Try using EXPORT_MACRO

Author: KangarooKoala

wpimath/CMakeLists.txt

@@ -10,14 +10,25 @@ file(GLOB wpimath_proto_src src/main/proto/*.proto)
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE)
 add_library(wpimathproto ${wpimath_proto_src})
 
-protobuf_generate(
-    TARGET
-    wpimathproto
-    # EXPORT_MACRO?
-    PROTOC_OUT_DIR
-    "${CMAKE_CURRENT_BINARY_DIR}/protobuf"
-    APPEND_PATH
-)
+if(MSVC)
+    protobuf_generate(
+        TARGET
+        wpimathproto
+        EXPORT_MACRO
+        "__declspec(dllexport)"
+        PROTOC_OUT_DIR
+        "${CMAKE_CURRENT_BINARY_DIR}/protobuf"
+        APPEND_PATH
+    )
+else()
+    protobuf_generate(
+        TARGET
+        wpimathproto
+        PROTOC_OUT_DIR
+        "${CMAKE_CURRENT_BINARY_DIR}/protobuf"
+        APPEND_PATH
+    )
+endif()
 
 target_compile_features(wpimathproto PUBLIC cxx_std_14)