diff --git a/include/flatbuffers/base.h b/include/flatbuffers/base.h
index a0c78fc2a..26adcc961 100644
--- a/include/flatbuffers/base.h
+++ b/include/flatbuffers/base.h
@@ -134,7 +134,7 @@
     (defined(__cpp_constexpr) && __cpp_constexpr >= 200704)
   #define FLATBUFFERS_CONSTEXPR constexpr
 #else
-  #define FLATBUFFERS_CONSTEXPR
+  #define FLATBUFFERS_CONSTEXPR const
 #endif
 
 #if (defined(__cplusplus) && __cplusplus >= 201402L) || \
diff --git a/include/flatbuffers/util.h b/include/flatbuffers/util.h
index 1ebb971e5..7509676c4 100644
--- a/include/flatbuffers/util.h
+++ b/include/flatbuffers/util.h
@@ -17,41 +17,19 @@
 #ifndef FLATBUFFERS_UTIL_H_
 #define FLATBUFFERS_UTIL_H_
 
-// clang-format off
+#include "flatbuffers/base.h"
+
+#include <errno.h>
 
 #ifndef FLATBUFFERS_PREFER_PRINTF
 #  include <sstream>
-#else // FLATBUFFERS_PREFER_PRINTF
+#else  // FLATBUFFERS_PREFER_PRINTF
 #  include <float.h>
 #  include <stdio.h>
-#endif // FLATBUFFERS_PREFER_PRINTF
-
-#ifdef _WIN32
-#  ifndef WIN32_LEAN_AND_MEAN
-#    define WIN32_LEAN_AND_MEAN
-#  endif
-#  ifndef NOMINMAX
-#    define NOMINMAX
-#  endif
-#  include <windows.h>  // Must be included before <direct.h>
-#  include <direct.h>
-#  include <winbase.h>
-#  undef interface  // This is also important because of reasons
-#else
-#  include <limits.h>
-#endif
-// clang-format on
-
-#include <errno.h>
-#include <stdint.h>
-#include <stdlib.h>
-#include <sys/stat.h>
-#include <sys/types.h>
+#endif  // FLATBUFFERS_PREFER_PRINTF
 
 #include <iomanip>
-#include <fstream>
-
-#include "flatbuffers/base.h"
+#include <string>
 
 namespace flatbuffers {
 
@@ -435,13 +413,7 @@ bool LoadFile(const char *name, bool binary, std::string *buf);
 // If "binary" is false data is written using ifstream's
 // text mode, otherwise data is written with no
 // transcoding.
-inline bool SaveFile(const char *name, const char *buf, size_t len,
-                     bool binary) {
-  std::ofstream ofs(name, binary ? std::ofstream::binary : std::ofstream::out);
-  if (!ofs.is_open()) return false;
-  ofs.write(buf, len);
-  return !ofs.bad();
-}
+bool SaveFile(const char *name, const char *buf, size_t len, bool binary);
 
 // Save data "buf" into file "name" returning true if
 // successful, false otherwise.  If "binary" is false
@@ -457,102 +429,35 @@ inline bool SaveFile(const char *name, const std::string &buf, bool binary) {
 // Windows ('/' or '\\') separators are used.
 
 // Any new separators inserted are always posix.
-
-// We internally store paths in posix format ('/'). Paths supplied
-// by the user should go through PosixPath to ensure correct behavior
-// on Windows when paths are string-compared.
-
-static const char kPathSeparator = '/';
-static const char kPathSeparatorWindows = '\\';
-static const char *PathSeparatorSet = "\\/";  // Intentionally no ':'
+FLATBUFFERS_CONSTEXPR char kPathSeparator = '/';
 
 // Returns the path with the extension, if any, removed.
-inline std::string StripExtension(const std::string &filepath) {
-  size_t i = filepath.find_last_of(".");
-  return i != std::string::npos ? filepath.substr(0, i) : filepath;
-}
+std::string StripExtension(const std::string &filepath);
 
 // Returns the extension, if any.
-inline std::string GetExtension(const std::string &filepath) {
-  size_t i = filepath.find_last_of(".");
-  return i != std::string::npos ? filepath.substr(i + 1) : "";
-}
+std::string GetExtension(const std::string &filepath);
 
 // Return the last component of the path, after the last separator.
-inline std::string StripPath(const std::string &filepath) {
-  size_t i = filepath.find_last_of(PathSeparatorSet);
-  return i != std::string::npos ? filepath.substr(i + 1) : filepath;
-}
+std::string StripPath(const std::string &filepath);
 
 // Strip the last component of the path + separator.
-inline std::string StripFileName(const std::string &filepath) {
-  size_t i = filepath.find_last_of(PathSeparatorSet);
-  return i != std::string::npos ? filepath.substr(0, i) : "";
-}
+std::string StripFileName(const std::string &filepath);
 
 // Concatenates a path with a filename, regardless of wether the path
 // ends in a separator or not.
-inline std::string ConCatPathFileName(const std::string &path,
-                                      const std::string &filename) {
-  std::string filepath = path;
-  if (filepath.length()) {
-    char &filepath_last_character = string_back(filepath);
-    if (filepath_last_character == kPathSeparatorWindows) {
-      filepath_last_character = kPathSeparator;
-    } else if (filepath_last_character != kPathSeparator) {
-      filepath += kPathSeparator;
-    }
-  }
-  filepath += filename;
-  // Ignore './' at the start of filepath.
-  if (filepath[0] == '.' && filepath[1] == kPathSeparator) {
-    filepath.erase(0, 2);
-  }
-  return filepath;
-}
+std::string ConCatPathFileName(const std::string &path,
+                               const std::string &filename);
 
 // Replaces any '\\' separators with '/'
-inline std::string PosixPath(const char *path) {
-  std::string p = path;
-  std::replace(p.begin(), p.end(), '\\', '/');
-  return p;
-}
+std::string PosixPath(const char *path);
 
 // This function ensure a directory exists, by recursively
 // creating dirs for any parts of the path that don't exist yet.
-inline void EnsureDirExists(const std::string &filepath) {
-  auto parent = StripFileName(filepath);
-  if (parent.length()) EnsureDirExists(parent);
-    // clang-format off
-
-  #ifdef _WIN32
-    (void)_mkdir(filepath.c_str());
-  #else
-    mkdir(filepath.c_str(), S_IRWXU|S_IRGRP|S_IXGRP);
-  #endif
-  // clang-format on
-}
+void EnsureDirExists(const std::string &filepath);
 
 // Obtains the absolute path from any other path.
 // Returns the input path if the absolute path couldn't be resolved.
-inline std::string AbsolutePath(const std::string &filepath) {
-  // clang-format off
-
-  #ifdef FLATBUFFERS_NO_ABSOLUTE_PATH_RESOLUTION
-    return filepath;
-  #else
-    #ifdef _WIN32
-      char abs_path[MAX_PATH];
-      return GetFullPathNameA(filepath.c_str(), MAX_PATH, abs_path, nullptr)
-    #else
-      char abs_path[PATH_MAX];
-      return realpath(filepath.c_str(), abs_path)
-    #endif
-      ? abs_path
-      : filepath;
-  #endif // FLATBUFFERS_NO_ABSOLUTE_PATH_RESOLUTION
-  // clang-format on
-}
+std::string AbsolutePath(const std::string &filepath);
 
 // To and from UTF-8 unicode conversion functions
 
diff --git a/src/util.cpp b/src/util.cpp
index f652f0f26..c1bb1975c 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -14,10 +14,31 @@
  * limitations under the License.
  */
 
-#include <clocale>
+// clang-format off
+// Dont't remove `format off`, it prevent reordering of win-includes.
+#ifdef _WIN32
+#  ifndef WIN32_LEAN_AND_MEAN
+#    define WIN32_LEAN_AND_MEAN
+#  endif
+#  ifndef NOMINMAX
+#    define NOMINMAX
+#  endif
+#  include <windows.h>  // Must be included before <direct.h>
+#  include <direct.h>
+#  include <winbase.h>
+#  undef interface  // This is also important because of reasons
+#else
+#  include <limits.h>
+#endif
+// clang-format on
 
+#include "flatbuffers/base.h"
 #include "flatbuffers/util.h"
 
+#include <sys/stat.h>
+#include <clocale>
+#include <fstream>
+
 namespace flatbuffers {
 
 bool FileExistsRaw(const char *name) {
@@ -88,6 +109,97 @@ FileExistsFunction SetFileExistsFunction(
   return previous_function;
 }
 
+bool SaveFile(const char *name, const char *buf, size_t len, bool binary) {
+  std::ofstream ofs(name, binary ? std::ofstream::binary : std::ofstream::out);
+  if (!ofs.is_open()) return false;
+  ofs.write(buf, len);
+  return !ofs.bad();
+}
+
+// We internally store paths in posix format ('/'). Paths supplied
+// by the user should go through PosixPath to ensure correct behavior
+// on Windows when paths are string-compared.
+
+static const char kPathSeparatorWindows = '\\';
+static const char *PathSeparatorSet = "\\/";  // Intentionally no ':'
+
+std::string StripExtension(const std::string &filepath) {
+  size_t i = filepath.find_last_of(".");
+  return i != std::string::npos ? filepath.substr(0, i) : filepath;
+}
+
+std::string GetExtension(const std::string &filepath) {
+  size_t i = filepath.find_last_of(".");
+  return i != std::string::npos ? filepath.substr(i + 1) : "";
+}
+
+std::string StripPath(const std::string &filepath) {
+  size_t i = filepath.find_last_of(PathSeparatorSet);
+  return i != std::string::npos ? filepath.substr(i + 1) : filepath;
+}
+
+std::string StripFileName(const std::string &filepath) {
+  size_t i = filepath.find_last_of(PathSeparatorSet);
+  return i != std::string::npos ? filepath.substr(0, i) : "";
+}
+
+std::string ConCatPathFileName(const std::string &path,
+                               const std::string &filename) {
+  std::string filepath = path;
+  if (filepath.length()) {
+    char &filepath_last_character = string_back(filepath);
+    if (filepath_last_character == kPathSeparatorWindows) {
+      filepath_last_character = kPathSeparator;
+    } else if (filepath_last_character != kPathSeparator) {
+      filepath += kPathSeparator;
+    }
+  }
+  filepath += filename;
+  // Ignore './' at the start of filepath.
+  if (filepath[0] == '.' && filepath[1] == kPathSeparator) {
+    filepath.erase(0, 2);
+  }
+  return filepath;
+}
+
+std::string PosixPath(const char *path) {
+  std::string p = path;
+  std::replace(p.begin(), p.end(), '\\', '/');
+  return p;
+}
+
+void EnsureDirExists(const std::string &filepath) {
+  auto parent = StripFileName(filepath);
+  if (parent.length()) EnsureDirExists(parent);
+    // clang-format off
+
+  #ifdef _WIN32
+    (void)_mkdir(filepath.c_str());
+  #else
+    mkdir(filepath.c_str(), S_IRWXU|S_IRGRP|S_IXGRP);
+  #endif
+  // clang-format on
+}
+
+std::string AbsolutePath(const std::string &filepath) {
+  // clang-format off
+
+  #ifdef FLATBUFFERS_NO_ABSOLUTE_PATH_RESOLUTION
+    return filepath;
+  #else
+    #ifdef _WIN32
+      char abs_path[MAX_PATH];
+      return GetFullPathNameA(filepath.c_str(), MAX_PATH, abs_path, nullptr)
+    #else
+      char abs_path[PATH_MAX];
+      return realpath(filepath.c_str(), abs_path)
+    #endif
+      ? abs_path
+      : filepath;
+  #endif // FLATBUFFERS_NO_ABSOLUTE_PATH_RESOLUTION
+  // clang-format on
+}
+
 // Locale-independent code.
 #if defined(FLATBUFFERS_LOCALE_INDEPENDENT) && \
     (FLATBUFFERS_LOCALE_INDEPENDENT > 0)
@@ -123,11 +235,10 @@ bool SetGlobalTestLocale(const char *locale_name, std::string *_value) {
   if (_value) *_value = std::string(the_locale);
   return true;
 }
-
-#ifdef _MSC_VER
-#  pragma warning(disable : 4996)  // _CRT_SECURE_NO_WARNINGS
-#endif
 bool ReadEnvironmentVariable(const char *var_name, std::string *_value) {
+  #ifdef _MSC_VER
+  __pragma(warning(disable : 4996)); // _CRT_SECURE_NO_WARNINGS
+  #endif
   auto env_str = std::getenv(var_name);
   if (!env_str) return false;
   if (_value) *_value = std::string(env_str);