docs(cpp): clarify MSVC preprocessor requirement

README.md

@@ -217,6 +217,9 @@ git_override(module_name = "fory", remote = "https://github.com/apache/fory.git"
 deps = ["@fory//cpp/fory/serialization:fory_serialization"]
 ```
 
+When building C++ with MSVC, enable the conforming preprocessor option
+`/Zc:preprocessor`; see the C++ installation guide for setup details.
+
 See the [C++ installation guide](https://fory.apache.org/docs/guide/cpp/#installation)
 for complete CMake, Bazel, and source-build details.
 

cpp/README.md

@@ -359,11 +359,20 @@ cpp/fory/
 
 - **C++ Standard**: C++17 or later
 - **Build System**: Bazel 8.2.1+ or CMake 3.16+
+- **MSVC**: configure your build system to pass `/Zc:preprocessor`.
 
 ## Building
 
 ### With Bazel
 
+When building with MSVC, add the conforming preprocessor option to your Bazel
+configuration:
+
+```bazel
+# .bazelrc
+build --cxxopt=/Zc:preprocessor
+```
+
 ```bash
 # Build all projects
 bazel build //cpp/...
@@ -377,6 +386,15 @@ bazel test $(bazel query //cpp/fory/serialization/...)
 
 ### With CMake
 
+When building with MSVC, add `/Zc:preprocessor` before bringing Fory into the
+build:
+
+```cmake
+if(MSVC)
+    add_compile_options(/Zc:preprocessor)
+endif()
+```
+
 ```bash
 mkdir build && cd build
 cmake ..

docs/guide/cpp/index.md

@@ -42,6 +42,9 @@ The C++ implementation supports both CMake and Bazel build systems.
 - CMake 3.16+ (for CMake build) or Bazel 8+ (for Bazel build)
 - C++17 compatible compiler (GCC 7+, Clang 5+, MSVC 2017+)
 
+When building with MSVC, configure your build system to pass
+`/Zc:preprocessor`.
+
 ### Using CMake (Recommended)
 
 The easiest way to use Fory is with CMake's `FetchContent` module:
@@ -107,6 +110,14 @@ cc_binary(
 )
 ```
 
+When building with MSVC, add the conforming preprocessor option to your Bazel
+configuration:
+
+```bazel
+# .bazelrc
+build --cxxopt=/Zc:preprocessor
+```
+
 Then build and run:
 
 ```bash