Move linking flags to build.rs to help with non-cargo build systems

.github/workflows/test.yml

@@ -6,6 +6,9 @@ on:
     branches: [ main ]
   schedule:
     - cron: "43 7 * * 0"
+concurrency:
+  group: ${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   test-default-features:
@@ -46,3 +49,14 @@ jobs:
       - uses: actions/checkout@v2
       - name: 'Test static-bindgen'
         run: 'make static-bindgen'
+  test-static-linking:
+    runs-on: ${{ matrix.runs-on }}
+    strategy:
+      matrix:
+        runs-on: [ubuntu-latest, macos-latest]
+    steps:
+      - uses: actions/checkout@v2
+      - if: matrix.runs-on == 'macos-latest'
+        run: make macos-test
+      - if: matrix.runs-on == 'ubuntu-latest'
+        run: make test

Makefile

@@ -73,6 +73,14 @@ docker-test:
 			${DOCKER_REPO}/${DOCKER_TEST_ENV}:${USED_BUILDENV_VERSION}
 .PHONY: docker-test
 
+# Test with the homebrew version of icu4c on macOS with static linking (the default way of linking for distribution on Apple platforms)
+macos-test:
+	brew install icu4c
+	RUST_ICU_LINK_SEARCH_DIR="$(shell brew --prefix)/opt/icu4c/lib" \
+	RUST_ICU_MAJOR_VERSION_NUMBER=${RUST_ICU_MAJOR_VERSION_NUMBER} \
+	cargo test --no-default-features --features=icu_version_64_plus,icu_version_67_plus,icu_version_68_plus,icu_version_in_env,renaming,static
+.PHONY: macos-test
+
 # Refreshes the static bindgen output (contents of ./rust_icu_sys/bindgen) based
 # on the currently present ICU versions in the test environment.
 #

README.md

@@ -142,6 +142,7 @@ Feature              | Default? | Description
 `renaming`           | Yes      | If set, ICU bindings are generated with version numbers appended. This is called "renaming" in ICU, and is normally needed only when linking against specific ICU version is required, for example to work around having to link different ICU versions. See [the ICU documentation](https://unicode-org.github.io/icu/userguide/icu/design.html) for a discussion of renaming. **This feature MUST be used when `bindgen` is NOT used.**
 `icu_config`         | Yes      | If set, the binary icu-config will be used to configure the library. Turn this feature off if you do not want `build.rs` to try to autodetect the build environment. You will want to skip this feature if your build environment configures ICU in a different way. **This feature is only meaningful when `bindgen` feature is used; otherwise it has no effect.**
 `icu_version_in_env` | No       | If set, ICU bindings are made for the ICU version specified in the environment variable `RUST_ICU_MAJOR_VERSION_NUMBER`, which is made available to cargo at build time. See section below for details on how to use this feature. **This feature is only meaningful when `bindgen` feature is NOT used; otherwise it has no effect.**
+`static`             | No       | If set, link ICU libraries statically (and the standard C++ dynamically). You can use `RUST_ICU_LINK_SEARCH_DIR` to add an extra path to the search path if you have a build of ICU in a non-standard directory.
 
 # Prerequisites
 

rust_icu_sys/build.rs

@@ -478,6 +478,24 @@ macro_rules! versioned_function {
     }
 }
 
+fn rustc_link_libs() {
+    if cfg!(feature = "static") {
+        println!("cargo:rustc-link-lib=static=icuuc");
+        println!("cargo:rustc-link-lib=static=icui18n");
+        println!("cargo:rustc-link-lib=static:+whole-archive,-bundle=icudata");
+        // On systems such as macOS, libc++ is the default library
+        if cfg!(target_vendor = "apple") {
+            println!("cargo:rustc-link-lib=dylib=c++");
+        } else {
+            println!("cargo:rustc-link-lib=dylib=stdc++");
+        }
+    } else {
+        println!("cargo:rustc-link-lib=dylib=icuuc");
+        println!("cargo:rustc-link-lib=dylib=icui18n");
+        println!("cargo:rustc-link-lib=dylib=icudata");
+    }
+}
+
 #[cfg(feature = "use-bindgen")]
 fn main() -> Result<(), anyhow::Error> {
     std::env::set_var("RUST_BACKTRACE", "full");
@@ -486,10 +504,17 @@ fn main() -> Result<(), anyhow::Error> {
         return Ok(());
     }
     inner::icu_config_autodetect()?;
+    rustc_link_libs();
     println!("done:true");
     Ok(())
 }
 
 /// No-op if use-bindgen is disabled.
 #[cfg(not(feature = "use-bindgen"))]
-fn main() {}
+fn main() {
+    // can be used to provide an extra path to find libicuuc, libicui18n and libicudata
+    if let Ok(lib_dir) = std::env::var("RUST_ICU_LINK_SEARCH_DIR") {
+        println!("cargo:rustc-link-search=native={}", lib_dir);
+    }
+    rustc_link_libs();
+}

rust_icu_sys/src/lib.rs

@@ -23,7 +23,7 @@
     non_upper_case_globals,
     unused_imports,
     rustdoc::bare_urls,
-    deref_nullptr,
+    deref_nullptr
 )]
 
 #[cfg(all(feature = "icu_version_in_env", feature = "icu_config"))]
@@ -80,24 +80,6 @@ impl std::fmt::Display for UErrorCode {
 
 extern crate libc;
 
-// A "fake" extern used to express link preferences.  The libraries mentioned
-// below will be converted to "-l" flags to the linker.
-#[cfg_attr(not(feature = "static"), link(name = "icui18n", kind = "dylib"))]
-#[cfg_attr(not(feature = "static"), link(name = "icuuc", kind = "dylib"))]
-#[cfg_attr(feature = "static", link(name = "icui18n", kind = "static"))]
-#[cfg_attr(feature = "static", link(name = "icuuc", kind = "static"))]
-#[cfg_attr(feature = "static", link(name = "icudata", kind = "static"))]
-// On systems such as macOS, libc++ is the default library
-#[cfg_attr(
-    all(target_vendor = "apple", feature = "static"),
-    link(name = "c++", kind = "dylib")
-)]
-#[cfg_attr(
-    not(all(target_vendor = "apple", feature = "static")),
-    link(name = "stdc++", kind = "dylib")
-)]
-extern "C" {}
-
 impl From<i8> for UCharCategory {
     fn from(value: i8) -> Self {
         match value {
@@ -132,7 +114,7 @@ impl From<i8> for UCharCategory {
             28 => UCharCategory::U_INITIAL_PUNCTUATION,
             29 => UCharCategory::U_FINAL_PUNCTUATION,
             30 => UCharCategory::U_CHAR_CATEGORY_COUNT,
-            _ => { 
+            _ => {
                 panic!("could not convert: {}", value);
             }
         }