diff -urEb protobuf-3.5.1.orig/src/google/protobuf/stubs/io_win32.cc protobuf-3.5.1/src/google/protobuf/stubs/io_win32.cc
--- protobuf-3.5.1.orig/src/google/protobuf/stubs/io_win32.cc	2023-03-26 20:13:45.095021011 +0200
+++ protobuf-3.5.1/src/google/protobuf/stubs/io_win32.cc	2023-03-26 20:19:19.932920102 +0200
@@ -91,7 +91,12 @@
 
 template <typename char_type>
 bool null_or_empty(const char_type* s) {
-  return s == nullptr || *s == 0;
+  /**
+   * "nullptr" is not known to Visual Studio 2008, because this is a
+   * C++11 construction, which shouldn't be present in protobuf 3.5.1
+   * that is supposed to comply with C++98.
+   **/
+  return s == NULL || *s == 0;
 }
 
 // Returns true if the path starts with a drive letter, e.g. "c:".