Fix Rust FFI build and linker issues

Changes:
1. build.rs: Only define SPIRV_RUST_TARGET_ENV when SPIRV_RUST_TARGET_ENV_DEFINE=1
   (Bazel). In CMake builds, context_bridge.cc provides implementations directly.

2. context_bridge.cc: Include source/table.h and properly implement
   dispatch_context_message using context->consumer. This allows the Rust FFI
   library to provide message dispatch without depending on linker order.

3. text.cpp: Remove duplicate FFI implementations. context_bridge.cc now
   provides these in all build scenarios.

4. build_rust_ffi.py: Handle Windows library extension (.lib vs .a).

This fixes:
- Undefined reference errors in CMake builds (linker ordering)
- Multiple definition errors when both files provided implementations
- Bazel Windows builds failing to find the output library

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: LegNeato

rust/scripts/build_rust_ffi.py

@@ -69,7 +69,14 @@ def main() -> int:
     workdir = manifest.parent
     subprocess.run(command, cwd=workdir, check=True, env=env)
 
-    lib_name = f"lib{package.replace('-', '_')}.a"
+    # Determine library name based on platform
+    # Windows MSVC: spirv_tools_ffi.lib
+    # Unix/MinGW: libspirv_tools_ffi.a
+    lib_base = package.replace("-", "_")
+    if sys.platform == "win32":
+        lib_name = f"{lib_base}.lib"
+    else:
+        lib_name = f"lib{lib_base}.a"
     built_lib = target_dir / profile_dir / lib_name
     if not built_lib.exists():
         raise FileNotFoundError(f"cargo did not produce {built_lib}")

rust/spirv-tools-ffi/build.rs

@@ -29,14 +29,22 @@ fn main() {
     .expect("failed to copy context bridge header");
 
     let mut bridge_builder = cxx_build::bridge("src/lib.rs");
-    // Always define SPIRV_RUST_TARGET_ENV when compiling context_bridge.cc via cargo.
-    // This ensures:
-    // 1. We skip C++ includes that need generated headers (reducer.h, libspirv.hpp)
-    // 2. We delegate to Rust implementations (validate_binary_rust, etc.)
-    // 3. We don't provide duplicate implementations of dispatch_context_message
-    //    and assemble_text_with_context (text.cpp provides these in CMake builds
-    //    when SPIRV_RUST_TARGET_ENV is defined there too)
-    bridge_builder.define("SPIRV_RUST_TARGET_ENV", None);
+    // Define SPIRV_RUST_TARGET_ENV only for standalone Rust/Bazel builds.
+    // This controls which implementations context_bridge.cc provides:
+    //
+    // - CMake builds (SPIRV_RUST_TARGET_ENV NOT defined):
+    //   context_bridge.cc provides full implementations using C++ APIs
+    //   (generated headers are available from CMake build)
+    //
+    // - Bazel builds (SPIRV_RUST_TARGET_ENV_DEFINE=1):
+    //   context_bridge.cc provides stub implementations
+    //   (generated headers not available, uses Rust fallbacks)
+    //
+    // Note: CMake also sets SPIRV_TOOLS_FFI_SKIP_CPP_LINK=1, but that only
+    // controls link directives, not the compile-time behavior.
+    if env::var("SPIRV_RUST_TARGET_ENV_DEFINE").is_ok() {
+        bridge_builder.define("SPIRV_RUST_TARGET_ENV", None);
+    }
     bridge_builder
         .file("src/context_bridge.cc")
         .include(repo_root)

rust/spirv-tools-ffi/src/context_bridge.cc

@@ -13,6 +13,7 @@
 #ifndef SPIRV_RUST_TARGET_ENV
 #include "source/reduce/reducer.h"
 #include "source/spirv_reducer_options.h"
+#include "source/table.h"
 #include "spirv-tools/libspirv.hpp"
 #endif
 
@@ -37,19 +38,34 @@ namespace spvtools::ffi {
 // assemble_text_with_context are provided by source/text.cpp using internal APIs.
 // In standalone Rust builds (Bazel), we provide them here.
 #ifndef SPIRV_RUST_TARGET_ENV
+namespace {
+spv_position_t ToSpvPosition(MessagePosition position) {
+  spv_position_t pos = {};
+  pos.line = position.line;
+  pos.column = position.column;
+  pos.index = position.index;
+  return pos;
+}
+}  // namespace
+
 void dispatch_context_message(std::size_t context_ptr, std::uint32_t level,
                               bool has_source, rust::Str source,
                               MessagePosition position, rust::Str message) {
-  // This function is intentionally a no-op in standalone Rust builds.
-  // Message dispatch to C++ consumers requires access to spv_context_t internals
-  // (specifically the `consumer` callback), which requires generated headers
-  // that are not available when compiling via Rust's build.rs.
-  (void)context_ptr;
-  (void)level;
-  (void)has_source;
-  (void)source;
-  (void)position;
-  (void)message;
+  auto* context = reinterpret_cast<spv_context>(context_ptr);
+  if (context == nullptr || !context->consumer) {
+    return;
+  }
+
+  std::string message_storage(message.data(), message.length());
+  const char* source_ptr = nullptr;
+  std::string source_storage;
+  if (has_source) {
+    source_storage.assign(source.data(), source.length());
+    source_ptr = source_storage.c_str();
+  }
+
+  context->consumer(static_cast<spv_message_level_t>(level), source_ptr,
+                    ToSpvPosition(position), message_storage.c_str());
 }
 
 AssembleResult assemble_text_with_context(std::size_t context_ptr,

source/text.cpp

@@ -1071,73 +1071,6 @@ spv_result_t spvTextToBinaryWithOptions(const spv_const_context context,
                                      sanitized_options, pBinary, pDiagnostic);
 }
 
-// FFI bridge functions for Rust integration. In CMake builds with SPIRV_RUST_TARGET_ENV,
-// we provide these functions here using internal C++ APIs. In standalone Rust builds (Bazel),
-// context_bridge.cc provides stubs (since generated headers aren't available there).
-#if defined(SPIRV_RUST_TARGET_ENV)
-namespace spvtools::ffi {
-namespace {
-spv_position_t ToSpvPosition(MessagePosition position) {
-  spv_position_t pos = {};
-  pos.line = position.line;
-  pos.column = position.column;
-  pos.index = position.index;
-  return pos;
-}
-}  // namespace
-
-void dispatch_context_message(std::size_t context_ptr, std::uint32_t level,
-                              bool has_source, rust::Str source,
-                              MessagePosition position, rust::Str message) {
-  auto* context = reinterpret_cast<spv_context>(context_ptr);
-  if (context == nullptr || !context->consumer) {
-    return;
-  }
-
-  std::string message_storage(message.data(), message.length());
-  const char* source_ptr = nullptr;
-  std::string source_storage;
-  if (has_source) {
-    source_storage.assign(source.data(), source.length());
-    source_ptr = source_storage.c_str();
-  }
-
-  context->consumer(static_cast<spv_message_level_t>(level), source_ptr,
-                    ToSpvPosition(position), message_storage.c_str());
-}
-
-AssembleResult assemble_text_with_context(std::size_t context_ptr,
-                                          rust::Slice<const std::uint8_t> text,
-                                          std::uint32_t options) {
-  AssembleResult result{false, ::rust::Vec<std::uint32_t>()};
-  auto* context = reinterpret_cast<spv_context>(context_ptr);
-  if (context == nullptr) {
-    return result;
-  }
-
-  spv_binary binary = nullptr;
-  spv_diagnostic diagnostic = nullptr;
-  const char* text_ptr = reinterpret_cast<const char*>(text.data());
-  const spv_result_t status = AssembleTextWithDiagnostics(
-      context, text_ptr, text.size(), options, &binary, &diagnostic);
-  if (diagnostic) {
-    spvDiagnosticDestroy(diagnostic);
-  }
-
-  if (status == SPV_SUCCESS && binary != nullptr) {
-    result.success = true;
-    result.binary.reserve(binary->wordCount);
-    for (size_t i = 0; i < binary->wordCount; ++i) {
-      result.binary.push_back(binary->code[i]);
-    }
-    spvBinaryDestroy(binary);
-  }
-
-  return result;
-}
-}  // namespace spvtools::ffi
-#endif
-
 void spvTextDestroy(spv_text text) {
   if (text) {
     if (text->str) delete[] text->str;