diff --git a/include/exiv2/asfvideo.hpp b/include/exiv2/asfvideo.hpp
index a8b3824a1f..3719c7e92d 100644
--- a/include/exiv2/asfvideo.hpp
+++ b/include/exiv2/asfvideo.hpp
@@ -39,7 +39,7 @@ class EXIV2API AsfVideo : public Image {
         method to get a temporary reference.
   */
 
-  explicit AsfVideo(BasicIo::UniquePtr io);
+  explicit AsfVideo(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -99,7 +99,7 @@ class EXIV2API AsfVideo : public Image {
     uint64_t remaining_size_{};
 
    public:
-    explicit HeaderReader(const BasicIo::UniquePtr& io);
+    explicit HeaderReader(const std::unique_ptr<BasicIo>& io);
 
     [[nodiscard]] uint64_t getSize() const {
       return size_;
@@ -178,7 +178,7 @@ class EXIV2API AsfVideo : public Image {
       Caller owns the returned object and the auto-pointer ensures that
       it will be deleted.
  */
-EXIV2API Image::UniquePtr newAsfInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newAsfInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a Windows Asf Video.
 EXIV2API bool isAsfType(BasicIo& iIo, bool advance);
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..f00cb54505 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"
 
@@ -57,7 +55,7 @@ class EXIV2API BmffImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  BmffImage(BasicIo::UniquePtr io, bool create, size_t max_box_depth = 1000);
+  BmffImage(std::unique_ptr<BasicIo> io, bool create, size_t max_box_depth = 1000);
   //@}
 
   //@{
@@ -170,7 +168,7 @@ class EXIV2API BmffImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newBmffInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newBmffInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a BMFF image.
 EXIV2API bool isBmffType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/bmpimage.hpp b/include/exiv2/bmpimage.hpp
index a607f94afd..5501a2c3f0 100644
--- a/include/exiv2/bmpimage.hpp
+++ b/include/exiv2/bmpimage.hpp
@@ -40,7 +40,7 @@ class EXIV2API BmpImage : public Image {
         instance after it is passed to this method.  Use the Image::io()
         method to get a temporary reference.
    */
-  explicit BmpImage(BasicIo::UniquePtr io);
+  explicit BmpImage(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -76,7 +76,7 @@ class EXIV2API BmpImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newBmpInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newBmpInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a Windows Bitmap image.
 EXIV2API bool isBmpType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/cr2image.hpp b/include/exiv2/cr2image.hpp
index 4a3151dd88..7ab762f628 100644
--- a/include/exiv2/cr2image.hpp
+++ b/include/exiv2/cr2image.hpp
@@ -43,7 +43,7 @@ class EXIV2API Cr2Image : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  Cr2Image(BasicIo::UniquePtr io, bool create);
+  Cr2Image(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -104,7 +104,7 @@ class EXIV2API Cr2Parser {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newCr2Instance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newCr2Instance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a CR2 image.
 EXIV2API bool isCr2Type(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/crwimage.hpp b/include/exiv2/crwimage.hpp
index 2d3c26352c..16d541cddc 100644
--- a/include/exiv2/crwimage.hpp
+++ b/include/exiv2/crwimage.hpp
@@ -52,7 +52,7 @@ class EXIV2API CrwImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  CrwImage(BasicIo::UniquePtr io, bool create);
+  CrwImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -123,7 +123,7 @@ class EXIV2API CrwParser {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newCrwInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newCrwInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a CRW image.
 EXIV2API bool isCrwType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/datasets.hpp b/include/exiv2/datasets.hpp
index ce959962ac..f103597f4c 100644
--- a/include/exiv2/datasets.hpp
+++ b/include/exiv2/datasets.hpp
@@ -13,6 +13,8 @@
 // included header files
 #include "metadatum.hpp"
 
+#include <map>
+
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
diff --git a/include/exiv2/epsimage.hpp b/include/exiv2/epsimage.hpp
index 27fb2db723..032778b089 100644
--- a/include/exiv2/epsimage.hpp
+++ b/include/exiv2/epsimage.hpp
@@ -54,7 +54,7 @@ class EXIV2API EpsImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  EpsImage(BasicIo::UniquePtr io, bool create);
+  EpsImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -84,7 +84,7 @@ class EXIV2API EpsImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newEpsInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newEpsInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a EPS image.
 EXIV2API bool isEpsType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/exif.hpp b/include/exiv2/exif.hpp
index 480c3f2185..ea9f4d2a13 100644
--- a/include/exiv2/exif.hpp
+++ b/include/exiv2/exif.hpp
@@ -13,12 +13,9 @@
 // *****************************************************************************
 #include "exiv2lib_export.h"
 
-#include "config.h"
-
 // included header files
 #include "config.h"
 #include "metadatum.hpp"
-#include "tags.hpp"
 
 // + standard includes
 #include <list>
@@ -33,6 +30,8 @@ namespace Exiv2 {
 // *****************************************************************************
 // class declarations
 class ExifData;
+class ExifKey;
+enum class IfdId : uint32_t;
 
 // *****************************************************************************
 // class definitions
@@ -63,7 +62,7 @@ class EXIV2API Exifdatum : public Metadatum {
   //! Copy constructor
   Exifdatum(const Exifdatum& rhs);
   //! Destructor
-  ~Exifdatum() override = default;
+  ~Exifdatum() override;
   //@}
 
   //! @name Manipulators
@@ -180,7 +179,7 @@ class EXIV2API Exifdatum : public Metadatum {
   [[nodiscard]] int64_t toInt64(size_t n = 0) const override;
   [[nodiscard]] float toFloat(size_t n = 0) const override;
   [[nodiscard]] Rational toRational(size_t n = 0) const override;
-  [[nodiscard]] Value::UniquePtr getValue() const override;
+  [[nodiscard]] std::unique_ptr<Value> getValue() const override;
   [[nodiscard]] const Value& value() const override;
   //! Return the size of the data area.
   [[nodiscard]] size_t sizeDataArea() const;
@@ -201,8 +200,8 @@ class EXIV2API Exifdatum : public Metadatum {
 
  private:
   // DATA
-  ExifKey::UniquePtr key_;  //!< Key
-  Value::UniquePtr value_;  //!< Value
+  std::unique_ptr<ExifKey> key_;  //!< Key
+  std::unique_ptr<Value> value_;  //!< Value
 
 };  // class Exifdatum
 
diff --git a/include/exiv2/gifimage.hpp b/include/exiv2/gifimage.hpp
index 443c256d2e..704e50172c 100644
--- a/include/exiv2/gifimage.hpp
+++ b/include/exiv2/gifimage.hpp
@@ -35,7 +35,7 @@ class EXIV2API GifImage : public Image {
         instance after it is passed to this method.  Use the Image::io()
         method to get a temporary reference.
    */
-  explicit GifImage(BasicIo::UniquePtr io);
+  explicit GifImage(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -80,7 +80,7 @@ class EXIV2API GifImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newGifInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newGifInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a GIF image.
 EXIV2API bool isGifType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/image.hpp b/include/exiv2/image.hpp
index 00bfe40c6c..44bfe2e4a0 100644
--- a/include/exiv2/image.hpp
+++ b/include/exiv2/image.hpp
@@ -3,15 +3,12 @@
 #ifndef EXIV2_IMAGE_HPP
 #define EXIV2_IMAGE_HPP
 
-#include "config.h"
-
 // *****************************************************************************
 #include "exiv2lib_export.h"
 
 // included header files
 #include "config.h"
 
-#include "basicio.hpp"
 #include "exif.hpp"
 #include "image_types.hpp"
 #include "iptc.hpp"
@@ -20,6 +17,7 @@
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
+class BasicIo;
 // *****************************************************************************
 // class definitions
 
@@ -63,9 +61,9 @@ class EXIV2API Image {
         metadata types and an auto-pointer that owns an IO instance.
         See subclass constructor doc.
    */
-  Image(ImageType type, uint16_t supportedMetadata, BasicIo::UniquePtr io);
+  Image(ImageType type, uint16_t supportedMetadata, std::unique_ptr<BasicIo> io);
   //! Virtual Destructor
-  virtual ~Image() = default;
+  virtual ~Image();
   //@}
 
   //! @name Manipulators
@@ -475,7 +473,7 @@ class EXIV2API Image {
 
  protected:
   // DATA
-  BasicIo::UniquePtr io_;             //!< Image data IO pointer
+  std::unique_ptr<BasicIo> io_;       //!< Image data IO pointer
   ExifData exifData_;                 //!< Exif data container
   IptcData iptcData_;                 //!< IPTC data container
   XmpData xmpData_;                   //!< XMP data container
@@ -509,7 +507,7 @@ class EXIV2API Image {
 };  // class Image
 
 //! Type for function pointer that creates new Image instances
-using NewInstanceFct = Image::UniquePtr (*)(BasicIo::UniquePtr io, bool create);
+using NewInstanceFct = Image::UniquePtr (*)(std::unique_ptr<BasicIo> io, bool create);
 //! Type for function pointer that checks image types
 using IsThisTypeFct = bool (*)(BasicIo& iIo, bool advance);
 
@@ -536,9 +534,9 @@ class EXIV2API ImageFactory {
     @throw Error If the file is not found or it is unable to connect to the server to
           read the remote file.
    */
-  static BasicIo::UniquePtr createIo(const std::string& path, bool useCurl = true);
+  static std::unique_ptr<BasicIo> createIo(const std::string& path, bool useCurl = true);
 #ifdef _WIN32
-  static BasicIo::UniquePtr createIo(const std::wstring& path);
+  static std::unique_ptr<BasicIo> createIo(const std::wstring& path);
 #endif
   /*!
     @brief Create an Image subclass of the appropriate type by reading
@@ -586,7 +584,7 @@ class EXIV2API ImageFactory {
         determined, the pointer is 0.
     @throw Error If opening the BasicIo fails
    */
-  static Image::UniquePtr open(BasicIo::UniquePtr io);
+  static Image::UniquePtr open(std::unique_ptr<BasicIo> io);
   /*!
     @brief Create an Image subclass of the requested type by creating a
         new image file. If the file already exists, it will be overwritten.
@@ -622,7 +620,7 @@ class EXIV2API ImageFactory {
         type. If the image type is not supported, the pointer is 0.
    */
 
-  static Image::UniquePtr create(ImageType type, BasicIo::UniquePtr io);
+  static Image::UniquePtr create(ImageType type, std::unique_ptr<BasicIo> io);
   /*!
     @brief Returns the image type of the provided file.
     @param path %Image file. The contents of the file are tested to
diff --git a/include/exiv2/iptc.hpp b/include/exiv2/iptc.hpp
index 8202325521..350864aae2 100644
--- a/include/exiv2/iptc.hpp
+++ b/include/exiv2/iptc.hpp
@@ -50,7 +50,7 @@ class EXIV2API Iptcdatum : public Metadatum {
   //! Copy constructor
   Iptcdatum(const Iptcdatum& rhs);
   //! Destructor
-  ~Iptcdatum() override = default;
+  ~Iptcdatum() override;
   //@}
 
   //! @name Manipulators
@@ -127,14 +127,14 @@ class EXIV2API Iptcdatum : public Metadatum {
   [[nodiscard]] int64_t toInt64(size_t n = 0) const override;
   [[nodiscard]] float toFloat(size_t n = 0) const override;
   [[nodiscard]] Rational toRational(size_t n = 0) const override;
-  [[nodiscard]] Value::UniquePtr getValue() const override;
+  [[nodiscard]] std::unique_ptr<Value> getValue() const override;
   [[nodiscard]] const Value& value() const override;
   //@}
 
  private:
   // DATA
-  IptcKey::UniquePtr key_;  //!< Key
-  Value::UniquePtr value_;  //!< Value
+  IptcKey::UniquePtr key_;        //!< Key
+  std::unique_ptr<Value> value_;  //!< Value
 
 };  // class Iptcdatum
 
diff --git a/include/exiv2/jp2image.hpp b/include/exiv2/jp2image.hpp
index 6ee14ec933..f559eb1351 100644
--- a/include/exiv2/jp2image.hpp
+++ b/include/exiv2/jp2image.hpp
@@ -36,7 +36,7 @@ class EXIV2API Jp2Image : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  Jp2Image(BasicIo::UniquePtr io, bool create);
+  Jp2Image(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -97,7 +97,7 @@ class EXIV2API Jp2Image : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newJp2Instance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newJp2Instance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a JPEG-2000 image.
 EXIV2API bool isJp2Type(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/jpgimage.hpp b/include/exiv2/jpgimage.hpp
index 3278e6f4bb..eaab3dd6d8 100644
--- a/include/exiv2/jpgimage.hpp
+++ b/include/exiv2/jpgimage.hpp
@@ -6,12 +6,12 @@
 #include "exiv2lib_export.h"
 
 // included header files
-#include "error.hpp"
 #include "image.hpp"
 
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
+enum class ErrorCode;
 // *****************************************************************************
 // class definitions
 
@@ -48,7 +48,7 @@ class EXIV2API JpegBase : public Image {
         valid image of the calling subclass.
     @param dataSize Size of initData in bytes.
    */
-  JpegBase(ImageType type, BasicIo::UniquePtr io, bool create, const byte initData[], size_t dataSize);
+  JpegBase(ImageType type, std::unique_ptr<BasicIo> io, bool create, const byte initData[], size_t dataSize);
   //@}
 
   //! @name Accessors
@@ -151,7 +151,7 @@ class EXIV2API JpegImage : public JpegBase {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  JpegImage(BasicIo::UniquePtr io, bool create);
+  JpegImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
   //! @name Accessors
   //@{
@@ -215,7 +215,7 @@ class EXIV2API ExvImage : public JpegBase {
     @param create Specifies if an existing image should be read (false)
            or if a new file should be created (true).
    */
-  ExvImage(BasicIo::UniquePtr io, bool create);
+  ExvImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
   //! @name Accessors
   //@{
@@ -249,7 +249,7 @@ class EXIV2API ExvImage : public JpegBase {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newJpegInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newJpegInstance(std::unique_ptr<BasicIo> io, bool create);
 //! Check if the file iIo is a JPEG image.
 EXIV2API bool isJpegType(BasicIo& iIo, bool advance);
 /*!
@@ -257,7 +257,7 @@ EXIV2API bool isJpegType(BasicIo& iIo, bool advance);
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newExvInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newExvInstance(std::unique_ptr<BasicIo> io, bool create);
 //! Check if the file iIo is an EXV file
 EXIV2API bool isExvType(BasicIo& iIo, bool advance);
 
diff --git a/include/exiv2/matroskavideo.hpp b/include/exiv2/matroskavideo.hpp
index 1101bafa80..9b0ed37528 100644
--- a/include/exiv2/matroskavideo.hpp
+++ b/include/exiv2/matroskavideo.hpp
@@ -112,7 +112,7 @@ class EXIV2API MatroskaVideo : public Image {
         instance after it is passed to this method. Use the Image::io()
         method to get a temporary reference.
    */
-  explicit MatroskaVideo(BasicIo::UniquePtr io);
+  explicit MatroskaVideo(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -180,7 +180,7 @@ class EXIV2API MatroskaVideo : public Image {
       Caller owns the returned object and the auto-pointer ensures that
       it will be deleted.
  */
-EXIV2API Image::UniquePtr newMkvInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newMkvInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a Matroska Video.
 EXIV2API bool isMkvType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/metadatum.hpp b/include/exiv2/metadatum.hpp
index 5bc3cdf2d1..db8f672523 100644
--- a/include/exiv2/metadatum.hpp
+++ b/include/exiv2/metadatum.hpp
@@ -7,7 +7,10 @@
 #include "exiv2lib_export.h"
 
 // included header files
-#include "value.hpp"
+#include "types.hpp"
+
+#include <cstdint>
+#include <memory>
 
 // *****************************************************************************
 // namespace extensions
@@ -15,6 +18,7 @@ namespace Exiv2 {
 // *****************************************************************************
 // class declarations
 class ExifData;
+class Value;
 
 // *****************************************************************************
 // class definitions
@@ -236,7 +240,7 @@ class EXIV2API Metadatum {
     @return An auto-pointer containing a pointer to a copy (clone) of the
             value, 0 if the value is not set.
    */
-  [[nodiscard]] virtual Value::UniquePtr getValue() const = 0;
+  [[nodiscard]] virtual std::unique_ptr<Value> getValue() const = 0;
   /*!
     @brief Return a constant reference to the value.
 
diff --git a/include/exiv2/mrwimage.hpp b/include/exiv2/mrwimage.hpp
index 589eba43a7..06d078635a 100644
--- a/include/exiv2/mrwimage.hpp
+++ b/include/exiv2/mrwimage.hpp
@@ -38,7 +38,7 @@ class EXIV2API MrwImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  MrwImage(BasicIo::UniquePtr io, bool create);
+  MrwImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -84,7 +84,7 @@ class EXIV2API MrwImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newMrwInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newMrwInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a MRW image.
 EXIV2API bool isMrwType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/orfimage.hpp b/include/exiv2/orfimage.hpp
index 9a4f02ba16..3a6aaea622 100644
--- a/include/exiv2/orfimage.hpp
+++ b/include/exiv2/orfimage.hpp
@@ -38,7 +38,7 @@ class EXIV2API OrfImage : public TiffImage {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  OrfImage(BasicIo::UniquePtr io, bool create);
+  OrfImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -92,7 +92,7 @@ class EXIV2API OrfParser {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newOrfInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newOrfInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is an ORF image.
 EXIV2API bool isOrfType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/pgfimage.hpp b/include/exiv2/pgfimage.hpp
index c6d9137820..e6b5d8cc65 100644
--- a/include/exiv2/pgfimage.hpp
+++ b/include/exiv2/pgfimage.hpp
@@ -38,7 +38,7 @@ class EXIV2API PgfImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  PgfImage(BasicIo::UniquePtr io, bool create);
+  PgfImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -84,7 +84,7 @@ class EXIV2API PgfImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newPgfInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newPgfInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a PGF image.
 EXIV2API bool isPgfType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/pngimage.hpp b/include/exiv2/pngimage.hpp
index cdfb8c04f0..536d8af4b0 100644
--- a/include/exiv2/pngimage.hpp
+++ b/include/exiv2/pngimage.hpp
@@ -38,7 +38,7 @@ class EXIV2API PngImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  PngImage(BasicIo::UniquePtr io, bool create);
+  PngImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -85,7 +85,7 @@ class EXIV2API PngImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newPngInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newPngInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a PNG image.
 EXIV2API bool isPngType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/preview.hpp b/include/exiv2/preview.hpp
index c9c0b9c79e..46f910d0a6 100644
--- a/include/exiv2/preview.hpp
+++ b/include/exiv2/preview.hpp
@@ -8,11 +8,16 @@
 // *****************************************************************************
 #include "exiv2lib_export.h"
 
-#include "image.hpp"
+#include "types.hpp"
+
+#include <string>
+#include <vector>
 
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
+class Image;
+struct DataBuf;
 // *****************************************************************************
 // class definitions
 
diff --git a/include/exiv2/psdimage.hpp b/include/exiv2/psdimage.hpp
index a603cc9aa2..2d218f026b 100644
--- a/include/exiv2/psdimage.hpp
+++ b/include/exiv2/psdimage.hpp
@@ -34,7 +34,7 @@ class EXIV2API PsdImage : public Image {
         instance after it is passed to this method.  Use the Image::io()
         method to get a temporary reference.
    */
-  explicit PsdImage(BasicIo::UniquePtr io);
+  explicit PsdImage(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -96,7 +96,7 @@ class EXIV2API PsdImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newPsdInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newPsdInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a Photoshop image.
 EXIV2API bool isPsdType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/quicktimevideo.hpp b/include/exiv2/quicktimevideo.hpp
index fcd798aa81..c946068ad6 100644
--- a/include/exiv2/quicktimevideo.hpp
+++ b/include/exiv2/quicktimevideo.hpp
@@ -51,7 +51,7 @@ class EXIV2API QuickTimeVideo : public Image {
         instance after it is passed to this method. Use the Image::io()
         method to get a temporary reference.
    */
-  explicit QuickTimeVideo(BasicIo::UniquePtr io, size_t max_recursion_depth = 1000);
+  explicit QuickTimeVideo(std::unique_ptr<BasicIo> io, size_t max_recursion_depth = 1000);
   //@}
 
   //! @name Manipulators
@@ -216,7 +216,7 @@ class EXIV2API QuickTimeVideo : public Image {
       Caller owns the returned object and the auto-pointer ensures that
       it will be deleted.
  */
-EXIV2API Image::UniquePtr newQTimeInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newQTimeInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a Quick Time Video.
 EXIV2API bool isQTimeType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/rafimage.hpp b/include/exiv2/rafimage.hpp
index 3d4593fb76..a01a193dfc 100644
--- a/include/exiv2/rafimage.hpp
+++ b/include/exiv2/rafimage.hpp
@@ -38,7 +38,7 @@ class EXIV2API RafImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  RafImage(BasicIo::UniquePtr io, bool create);
+  RafImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -85,7 +85,7 @@ class EXIV2API RafImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newRafInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newRafInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a RAF image.
 EXIV2API bool isRafType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/riffvideo.hpp b/include/exiv2/riffvideo.hpp
index 8ddad17d30..587a7d5ab4 100644
--- a/include/exiv2/riffvideo.hpp
+++ b/include/exiv2/riffvideo.hpp
@@ -29,7 +29,7 @@ class EXIV2API RiffVideo : public Image {
         instance after it is passed to this method. Use the Image::io()
         method to get a temporary reference.
    */
-  explicit RiffVideo(BasicIo::UniquePtr io);
+  explicit RiffVideo(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -49,7 +49,7 @@ class EXIV2API RiffVideo : public Image {
     uint64_t size_ = 0;
 
    public:
-    explicit HeaderReader(const BasicIo::UniquePtr& io);
+    explicit HeaderReader(const std::unique_ptr<BasicIo>& io);
 
     [[nodiscard]] uint64_t getSize() const {
       return size_;
@@ -178,7 +178,7 @@ class EXIV2API RiffVideo : public Image {
       Caller owns the returned object and the auto-pointer ensures that
       it will be deleted.
  */
-EXIV2API Image::UniquePtr newRiffInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newRiffInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a Riff Video.
 EXIV2API bool isRiffType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/rw2image.hpp b/include/exiv2/rw2image.hpp
index 06e040f2d5..8f573eb4e9 100644
--- a/include/exiv2/rw2image.hpp
+++ b/include/exiv2/rw2image.hpp
@@ -36,7 +36,7 @@ class EXIV2API Rw2Image : public Image {
         instance after it is passed to this method.  Use the Image::io()
         method to get a temporary reference.
    */
-  explicit Rw2Image(BasicIo::UniquePtr io);
+  explicit Rw2Image(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -99,7 +99,7 @@ class EXIV2API Rw2Parser {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newRw2Instance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newRw2Instance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a RW2 image.
 EXIV2API bool isRw2Type(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/tgaimage.hpp b/include/exiv2/tgaimage.hpp
index edea1f3f16..d1fa94d3f5 100644
--- a/include/exiv2/tgaimage.hpp
+++ b/include/exiv2/tgaimage.hpp
@@ -34,7 +34,7 @@ class EXIV2API TgaImage : public Image {
         instance after it is passed to this method.  Use the Image::io()
         method to get a temporary reference.
    */
-  explicit TgaImage(BasicIo::UniquePtr io);
+  explicit TgaImage(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -79,7 +79,7 @@ class EXIV2API TgaImage : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newTgaInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newTgaInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a Targa v2 image.
 EXIV2API bool isTgaType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/tiffimage.hpp b/include/exiv2/tiffimage.hpp
index 9d11b20981..51f78376e2 100644
--- a/include/exiv2/tiffimage.hpp
+++ b/include/exiv2/tiffimage.hpp
@@ -12,6 +12,7 @@
 // *****************************************************************************
 // namespace extensions
 namespace Exiv2 {
+class BasicIo;
 // *****************************************************************************
 // class definitions
 
@@ -38,7 +39,7 @@ class EXIV2API TiffImage : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new file should be created (true).
    */
-  TiffImage(BasicIo::UniquePtr io, bool create);
+  TiffImage(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -152,7 +153,7 @@ class EXIV2API TiffParser {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newTiffInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newTiffInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a TIFF image.
 EXIV2API bool isTiffType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/webpimage.hpp b/include/exiv2/webpimage.hpp
index 1d5eec24fb..46d6d5611a 100644
--- a/include/exiv2/webpimage.hpp
+++ b/include/exiv2/webpimage.hpp
@@ -33,7 +33,7 @@ class EXIV2API WebPImage : public Image {
         instance after it is passed to this method. Use the Image::io()
         method to get a temporary reference.
    */
-  explicit WebPImage(BasicIo::UniquePtr io);
+  explicit WebPImage(std::unique_ptr<BasicIo> io);
   //@}
 
   //! @name Manipulators
@@ -94,7 +94,7 @@ class EXIV2API WebPImage : public Image {
       Caller owns the returned object and the auto-pointer ensures that
       it will be deleted.
  */
-EXIV2API Image::UniquePtr newWebPInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newWebPInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is a WebP Video.
 EXIV2API bool isWebPType(BasicIo& iIo, bool advance);
diff --git a/include/exiv2/xmp_exiv2.hpp b/include/exiv2/xmp_exiv2.hpp
index 7a17267e46..a5928027fc 100644
--- a/include/exiv2/xmp_exiv2.hpp
+++ b/include/exiv2/xmp_exiv2.hpp
@@ -106,7 +106,7 @@ class EXIV2API Xmpdatum : public Metadatum {
   [[nodiscard]] int64_t toInt64(size_t n = 0) const override;
   [[nodiscard]] float toFloat(size_t n = 0) const override;
   [[nodiscard]] Rational toRational(size_t n = 0) const override;
-  [[nodiscard]] Value::UniquePtr getValue() const override;
+  [[nodiscard]] std::unique_ptr<Value> getValue() const override;
   [[nodiscard]] const Value& value() const override;
   //@}
 
diff --git a/include/exiv2/xmpsidecar.hpp b/include/exiv2/xmpsidecar.hpp
index 332be68129..dab8eca275 100644
--- a/include/exiv2/xmpsidecar.hpp
+++ b/include/exiv2/xmpsidecar.hpp
@@ -35,7 +35,7 @@ class EXIV2API XmpSidecar : public Image {
     @param create Specifies if an existing image should be read (false)
         or if a new image should be created (true).
    */
-  XmpSidecar(BasicIo::UniquePtr io, bool create);
+  XmpSidecar(std::unique_ptr<BasicIo> io, bool create);
   //@}
 
   //! @name Manipulators
@@ -67,7 +67,7 @@ class EXIV2API XmpSidecar : public Image {
          Caller owns the returned object and the auto-pointer ensures that
          it will be deleted.
  */
-EXIV2API Image::UniquePtr newXmpInstance(BasicIo::UniquePtr io, bool create);
+EXIV2API Image::UniquePtr newXmpInstance(std::unique_ptr<BasicIo> io, bool create);
 
 //! Check if the file iIo is an XMP sidecar file.
 EXIV2API bool isXmpType(BasicIo& iIo, bool advance);
diff --git a/src/bmffimage.cpp b/src/bmffimage.cpp
index dae309dff1..a857560ac8 100644
--- a/src/bmffimage.cpp
+++ b/src/bmffimage.cpp
@@ -10,7 +10,7 @@
 #include "futils.hpp"
 #include "image.hpp"
 #include "image_int.hpp"
-#include "safe_op.hpp"
+#include "tags.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
 #include "types.hpp"
@@ -18,6 +18,7 @@
 
 #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/canonmn_int.cpp b/src/canonmn_int.cpp
index 630217436b..f2538cf5d5 100644
--- a/src/canonmn_int.cpp
+++ b/src/canonmn_int.cpp
@@ -13,6 +13,7 @@
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
 #include "makernote_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "types.hpp"
 #include "utils.hpp"
diff --git a/src/convert.cpp b/src/convert.cpp
index 3f4ed29dfa..bb2e23c15b 100644
--- a/src/convert.cpp
+++ b/src/convert.cpp
@@ -7,17 +7,17 @@
              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"
+#include "tags.hpp"
 #include "types.hpp"
+#include "value.hpp"
 #include "xmp_exiv2.hpp"
 
 // + standard includes
@@ -25,6 +25,9 @@
 #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/cr2image.cpp b/src/cr2image.cpp
index 091603d069..eb66494d10 100644
--- a/src/cr2image.cpp
+++ b/src/cr2image.cpp
@@ -3,11 +3,13 @@
 // included header files
 #include "cr2image.hpp"
 
+#include "basicio.hpp"
 #include "config.h"
 #include "cr2header_int.hpp"
 #include "error.hpp"
 #include "futils.hpp"
 #include "image.hpp"
+#include "tags.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
 
diff --git a/src/crwimage.cpp b/src/crwimage.cpp
index a1acf6c7e5..3b7ff6663a 100644
--- a/src/crwimage.cpp
+++ b/src/crwimage.cpp
@@ -5,14 +5,16 @@
   History:   28-Aug-05, ahu: created
  */
 // included header files
-#include "config.h"
-
 #include "crwimage.hpp"
+#include "basicio.hpp"
+#include "config.h"
 #include "crwimage_int.hpp"
 #include "error.hpp"
 #include "futils.hpp"
 #include "tags.hpp"
 
+#include <cstring>
+
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
 #endif
diff --git a/src/crwimage_int.cpp b/src/crwimage_int.cpp
index 4ca559b543..af6525cedb 100644
--- a/src/crwimage_int.cpp
+++ b/src/crwimage_int.cpp
@@ -1,14 +1,13 @@
 // 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.
 #include "image.hpp"
 #include "image_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 
 #include <algorithm>
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..fc3598cab9 100644
--- a/src/easyaccess.cpp
+++ b/src/easyaccess.cpp
@@ -1,8 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 // included header files
 #include "easyaccess.hpp"
+
+#include "tags.hpp"
 #include "utils.hpp"
+#include "value.hpp"
 
+#include <cstring>
 #include <sstream>
 
 // *****************************************************************************
diff --git a/src/epsimage.cpp b/src/epsimage.cpp
index d139fc12bc..ac5b54ca1d 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"
@@ -22,6 +22,7 @@
 #include <algorithm>
 #include <array>
 #include <cstring>
+#include <limits>
 #include <sstream>
 #include <string>
 
diff --git a/src/exif.cpp b/src/exif.cpp
index ad489238a2..3faffdb3be 100644
--- a/src/exif.cpp
+++ b/src/exif.cpp
@@ -163,6 +163,8 @@ Exifdatum::Exifdatum(const Exifdatum& rhs) {
     value_ = rhs.value_->clone();  // deep copy
 }
 
+Exifdatum::~Exifdatum() = default;
+
 std::ostream& Exifdatum::write(std::ostream& os, const ExifData* pMetadata) const {
   if (value().count() == 0)
     return os;
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/gifimage.cpp b/src/gifimage.cpp
index e00f43a106..2f243b647e 100644
--- a/src/gifimage.cpp
+++ b/src/gifimage.cpp
@@ -2,7 +2,7 @@
 
 // included header files
 #include "gifimage.hpp"
-
+#include "basicio.hpp"
 #include "config.h"
 #include "error.hpp"
 #include "futils.hpp"
diff --git a/src/http.cpp b/src/http.cpp
index 6a93026e8a..a45c865f77 100644
--- a/src/http.cpp
+++ b/src/http.cpp
@@ -1,13 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include "http.hpp"
 #include "config.h"
-
 #include "futils.hpp"
-#include "http.hpp"
 
 #include <array>
 #include <cerrno>
 #include <chrono>
+#include <cstring>
 #include <thread>
 
 ////////////////////////////////////////
diff --git a/src/image.cpp b/src/image.cpp
index eaa78c8fd4..6dfd8a82bc 100644
--- a/src/image.cpp
+++ b/src/image.cpp
@@ -3,6 +3,7 @@
 // included header files
 #include "image.hpp"
 
+#include "basicio.hpp"
 #include "config.h"
 #include "enforce.hpp"
 #include "error.hpp"
@@ -32,6 +33,7 @@
 #include "psdimage.hpp"
 #include "rafimage.hpp"
 #include "rw2image.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "tgaimage.hpp"
 #include "tiffimage.hpp"
@@ -138,6 +140,8 @@ Image::Image(ImageType type, uint16_t supportedMetadata, BasicIo::UniquePtr io)
     io_(std::move(io)), imageType_(type), supportedMetadata_(supportedMetadata) {
 }
 
+Image::~Image() = default;
+
 void Image::printStructure(std::ostream&, PrintStructureOption, size_t /*depth*/) {
   throw Error(ErrorCode::kerUnsupportedImageType, io_->path());
 }
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..340ae5b6a0 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"
@@ -67,6 +65,8 @@ Iptcdatum::Iptcdatum(const Iptcdatum& rhs) {
     value_ = rhs.value_->clone();  // deep copy
 }
 
+Iptcdatum::~Iptcdatum() = default;
+
 size_t Iptcdatum::copy(byte* buf, ByteOrder byteOrder) const {
   return value_ ? value_->copy(buf, byteOrder) : 0;
 }
diff --git a/src/jp2image.cpp b/src/jp2image.cpp
index a538db8d7f..e4942a609a 100644
--- a/src/jp2image.cpp
+++ b/src/jp2image.cpp
@@ -18,6 +18,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cstring>
 #include <iostream>
 
 #ifdef EXIV2_DEBUG_MESSAGES
diff --git a/src/jpgimage.cpp b/src/jpgimage.cpp
index 5863d6bf97..a08f0ecebb 100644
--- a/src/jpgimage.cpp
+++ b/src/jpgimage.cpp
@@ -1,17 +1,16 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 // included header files
+#include "jpgimage.hpp"
+#include "basicio.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..7701787175 100644
--- a/src/makernote_int.cpp
+++ b/src/makernote_int.cpp
@@ -5,16 +5,18 @@
   History:   11-Apr-06, ahu: created
  */
 // included header files
-#include "config.h"
-
 #include "makernote_int.hpp"
+#include "config.h"
 #include "safe_op.hpp"
+#include "tags.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
 #include "tiffvisitor_int.hpp"
 #include "utils.hpp"
+#include "value.hpp"
 
 // + standard includes
+#include <cstring>
 #include <iostream>
 
 #ifdef EXV_ENABLE_FILESYSTEM
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/minoltamn_int.cpp b/src/minoltamn_int.cpp
index 10523e5f0b..504ae7f7b0 100644
--- a/src/minoltamn_int.cpp
+++ b/src/minoltamn_int.cpp
@@ -6,6 +6,7 @@
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
 #include "makernote_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "value.hpp"
 
diff --git a/src/mrwimage.cpp b/src/mrwimage.cpp
index 6e8a17d4b4..2b5fdf66ec 100644
--- a/src/mrwimage.cpp
+++ b/src/mrwimage.cpp
@@ -9,9 +9,11 @@
 #include "error.hpp"
 #include "futils.hpp"
 #include "image.hpp"
+#include "tags.hpp"
 #include "tiffimage.hpp"
 
 #include <array>
+#include <cstring>
 
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
diff --git a/src/nikonmn_int.cpp b/src/nikonmn_int.cpp
index c8674e14ef..96958aa988 100644
--- a/src/nikonmn_int.cpp
+++ b/src/nikonmn_int.cpp
@@ -1,14 +1,13 @@
 // 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"
 #include "makernote_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "utils.hpp"
 #include "value.hpp"
diff --git a/src/olympusmn_int.cpp b/src/olympusmn_int.cpp
index e03f262684..4428962d74 100644
--- a/src/olympusmn_int.cpp
+++ b/src/olympusmn_int.cpp
@@ -8,12 +8,11 @@
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
 #include "makernote_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "utils.hpp"
 #include "value.hpp"
 
-#include <array>
-
 // *****************************************************************************
 // class member definitions
 namespace Exiv2::Internal {
diff --git a/src/orfimage.cpp b/src/orfimage.cpp
index ed60f95a00..946324afb1 100644
--- a/src/orfimage.cpp
+++ b/src/orfimage.cpp
@@ -9,6 +9,7 @@
 #include "futils.hpp"
 #include "image.hpp"
 #include "orfimage_int.hpp"
+#include "tags.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage.hpp"
 #include "tiffimage_int.hpp"
diff --git a/src/pgfimage.cpp b/src/pgfimage.cpp
index 1657ed4014..394cf1d9e0 100644
--- a/src/pgfimage.cpp
+++ b/src/pgfimage.cpp
@@ -11,7 +11,8 @@
 #include "image.hpp"
 
 #include <array>
-#include <bit>
+#include <cstring>
+#include <limits>
 
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
diff --git a/src/photoshop.cpp b/src/photoshop.cpp
index fbb6f7fc87..c7845c4fd8 100644
--- a/src/photoshop.cpp
+++ b/src/photoshop.cpp
@@ -6,6 +6,8 @@
 #include "image.hpp"
 #include "safe_op.hpp"
 
+#include <cstring>
+
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
 #endif
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/pngimage.cpp b/src/pngimage.cpp
index 63e3a58fca..f213c824b2 100644
--- a/src/pngimage.cpp
+++ b/src/pngimage.cpp
@@ -20,6 +20,7 @@
 #include "utils.hpp"
 
 #include <array>
+#include <cstring>
 #include <iostream>
 
 namespace {
diff --git a/src/preview.cpp b/src/preview.cpp
index b281253d12..b9bb99cb59 100644
--- a/src/preview.cpp
+++ b/src/preview.cpp
@@ -2,7 +2,7 @@
 
 // included header files
 #include "preview.hpp"
-
+#include "basicio.hpp"
 #include "config.h"
 #include "enforce.hpp"
 #include "futils.hpp"
@@ -10,11 +10,14 @@
 #include "photoshop.hpp"
 #include "properties.hpp"
 #include "safe_op.hpp"
+#include "tags.hpp"
 #include "tiffimage.hpp"
 #include "tiffimage_int.hpp"
+#include "value.hpp"
 
 #include <algorithm>
 #include <climits>
+#include <cstring>
 
 namespace {
 using namespace Exiv2;
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/rafimage.cpp b/src/rafimage.cpp
index 39b95e53e1..db2d7f9626 100644
--- a/src/rafimage.cpp
+++ b/src/rafimage.cpp
@@ -12,6 +12,7 @@
 #include "image_int.hpp"
 #include "jpgimage.hpp"
 #include "safe_op.hpp"
+#include "tags.hpp"
 #include "tiffimage.hpp"
 
 #include <array>
diff --git a/src/riffvideo.cpp b/src/riffvideo.cpp
index f90d2f09bf..40f523bf96 100644
--- a/src/riffvideo.cpp
+++ b/src/riffvideo.cpp
@@ -8,6 +8,8 @@
 
 // included header files
 #include "riffvideo.hpp"
+#include "basicio.hpp"
+#include "config.h"
 #include "enforce.hpp"
 #include "error.hpp"
 #include "futils.hpp"
diff --git a/src/rw2image.cpp b/src/rw2image.cpp
index e00106ac62..c9e0c6c89d 100644
--- a/src/rw2image.cpp
+++ b/src/rw2image.cpp
@@ -2,20 +2,23 @@
 
 // included header files
 #include "rw2image.hpp"
-
+#include "basicio.hpp"
 #include "config.h"
 #include "error.hpp"
 #include "futils.hpp"
 #include "image.hpp"
 #include "preview.hpp"
 #include "rw2image_int.hpp"
+#include "tags.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
 
 // + standard includes
 #include <array>
+
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
+#include "value.hpp"
 #endif
 
 // *****************************************************************************
diff --git a/src/sonymn_int.cpp b/src/sonymn_int.cpp
index 570aed2aad..665c230384 100644
--- a/src/sonymn_int.cpp
+++ b/src/sonymn_int.cpp
@@ -8,6 +8,7 @@
 #include "i18n.h"  // NLS support.
 #include "image_int.hpp"
 #include "minoltamn_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "tiffcomposite_int.hpp"
 #include "utils.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 81bef9ada4..e20c1b6983 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/tgaimage.cpp b/src/tgaimage.cpp
index 388b9822b7..f6556b979c 100644
--- a/src/tgaimage.cpp
+++ b/src/tgaimage.cpp
@@ -9,6 +9,8 @@
 #include "futils.hpp"
 #include "image.hpp"
 
+#include <cstring>
+
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
 #endif
diff --git a/src/tiffcomposite_int.cpp b/src/tiffcomposite_int.cpp
index 3ab2d659cb..45007c1a1d 100644
--- a/src/tiffcomposite_int.cpp
+++ b/src/tiffcomposite_int.cpp
@@ -1,16 +1,15 @@
 // 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"
 #include "makernote_int.hpp"
 #include "safe_op.hpp"
 #include "sonymn_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "tiffimage_int.hpp"
 #include "tiffvisitor_int.hpp"
@@ -95,6 +94,25 @@ 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 +131,18 @@ 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.cpp b/src/tiffimage.cpp
index e2743015a8..ed3b3bd7f3 100644
--- a/src/tiffimage.cpp
+++ b/src/tiffimage.cpp
@@ -8,9 +8,11 @@
 #include "error.hpp"
 #include "futils.hpp"
 #include "image.hpp"
+#include "tags.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
 #include "types.hpp"
+#include "value.hpp"
 
 #include <array>
 #include <iostream>
diff --git a/src/tiffimage_int.cpp b/src/tiffimage_int.cpp
index 60bc023959..a835c5ca46 100644
--- a/src/tiffimage_int.cpp
+++ b/src/tiffimage_int.cpp
@@ -1,16 +1,17 @@
 // 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 "tags.hpp"
 #include "tiffcomposite_int.hpp"
-#include "tiffimage_int.hpp"
 #include "tiffvisitor_int.hpp"
+#include "value.hpp"
 
 #ifdef EXIV2_DEBUG_MESSAGES
 #include "tags_int.hpp"
@@ -25,6 +26,9 @@
 #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..7c59309633 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"
@@ -13,6 +12,7 @@
 #include "photoshop.hpp"
 #include "safe_op.hpp"
 #include "sonymn_int.hpp"
+#include "tags.hpp"
 #include "tags_int.hpp"
 #include "tiffcomposite_int.hpp"
 #include "tiffimage_int.hpp"
@@ -344,8 +344,6 @@ 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/tiffvisitor_int.hpp b/src/tiffvisitor_int.hpp
index 1a814553fb..2bb0132ce4 100644
--- a/src/tiffvisitor_int.hpp
+++ b/src/tiffvisitor_int.hpp
@@ -10,6 +10,7 @@
 #include "tiffcomposite_int.hpp"
 
 #include <array>
+#include <map>
 
 // *****************************************************************************
 // namespace extensions
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/webpimage.cpp b/src/webpimage.cpp
index fa63d9c7b0..cd89c1b30f 100644
--- a/src/webpimage.cpp
+++ b/src/webpimage.cpp
@@ -18,6 +18,7 @@
 #include "types.hpp"
 
 #include <array>
+#include <cstring>
 #include <iostream>
 
 namespace {
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>
diff --git a/src/xmpsidecar.cpp b/src/xmpsidecar.cpp
index 8001b1a3ee..94623f94b7 100644
--- a/src/xmpsidecar.cpp
+++ b/src/xmpsidecar.cpp
@@ -9,8 +9,11 @@
 #include "image.hpp"
 #include "properties.hpp"
 #include "utils.hpp"
+#include "value.hpp"
 #include "xmp_exiv2.hpp"
 
+#include <cstring>
+
 #ifdef EXIV2_DEBUG_MESSAGES
 #include <iostream>
 #endif
diff --git a/unitTests/test_asfvideo.cpp b/unitTests/test_asfvideo.cpp
index 37b962b912..3980a1ca74 100644
--- a/unitTests/test_asfvideo.cpp
+++ b/unitTests/test_asfvideo.cpp
@@ -3,6 +3,7 @@
 #include <gtest/gtest.h>
 
 #include <exiv2/asfvideo.hpp>
+#include <exiv2/basicio.hpp>
 
 using namespace Exiv2;
 
diff --git a/unitTests/test_bmpimage.cpp b/unitTests/test_bmpimage.cpp
index 6d3250105d..a6fc5b6534 100644
--- a/unitTests/test_bmpimage.cpp
+++ b/unitTests/test_bmpimage.cpp
@@ -3,6 +3,7 @@
 #include <gtest/gtest.h>
 
 #include <array>
+#include <exiv2/basicio.hpp>
 #include <exiv2/bmpimage.hpp>
 
 using namespace Exiv2;
diff --git a/unitTests/test_jp2image.cpp b/unitTests/test_jp2image.cpp
index faacb64b4b..c52fd3f390 100644
--- a/unitTests/test_jp2image.cpp
+++ b/unitTests/test_jp2image.cpp
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include <exiv2/basicio.hpp>
 #include <exiv2/jp2image.hpp>
 
 #include <gtest/gtest.h>
diff --git a/unitTests/test_matroskavideo.cpp b/unitTests/test_matroskavideo.cpp
index 3dd1fafd7f..525116a42b 100644
--- a/unitTests/test_matroskavideo.cpp
+++ b/unitTests/test_matroskavideo.cpp
@@ -2,6 +2,7 @@
 
 #include <gtest/gtest.h>
 
+#include <exiv2/basicio.hpp>
 #include <exiv2/matroskavideo.hpp>
 
 using namespace Exiv2;
diff --git a/unitTests/test_pngimage.cpp b/unitTests/test_pngimage.cpp
index 5f8f568b57..49c7731b74 100644
--- a/unitTests/test_pngimage.cpp
+++ b/unitTests/test_pngimage.cpp
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include <exiv2/basicio.hpp>
 #include <exiv2/pngimage.hpp>
 #include "pngchunk_int.hpp"  // This is not part of the public API
 
diff --git a/unitTests/test_riffVideo.cpp b/unitTests/test_riffVideo.cpp
index 243e86dbe8..d92d3ddaf9 100644
--- a/unitTests/test_riffVideo.cpp
+++ b/unitTests/test_riffVideo.cpp
@@ -2,6 +2,7 @@
 
 #include <gtest/gtest.h>
 
+#include <exiv2/basicio.hpp>
 #include <exiv2/riffvideo.hpp>
 
 using namespace Exiv2;