Merge pull request #204 from ordian/master

secp256k1-sys: remove restriction on cc version

.travis.yml

@@ -26,6 +26,9 @@ matrix:
     os: windows
 
 script:
+  - if [ "$TRAVIS_RUST_VERSION" == "1.22.0" ]; then 
+    cargo generate-lockfile --verbose && cargo update -p cc --precise "1.0.41" --verbose;
+    fi
   - cargo build --verbose --no-default-features
   - cargo build --verbose --no-default-features --features="serde"
   - cargo build --verbose --no-default-features --features="lowmemory"

README.md

@@ -21,3 +21,17 @@ Contributions to this library are welcome. A few guidelines:
 * No new dependencies, please.
 * No crypto should be implemented in Rust, with the possible exception of hash functions. Cryptographic contributions should be directed upstream to libsecp256k1.
 * This library should always compile with any combination of features on **Rust 1.22**.
+
+## A note on Rust 1.22 support
+
+The build dependency `cc` might require a more recent version of the Rust compiler.
+To ensure compilation with Rust 1.22.0, pin its version in your `Cargo.lock`
+with `cargo update -p cc --precise 1.0.41`. If you're using `secp256k1` in a library,
+to make sure it compiles in CI, you'll need to generate a lockfile first.
+Example for Travis CI:
+```yml
+before_script:
+  - if [ "$TRAVIS_RUST_VERSION" == "1.22.0" ]; then
+    cargo generate-lockfile --verbose && cargo update -p cc --precise "1.0.41" --verbose;
+    fi
+```

secp256k1-sys/Cargo.toml

@@ -19,7 +19,7 @@ links = "rustsecp256k1_v0_1_1"
 features = [ "recovery", "endomorphism", "lowmemory" ]
 
 [build-dependencies]
-cc = ">= 1.0.28, <= 1.0.41"
+cc = "1.0.28"
 
 [lib]
 name = "secp256k1_sys"