Why does the last platform-specific dependency take precedence in Cargo?

Question

I have a dependency in my Cargo file that needs to be different by platform, specifically, the default features. Here's what I am trying to do:

[package]
name = "..blah.."
version = "..blah.."
authors = ["..blah.."]

[target.'cfg(target_os = "macos")'.dependencies]
hyper = { version = "0.9", default-features = false, features = ["security-framework"] }

[target.'cfg(target_os = "linux")'.dependencies]
hyper = { version = "0.9", default-features = true }

But this doesn't seem to do what I want. On my Mac it appears to be using the bottom target line as if I just specified hyper = "0.9". If I do cargo build as specified, I get errors with regard to openssl:

cargo:warning=#include <openssl/ssl.h>

However, if I build it like this:

[dependencies]
hyper = { version = "0.9", default-features = false, features = ["security-framework"] }

Then it builds fine. This indicates to me that the cfg for "macos" isn't working.

How do I make this work, or more specifically, how do I solve the problem where I need my dependency to use different features by platform?

Answer 1

It does not look like it is possible with Rust 1.13.0 and Cargo 0.13.0-nightly. See Cargo issues 3195 and 1197.

As a workaround, you can tell Cargo to use Homebrew's OpenSSL:

export OPENSSL_INCLUDE_DIR=`brew --prefix openssl`/include
export OPENSSL_LIB_DIR=`brew --prefix openssl`/lib
export DEP_OPENSSL_INCLUDE=`brew --prefix openssl`/include