- make the build self-contained and cross-compile friendly: vendor the Eigen 3.4.0 headers (instead of the flaky gitlab clone / a system libeigen3-dev package), align the msvc C runtime with the dynamic one used by the rest of cross builds (xwin), and pass the -D_LIBCPP_* macros to bindgen so it parses zig's bundled libc++ regardless of ziglang/cargo-zigbuild versions

build.rs

@@ -133,6 +133,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         let libcziapi_src = libczi_dir.join("Src/libCZIAPI/src");
         let libcziapi_h = libcziapi_inc.join("libCZIApi.h");
 
+        let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR")?);
         let mut cmake_config = cmake::Config::new(&libczi_dir);
         cmake_config
             .cxxflag("-fms-extensions")
@@ -141,19 +142,32 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             .define("LIBCZI_BUILD_UNITTESTS", "OFF")
             .define("LIBCZI_BUILD_CZICMD", "OFF")
             .define("LIBCZI_BUILD_DYNLIB", "OFF")
-            .define("LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_EIGEN3", "OFF")
             .define("LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_ZSTD", "OFF")
             .define("LIBCZI_BUILD_CURL_BASED_STREAM", "OFF")
             .define("LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_LIBCURL", "OFF")
             .define("LIBCZI_BUILD_AZURESDK_BASED_STREAM", "OFF")
             .define("LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_RAPIDJSON", "OFF")
-            .define("LIBCZI_BUILD_LIBCZIAPI", "ON");
+            .define("LIBCZI_BUILD_LIBCZIAPI", "ON")
+            // vendored Eigen 3.4.0 headers (eigen/, see its README) so neither a
+            // network clone (libCZI's gitlab ExternalProject) nor a system
+            // libeigen3-dev package is required; Eigen3_DIR finds the package
+            // via eigen/Eigen3Config.cmake
+            .define("LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_EIGEN3", "ON")
+            .define("Eigen3_DIR", manifest_dir.join("eigen"));
 
         if is_cross {
             if is_windows {
                 cmake_config
                     .define("CMAKE_SYSTEM_NAME", "Windows")
-                    .define("CRASH_ON_UNALIGNED_ACCESS", "FALSE");
+                    .define("CRASH_ON_UNALIGNED_ACCESS", "FALSE")
+                    // the rest of the cross build (Rust std, cc-rs-compiled
+                    // vendored code) uses the dynamic C runtime (/MD), but
+                    // libCZI hardwires the static one (/MT); the MSVC linker
+                    // (lld-link) rejects the mix. Use libCZI's upstream option
+                    // to leave the runtime choice to CMake, aligned with
+                    // the dynamic runtime (only affects the msvc target)
+                    .define("LIBCZI_DO_NOT_SET_MSVC_RUNTIME_LIBRARY", "ON")
+                    .define("CMAKE_MSVC_RUNTIME_LIBRARY", "MultiThreadedDLL$<$<CONFIG:Debug>:Debug>");
 
                 let has_toolchain_file = env::var("TARGET_CMAKE_TOOLCHAIN_FILE").is_ok()
                     || env::var(format!("CMAKE_TOOLCHAIN_FILE_{}", target.replace('-', "_")))
@@ -212,6 +226,19 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                     .to_str()
                     .ok_or(Error::msg("cannot into string"))?,
             ])
+            // cargo-zigbuild puts zig's bundled libc++ on the include path
+            // (CPATH); its hardening.h requires the -D_LIBCPP_* config macros.
+            // Pass them ourselves so parsing works with any ziglang /
+            // cargo-zigbuild version (they are ignored by other stdlibs)
+            .clang_args([
+                "-D_LIBCPP_ASSERTION_SEMANTIC_DEFAULT=_LIBCPP_ASSERTION_SEMANTIC_ENFORCE",
+                "-D_LIBCPP_PSTL_BACKEND_SERIAL",
+                "-D_LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS=0",
+                "-D_LIBCPP_HAS_TERMINAL",
+                "-D_LIBCPP_HAS_RANDOM_DEVICE",
+                "-D_LIBCPP_HAS_NO_STD_MODULES",
+                "-D_LIBCPP_HAS_FILESYSTEM=1",
+            ])
             .header(
                 libcziapi_h
                     .to_str()