Fix and cover the windows-static-ssl feature (curl+OpenSSL on Windows)

.github/workflows/main.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        build: [x86_64, i686, x86_64-musl, mingw, system-curl, x86_64-beta, x86_64-nightly, macos, win64, win32]
+        build: [x86_64, i686, x86_64-musl, mingw, system-curl, x86_64-beta, x86_64-nightly, macos, win64-static-ssl, win64, win32]
         include:
           - build: x86_64
             os: ubuntu-latest
@@ -67,6 +67,11 @@ jobs:
             os: windows-latest
             rust: stable
             target: x86_64-pc-windows-msvc
+          - build: win64-static-ssl
+            os: windows-latest
+            rust: stable
+            target: x86_64-pc-windows-msvc
+            static_ssl: windows
     steps:
     - uses: actions/checkout@v1
       with:
@@ -75,7 +80,29 @@ jobs:
       run: rustup update ${{ matrix.rust }} --no-self-update && rustup default ${{ matrix.rust }}
       shell: bash
     - run: rustup target add ${{ matrix.target }}
-    - run: TARGET=${{ matrix.target }} ./ci/run.sh
+    - name: Compute vcpkg cache entries
+      if: matrix.static_ssl == 'windows'
+      id: vcpkg-cache
+      shell: bash
+      run: |
+        echo "path=${{ runner.temp }}/vcpkg-cache" >> "$GITHUB_OUTPUT"
+        echo "key=vcpkg-${{ matrix.target }}-${{ hashFiles('vcpkg.json') }}-$ImageVersion" >> "$GITHUB_OUTPUT"
+    - name: Restore vcpkg binary cache (files backend)
+      if: matrix.static_ssl == 'windows'
+      uses: actions/cache@v5
+      with:
+        path: ${{ steps.vcpkg-cache.outputs.path }}
+        key: ${{ steps.vcpkg-cache.outputs.key }}
+    - name: Install vcpkg dependencies (for windows-static-ssl)
+      if: matrix.static_ssl == 'windows'
+      shell: bash
+      env:
+        VCPKG_BINARY_SOURCES: "clear;files,${{ steps.vcpkg-cache.outputs.path }},readwrite"
+      run: |
+        vcpkg install --triplet=x64-windows-static-md \
+          --x-install-root="$VCPKG_INSTALLATION_ROOT/installed"
+        echo "VCPKG_ROOT=$VCPKG_INSTALLATION_ROOT" >> "$GITHUB_ENV"
+    - run: TARGET=${{ matrix.target }} STATIC_SSL=${{ matrix.static_ssl }} ./ci/run.sh
       if: matrix.os != 'ubuntu-latest'
       name: Run non-docker tests
       shell: bash

ci/run.sh

@@ -16,6 +16,16 @@ if [ "$TARGET" = "x86_64-unknown-linux-musl" ]; then
   features="--features static-ssl"
 fi
 
+# `windows-static-ssl` (curl + OpenSSL on Windows) needs vcpkg-installed
+# OpenSSL and `VCPKG_ROOT` set for vcpkg-rs's discovery.
+if [ "$STATIC_SSL" = "windows" ]; then
+  features="--features windows-static-ssl --no-default-features"
+  # Enable the Windows native CA store for the test suite so doctests that
+  # make HTTPS requests can verify server certificates. Not baked into
+  # build.rs to avoid forcing the default on library consumers.
+  export CFLAGS="-DCURL_CA_NATIVE"
+fi
+
 cargo test --target $TARGET --no-run $features
 # First test with no extra protocols enabled.
 cargo test --target $TARGET --no-run --features static-curl $features
@@ -28,7 +38,11 @@ cargo test --target $TARGET --no-run --features static-curl $features
 # Compiling on i686-windows requires nasm to be installed (other platforms
 # have pre-compiled object files), which is just slightly too much
 # inconvenience for me.
-if [ "$TARGET" != "x86_64-pc-windows-gnu" ] && [ "$TARGET" != "i686-pc-windows-msvc" ]
+#
+# Note also that rustls silently wins over windows-static-ssl in curl-sys's
+# build.rs else-if, so we skip this on the win64-static-ssl entry and keep
+# actually exercising windows-static-ssl in the tests below.
+if [ "$TARGET" != "x86_64-pc-windows-gnu" ] && [ "$TARGET" != "i686-pc-windows-msvc" ] && [ "$STATIC_SSL" != "windows" ]
 then
     cargo test --target $TARGET --no-run --features rustls,static-curl $features
 fi

curl-sys/build.rs

@@ -360,17 +360,39 @@ fn main() {
         if windows {
             cfg.define("USE_OPENSSL", None)
                 .file("curl/lib/vtls/openssl.c");
-            // We need both openssl and zlib
-            // Those can be installed with
-            // ```shell
-            // git clone https://github.com/microsoft/vcpkg
-            // cd vcpkg
-            // ./bootstrap-vcpkg.bat -disableMetrics
-            // ./vcpkg.exe integrate install
-            // ./vcpkg.exe install openssl:x64-windows-static-md
-            // ```
-            #[cfg(target_env = "msvc")]
-            vcpkg::Config::new().find_package("openssl").ok();
+            // Probe `<TARGET>_OPENSSL_DIR` / `OPENSSL_DIR` before falling
+            // back to vcpkg. Matches openssl-sys's env-lookup convention so
+            // a single env var can point both `openssl-sys` and `curl-sys`
+            // at the same OpenSSL install.
+            if let Some(dir) = openssl_dir_from_env(&target) {
+                cfg.include(dir.join("include"));
+                println!(
+                    "cargo:rustc-link-search=native={}",
+                    dir.join("lib").display()
+                );
+                println!("cargo:rustc-link-lib=libssl");
+                println!("cargo:rustc-link-lib=libcrypto");
+            } else {
+                // vcpkg openssl fallback. Install with:
+                // ```shell
+                // git clone https://github.com/microsoft/vcpkg
+                // cd vcpkg
+                // ./bootstrap-vcpkg.bat -disableMetrics
+                // ./vcpkg.exe integrate install
+                // ./vcpkg.exe install openssl:x64-windows-static-md
+                // ```
+                // `find_package` emits `rustc-link-search` + `rustc-link-lib`
+                // for the linker, but the returned `Library`'s `include_paths`
+                // still have to be threaded into `cc-rs` explicitly.
+                #[cfg(target_env = "msvc")]
+                if let Ok(lib) = vcpkg::Config::new().find_package("openssl") {
+                    for path in &lib.include_paths {
+                        cfg.include(path);
+                    }
+                }
+            }
+            // OpenSSL static libs reference MessageBoxA (OPENSSL_showfatal).
+            println!("cargo:rustc-link-lib=user32");
             #[cfg(target_env = "msvc")]
             vcpkg::Config::new().find_package("zlib").ok();
         } else {
@@ -529,6 +551,20 @@ fn main() {
     }
 }
 
+/// Probe `<TARGET>_OPENSSL_DIR` first, then plain `OPENSSL_DIR`, matching
+/// openssl-sys's env-lookup convention (`build/main.rs::env`). Always emits
+/// `rerun-if-env-changed` for both names so the build is invalidated when
+/// the env changes, even when neither is set at build time.
+fn openssl_dir_from_env(target: &str) -> Option<PathBuf> {
+    let prefix = target.to_uppercase().replace('-', "_");
+    let prefixed = format!("{prefix}_OPENSSL_DIR");
+    println!("cargo:rerun-if-env-changed={prefixed}");
+    println!("cargo:rerun-if-env-changed=OPENSSL_DIR");
+    env::var_os(&prefixed)
+        .or_else(|| env::var_os("OPENSSL_DIR"))
+        .map(PathBuf::from)
+}
+
 #[cfg(not(target_env = "msvc"))]
 fn try_vcpkg() -> bool {
     false

src/lib.rs

@@ -56,6 +56,13 @@
 #![deny(missing_docs, missing_debug_implementations)]
 #![doc(html_root_url = "https://docs.rs/curl/0.4")]
 
+// `ssl` (Schannel on Windows) and `windows-static-ssl` (OpenSSL) are mutually
+// exclusive TLS backends for libcurl.
+// Gated on `not(doc)` so that `cargo doc --all-features` still generates a
+// union of feature-conditional items.
+#[cfg(all(feature = "ssl", feature = "windows-static-ssl", not(doc)))]
+compile_error!("`ssl` and `windows-static-ssl` are mutually exclusive TLS backends");
+
 use std::ffi::CStr;
 use std::str;
 use std::sync::Once;

systest/Cargo.toml

@@ -16,3 +16,4 @@ ctest2 = "0.4"
 
 [features]
 static-ssl = ['curl-sys/static-ssl']
+windows-static-ssl = ['curl-sys/windows-static-ssl']

vcpkg.json

@@ -0,0 +1,13 @@
+{
+  "builtin-baseline": "960d40ee7351cca3fc648e9d38993b59f01dfd2b",
+  "dependencies": [
+    "openssl"
+  ],
+  "overrides": [
+    {
+      "name": "openssl",
+      "version": "3.6.4",
+      "port-version": 1
+    }
+  ]
+}