How to check if libc++ is installed?

Question

I am building something from source. My system's gcc and stdlibc++ are too old, but there is a clang build I can use. By default, clang uses stdlibc++, but libc++ may optionally be installed for clang to use.

What is the best way to check if libc++ is installed with clang?

Answer 1

Slightly better answer than @n.n:

printf "#include <ciso646>\nint main () {}" | clang -E -stdlib=libc++ -x c++ -dM - | grep _LIBCPP_VERSION

If that prints something like: #define _LIBCPP_VERSION 3700, then you've got libc++.

Answer 2

The most straightforward way to check if libc++ is installed is to use it on a trivial program:

 clang++ -xc++ -stdlib=libc++ - <<EOF
 int main(){}
 EOF

If this fails, you don't have libc++.

In a real-world application, add user-supplied compiler and linker options:

 clang++ $(CXXFLAGS) $(LDFLAGS) -xc++ -stdlib=libc++ - <<EOF

so that the user has a chance to specify that libc++ is installed in a non-standard place.