clang++-mp-X.Y seems to trip up when told to use libc++
clang++-mp-X.Y -std=c++0x -std=libc++ SOME_SOURCE_FILE
Often generates errors which I do not see when using
clang++- -std=c++0x -std=libc++ SOME_SOURCE_FILE
I'm guessing that the system libc++ and system clang (XCode 4.2.1) are made for each other. How can I get macports's clang to use a version of libc++ that it will work with?
From libc++:
To use your tip-of-trunk libc++ on Mac OS with clang you can:
export DYLD_LIBRARY_PATH=<path-to-libcxx>/lib
clang++ -std=c++11 -stdlib=libc++ -nostdinc++ -I<path-to-libcxx>/include -L<path-to-libcxx>/lib test.cpp
Related
My Xcode 9.2 has the option to compile C++ using: -std=c++17 or -std=gnu++17.
My C++ code that has some C++17 features compiles successfully.
However, if I try to compile the same code in my Terminal using the same flags, I get the following errors:
clang++ -std=c++17 test.cpp -o test
error: invalid value 'c++17' in '-std=c++17'
and
clang++ -std=gnu++17 test.cpp -o test
error: invalid value 'gnu++17' in '-std=gnu++17'
My OSX version is 10.13.3 and my Clang++ version is:
Apple LLVM version 9.0.0 (clang-900.0.39.2)
Target: x86_64-apple-darwin17.4.0
I thought that Terminal would use the same compiler from Xcode. That may be the case, but I can't use the same options. At least I couldn't.
I tried using -std=C++1z, but it didn't compile my code because it doesn't understand some new features from C++17.
So my question is: Is there a way to use -std=c++17 or -std=gnu++17 that are currently available in my Xcode 9.2, in my Terminal app?
This questions is not the same as the others available at stackoverflow because all the answers I found the -std=c++17options was not available in Xcode. Now we have this options, but I can't figure out how to use it in Terminal.
The compiler Apple currently ships with Xcode 9.2 (clang-900.0.39.2) does not support the -std=c++17 flag.
Xcode uses the -std=c++1z flag when you enable c++17 support. If you want to use -std=c++17 you need to manually install clang. You could do that using brew install llvm (assuming you have homebrew installed).
You can compile your program with
/usr/local/Cellar/llvm/5.0.0/bin/clang++ -std=c++17 test.cpp -o test
You change the symlinks in usr/bin/clang++ to point at the new destination if you don't want to use the full path to the compiler.
The compiler which is shipped with Xcode 9.3 will be
Apple LLVM version 9.1.0 (clang-902.0.30)
This can handle the -std=c++17 flag.
On my new macbook pro, after install xcode, I found:
Both gcc and clang are linking to LLVM 7.3. I guess gcc is just an alias of clang here, right?
As long as gcc supports -std=c++11 and -std=c++14 parameter, why the /usr/include/c++ only has a directory named "4.1.2"? I know gcc 4.1.2 is quite an old version,
I want to replace gcc with clang (3.3) to build my C++11 code, so I should use clang's option -stdlib=libstdc++ (to make it see STL headers). The option works: clang see headers like string, but can't find c++11 headers (type_traits) because clang searches in 4.2 directories:
clang++ -stdlib=libstdc++ -E -x c++ - -v < /dev/null
...
/usr/include/c++/4.2
/usr/include/c++/4.2/backward
/usr/include/clang/3.3
/usr/include
...
How to make it look at never versions of GCC's headers?
As far as I understand, only libc++ (not libstdc++) is supported by clang for C++11 so the only way it so install libc++?
Either uninstall gcc 4.2 or use the --gcc-toolchain=<value> option.
--gcc-toolchain=<value> Use the gcc toolchain at the given directory
For example: clang++ --gcc-toolchain=/usr/local/... -stdlib=libstdc++ ...
As far as I understand, only libc++ (not libstdc++) is supported by clang for C++11 so the only way it so install libc++?
Both C++ standard libraries are supported.
This is the first time I use clang. What I notices is that any error from clang referencing the std library looks like this:
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/ostream:245:7:
^^^ ^^^ ^^^
So it looks like clang links — or at least includes — the gcc libraries.
The command I used: clang++ -c -Wall -Wextra -Werror -g test.cpp -o test.o. (The program had a intentional error just to prove this).
How is this possible? What can I do to make clang use its own libraries (but not break gcc)?
Additional information:
I am on a Ubuntu 14.04 machine.
clang++ --version
Ubuntu clang version 3.5-1ubuntu1 (trunk) (based on LLVM 3.5)
Target: x86_64-pc-linux-gnu
Thread model: posix
g++ --version
g++ (Ubuntu 4.8.2-19ubuntu1) 4.8.2
Copyright (C) 2013 Free Software Foundation, Inc.
I had previously installed several versions (at the same time, used them with update-alternatives) of gcc with apt-get. Right now I have only 4.8 (I have uninstalled the others). Could I have messed up something then? I have never installed clang (I guess it is default with Ubuntu).
Just to clarify: the correct programs compile and run in clang++.
Further tests: I know that gcc didn’t implement yet types like is_trivially_constructible and move operations on iostream in their standard c++11 library (https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html) and that clang has full c++11 conforming library so I tested those compiling with clang and I got the corresponding gcc errors, which only confirms that clang is using gcc libraries.
A very basic program
#include <iostream>
using namespace std;
int main() {
cout << "Yada Yada" << endl;
return 0;
}
gives this error when compiling with -std=c++1y in clang++:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/iostream:39:
...
/usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/cstdio:120:11: error: no member named 'gets' in the global namespace
using ::gets;
~~^
So right now I can’t compile anything with c++1y in clang.
You need to install libc++ and make clang use it with -stdlib=libc++
I had similar issue: GCC (g++) already was installed on my LinuxMint (Ubuntu base) so when compile with clang, was getting an " error: no member named 'gets' in the global namespace using ::gets ".
resolved by installing libc++-dev (sudo apt-get install libc++-dev) and compiling with -stdlib++ (clang++ -g -std=c++1y -stdlib=libc++ helloworld.cpp -o helloworld)
Your real problem is that you're using C++14 (c++1y was the informal name used to refer to it when it wasn't yet fully formed), with a C++ library belonging to GCC 4.8. GCC 4.8 has complete C++11 support, but hardly even started on C++14 features.
This is caused by C++14 removing std::gets, and the GNU C library anticipating on that by not defining gets in the global namespace while the C++ library has not yet caught up and is trying to make it available in the std namespace.
The proper way to solve this does not require using libc++, just to use a C++ library with C++14 support. GLIBCXX 4.9 (aka libstdc++) already suffices.
I have Xcode 4.5.2 on Moutain Lion, and I have install the lastest "Command Line Tools" but when I tried to compile with g++ or clang++ (and the options -std=c++11 -stdlib=libc++) I get an error.
With g++:
cc1plus: error: unrecognized command line option "-std=c++11"
cc1plus: error: unrecognized command line option "-stdlib=libc++"
With clang++:
clang: error: invalid deployment target for -stdlib=libc++ (requires OS X 10.7 or later)
It's in a Qt project.
So how can I used the C++11 on my Mac ?
As you found, g++ does not support those command line options.
It sounds like you're using Xcode.
For clang, you should look at the project settings, and make sure that the "Deployment Target" is set to 10.7 (or 10.8)
What the error message is telling you is that libc++ is not available for 10.6 and before.
I installed gcc-4.7 on my Mac to make C++11 work. GCC in its current version is fairly good at supporting C++11, so this should be a fair choice.
The installation can be done by Homebrew and is not that complicated (at least I was able to do it...)
To install Homebrew if you do not already have it:
ruby -e "$(curl -fsSkL raw.github.com/mxcl/homebrew/go)"
Now run
brew doctor
and fix whatever problems come up (there is something written in the hombrew documentation for that). Finally, install current gcc:
brew install gcc
If everything goes well you should be able to access g++-4.7, which allows -std=c++0x.
Try -std=c++0x if c++11 doesn't work. Support for the -std=c++11 option is relatively new in GCC and you might not have a recent enough version.
I'd trust Marshall on the libc++ issue.