I'm trying to compile C++11 code that declares a variable of type std::atomic_bool. This is on Mac OS 10.8.2 with clang:
clang --version
Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin12.2.0
Thread model: posix
clang complains about std::atomic_bool:
clang++ -c -stdlib=libc++ -msse4 -std=c++11 -Wno-unused-parameter -I. -o query.o query.cpp
In file included from query.cpp:1:
[...]
./threadutils.h:33:10: error: no type named 'atomic_bool' in namespace 'std'; did you mean 'atomic_long'?
std::atomic_bool work;
However, the same file compiles fine in an XCode project using the same compiler. So I assume I'm missing something in my manual compiler invocation.
I tried a few variations such as -std=c++0x and -std=gnu++11, to no avail.
I figured it out. Unfortunately I planted a false flag into my question: it didn't work in XCode either, I had a different version of the source file imported there.
The problem was that C++11 defines "a named type atomic_bool corresponding to the specified atomic<bool>", but clang doesn't support that.
Renaming the type from atomic_bool to atomic<bool> fixed it.
I found the same problem. In my case I resolved it by including atomic:
#include <atomic>
static std::atomic_bool varname;
After this, I could call g++ with std=c++11 on a Linux (Ubuntu) as well as compile on XCode.
Related
I can't compile with -std=c++17, I got :
error: invalid value 'c++17' in '-std=c++17'
However I update Xcode and clang.
My Clang version is:
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 9.0.0 (clang-900.0.39.2)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin`
And I load the newest header like optional, I have to do
#include <experimental/optional>
instead of
#include <optional>
Xcode brings its own complete toolchain, including headers and the actual compiler.
Apple LLVM version 9.0.0 (clang-900.0.39.2) (which ships with Xcode 9.2) does not support the usage of the flag -std=c++17 since its too old. The optional header is only included under the folder experimental/. Which is why you need to #include <experimental/optional>
In order to compile your program with c++17 support using the compiler which comes with Xcode 9.2 you need to use the -std=c++1z flag.
Xcode 9.3 will be shipped with Apple LLVM version 9.1.0 (clang-902.0.30) which has support for the -std=c++17 flag. However the optional header is as of today still under the experimental/ subdirectory. This might change during the betas.
Here is what I get with this tests:
#include <experimental/optional>
int main(int, char* []) {
return 0;
}
g++ -std=c++17 -o test test.cpp
error: invalid value 'c++17' in '-std=c++17'
g++ -std=c++1z -o test test.cpp
Did you try the c++1z argument?
Also of note my test compiles without the -std=c++1z argument provided.
I think I'm on a newer version of OSX than you:
Target: x86_64-apple-darwin17.4.0
You should use -std=c++1z as flag.
libc++ with c++17 support since macos 15
-std=c++1z also works on Apple LLVM version 8.1.0 (clang-802.0.42)
I need to compile my cpp in C++98, not C++11 for my school project.
So I used -std=c++98 to compile:
CPPFLAGS = -Wall -Werror -Wextra -std=c++98
but I made a mistake and use the C++11 std::stoi function.
i = std::stoi(index);
I tried without the -std=c+=98 flag but it didn't change anything.
I am working on MAC 10.12.6
My code compiles without any warning or any error.
If I am not mistaken, clang should shout at me for using a C++11 function.
Why?
edit clang version:
Apple LLVM version 8.1.0 (clang-802.0.42)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
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.
Originally, I used clang++ with -std=c++11 compile my C++11 code, everything was OK. Recently, I updated the Xcode in AppStore, I compiled the SAME program in command line again, it doesn't work anymore, it shows errors like below:
/usr/include/c++/4.2.1/bits/stl_construct.h:81:38: error: no matching
constructor for initialization of
'std::basic_string'
::new(static_cast(__p)) T1(_value);
It seems the clang++ is using gcc's header files, apparently, gcc's version is very old. However, if I compile the same program by using Xcode, everything is fine.
It seems, at command line , the clang++ can't find the correct header files anymore.
More information, running command clang++ --version, following output:
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin12.5.0 Thread model: posix
which clang++
/usr/bin/clang++
RESOLVED with option -stdlib=libc++
I have the following file foo.cpp:
#include <vector>
struct MyClass
{
std::vector<int> v;
};
It can be successfully compiled with clang (I'm using clang 3.3 on Ubuntu 13.04 32bit):
clang++ -c foo.cpp
Now I want to print AST:
clang++ -cc1 -ast-print foo.cpp
and I've got the following error
foo.cpp:1:10: fatal error: 'vector' file not found
#include <vector>
^
struct MyClass {
};
1 error generated.
It looks like clang++ -cc1 doesn't know about system include files etc.
I'm wondering how to set up includes for clang++ -cc1?
You need to set up the right include paths.
on my system I added
-I/usr/include/i386-linux-gnu/c++/4.8 -I/usr/include/c++/4.8
to the compiler flags. The first one was so that it could find
bits/c++config.h
Of course the 4.8 is due to the fact I am using a compiler compatible with g++-4.8
I also added
-std=c++11 -stdlib=libstdc++
as compiler options.
Hope this helps
It's a Frequently Asked Question
#john is correct. For posterity, the relevant portions of the FAQ are (with names tweaked to match the question) :
clang -cc1 is the frontend, clang is the driver. The driver invokes the frontend with options appropriate for your system. To see these options, run:
$ clang++ -### -c foo.cpp
Some clang command line options are driver-only options, some are frontend-only options. Frontend-only options are intended to be used only by clang developers. Users should not run clang -cc1 directly, because -cc1 options are not guaranteed to be stable.
If you want to use a frontend-only option (“a -cc1 option”), for example -ast-dump, then you need to take the clang -cc1 line generated by the driver and add the option you need. Alternatively, you can run clang -Xclang <option> ... to force the driver [to] pass <option> to clang -cc1.
I did the latter (-Xclang) for emitting precompiled headers:
/usr/bin/clang++ -x c++-header foo.hpp -Xclang -emit-pch -o foo.hpp.pch <other options>
^^^^^^^
Without the -Xclang, clang++ ignored the -emit-pch. When I tried -cc1, I had the same problem as the OP — clang++ accepted -emit-pch but didn't have the other options the driver normally provides.