fix(build): update CUDA linking strategy for Windows.

This build script is modified to properly handle platform-specific CUDA linking:

On Windows:

NVIDIA’s CUDA SDK does not ship culibos.lib, and static libraries like cublas_static.lib are typically unavailable.

Attempting to statically link cudart_static on Windows will fail due to missing symbols provided by culibos.

Therefore, on Windows, dynamic linking is preferred. The .lib files (like cudart.lib) act as import libraries for corresponding .dll files (e.g., cudart64_*.dll).

Author: DAIMENGEN

llama-cpp-sys-2/build.rs

@@ -410,28 +410,44 @@ fn main() {
     println!("cargo:rustc-link-search={}", build_dir.display());
 
     if cfg!(feature = "cuda") && !build_shared_libs {
+        // Re-run build script if CUDA_PATH environment variable changes
         println!("cargo:rerun-if-env-changed=CUDA_PATH");
 
+        // Add CUDA library directories to the linker search path
         for lib_dir in find_cuda_helper::find_cuda_lib_dirs() {
             println!("cargo:rustc-link-search=native={}", lib_dir.display());
         }
 
-        // Logic from ggml-cuda/CMakeLists.txt
-        println!("cargo:rustc-link-lib=static=cudart_static");
-        if matches!(target_os, TargetOs::Windows(_)) {
-            println!("cargo:rustc-link-lib=static=cublas");
-            println!("cargo:rustc-link-lib=static=cublasLt");
+        // Platform-specific linking
+        if cfg!(target_os = "windows") {
+            // ✅ On Windows, use dynamic linking.
+            // Static linking is problematic because NVIDIA does not provide culibos.lib,
+            // and static CUDA libraries (like cublas_static.lib) are usually not shipped.
+
+            println!("cargo:rustc-link-lib=cudart");       // Links to cudart64_*.dll
+            println!("cargo:rustc-link-lib=cublas");       // Links to cublas64_*.dll
+            println!("cargo:rustc-link-lib=cublasLt");     // Links to cublasLt64_*.dll
+
+            // Link to CUDA driver API (nvcuda.dll via cuda.lib)
+            if !cfg!(feature = "cuda-no-vmm") {
+                println!("cargo:rustc-link-lib=cuda");
+            }
         } else {
+            // ✅ On non-Windows platforms (e.g., Linux), static linking is preferred and supported.
+            // Static libraries like cudart_static and cublas_static depend on culibos.
+
+            println!("cargo:rustc-link-lib=static=cudart_static");
             println!("cargo:rustc-link-lib=static=cublas_static");
             println!("cargo:rustc-link-lib=static=cublasLt_static");
-        }
 
-        // Need to link against libcuda.so unless GGML_CUDA_NO_VMM is defined.
-        if !cfg!(feature = "cuda-no-vmm") {
-            println!("cargo:rustc-link-lib=cuda");
-        }
+            // Link to CUDA driver API (libcuda.so)
+            if !cfg!(feature = "cuda-no-vmm") {
+                println!("cargo:rustc-link-lib=cuda");
+            }
 
-        println!("cargo:rustc-link-lib=static=culibos");
+            // culibos is required when statically linking cudart_static
+            println!("cargo:rustc-link-lib=static=culibos");
+        }
     }
 
     // Link libraries