards.
On another development host I happend to have RHEL 6.4 and gcc 4.4, which knows unordered_map, but gives the following warning:
../include/c++/4.4.7/c++0x_warning.h:31:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.
From the gcc homepage I can't seem to find out which gcc version supports unordered_map.
[edit]
To clarify my question:
I am stuck to several operating systems and their versions by customer requirements, therefore I cannot always update to the latest GCC version and be happy. I need to maintain compatibility of my software across all platforms.
I am therefore searching for the minimum GCC version required to use unordered_map. I am aware of the fact that supplying -std=c++0x to GCC fixes the error above, but I dont know how far the "experimental" warning means I should not be using unordered_map.
Some guys in this thread strongly advise not to use this experimental C++11 implementation
... so what should I do?
You cannot find such information on the GCC page. There is information about library features, but only about current version of GCC. In your GCC 4.4, you can simply use -std=c++0x flag to remove the warning.
If you are scared about experimental and cannot update the compiler - just don't use unordered_map from C++11. You can write your own, use one from tr1, or use the one from boost, no matter.
If you just look at GCC site - there is message there:
Important: GCC's support for C++11 is still experimental. Some
features were implemented based on early proposals, and no attempt
will be made to maintain backward compatibility when they are updated
to match the final C++11 standard.
By the way, all features of the C++11 standard are realized in GCC, it's actually old standard, since now C++14 is already approved, but support is still expiremental.
I have no idea WHY it's still experimental, for example on clang site:
Clang fully implements all published ISO C++ standards including
C++11, as well as the upcoming C++14 standard, and some parts of the
fledgling C++1z standard, and is considered a production-quality C++
compiler.
And only C++1z support is experimental.
You should upgrade to gcc 4.9.2, if you can. Otherwise use gcc 4.4. They'll both need the -std=c++0x option.
I was happy see that map::at() was added to c++11, but upon digging around, I see that's it's already defined in gcc libraries, and works with -std=c++0x, and c++98.
Is using this method for code compiled with a standard before c++0x considered portable?
I think you are misinterpreting what -std=c++0x means. From C dialect options:
'c++11'
'c++0x'
The 2011 ISO C++ standard plus amendments. Support for C++11 is still experimental, and may change in incompatible ways in future
releases. The name 'c++0x' is deprecated.
As you can see c++0x and c++11 are equivalent and c++0x is deprecated.
This question already has answers here:
How to determine the version of the C++ standard used by the compiler?
(9 answers)
Closed 6 years ago.
Recently I had faced compiling errors in a c++ code I wrote so I've been asked if I was using a C++11 compiler, but honestly I don't know how to check on my compiler version ! so any idea how to figure this out ??
Btw I'm using codeblocks as an IDE which includes the GCC compiler and GDB debugger from MinGW. also if I'm compiling my c++ code under Linux what command should I run to know my compiler version ?
That can be a tricky question. C++11 refers to a version of the
standard, not to a version of the compiler. Different compilers, and
different versions of any given compiler, will typically implement a mix
of versions of the standard, at least for recent versions. More or
less, because any implementation of C++11 will be fairly new, and thus
probably fairly buggy.
Most compilers have options to output the version; many will output it
systematically in verbose mode. For g++, try g++ --version. Recent
versions of g++ do have some support for C++11, but you have to activate
it with -std=c++0x (rather than the usual -std=c++03 or
-std=c++98). As the name (c++0x, rather than c++11) indicates, it
is not truly C++11; it is an implementation of some (most?) of the
major new features, in a preliminary version based on various working
papers, and not the final standard.
(FWIW: I don't think any compiler fully implements all of C++11, but I'd
love to be proven wrong.)
You can find out your compiler version like this:
g++ --version
That doesn't tell you if you are using c++11. To use c++11 features, you would have to call the compiler with thr -std=c++0x flag:
g++ -std=c++0x ....
Bear in mind that gcc doesn't implement 100% of c++11 yet, and how much it implements depends on the version. See here for a table of supported features.
EDIT: strictly speaking, if you are using GCC you cannot be using a fully compliant c++11 compiler due to the missing features. But versions 4.6.1 onwards cover a great deal of the standard.
If you're in linux, checking the version is easy.
> gcc --version
Will tell you the version you have. Note that GCC C++11 support is incomplete still, you can find the details here: http://gcc.gnu.org/projects/cxx0x.html
I've used a few C++11 features myself, namely initializer lists, and the nullptr constant. I'm using GCC 4.6 and it's working fine.
edit: And yes, as #jaunchopanza said, you'll need the -std=c++0x compiler flag to make it work. If you're using Code::Blocks, just right-click on your project, choose Build options..., and check the item that says Have g++ follow the coming C++0x ISO C++ language standard [-std=c++0x]
I'm interested in learning C++ more thoroughly now that C++11 is apparently ratified. What compiler currently implements the closest thing available to full C++11 support? How close is said compiler to full support? Are there still major features missing or just language lawyer minutiae?
There's a support matrix on the Apache wiki.
I think the one Scott Meyers maintains on his homepage is pretty good:
http://www.aristeia.com/C++0x/C++0xFeatureAvailability.htm
The llvm C++ compiler "clang" has partial C++11 support; you can see its current state at http://clang.llvm.org/cxx_status.html.
There's also GCC C++0x (or C++11) status page : http://gcc.gnu.org/projects/cxx0x.html
IBM's xlC++ compiler has a basic C++11 feature support page.
To anyone reading this now, as of Jan 2013 Clang 3.2 is probably the most complete C++11 compiler, although the latest dev branch of GCC (4.8.x) is going to bring GCC back on par by the looks of it.
http://clang.llvm.org/cxx_status.html
Just look at that support table! Epic stuff. That's only accounting for currently available stable versions as well whereas the GCC table contains some 4.8 entries.
Like I said though, when GCC 4.8 hits stable release, it's going to be tight between the two again:
http://gcc.gnu.org/projects/cxx0x.html