Add zlib-ng-no-cmake feature

Cargo-zng.toml

@@ -26,7 +26,7 @@ exclude = [
     "/systest",
 ]
 
-build = "build_zng.rs"
+build = "zng/cmake.rs"
 readme = "README-zng.md"
 
 [workspace]
@@ -36,4 +36,4 @@ members = ["systest"]
 libc = "0.2.43"
 
 [build-dependencies]
-cc = "1.0"
+cmake = "0.1"

Cargo.toml

@@ -37,6 +37,7 @@ libc = { version = "0.2.43", optional = true }
 [build-dependencies]
 pkg-config = "0.3.9"
 cc = "1.0.18"
+cmake = { version = "0.1.50", optional = true }
 vcpkg = "0.2"
 
 [features]
@@ -58,12 +59,9 @@ default = ["libc", "stock-zlib"]
 #
 # This allows higher-level crates depending on your library to opt into zlib-ng
 # if desired.
-zlib-ng = ["libc"]
-# AVX-512 is nightly-only currently <https://github.com/rust-lang/rust/issues/44839>,
-# enabling this feature means that AVX-512 support is probed for in the C compiler.
-#
-# No effect on non-x86 arches
-zlib-ng-avx512 = ["zlib-ng"]
+zlib-ng = ["libc", "cmake"]
+# Builds zlib-ng from source using cc instead of cmake
+zlib-ng-no-cmake = ["libc"]
 stock-zlib = []
 # Deprecated: the assembly routines are outdated, and either reduce performance
 # or cause segfaults.

README.md

@@ -43,6 +43,11 @@ libz-sys = { version = "1.1.0", default-features = false, features = ["libc"] }
 This allows higher-level crates depending on your library to opt into zlib-ng
 if desired.
 
+Building zlib-ng requires `cmake` unless the `zlib-ng-no-cmake` feature is enabled,
+in which case `cc` is used instead. Note that this option enables _all_ compiler
+features that are supported for the given target, which may not compile on older
+compilers or targets without certain headers.
+
 Crates that don't require compatibility with the zlib C API, and use zlib
 exclusively from Rust or support the zlib-ng native C API (prefixed with
 `zng_`) can use [`libz-ng-sys`](https://crates.io/crates/libz-ng-sys) instead,

build.rs

@@ -5,12 +5,16 @@ use std::path::PathBuf;
 fn main() {
     println!("cargo:rerun-if-env-changed=LIBZ_SYS_STATIC");
     println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=zng/cmake.rs");
+    println!("cargo:rerun-if-changed=zng/cc.rs");
+
     let host = env::var("HOST").unwrap();
     let target = env::var("TARGET").unwrap();
 
     let host_and_target_contain = |s| host.contains(s) && target.contains(s);
 
-    let want_ng = cfg!(feature = "zlib-ng") && !cfg!(feature = "stock-zlib");
+    let want_ng = cfg!(any(feature = "zlib-ng", feature = "zlib-ng-no-cmake"))
+        && !cfg!(feature = "stock-zlib");
 
     if want_ng && target != "wasm32-unknown-unknown" {
         return build_zlib_ng(&target, true);
@@ -161,13 +165,19 @@ fn build_zlib(cfg: &mut cc::Build, target: &str) {
     println!("cargo:include={}/include", dst.to_str().unwrap());
 }
 
-#[cfg(not(feature = "zlib-ng"))]
-fn build_zlib_ng(_target: &str, _compat: bool) {}
+#[cfg(any(feature = "zlib-ng", feature = "zlib-ng-no-cmake"))]
+mod zng {
+    #[cfg_attr(feature = "zlib-ng", path = "cmake.rs")]
+    #[cfg_attr(feature = "zlib-ng-no-cmake", path = "cc.rs")]
+    mod build_zng;
+
+    pub(super) use build_zng::build_zlib_ng;
+}
 
-#[cfg(feature = "zlib-ng")]
-mod build_zng;
-#[cfg(feature = "zlib-ng")]
-use build_zng::build_zlib_ng;
+fn build_zlib_ng(_target: &str, _compat: bool) {
+    #[cfg(any(feature = "zlib-ng", feature = "zlib-ng-no-cmake"))]
+    zng::build_zlib_ng(_target, _compat);
+}
 
 fn try_vcpkg() -> bool {
     // see if there is a vcpkg tree with zlib installed