title: How can I prevent linking to the same native library by multiple dependencies?
body: <p>Question: How can I work around (or fix) the situation where two dependencies of mine link to the same library, but that library can't be linked twice? This seems like something that would typically be solved with a shared library, but I'm not sure how to approach it with Rust.</p>
  
  <p>Details:</p>
  
  <p>I'm making a web app in Rust using the <a href="https://github.com/nickel-org/nickel.rs/" rel="nofollow">Nickel framework</a> and <a href="https://github.com/sfackler/rust-postgres" rel="nofollow">rust-postgres</a> for a database. I get the following error when building:</p>
  
  <pre><code>&gt; cargo build
  native library `openssl` is being linked to by more than one package, and can only be linked to by one package
  
    openssl-sys v0.3.3 (https://github.com/sfackler/rust-openssl.git#ee66da60)
    openssl-sys v0.3.3
  </code></pre>
  
  <p>Looking through Cargo.lock, openssl is referenced by http (which is a dependency of nickel) and rust-postgres.</p>
  
  <p>My Cargo.toml looks like this:</p>
  
  <pre><code>[package]
  
  name = "goodoldweb"
  version = "0.0.1"
  authors = ["..."]
  
  [dependencies.nickel]
  git="https://github.com/nickel-org/nickel.rs.git"
  
  [dependencies.postgres]
  git="https://github.com/sfackler/rust-postgres.git"
  </code></pre>
  
  <p>Here's the full Cargo.lock:</p>
  
  <pre><code>[root]
  name = "goodoldweb"
  version = "0.0.1"
  dependencies = [
   "nickel 0.1.0 (git+https://github.com/nickel-org/nickel.rs.git)",
   "postgres 0.6.1 (git+https://github.com/sfackler/rust-postgres.git)",
  ]
  
  [[package]]
  name = "byteorder"
  version = "0.2.4"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "gcc"
  version = "0.1.7"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "groupable"
  version = "0.1.0"
  source = "git+https://github.com/nickel-org/groupable-rs#efc8d769f611558f086322cd8d2d5ff53314e435"
  
  [[package]]
  name = "http"
  version = "0.1.0-pre"
  source = "git+https://github.com/nickel-org/rust-http.git#1997192b7662ee5bf3bf381bfd9e2aa70f85a545"
  dependencies = [
   "openssl 0.3.3 (git+https://github.com/sfackler/rust-openssl.git)",
   "time 0.1.17 (git+https://github.com/rust-lang/time)",
   "url 0.2.18 (git+https://github.com/nickel-org/rust-url.git)",
  ]
  
  [[package]]
  name = "libc"
  version = "0.1.2"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "libressl-pnacl-sys"
  version = "2.1.4"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "pnacl-build-helper 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "log"
  version = "0.2.3"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "matches"
  version = "0.1.2"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "nickel"
  version = "0.1.0"
  source = "git+https://github.com/nickel-org/nickel.rs.git#8c2e6a9bdbce0a3ec53d559b86f5060ee1ea6c29"
  dependencies = [
   "groupable 0.1.0 (git+https://github.com/nickel-org/groupable-rs)",
   "http 0.1.0-pre (git+https://github.com/nickel-org/rust-http.git)",
   "log 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
   "nickel_macros 0.0.1 (git+https://github.com/nickel-org/nickel.rs.git)",
   "plugin 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
   "regex 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
   "regex_macros 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
   "rust-mustache 0.3.0 (git+https://github.com/nickel-org/rust-mustache.git)",
   "rustc-serialize 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
   "time 0.1.17 (git+https://github.com/rust-lang/time)",
   "typemap 0.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
   "url 0.2.18 (git+https://github.com/nickel-org/rust-url.git)",
  ]
  
  [[package]]
  name = "nickel_macros"
  version = "0.0.1"
  source = "git+https://github.com/nickel-org/nickel.rs.git#8c2e6a9bdbce0a3ec53d559b86f5060ee1ea6c29"
  
  [[package]]
  name = "openssl"
  version = "0.3.3"
  source = "git+https://github.com/sfackler/rust-openssl.git#ee66da6060c57bc86906261ee3d684fac1fd05e4"
  dependencies = [
   "openssl-sys 0.3.3 (git+https://github.com/sfackler/rust-openssl.git)",
  ]
  
  [[package]]
  name = "openssl"
  version = "0.3.3"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "openssl-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "openssl-sys"
  version = "0.3.3"
  source = "git+https://github.com/sfackler/rust-openssl.git#ee66da6060c57bc86906261ee3d684fac1fd05e4"
  dependencies = [
   "gcc 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
   "libressl-pnacl-sys 2.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
   "pkg-config 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "openssl-sys"
  version = "0.3.3"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "gcc 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
   "libressl-pnacl-sys 2.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
   "pkg-config 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "phantom"
  version = "0.0.3"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "phf"
  version = "0.6.6"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "phf_shared 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "phf_macros"
  version = "0.6.6"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "phf_shared 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
   "rand 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "phf_shared"
  version = "0.6.6"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "pkg-config"
  version = "0.2.0"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "plugin"
  version = "0.2.1"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "typemap 0.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "pnacl-build-helper"
  version = "1.3.2"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "postgres"
  version = "0.6.1"
  source = "git+https://github.com/sfackler/rust-postgres.git#fe6ae0c63a6e5d66d2afb785605b7d89ec47062d"
  dependencies = [
   "byteorder 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
   "log 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
   "openssl 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
   "phf 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
   "phf_macros 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
   "rustc-serialize 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
   "time 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "rand"
  version = "0.1.2"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "libc 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
   "log 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "regex"
  version = "0.1.14"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "regex_macros"
  version = "0.1.8"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "regex 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "rust-mustache"
  version = "0.3.0"
  source = "git+https://github.com/nickel-org/rust-mustache.git#58ed857c88f8e5230913c382034601f37141b4ee"
  dependencies = [
   "log 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
   "rustc-serialize 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "rustc-serialize"
  version = "0.2.12"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "time"
  version = "0.1.17"
  source = "git+https://github.com/rust-lang/time#0960d5e21b332088b04f62117514b0a02fd31259"
  dependencies = [
   "gcc 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
   "libc 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "time"
  version = "0.1.17"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "gcc 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
   "libc 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "typemap"
  version = "0.0.8"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  dependencies = [
   "phantom 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
   "unsafe-any 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  
  [[package]]
  name = "unsafe-any"
  version = "0.2.2"
  source = "registry+https://github.com/rust-lang/crates.io-index"
  
  [[package]]
  name = "url"
  version = "0.2.18"
  source = "git+https://github.com/nickel-org/rust-url.git#5801582b307c16f759b5fe11dec71385af86180c"
  dependencies = [
   "matches 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
   "rustc-serialize 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
  ]
  </code></pre>