Cannot Find Libc++

Beginners
1

Hi,

I just installed llvm via brew and added it to my path. I went ahead and tried to compile a simple c++ file using the following command:

clang++ -L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib -g -O3 hello.cpp

Unfortunately, it seems that the error suggests that clang is unable to find the libc++. What could be the issue? Here is a summarized error:

In file included from hello.cpp:1:
In file included from /opt/homebrew/opt/llvm/bin/../include/c++/v1/iostream:43:
In file included from /opt/homebrew/opt/llvm/bin/../include/c++/v1/ios:221:
In file included from /opt/homebrew/opt/llvm/bin/../include/c++/v1/__ios/fpos.h:14:
In file included from /opt/homebrew/opt/llvm/bin/../include/c++/v1/iosfwd:106:
In file included from /opt/homebrew/opt/llvm/bin/../include/c++/v1/__std_mbstate_t.h:14:
/opt/homebrew/opt/llvm/bin/../include/c++/v1/__mbstate_t.h:51:5: error: "We don't know how to get the definition of mbstate_t without <wchar.h> on your platform."
   51 | #   error "We don't know how to get the definition of mbstate_t without <wchar.h> on your platform."
      |     ^

.
.
.

/opt/homebrew/opt/llvm/bin/../include/c++/v1/math.h:388:52: error: use of undeclared identifier 'FP_NORMAL'
  388 |   return __builtin_fpclassify(FP_NAN, FP_INFINITE, FP_NORMAL, FP_SUBNORMAL, FP_ZERO, __x);
      |                                                    ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

The clang++ command is the one shipped with brew’s llvm.

1 Like
2

Try adding -stdlib=libc++.

3

I tried clang++ -stdlib=libc++ -L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib -g -O3 hello.cpp but this produces the same error.

4

I’m having exactly the same issue, any help much appreciated!

(I first tried to use homebrew clang++ in a CMake project, which didn’t work, so fell back to trying a similar simple compilation and hit the same error).