Although there are some questions here concerning the C++11 support of clang, I don't seem to be able to get clang++ to eat my C++11 code.
$ clang++ --version
clang version 2.9 (tags/RELEASE_29/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
According to the clang C++11 status page I should have at least partial support (e.g. right angle brackets), but it refuses all features I tested.
Is there any switch to tell clang to use C++11?
Example test:
$ clang++ -stdlib=libstdc++ cpp11.cpp
cpp11.cpp:16:33: error: a space is required between consecutive right angle brackets (use '> >')
std::vector<std::pair<int,char>> xs;
^~
> >
cpp11.cpp:18:8: error: C++ requires a type specifier for all declarations
auto y = x;
~~~~ ^
2 errors generated
ildjarn points out the correct argument, -std=c++0x or -std=c++11. The errors you're getting with that argument may be because the version of libstdc++ you're using uses some C++11, or non-standard C++, that clang 2.9 doesn't support.
Related
I was attempting to compile and run the example on this page that explores function pointers as a function input. The example I was running was the 66 line one about halfway down the page.
https://www.learncpp.com/cpp-tutorial/function-pointers/
I am on Mac iOS 12.3.1. I tried to compile with
g++ sort.cc
and was getting errors that no semicolons were in my for loops, i believe due to the bracket initialization throughout the code. And when I run it with:
g++ -std=c++11 sort.cc
It works fine.
BUT
Shouldn't my clang be compiling at at least C++11? running
clang -v
I get
Apple clang version 13.1.6 (clang-1316.0.21.2)
Target: x86_64-apple-darwin21.4.0
And from what I can tell clang versions past 4 default to c++14.
Also, when I run using clang or gcc I get errors setting -std=c++xx, but it works fine with g++. But as far as I can tell, g++ and gcc are aliases to clang, and running gcc -v or g++ -v gives me clang version 13.1.6.
So whats going on?
Xcode clang defaults to C++98. Compiling a simple program which has C++11 or later features will tell you that C++11 or later isn't the default. e.g.,
// a.cpp
constexpr int i = 10;
clang a.cpp -c
a.cpp:1:1: error: unknown type name 'constexpr'
constexpr int i = 10;
^
1 error generated.
while clang a.cpp -c -std=c++11 works fine.
Also see: https://trac.macports.org/wiki/CompilerSelection
Problem Solved => see the update at the end
I'm trying to use std::function but it looks like just include <functional> does not provide the definition. I have tried to compile following code:
#include <functional>
std::function<int(int)> f = nullptr;
with c++11 as compile option:
% clang++ -c -std=c++11 t.cc
cause:
t.cc:3:6: error: no type named 'function' in namespace 'std'
std::function<int(int)> f = nullptr;
~~~~~^
t.cc:3:14: error: expected unqualified-id
std::function<int(int)> f = nullptr;
^
2 errors generated.
what am I missing? I know C++ well but new to clang++/C++11 thus I lack of important knowledge, I guess.
I'm using clang++ on MacOS X 10.8.
Update 1
I have tried a sample at cppreference.com site but it won't compile too. Giving some option solve the problem?
Update 2
Tried above sample from cppreference.com with clang++ -c -std=c++11 -stdlib=libc++11 x.cc, and compiler still says:
x.cc:1:10: fatal error: 'functional' file not found
#include <functional>
^
1 error generated.
Where is functional? I guess I should give -stdlib=libc++11 or whatever but it does not work too:
clang: error: invalid library name in argument '-stdlib=libc++11'
How I can find list of argument for -stdlib? (note: in man page, only available options are libc++ and libstdc++ both of them don't work)
Or functional just does not work?
This is not about the definition of the function. You don't have a linker error. You have a compiler error. The problem is, presumably, that the BSD/GNU/Darwin standard library installed in the real sysroot doesn't support C++11. You have to use the one that comes with Clang by specifying the -stdlib=libc++ compiler flag.
For C++11, it's best to always invoke clang as: clang++ -std=c++11 -stdlib=libc++
I use this most of the time, so I set the environment variable $CXX to this value. That way, I'm getting the dialect and library option in both compilation and linking. -std=c++11 is insufficient, as clang will still use the (old) system gcc headers in /usr/include/c++/4.2.1.
-stdlib=libc++ will use the clang headers in /usr/lib/c++/v1 such as <functional>.
There's a similar question with an answer by Howard Hinnant, who is (IIRC) an Apple engineer.
I'd like to try the new Hinnant's short_alloc allocator that, as far as I can understand, replaces the old stack_alloc allocator. However, I can't manage to compile the vector example. g++ says:
~# g++ -std=c++11 stack-allocator-test.cpp -o stack-allocator-test
In file included from stack-allocator-test.cpp:6:0:
short_alloc.h:11:13: error: ‘alignment’ is not a type
short_alloc.h:11:22: error: ISO C++ forbids declaration of ‘alignas’ with no type [-fpermissive]
short_alloc.h:11:22: error: expected ‘;’ at end of member declaration
As far as I can tell, g++ complains about line 10 and 11:
static const std::size_t alignment = 16;
alignas(alignment) char buf_[N];
It seems that the compiler doesn't like the "expression version" of alignas but it expects just the "type-id version".
I'm using g++ 4.7.2 under Ubuntu 12.10.
~# g++ --version
g++ (Ubuntu/Linaro 4.7.2-2ubuntu1) 4.7.2
Probably I'm missing something obvious, but I can't figure it out. Any help would be appreciated. (Please don't tell me I have to upgrade to a newer g++, I'm too lazy to do that :)
g++-4.7.2 doesn't support alignas. From http://gcc.gnu.org/projects/cxx0x.html:
Alignment support | N2341 | GCC 4.8
Try using g++-4.8.0 or clang; alternatively you may be able to use the __attribute__((aligned)):
__attribute__((aligned (8))) char buf_[12];
Note that __attribute__((aligned)) only accepts certain integer constant expressions (literals, template parameters); it doesn't accept static const variables.
The offending code:
template <class Bar,
size_t MAX_SIZE = std::numeric_limits<size_t>::max()>
size_t foo(Bar const& b) { omitted... }
It compiles fine on gcc 4.7.2 with -std=c++11. On clang 3.0 I get the following error:
foo.hpp:35:28: error: non-type template argument of type 'unsigned long' is not an integral constant expression
size_t MAX_SIZE = std::numeric_limits<size_t>::max()>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As far as I can tell, I am supposed to be able to use numeric_limits in this way in c++11. Is clang wrong here, or am I unaware of something?
EDIT:
Compilation flags are: clang++ -o foo.o -c -W -Wall -Wextra -Werror -std=c++11 -stdlib=libc++ -g -I. foo.cpp
Your code compiles just fine with clang++ 3.2, see here.
I would say there is nothing wrong with your code but you should upgrade to a newer version of clang.
Note: The code doesn't compile with the Intel C++ Compiler 13.0.1 due to a compiler bug (thanks #Xeo):
Compilation finished with errors:
source.cpp(6): internal error: assertion failed: ensure_il_scope_exists: NULL IL scope (shared/cfe/edgcpfe/il.c, line 7439)
size_t MAX_SIZE = std::numeric_limits<size_t>::max()>
^
compilation aborted for source.cpp (code 4)
To use C++11 library features with clang you need to use the libc++ standard library implementation, otherwise you get the ancient library from GCC 4.1.2, which doesn't support C++11
See https://stackoverflow.com/a/14790442/981959 and https://stackoverflow.com/a/14150421/981959 and many other questions.
I have this C++ 11 code that uses lambda, this is an example.
#include <iostream>
using namespace std;
int main()
{
auto func = [] () { cout << "Hello world"; };
func(); // now call the function
}
When I compiled this code with clang 3.1 (Apple clang version 3.1 (tags/Apple/clang-318.0.54) (based on LLVM 3.1svn)), I got this error
lambda.cpp:7:17: error: expected expression
auto func = [] () { cout << "Hello world"; };
What might be wrong? In this site, lambda seems to be supported with clang 3.1.
ADDED
With -std=gnu++11 or c++11 option, I got these error messages.
0. Program arguments: /usr/bin/clang -cc1 -triple x86_64-apple-macosx10.7.4 -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name lambda.cpp -pic-level 1 -mdisable-fp-elim -relaxed-aliasing -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 128.2 -resource-dir /usr/bin/../lib/clang/3.1 -fmodule-cache-path /var/folders/ng/h2hkycqd2q5g2hz42c47bt4w0000gn/T/clang-module-cache -std=gnu++11 -fdeprecated-macro -fdebug-compilation-dir /Users/smcho/Desktop/C++test -ferror-limit 19 -fmessage-length 173 -stack-protector 1 -fblocks -fobjc-runtime-has-arc -fobjc-runtime-has-weak -fobjc-dispatch-method=mixed -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/ng/h2hkycqd2q5g2hz42c47bt4w0000gn/T/lambda-XvZzHg.o -x c++ lambda.cpp
1. lambda.cpp:7:49: current parser token ';'
2. lambda.cpp:6:1: parsing function body 'main'
3. lambda.cpp:6:1: in compound statement ('{}')
clang: error: unable to execute command: Segmentation fault: 11
clang: error: clang frontend command failed due to signal 2 (use -v to see invocation)
clang: note: diagnostic msg: Please submit a bug report to http://developer.apple.com/bugreporter/ and include command line arguments and all diagnostic information.
clang: note: diagnostic msg: Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg: /var/folders/ng/h2hkycqd2q5g2hz42c47bt4w0000gn/T/lambda-roTwCZ.ii
clang: note: diagnostic msg: /var/folders/ng/h2hkycqd2q5g2hz42c47bt4w0000gn/T/lambda-roTwCZ.sh
This is because clang++ by default compiles your code using ISO C++ 1998 standard (including the defects addressed in the ISO C++ 2003 standard) except for 'export' (which has been removed in C++11)
Lambdas are part of Clang's C++11 Language Extension, therefore you need to compile your code with -std=c++11 or -std=gnu++11
Also see: Clang 3.1 and C++11 support status and Activating C++11 support in Clang
EDIT: I think you are trying to compile your program with the C compiler (clang) rather than C++ compiler (clang++) or your installation of Clang doesn't link to libc or libstdc++. Try to link against each library to see which one works for you, it is possible that libc might not be installed on your system.
Try to compile your program with C++11 mode using the clang++ executable (the C++ compiler) and link it either with Clang C++ Standard Library or the GNU Standard C++ Library
1)
# Uses Clang C++ Library and enables C++11 mode
clang++ -stdlib=libc++ -std=c++11 [input]
2)
# Uses GNU Standard C++ Library and enables C++11 mode
clang++ -stdlib=libstdc++ -std=c++11 [input]
Another possible problem might be that you haven't compiled Clang with the right options to enable C++11 language extensions, try and check the documentation for correct flags to use when you configure the compilation process for Clang.
The Xcode is updated using AppStore, but it still crashes on my Mac (Lion 10.7.5)
I could download the macport to compile the example successfully.
sudo port install clang-3.1
clang++-mp-3.1 -std=c++11 lambda.cpp
Responding to the newly edited post:
I investigated this issue a bit, and it's a bug that was corrected in release versions of clang 3.1. I'm currently using:
Debian clang version 3.1-3eudoxos1 (branches/release_31) (based on LLVM 3.1)
However when I tested with clang 3.0-6ubuntu3 I get a similar error to the one you posted.
Because your version is marked from SVN I assume that your issue is that it's from the prerelease versions of 3.1 and lambda support hadn't been fully implemented yet.
I can confirm that lambdas do work in clang because I'm working on a project that uses them and we target both clang and gcc. There are a few compiler boogs that crop up from time to time; however, nothing as simple as your given example, of course.
So, my recommendation is to update your version of clang.
I needed to install command line tools as is this post explains - Does Xcode 4.4 come with subversion?