How can I prevent linking to the same native library by multiple dependencies?

Question

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.

Details:

I'm making a web app in Rust using the Nickel framework and rust-postgres for a database. I get the following error when building:

> 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

Looking through Cargo.lock, openssl is referenced by http (which is a dependency of nickel) and rust-postgres.

My Cargo.toml looks like this:

[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"

Here's the full Cargo.lock:

[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)",
]

Answer 1

It seems that the culprit is the fact that nickel-org's rust-http (which is a dependency of nickel) brings in sfackler/rust-openssl instead of the "official" openssl on crates.io. Unfortunately the rust-http repo doesn't have issues enabled, but I opened one on nickel's main repo: #139