diff --git a/include/exiv2/basicio.hpp b/include/exiv2/basicio.hpp
index a96a166528..d8d9a05320 100644
--- a/include/exiv2/basicio.hpp
+++ b/include/exiv2/basicio.hpp
@@ -3,8 +3,6 @@
 #ifndef EXIV2_BASICIO_HPP
 #define EXIV2_BASICIO_HPP
 
-#include "config.h"
-
 // *****************************************************************************
 #include "exiv2lib_export.h"
 
diff --git a/include/exiv2/bmffimage.hpp b/include/exiv2/bmffimage.hpp
index 849d728747..a5d8c0425c 100644
--- a/include/exiv2/bmffimage.hpp
+++ b/include/exiv2/bmffimage.hpp
@@ -3,8 +3,6 @@
 #ifndef EXIV2_BMFFIMAGE_HPP
 #define EXIV2_BMFFIMAGE_HPP
 
-#include "config.h"
-
 // *****************************************************************************
 #include "exiv2lib_export.h"
 
diff --git a/include/exiv2/exif.hpp b/include/exiv2/exif.hpp
index 480c3f2185..0c3fc781f5 100644
--- a/include/exiv2/exif.hpp
+++ b/include/exiv2/exif.hpp
@@ -13,8 +13,6 @@
 // *****************************************************************************
 #include "exiv2lib_export.h"
 
-#include "config.h"
-
 // included header files
 #include "config.h"
 #include "metadatum.hpp"
diff --git a/include/exiv2/image.hpp b/include/exiv2/image.hpp
index 00bfe40c6c..456523b86a 100644
--- a/include/exiv2/image.hpp
+++ b/include/exiv2/image.hpp
@@ -3,8 +3,6 @@
 #ifndef EXIV2_IMAGE_HPP
 #define EXIV2_IMAGE_HPP
 
-#include "config.h"
-
 // *****************************************************************************
 #include "exiv2lib_export.h"
 
diff --git a/src/bmffimage.cpp b/src/bmffimage.cpp
index dae309dff1..6d33be0234 100644
--- a/src/bmffimage.cpp
+++ b/src/bmffimage.cpp
@@ -10,7 +10,6 @@
 #include "futils.hpp"
 #include "image.hpp"
 #include "image_int.hpp"
-#include "safe_op.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
 #include "types.hpp"
@@ -18,6 +17,7 @@
 
 #ifdef EXV_HAVE_BROTLI
 #include <brotli/decode.h>  // for JXL brob
+#include "safe_op.hpp"
 #endif
 
 // + standard includes
diff --git a/src/bmpimage.cpp b/src/bmpimage.cpp
index c6681c9fa0..1b889ac2ec 100644
--- a/src/bmpimage.cpp
+++ b/src/bmpimage.cpp
@@ -7,6 +7,7 @@
 
 #include "bmpimage.hpp"
 #include "basicio.hpp"
+#include "config.h"
 #include "error.hpp"
 #include "futils.hpp"
 #include "image.hpp"
diff --git a/src/convert.cpp b/src/convert.cpp
index 3f4ed29dfa..1143a07db9 100644
--- a/src/convert.cpp
+++ b/src/convert.cpp
@@ -7,13 +7,11 @@
              20-May-08, vn:  added actual conversion logic
  */
 // *****************************************************************************
-#include "config.h"
-
 // included header files
 #include "convert.hpp"
+#include "config.h"
 #include "error.hpp"
 #include "exif.hpp"
-#include "futils.hpp"
 #include "image_int.hpp"
 #include "iptc.hpp"
 #include "properties.hpp"
@@ -25,6 +23,9 @@
 #include <functional>
 
 #ifdef EXV_HAVE_ICONV
+#ifndef SUPPRESS_WARNINGS
+#include "futils.hpp"
+#endif
 #include <iconv.h>
 #elif defined _WIN32
 #include <windows.h>
diff --git a/src/cr2header_int.cpp b/src/cr2header_int.cpp
index abb1cf6e45..b784defe81 100644
--- a/src/cr2header_int.cpp
+++ b/src/cr2header_int.cpp
@@ -2,11 +2,13 @@
 
 #include "cr2header_int.hpp"
 
+#include "tags.hpp"
 #include "tiffimage_int.hpp"
 #include "types.hpp"
 
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 
 namespace Exiv2::Internal {
 Cr2Header::Cr2Header(ByteOrder byteOrder) : TiffHeaderBase(42, 16, byteOrder, 0x00000010) {
diff --git a/src/crwimage.cpp b/src/crwimage.cpp
index a1acf6c7e5..a47b4f8a73 100644
--- a/src/crwimage.cpp
+++ b/src/crwimage.cpp
@@ -5,9 +5,8 @@
   History:   28-Aug-05, ahu: created
  */
 // included header files
-#include "config.h"
-
 #include "crwimage.hpp"
+#include "config.h"
 #include "crwimage_int.hpp"
 #include "error.hpp"
 #include "futils.hpp"
diff --git a/src/crwimage_int.cpp b/src/crwimage_int.cpp
index 4ca559b543..aadd1a362d 100644
--- a/src/crwimage_int.cpp
+++ b/src/crwimage_int.cpp
@@ -1,9 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
-
-#include "config.h"
-
-#include "canonmn_int.hpp"
 #include "crwimage_int.hpp"
+#include "canonmn_int.hpp"
+#include "config.h"
 #include "enforce.hpp"
 #include "error.hpp"
 #include "i18n.h"  // NLS support.
diff --git a/src/crwimage_int.hpp b/src/crwimage_int.hpp
index e7025cf2cd..5cd355bab0 100644
--- a/src/crwimage_int.hpp
+++ b/src/crwimage_int.hpp
@@ -5,7 +5,6 @@
 
 // *****************************************************************************
 // included header files
-#include "tags.hpp"
 #include "types.hpp"
 
 // + standard includes
@@ -18,6 +17,8 @@
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
+enum class IfdId : uint32_t;
+class ExifData;
 class Image;
 
 namespace Internal {
diff --git a/src/datasets.cpp b/src/datasets.cpp
index 3d257b2208..551d0ad4c0 100644
--- a/src/datasets.cpp
+++ b/src/datasets.cpp
@@ -9,9 +9,8 @@
 #include "datasets.hpp"
 #include "error.hpp"
 #include "i18n.h"  // NLS support.
-#include "types.hpp"
-
 #include "image_int.hpp"
+#include "types.hpp"
 
 #include <iomanip>
 
diff --git a/src/easyaccess.cpp b/src/easyaccess.cpp
index a6172b2395..bec58a9a79 100644
--- a/src/easyaccess.cpp
+++ b/src/easyaccess.cpp
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 // included header files
 #include "easyaccess.hpp"
+
 #include "utils.hpp"
 
 #include <sstream>
diff --git a/src/epsimage.cpp b/src/epsimage.cpp
index d139fc12bc..af55f9c88b 100644
--- a/src/epsimage.cpp
+++ b/src/epsimage.cpp
@@ -8,11 +8,11 @@
  */
 // *****************************************************************************
 // included header files
-#include "config.h"
+#include "epsimage.hpp"
 
 #include "basicio.hpp"
+#include "config.h"
 #include "enforce.hpp"
-#include "epsimage.hpp"
 #include "error.hpp"
 #include "futils.hpp"
 #include "image.hpp"
diff --git a/src/fujimn_int.cpp b/src/fujimn_int.cpp
index 7a3e25e671..e05d42f35d 100644
--- a/src/fujimn_int.cpp
+++ b/src/fujimn_int.cpp
@@ -10,6 +10,7 @@
 // included header files
 #include "fujimn_int.hpp"
 #include "i18n.h"  // NLS support.
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "types.hpp"
 
diff --git a/src/http.cpp b/src/http.cpp
index 6a93026e8a..486883f0a9 100644
--- a/src/http.cpp
+++ b/src/http.cpp
@@ -1,9 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include "http.hpp"
 #include "config.h"
-
 #include "futils.hpp"
-#include "http.hpp"
 
 #include <array>
 #include <cerrno>
diff --git a/src/image_int.cpp b/src/image_int.cpp
index 255015bf6b..6ae8f92189 100644
--- a/src/image_int.cpp
+++ b/src/image_int.cpp
@@ -1,7 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
 #include "image_int.hpp"
 
 #include <cstddef>
diff --git a/src/iptc.cpp b/src/iptc.cpp
index 6066cc2785..da1d0f5826 100644
--- a/src/iptc.cpp
+++ b/src/iptc.cpp
@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
 // included header files
 #include "iptc.hpp"
-
+#include "config.h"
 #include "datasets.hpp"
 #include "enforce.hpp"
 #include "error.hpp"
diff --git a/src/jpgimage.cpp b/src/jpgimage.cpp
index 5863d6bf97..723acff68a 100644
--- a/src/jpgimage.cpp
+++ b/src/jpgimage.cpp
@@ -1,17 +1,15 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 // included header files
+#include "jpgimage.hpp"
 #include "config.h"
-
 #include "enforce.hpp"
 #include "error.hpp"
 #include "futils.hpp"
 #include "helper_functions.hpp"
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
-#include "jpgimage.hpp"
 #include "photoshop.hpp"
-#include "safe_op.hpp"
 #include "tags_int.hpp"
 
 #include <array>
diff --git a/src/makernote_int.cpp b/src/makernote_int.cpp
index 84fdf0736e..bdb1ada678 100644
--- a/src/makernote_int.cpp
+++ b/src/makernote_int.cpp
@@ -5,9 +5,8 @@
   History:   11-Apr-06, ahu: created
  */
 // included header files
-#include "config.h"
-
 #include "makernote_int.hpp"
+#include "config.h"
 #include "safe_op.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
diff --git a/src/makernote_int.hpp b/src/makernote_int.hpp
index 6b948874e6..5bdfa46582 100644
--- a/src/makernote_int.hpp
+++ b/src/makernote_int.hpp
@@ -5,12 +5,14 @@
 
 // *****************************************************************************
 // included header files
-#include "tags.hpp"
+#include "types.hpp"
 
 #include <memory>
 
 // namespace extensions
-namespace Exiv2::Internal {
+namespace Exiv2 {
+enum class IfdId : uint32_t;
+namespace Internal {
 class IoWrapper;
 class TiffComponent;
 // *****************************************************************************
@@ -673,6 +675,7 @@ int nikonSelector(uint16_t tag, const byte* pData, size_t size, TiffComponent* p
  */
 DataBuf nikonCrypt(uint16_t tag, const byte* pData, size_t size, TiffComponent* pRoot);
 
-}  // namespace Exiv2::Internal
+}  // namespace Internal
+}  // namespace Exiv2
 
 #endif  // EXIV2_MAKERNOTE_INT_HPP
diff --git a/src/matroskavideo.cpp b/src/matroskavideo.cpp
index 3c74841ebf..7359130e98 100644
--- a/src/matroskavideo.cpp
+++ b/src/matroskavideo.cpp
@@ -19,14 +19,13 @@
  */
 // *****************************************************************************
 // included header files
-#include "config.h"
-
+#include "matroskavideo.hpp"
 #include "basicio.hpp"
+#include "config.h"
 #include "enforce.hpp"
 #include "error.hpp"
 #include "futils.hpp"
 #include "helper_functions.hpp"
-#include "matroskavideo.hpp"
 
 // + standard includes
 #include <cmath>
diff --git a/src/nikonmn_int.cpp b/src/nikonmn_int.cpp
index c8674e14ef..d4b5593416 100644
--- a/src/nikonmn_int.cpp
+++ b/src/nikonmn_int.cpp
@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
 // included header files
 #include "nikonmn_int.hpp"
-
+#include "config.h"
 #include "exif.hpp"
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
diff --git a/src/olympusmn_int.cpp b/src/olympusmn_int.cpp
index e03f262684..4329d53917 100644
--- a/src/olympusmn_int.cpp
+++ b/src/olympusmn_int.cpp
@@ -12,8 +12,6 @@
 #include "utils.hpp"
 #include "value.hpp"
 
-#include <array>
-
 // *****************************************************************************
 // class member definitions
 namespace Exiv2::Internal {
diff --git a/src/pgfimage.cpp b/src/pgfimage.cpp
index 1657ed4014..e54d3a78d7 100644
--- a/src/pgfimage.cpp
+++ b/src/pgfimage.cpp
@@ -11,7 +11,6 @@
 #include "image.hpp"
 
 #include <array>
-#include <bit>
 
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
diff --git a/src/pngchunk_int.cpp b/src/pngchunk_int.cpp
index 975fbb524c..3169438b20 100644
--- a/src/pngchunk_int.cpp
+++ b/src/pngchunk_int.cpp
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 // included header files
+#include "pngchunk_int.hpp"
 #include "config.h"
 
 #ifdef EXV_HAVE_LIBZ
@@ -14,7 +15,6 @@
 #include "image_int.hpp"
 #include "iptc.hpp"
 #include "photoshop.hpp"
-#include "pngchunk_int.hpp"
 #include "safe_op.hpp"
 #include "tiffimage.hpp"
 
diff --git a/src/pngchunk_int.hpp b/src/pngchunk_int.hpp
index 51e1ee50b0..432dec1dd2 100644
--- a/src/pngchunk_int.hpp
+++ b/src/pngchunk_int.hpp
@@ -5,11 +5,15 @@
 
 // *****************************************************************************
 // included header files
-#include "pngimage.hpp"
+#include "types.hpp"
 
 // *****************************************************************************
 // namespace extensions
-namespace Exiv2::Internal {
+namespace Exiv2 {
+struct DataBuf;
+class Image;
+class PngImage;
+namespace Internal {
 // *****************************************************************************
 // class definitions
 
@@ -136,6 +140,7 @@ class PngChunk {
 
 };  // class PngChunk
 
-}  // namespace Exiv2::Internal
+}  // namespace Internal
+}  // namespace Exiv2
 
 #endif  // #ifndef PNGCHUNK_INT_HPP_
diff --git a/src/properties.cpp b/src/properties.cpp
index b68d6eb601..29586672ea 100644
--- a/src/properties.cpp
+++ b/src/properties.cpp
@@ -1,13 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
 // included header files
 #include "properties.hpp"
-
+#include "config.h"
 #include "error.hpp"
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "types.hpp"
 #include "value.hpp"
diff --git a/src/quicktimevideo.cpp b/src/quicktimevideo.cpp
index 365472f68c..583f595937 100644
--- a/src/quicktimevideo.cpp
+++ b/src/quicktimevideo.cpp
@@ -19,16 +19,15 @@
  */
 // *****************************************************************************
 // included header files
-#include "config.h"
-
+#include "quicktimevideo.hpp"
 #include "basicio.hpp"
+#include "config.h"
 #include "enforce.hpp"
 #include "error.hpp"
 #include "futils.hpp"
 #include "helper_functions.hpp"
 #include "image_int.hpp"
 #include "properties.hpp"
-#include "quicktimevideo.hpp"
 #include "safe_op.hpp"
 #include "tags.hpp"
 #include "tags_int.hpp"
diff --git a/src/riffvideo.cpp b/src/riffvideo.cpp
index f90d2f09bf..e8b52f1c94 100644
--- a/src/riffvideo.cpp
+++ b/src/riffvideo.cpp
@@ -8,6 +8,7 @@
 
 // included header files
 #include "riffvideo.hpp"
+#include "config.h"
 #include "enforce.hpp"
 #include "error.hpp"
 #include "futils.hpp"
diff --git a/src/sonymn_int.hpp b/src/sonymn_int.hpp
index 6c2621b172..d2e6be1210 100644
--- a/src/sonymn_int.hpp
+++ b/src/sonymn_int.hpp
@@ -9,7 +9,11 @@
 
 // *****************************************************************************
 // namespace extensions
-namespace Exiv2::Internal {
+namespace Exiv2 {
+class ExifData;
+class Value;
+struct TagInfo;
+namespace Internal {
 // *****************************************************************************
 // class definitions
 
@@ -125,6 +129,7 @@ class SonyMakerNote {
 DataBuf sonyTagDecipher(uint16_t, const byte*, size_t, TiffComponent*);
 DataBuf sonyTagEncipher(uint16_t, const byte*, size_t, TiffComponent*);
 
-}  // namespace Exiv2::Internal
+}  // namespace Internal
+}  // namespace Exiv2
 
 #endif  // #ifndef SONYMN_INT_HPP_
diff --git a/src/tags_int.cpp b/src/tags_int.cpp
index 021bca91d2..1cad89d8e6 100644
--- a/src/tags_int.cpp
+++ b/src/tags_int.cpp
@@ -6,6 +6,7 @@
 #include "convert.hpp"
 #include "enforce.hpp"
 #include "i18n.h"  // NLS support.
+#include "tags.hpp"
 
 #include "canonmn_int.hpp"
 #include "casiomn_int.hpp"
diff --git a/src/tags_int.hpp b/src/tags_int.hpp
index 36ac87b59d..02f9ddc849 100644
--- a/src/tags_int.hpp
+++ b/src/tags_int.hpp
@@ -5,7 +5,8 @@
 
 // *****************************************************************************
 // included header files
-#include "tags.hpp"
+#include "types.hpp"
+#include "value.hpp"
 
 #include "i18n.h"
 
@@ -13,8 +14,11 @@
 // namespace extensions
 
 namespace Exiv2 {
+enum class IfdId : uint32_t;
+enum class SectionId;
 class ExifData;
-class Value;
+struct GroupInfo;
+struct TagInfo;
 
 namespace Internal {
 // *****************************************************************************
diff --git a/src/tiffcomposite_int.cpp b/src/tiffcomposite_int.cpp
index 3ab2d659cb..90150bfeb1 100644
--- a/src/tiffcomposite_int.cpp
+++ b/src/tiffcomposite_int.cpp
@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 // included header files
-#include "config.h"
-
 #include "tiffcomposite_int.hpp"
-
 #include "basicio.hpp"
+#include "config.h"
 #include "enforce.hpp"
 #include "error.hpp"
 #include "image_int.hpp"
@@ -95,6 +93,25 @@ TiffBinaryArray::TiffBinaryArray(uint16_t tag, IfdId group, const ArraySet* arra
   // We'll figure out the correct cfg later
 }
 
+TiffBinaryArray::TiffBinaryArray(const TiffBinaryArray& rhs) :
+    TiffEntryBase(rhs),
+    cfgSelFct_(rhs.cfgSelFct_),
+    arraySet_(rhs.arraySet_),
+    arrayCfg_(rhs.arrayCfg_),
+    arrayDef_(rhs.arrayDef_),
+    defSize_(rhs.defSize_),
+    setSize_(rhs.setSize_),
+    origData_(rhs.origData_),
+    origSize_(rhs.origSize_),
+    pRoot_(rhs.pRoot_) {
+}
+
+TiffEntryBase::TiffEntryBase(uint16_t tag, IfdId group, TiffType tiffType) :
+    TiffComponent(tag, group), tiffType_(tiffType) {
+}
+
+TiffEntryBase::~TiffEntryBase() = default;
+
 TiffEntryBase::TiffEntryBase(const TiffEntryBase& rhs) :
     TiffComponent(rhs),
     tiffType_(rhs.tiffType_),
@@ -113,17 +130,18 @@ TiffDirectory::TiffDirectory(const TiffDirectory& rhs) : TiffComponent(rhs), has
 TiffSubIfd::TiffSubIfd(const TiffSubIfd& rhs) : TiffEntryBase(rhs), newGroup_(rhs.newGroup_) {
 }
 
-TiffBinaryArray::TiffBinaryArray(const TiffBinaryArray& rhs) :
-    TiffEntryBase(rhs),
-    cfgSelFct_(rhs.cfgSelFct_),
-    arraySet_(rhs.arraySet_),
-    arrayCfg_(rhs.arrayCfg_),
-    arrayDef_(rhs.arrayDef_),
-    defSize_(rhs.defSize_),
-    setSize_(rhs.setSize_),
-    origData_(rhs.origData_),
-    origSize_(rhs.origSize_),
-    pRoot_(rhs.pRoot_) {
+TiffDataEntryBase::TiffDataEntryBase(uint16_t tag, IfdId group, uint16_t szTag, IfdId szGroup) :
+    TiffEntryBase(tag, group), szTag_(szTag), szGroup_(szGroup) {
+}
+
+TiffDataEntryBase::~TiffDataEntryBase() = default;
+
+TiffSizeEntry::TiffSizeEntry(uint16_t tag, IfdId group, uint16_t dtTag, IfdId dtGroup) :
+    TiffEntryBase(tag, group), dtTag_(dtTag), dtGroup_(dtGroup) {
+}
+
+TiffMnEntry::TiffMnEntry(uint16_t tag, IfdId group, IfdId mnGroup) :
+    TiffEntryBase(tag, group, ttUndefined), mnGroup_(mnGroup) {
 }
 
 TiffComponent::UniquePtr TiffComponent::clone() const {
diff --git a/src/tiffcomposite_int.hpp b/src/tiffcomposite_int.hpp
index 420d1076ca..7bbd3d3aff 100644
--- a/src/tiffcomposite_int.hpp
+++ b/src/tiffcomposite_int.hpp
@@ -13,6 +13,7 @@
 // namespace extensions
 namespace Exiv2 {
 class BasicIo;
+class Value;
 
 namespace Internal {
 // *****************************************************************************
@@ -383,12 +384,10 @@ class TiffEntryBase : public TiffComponent {
   //! @name Creators
   //@{
   //! Default constructor.
-  constexpr TiffEntryBase(uint16_t tag, IfdId group, TiffType tiffType = ttUndefined) :
-      TiffComponent(tag, group), tiffType_(tiffType) {
-  }
+  TiffEntryBase(uint16_t tag, IfdId group, TiffType tiffType = ttUndefined);
 
   //! Virtual destructor.
-  ~TiffEntryBase() override = default;
+  ~TiffEntryBase() override;
   //@}
 
   //! @name NOT implemented
@@ -593,9 +592,7 @@ class TiffDataEntryBase : public TiffEntryBase {
   //! @name Creators
   //@{
   //! Constructor
-  constexpr TiffDataEntryBase(uint16_t tag, IfdId group, uint16_t szTag, IfdId szGroup) :
-      TiffEntryBase(tag, group), szTag_(szTag), szGroup_(szGroup) {
-  }
+  TiffDataEntryBase(uint16_t tag, IfdId group, uint16_t szTag, IfdId szGroup);
   //@}
 
   ~TiffDataEntryBase() override;
@@ -777,10 +774,7 @@ class TiffSizeEntry : public TiffEntryBase {
   //! @name Creators
   //@{
   //! Constructor
-  constexpr TiffSizeEntry(uint16_t tag, IfdId group, uint16_t dtTag, IfdId dtGroup) :
-      TiffEntryBase(tag, group), dtTag_(dtTag), dtGroup_(dtGroup) {
-  }
-
+  TiffSizeEntry(uint16_t tag, IfdId group, uint16_t dtTag, IfdId dtGroup);
   //@}
 
   //! @name Accessors
@@ -1012,9 +1006,7 @@ class TiffMnEntry : public TiffEntryBase {
   //! @name Creators
   //@{
   //! Default constructor
-  constexpr TiffMnEntry(uint16_t tag, IfdId group, IfdId mnGroup) :
-      TiffEntryBase(tag, group, ttUndefined), mnGroup_(mnGroup) {
-  }
+  TiffMnEntry(uint16_t tag, IfdId group, IfdId mnGroup);
 
  protected:
   //! @name Protected Manipulators
diff --git a/src/tifffwd_int.hpp b/src/tifffwd_int.hpp
index c14f756a48..a8083c8fe3 100644
--- a/src/tifffwd_int.hpp
+++ b/src/tifffwd_int.hpp
@@ -5,7 +5,7 @@
 
 // *****************************************************************************
 // included header files
-#include "tags.hpp"
+#include "types.hpp"
 
 // + standard includes
 #include <memory>
@@ -16,6 +16,7 @@
 // *****************************************************************************
 // Exiv2 namespace extensions
 namespace Exiv2 {
+enum class IfdId : uint32_t;
 class Exifdatum;
 
 namespace Internal {
diff --git a/src/tiffimage_int.cpp b/src/tiffimage_int.cpp
index 60bc023959..e472d991e1 100644
--- a/src/tiffimage_int.cpp
+++ b/src/tiffimage_int.cpp
@@ -1,15 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
+#include "tiffimage_int.hpp"
 #include "basicio.hpp"
+#include "config.h"
 #include "error.hpp"
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
 #include "makernote_int.hpp"
 #include "sonymn_int.hpp"
 #include "tiffcomposite_int.hpp"
-#include "tiffimage_int.hpp"
 #include "tiffvisitor_int.hpp"
 
 #ifdef EXIV2_DEBUG_MESSAGES
@@ -25,6 +24,9 @@
 #define EXV_COMPLEX_BINARY_ARRAY(arraySet, cfgSelFct) &newTiffBinaryArray2<std::size(arraySet), arraySet, cfgSelFct>
 
 namespace Exiv2::Internal {
+bool FindExifdatum::operator()(const Exiv2::Exifdatum& md) const {
+  return ifdId_ == md.ifdId();
+}
 //! Constant for non-encrypted binary arrays
 constexpr CryptFct notEncrypted = nullptr;
 
diff --git a/src/tiffimage_int.hpp b/src/tiffimage_int.hpp
index c7586dbfb6..f4bf05e508 100644
--- a/src/tiffimage_int.hpp
+++ b/src/tiffimage_int.hpp
@@ -5,15 +5,16 @@
 
 // *****************************************************************************
 // included header files
-#include "exif.hpp"
 #include "tifffwd_int.hpp"
 
+#include <map>
 #include <unordered_map>
 
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
 class BasicIo;
+class ExifData;
 class IptcData;
 class XmpData;
 
@@ -348,9 +349,7 @@ class FindExifdatum {
   explicit FindExifdatum(Exiv2::IfdId ifdId) : ifdId_(ifdId) {
   }
   //! Returns true if IFD id matches.
-  bool operator()(const Exiv2::Exifdatum& md) const {
-    return ifdId_ == md.ifdId();
-  }
+  bool operator()(const Exiv2::Exifdatum& md) const;
 
  private:
   Exiv2::IfdId ifdId_;
diff --git a/src/tiffvisitor_int.cpp b/src/tiffvisitor_int.cpp
index 9f3b769917..2469f2e97c 100644
--- a/src/tiffvisitor_int.cpp
+++ b/src/tiffvisitor_int.cpp
@@ -1,10 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
 // included header files
 #include "tiffvisitor_int.hpp"  // see bug #487
 
+#include "config.h"
 #include "enforce.hpp"
 #include "exif.hpp"
 #include "image_int.hpp"
@@ -344,8 +343,6 @@ static const TagInfo* findTag(const TagInfo* pList, uint16_t tag) {
   return pList->tag_ != 0xffff ? pList : nullptr;
 }
 
-TiffDataEntryBase::~TiffDataEntryBase() = default;
-
 void TiffDecoder::decodeCanonAFInfo(const TiffEntryBase* object) {
   // report Exif.Canon.AFInfo as usual
   TiffDecoder::decodeStdTiffEntry(object);
diff --git a/src/types.cpp b/src/types.cpp
index e40430e92f..cb110c26bb 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -1,13 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
 // included header files
 #include "types.hpp"
-
+#include "config.h"
 #include "enforce.hpp"
-#include "futils.hpp"
-#include "i18n.h"  // for _exvGettext
 #include "utils.hpp"
 
 // + standard includes
@@ -18,10 +14,12 @@
 #include <iomanip>
 #include <numeric>
 
+#ifdef EXV_ENABLE_NLS
+#include "futils.hpp"
+
 #include <filesystem>
 namespace fs = std::filesystem;
 
-#ifdef EXV_ENABLE_NLS
 #include <libintl.h>
 #endif
 
diff --git a/src/value.cpp b/src/value.cpp
index 2c01fee9b4..db0ae1603c 100644
--- a/src/value.cpp
+++ b/src/value.cpp
@@ -1,16 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "config.h"
-
 // included header files
 #include "value.hpp"
-
+#include "config.h"
 #include "convert.hpp"
 #include "enforce.hpp"
 #include "error.hpp"
-#include "types.hpp"
-
 #include "image_int.hpp"
+#include "types.hpp"
 
 // + standard includes
 #include <iterator>
diff --git a/src/version.cpp b/src/version.cpp
index 42a5303724..e0b888a503 100644
--- a/src/version.cpp
+++ b/src/version.cpp
@@ -1,25 +1,23 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include "version.hpp"
 #include "config.h"
-
-#ifdef EXV_USE_CURL
-#include <curl/curl.h>
-#endif
-
 #include "futils.hpp"
 #include "makernote_int.hpp"
-#include "version.hpp"
+
+// + standard includes
+#include <fstream>
+#include <iomanip>
+#include <set>
 
 // Adobe XMP Toolkit
 #ifdef EXV_HAVE_XMP_TOOLKIT
 #include "properties.hpp"
-#include "xmp_exiv2.hpp"
 #endif
 
-// + standard includes
-#include <fstream>
-#include <iomanip>
-#include <set>
+#ifdef EXV_USE_CURL
+#include <curl/curl.h>
+#endif
 
 // #1147
 #ifndef _WIN32
diff --git a/src/xmp.cpp b/src/xmp.cpp
index 1a92dc9ac7..79859ca824 100644
--- a/src/xmp.cpp
+++ b/src/xmp.cpp
@@ -6,7 +6,6 @@
 #include "error.hpp"
 #include "properties.hpp"
 #include "types.hpp"
-#include "utils.hpp"
 #include "value.hpp"
 #include "xmp_exiv2.hpp"
 
@@ -17,6 +16,7 @@
 // Adobe XMP Toolkit
 #ifdef EXV_HAVE_XMP_TOOLKIT
 #include <expat.h>
+#include "utils.hpp"
 #define TXMP_STRING_TYPE std::string
 #ifdef EXV_ADOBE_XMPSDK
 #include <XMP.hpp>