On mac, g++ (clang) fails to search /usr/local/include and /usr/local/lib by default
clang, gcc, macos, xcode
Solution
I also use Homebrew and had a similar problem on Mac OSX Maverick 10.9.5 and Xcode 6.0.1, but it was solved by running:
`xcode-select --install`
Note that it doesn't work without the double hyphens given by the previous answer. This installs the command-line tools that also create `/usr/lib/` and `/usr/include/`. I don't know why Homebrew doesn't automatically check this upon installation, since it does check for Xcode...
If you want to check exactly what folders your compiler is looking through for header files you can write:
`cpp -v`
Problem
I'm on a mac and I used `homebrew` to install `gmp`. ``` Kyumins-iMac:gcjlib math4tots$ g++ main.cpp -lgmp -lgmpxx In file included from main.cpp:2: ./gcjlib.hpp:4:10: fatal error: 'gmpxx.h' file not found #include <gmpxx.h> ^ 1 error generated. ``` So then I explicitly told `g++` to use `/usr/local/include` ``` Kyumins-iMac:gcjlib math4tots$ g++ main.cpp -lgmp -lgmpxx -I/usr/local/include ld: library not found for -lgmp clang: error: linker command failed with exit code 1 (use -v to see invocation) ``` So then I explicitly told `g++` to use `/usr/local/lib` ``` Kyumins-iMac:gcjlib math4tots$ g++ main.cpp -lgmp -lgmpxx -I/usr/local/include -L/usr/local/lib Kyumins-iMac:gcjlib math4tots$ ./a.out sum is -4444 absolute value is 4444 ``` So the only issue seems to be that `g++` fails to acknowledge `/usr/local`. But it is tedious to type all this out all the time, especially when I'm just writing small single file programs. Is there a way for me to get `g++` to acknowledge the stuff in `/usr/local` by default? Is there a standard way `homebrew` users do this? I'm on OS X 10.9.3 with Xcode 5.1.1 in case it is relevant.