Using the OpenSSL library with macOS Sierra

Working with C++ libraries on a Mac can be a pain and OpenSSL, a very popular one that’s used in many other libraries, led me scrambling around the web and going through different StackOverflow posts, Github issues, and blog posts/forums trying to figure out a way to do it without reinstalling everything.

Usually, you would just install OpenSSL with Homebrew….

$ brew install openssl

And then link it…

$ brew link --force openssl
Warning: Refusing to link: openssl
Linking keg-only openssl means you may end up linking against the insecure,
deprecated system OpenSSL while using the headers from Homebrew's openssl.
Instead, pass the full include/library paths to your compiler e.g.:
-I/usr/local/opt/openssl/include -L/usr/local/opt/openssl/lib

But don’t worry! There’s a fix. Homebrew installs OpenSSL but doesn’t link it to /usr/local/include, where the compiler looks into during #include< …> Thus, you must manually link it instead:

$ ln -s /usr/local/opt/openssl/include/openssl /usr/local/include

You also might want to link:

$ ln -s /usr/local/Cellar/openssl/[version]/include/openssl /usr/bin/openssl
$ ln -s /usr/local/opt/openssl/lib/libssl.1.0.0.dylib /usr/local/lib/

An example of [version] is 1.0.2j. And just in case, check whether you compiler looks into /usr/local/include. For clang, it is:

clang -x c -v -E /dev/null

And it should output this if clang searches through /usr/local/include

#include <...> search starts here:

And you should be able to start using OpenSSL! This fix also doesn’t just work with your C++ project but any project(e.g. Ruby project) you are building that uses OpenSSL.

And just a reminder — remember to add -lssl and -lcrypto flags for your compiler.

I hope this guide helped solve a headache of yours! I’m pretty new at this and I’d like to get better — any response is welcome :)

Check out my other posts and tutorials!

CompE @ UIUC.

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