Clang -std=c++11 -stdlib=libc++ Should enable C++ 11

neilms

neilms

I am trying to compile a program that has C++ 11 features. I should say that I first compiled it successfully on a Linux machine running Debian, using g++. I thought that getting the program to work on FreeBSD 9.1 would only require a few changes to my Makefile.

After changing my Makefile, clang is passed the options in the title header above. Using these options should enable 100% of the C++ 11 features. My program fails to compile with one fatal error:

Code: 
clang -std=c++11 -stdlib=libc++ ....
test.cpp:1:10: fatal error: 'iostream' file not found
#include <iostream>
1 error generated.

At first, I thought well maybe the new standard libc++ has changed c++ and iostream is no longer used. So I looked for documentation on libc++ and could not find any.

On my system I found that libc++ is in /usr/src/contrib/libc++. I then included the path in my makefile. My program compiles, but I get this error:

Code: 
/usr/bin/ld: cannot find -lc++
clang: error: linker command failed with exit code 1

How can I fix this?
 
clang++ is only a symbolic link to clang. In any event I tried that and the error is still the same. I have added the path to llvm-link to my shell $PATH, but it seems that the gnu linker ld automatically kicks in from /usr/bin.
 
Try something like

Code: 
clang++ -std=c++11 the_source_file.cpp -o the_linked_binary

Without the option -stdlib=libc++ --- let clang++ find its libc++ by itself.

As a side note, at my system, I cannot compile *.cpp files with clang, I need to call clang++.
 
If those libs are only in /usr/src/ then they were not included in the system. AFAIK you need to add WITH_LIBCPLUSPLUS=true to /etc/make.conf (or /etc/src.conf). And use clang++.

Not sure to what extent everything got merged to FreeBSD 9.1.
 
neilms said:
clang++ is only a symbolic link to clang. In any event I tried that and the error is still the same. I have added the path to llvm-link to my shell $PATH, but it seems that the gnu linker ld automatically kicks in from /usr/bin.
Click to expand...

While they two may be identical, the name of the executable determines the behavior. Use clang++.
 
Not really *full* support but yeah, the support is quite good ... the clang site seems down atm so I couldn't check (I haven't seen the 3.2 goodies yet)
There you have a grasp on the actual support → http://web.archive.org/web/20120922231808/http://clang.llvm.org/cxx_status.html

And for the "sake of comparison", here's the gcc status on this → http://gcc.gnu.org/projects/cxx0x.html

If you make your code c++11-enabled, please, check those "charts" to see in which version which feature is enabled and do proper preprocessor with an #error or a #warning
so if the code that doesn't compile, at least it spits an readable error in case a feature is missing (because yes, if you use a missing feature you'll get all kinds of nasty errors but nothing that really makes sense), and the user/developer compiling the code can try another compiler/version

With clang I use __has_feature() → http://web.archive.org/web/20120922231829/http://clang.llvm.org/docs/LanguageExtensions.html#cxx11
And with GCC I'm not aware of something similar, so I read the "chart" and pick the lowest version to get a working code (If you get all excited, you could a more in-depth analysis of the version and error showing which features the actual compiler doesn't have) : __GNUC__ for major and __GNUC_MINOR__ for minor

Regards.
 
neilms said:
clang++ is only a symbolic link to clang
Click to expand...

Wow, it's true: clang, clang++ and clang-cpp have the same inode number.

In any case, you can try compiling maybe with lang/gcc47. It's the same compiler that Debian uses by default (at least I think it's true for Debian-TESTING). See this document for more info on how to do it properly.
 
jozze said:
Wow, it's true: clang, clang++ and clang-cpp have the same inode number.

In any case, you can try compiling maybe with lang/gcc47. It's the same compiler that Debian uses by default (at least I think it's true for Debian-TESTING).
Click to expand...

Code: 
int main(int argc, char** argv)
{
    if (string(argv[0]) == "./a.out") {...}
    else if (string(argv[0]) == "./foo") {...}
    return 1;
}

Code: 
ln a.out foo
./a.out
./foo
 
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