macos - OpenSSL crate fails compilation on Mac OS X 10.11

Question

I tried to install the Iron framework for Rust on Mac OS X 10.11.2, but it failed when I run cargo build or cargo run on compiling openssl's stuff:

failed to run custom build command for `openssl-sys-extras v0.7.4`
Process didn't exit successfully: `/xxx/rust/hello/target/debug/build/openssl-sys-extras-413d6c73b37a590d/build-script-build` (exit code: 101)
--- stdout
TARGET = Some("x86_64-apple-darwin")
OPT_LEVEL = Some("0")
PROFILE = Some("debug")
TARGET = Some("x86_64-apple-darwin")
debug=true opt-level=0
HOST = Some("x86_64-apple-darwin")
TARGET = Some("x86_64-apple-darwin")
TARGET = Some("x86_64-apple-darwin")
HOST = Some("x86_64-apple-darwin")
CC_x86_64-apple-darwin = None
CC_x86_64_apple_darwin = None
HOST_CC = None
CC = None
HOST = Some("x86_64-apple-darwin")
TARGET = Some("x86_64-apple-darwin")
HOST = Some("x86_64-apple-darwin")
CFLAGS_x86_64-apple-darwin = None
CFLAGS_x86_64_apple_darwin = None
HOST_CFLAGS = None
CFLAGS = None
running: "cc" "-O0" "-ffunction-sections" "-fdata-sections" "-g" "-m64" "-fPIC" "-o" "/xxx/rust/hello/target/debug/build/openssl-sys-extras-413d6c73b37a590d/out/src/openssl_shim.o" "-c" "src/openssl_shim.c"
ExitStatus(Code(1))


command did not execute successfully, got: exit code: 1



--- stderr
src/openssl_shim.c:1:10: fatal error: 'openssl/hmac.h' file not found
#include <openssl/hmac.h>
     ^
1 error generated.
thread '<main>' panicked at 'explicit panic', /xxx/.cargo/registry/src/github.com-0a35038f75765ae4/gcc-0.3.21/src/lib.rs:772

openssl version seems OK:

$ openssl version
OpenSSL 0.9.8zg 14 July 2015

I don't know what I have to do in order to make this installation work and give Iron a try.

Answer 1

As of rust-openssl version 0.8, Homebrew-installed OpenSSL libraries will be automatically detected by the crate, there is no need to set extra environment variables.

If you need to support a version prior to that or choose to not use Homebrew, read on.

---

This is a known issue (also this and this), but not one that the crate can fix.

The quick solution is to install OpenSSL with Homebrew and then explicitly point to the directories where OpenSSL is found by setting the OPENSSL_INCLUDE_DIR and OPENSSL_LIB_DIR environment variables:

OPENSSL_INCLUDE_DIR=/usr/local/Cellar/openssl/1.0.2e/include 
OPENSSL_LIB_DIR=/usr/local/Cellar/openssl/1.0.2e/lib 
cargo build

If you've already done one cargo build, you will need to run cargo clean first to clear our some stale cached information.

If you don't want to set this for every shell you open, add it to your shell initialization files (like ~/.bash_profile). You can make it a bit less brittle by not hard-coding the version number:

export OPENSSL_INCLUDE_DIR=$(brew --prefix openssl)/include
export OPENSSL_LIB_DIR=$(brew --prefix openssl)/lib

If you don't want to use Homebrew, follow the same process but using the appropriate path to your copy of OpenSSL.

---

The longer reason is well described by andrewtj:

OpenSSL doesn't have a stable ABI so for compatibility purposes Apple have maintained a fork that's compatible with one of the earlier ABIs. They deprecated OpenSSL in 10.7 and finally dropped the headers in 10.11 to push OS X app developers toward bundling their own OpenSSL or using their frameworks. The dylibs have been left around so apps that haven't been updated don't break. You can still link against them but you're opening yourself up to odd compatibility issues by doing so (unless you grab the headers from an earlier OS X release).