===================================
DCMTK COMPILE TIME FLAGS AND MACROS
===================================

The behavior of several DCMTK tools and libraries can be modified by a number
of compile time flags (macros), which are explained below.
Most of these macros enable experimental or rarely needed features in DCMTK,
others disable certain functions.  So please, use with care!

Note: CMake users simply need to add a new definition to CXXFLAGS, e.g.:

  CXXFLAGS=-DENABLE_DCMJPLS_INTERLEAVE_NONE && cmake [...] /path/to/dcmtk

ALLOW_ILLUMINATION_OVERRIDE
  Affected: dcmprscu
  Type of modification: Activates experimental or rarely used feature
  Explanation: Allows the settings for Illumination and Reflected Ambient Light,
    which are stored in a Stored Print object, to be overridden from the print
    job command file.

BUGGY_IMPLEMENTATION_CLASS_UID_PREFIX
  Affected: storescp
  Type of modification: Activates workaround for known bug in other product
  Explanation: The dcmnet module contains a workaround that allows to
    communicate with some buggy Storage SCUs.  If the global flag
    dcmPeerRequiresExactUIDCopy is enabled, an illegal space padding in the
    Affected SOP Instance UID field of the C-STORE-RQ message is retained in the
    corresponding C-STORE-RSP message.  When this preprocessor macro is defined,
    it should contain the prefix of an implementation class UID of an
    implementation known to exhibit the buggy behavior.  The workaround is then
    activated in storescp whenever a Storage SCU with the given implementation
    class UID root connects.

DCMTK_BUILD_DATE
  Affected: dcmdata
  Type of modification: Toolkit customization
  Explanation: When this macro is defined (typically in config/Makefile.def),
    the given date is used instead of the official DCMTK release data.  This
    allows for example to specify the date of a current development snapshot.

DCMTK_BUILD_IN_PROGRESS
  Affected: all modules
  Type of modification: Toolkit customization
  Explanation: When building DLLs, exported symbols must be marked differently
    if the DLL itself is built or when the DLL shall be used.  This macro is
    defined when the DCMTK gets built and should not be defined when user code
    that just uses the DCMTK is built.  Based on this, the correct annotation
    gets selected and is used in the code.  There should be no valid reasons to
    define this macro yourself since this is done automatically by the build
    system.

DCMTK_UNDEF_SANITIZER
  Affected: all modules
  Type of modification: Toolkit customization
  Explanation: When compiling with the GCC undefined behavior sanitizer
    (-fsanitize=undefined), this macro must be defined to disable certain code
    in config/tests/arith.cc that would otherwise trigger a runtime error to be
    raised by the sanitizer and thus prevent the CMake configure phase from
    completing.

DCMTK_ENABLE_STRICT_HUFFMAN_TABLE_CHECK
  Affected: dcmjpeg
  Type of modification: Activates feature
  Explanation: DCMTK releases up to 3.6.6 contained a relatively strict check
    for the validity of Huffman tables for DC components in the JPEG decoder.
    At least one JPEG implementation produces valid JPEG images that fail this
    test (see DCMTK issue #1018).  The test has, therefore, been disabled.  This
    macro re-enables the old behavior.

DCMTK_ENABLE_UNSAFE_VSNPRINTF
  Affected: ofstd
  Type of modification: Activates feature
  Explanation: DCMTK requires the snprintf(3)/vsnprintf(3) function, which was
    introduced with C99 and may not be supported by very old compilers.  As a
    "last resort", an implementation interally using sprintf/vsprintf can be
    enabled with this macro, which allows the user to compile DCMTK on platforms
    that do not have the new functions.
    The implementation allocates a buffer that is 1 kByte larger than the "size"
    parameter, formats the string into that buffer, and then uses strlcpy() to
    copy the formatted string into the output buffer, truncating if necessary.
    This will work in most cases, since few snprintf calls should overrun their
    buffer by more than 1K, but it can be easily abused by a malicious attacker
    to cause a buffer overrun.
    Therefore, this implementation should only be used as a "last resort" and we
    strongly advise against using it in production code.

DCMTK_GUI
  Affected: all modules
  Type of modification: Activates experimental or rarely used feature
  Explanation: When this macro is defined, DCMTK re-assigns the standard output
    and error streams maintained by ofConsole to string streams.  This will
    allow a GUI based application to extract the messages and either present
    them to the user or store them in a log file.  See comments in
    ofstd/include/dcmtk/ofstd/ofconsol.h.

DCMTK_LOG4CPLUS_AVOID_WIN32_FLS
  Affected: oflog
  Type of modification: Disables feature
  Explanation: Starting with release 3.6.5, DCMTK uses fiber local storage
    instead of thread local storage in the oflog module on Windows to store
    thread-specific information.  This has the advantage that a callback can
    be (and is) registered that automatically cleans up the memory when a
    thread ends.  The old behavior can be re-activated with this macro.
    This may be necessary when an application wants to use multiple fibers
    within a single thread.  In that case, before ending a thread,
    dcmtk::log4cplus::threadCleanup() should be called by the user code in
    order to clean-up oflog's thread local storage.

DCMTK_MERGE_STDERR_TO_STDOUT
  Affected: dcmdata
  Type of modification: Activates feature
  Explanation: DCMTK releases up to 3.6.6 redirected the stderr stream to stdout
    on Windows to make it easier to pipe the output of the command line tools to
    "more".  With the introduction of the ability to write DICOM files to
    stdout, this feature has been disabled as debug output will otherwise get
    mixed into the DICOM file.  The old behavior can be re-activated by
    compiling with this macro.  In this case, DICOM files should never be
    written to stdout as this will be unreliable.

DICOMDIR_WITHOUT_BACKUP
  Affected: dcmdata
  Type of modification: Disables feature
  Explanation: By default, DCMTK creates a backup of an existing DICOMDIR
    (using the name DICOMDIR.$$$) when a DcmDicomDir object is written to file.
    The creation of the backup can be disabled with this macro.

DISABLE_COMPRESSION_EXTENSION
  Affected: dcmqrdb
  Type of modification: Disables feature
  Explanation: Disables the support of compression (various transfer syntaxes)
    in dcmqrdb, a feature which is still experimental.

DISABLE_FF_JPEG_BITSTREAM_PADDING
  Affected: dcmjpeg, dcmjpls (dcmjpls only up to DCMTK 3.6.4)
  Type of modification: Disables feature
  Explanation: Starting with release 3.6.2, DCMTK pads JPEG and JPEG-LS
    bitstreams that have odd length with an "extended" end of image (EOI)
    marker, writing "ff/ff/d9" instead of adding a zero byte after the EOI
    marker, i.e. writing "ff/d9/00".  The old behavior can be restored by
    defining this macro.
    In the dcmjpls module, the macro has been replaced by a codec parameter that
    can be set at runtime starting with DCMTK 3.6.5.

DISABLE_NAGLE_ALGORITHM
  Affected: dcmnet
  Type of modification: Disables feature
  Explanation: By default, DCMTK does not disable the so-called Nagle algorithm,
    which allows for improving the efficiency of TCP/IP networks by reducing the
    number of packets that need to be sent over the network.  When compiled with
    this macro, the Nagle algorithm is disabled for each DICOM transport
    connection.  This was the default in earlier versions of the DCMTK but does
    not seem to be appropriate anymore for most modern operating systems.
    The default behavior can be changed by setting the environment variable
    TCP_NODELAY accordingly (see config/docs/envvars.txt or
    /usr/local/share/doc/dcmtk/envvars.txt).

DISABLE_OFSTD_ATOF
  Affected: all modules
  Type of modification: Disables feature
  Explanation: By default, DCMTK uses its own implementation of atof() to
    convert strings to double numbers in a locale-independent manner.
    This flag forces DCMTK to use the standard sscanf() function instead, which
    is normally much faster and gives a higher precision than DCMTK's built in
    code, but is locale dependent, i.e. cannot be used with locales such as
    German since DICOM decimal strings always use the Posix locale.

DISABLE_OFSTD_FTOA
  Affected: all modules
  Type of modification: Disables feature
  Explanation: By default, DCMTK uses its own implementation to convert double
    numbers to strings to in a locale-independent manner.
    This flag forces DCMTK to use the standard sprintf() function instead, which
    is locale dependent, i.e. cannot be used with locales such as German since
    DICOM decimal strings always use the Posix locale.

DISABLE_PORT_PERMISSION_CHECK
  Affected: most/all network server tools
  Type of modification: Disables feature
  Explanation: By default, most network server tools (e.g. storescp) check for
    sufficient privileges to listen on the specified port (if geteuid() is
    available on the particular system).  For examples, on Unix systems
    listening on port < 1024 usually requires root privileges.  However, the
    port permission check might prevent the tool from being run on such ports on
    systems with fine-grained permission control (e.g. Linux).  Therefore, this
    check can be disabled using this flag.

DISABLE_RECV_TIMEOUT
  This macro is not supported anymore since the timeout for the recv() function
  is now configurable at runtime.  See global variable dcmSocketReceiveTimeout.

DISABLE_SEND_TIMEOUT
  This macro is not supported anymore since the timeout for the send() function
  is now configurable at runtime.  See global variable dcmSocketSendTimeout.

DONT_DISABLE_NAGLE_ALGORITHM
  This macro is not supported anymore since the Nagle algorithm is no longer
  disabled by default.  See DISABLE_NAGLE_ALGORITHM for details.

DOXYGEN
  Affected: everything
  Type of modification: Hides complexity from Doxygen
  Explanation: Doxygen is unable to parse some complex statements correctly and
    it is sometimes sufficient to provide documentation for the basic
    functionality instead of documenting every detail.
    This macro is defined when creating the documentation with Doxygen and
    should NEVER be defined when compiling DCMTK with a C/C++ compiler.
    NOTE: Doxygen is still unable to expand some macros correctly (e.g.
          HAVE_WINDOWS_H).  Using this macro at the appropriate locations could
          be a solution for this problem.

DCM_DICT_DEFAULT
  Affected: dcmdata
  Type of modification: Activates feature
  Explanation: This macro controls which kind of default dictionary is loaded
    on startup.  Three settings are possible:
      0: Do not load any default dictionary on startup
      1: Load builtin dictionary on startup
      2: Load external (i.e. file-based) dictionary on startup
    See dcmtk/dcmdata/docs/datadict.txt for further details.

DCM_DICT_USE_DCMDICTPATH
  Affected: dcmdata
  Type of modification: Activates feature
  Explanation: This macro controls whether DCMDICTPATH environment variable is
    evaluated on startup.  If so, any dictionary files provided through
    DCMDICTPATH will be loaded on startup.
    See dcmtk/dcmdata/docs/datadict.txt for further details.

ENABLE_DCMJPLS_INTERLEAVE_NONE
  Affected: dcmjpls
  Type of modification: Enables feature
  Explanation: Re-enables the option for uninterleaved encoding
    (--interleave-none) in the JPEG-LS encoder on command line and library
    level.  This option was removed after DCMTK 3.6.5 since it may in certain
    cases (color image with BitsStored > 12) create compressed images that
    are correct but cannot be decoded by the JPEG-LS library due to a known
    bug (DCMTK issue #892).  The option will be re-enabled permanently once
    DCMTK has been ported to CharLS 2.x, another branch of the JPEG-LS library
    that requires a C++14 compiler, however.

EXPERIMENTAL_READ_FROM_FILE
  Affected: dump2dcm
  Type of modification: Activates experimental or rarely used feature
  Explanation: When this macro is defined, the relatively new function
    createValueFromTempFile() is used for reading large binary data files.

LOCK_IMAGE_FILES
  Affected: dcmpstat, dcmqrdb
  Type of modification: Activates experimental or rarely used feature
  Explanation: When this macro is defined, the DICOM image file to be send or
    received/created is locked exclusively.

LOG4CPLUS_DISABLE_xxx
(where xxx is one of TRACE, DEBUG, INFO, WARN, ERROR and FATAL)
  Affected: oflog
  Type of modification: Disables feature
  Explanation: When one of these macros is defined, all log message of this type
    and lower are disabled and optimized away.

NO_GET_SUPPORT
  Affected: dcmqrdb
  Type of modification: Disables feature
  Explanation: Disables the experimental C-GET support in dcmqrdb.

NO_PATIENTSTUDYONLY_SUPPORT
  Affected: dcmqrdb
  Type of modification: Disables feature
  Explanation: Disables support for the Patient/Study Only Query/Retrieve Model
    in dcmqrdb.

OFCONDITION_IMPLICIT_BOOL_CONVERSION
  Affected: ofstd
  Type of modification: Activates experimental or rarely used feature
  Explanation: Activates an implicit conversion from OFCondition to OFBool, i.e.
    operator OFBool().  Implicit conversion might not always be a good idea
    since it can hide unwanted constructs.  Therefore, this operator is disabled
    by default.

ON_THE_FLY_COMPRESSION
  Affected: storescu
  Type of modification: Activates experimental or rarely used feature
  Explanation: When this macro is defined, the storescu tries to compress or
    decompress the DICOM image to be sent (if required) depending on the
    negotiated transfer syntax.

OLD_USER_INFO_SUB_ITEM_ORDER
  Affected: dcmnet
  Type of modification: Activates experimental or rarely used feature
  Explanation: Prior DCMTK releases did not encode A-ASSOCIATE user information
    sub-items in ascending order, i.e. they sent 55H followed by 54H and 56H.
    This behavior has been "legalized" by DICOM CP-280, but is known to create
    problems with some other toolkits.  The current DCMTK release always sends
    the user information sub-items in ascending order, but can be "forced" with
    this macro to revert to the old behavior.  It should be re-activated for
    testing purposes only.

PASTEL_COLOR_OUTPUT
  Affected: dcmimgle, dcmimage
  Type of modification: Activates experimental or rarely used feature
  Explanation: Activates experimental code in dcmimgle/dcmimage that renders
    monochrome images with pastel colors.

PDV_TEST
  Affected: dcmnet
  Type of modification: Activates experimental or rarely used feature
  Explanation: Causes the network module to insert a false, zero-length PDV
    (2-byte header) into each P-DATA-PDU.

PIXELSTACK_MEMORY_LEAK_WORKAROUND
  Affected: dcmdata
  Type of modification: Activates experimental or rarely used feature
  Explanation: On certain platforms there seems to be a memory leak in
    DcmDataset::chooseRepresentation().  The work-around activated by this macro
    should solve this issue.

PRINT_REPLACED_DICTIONARY_ENTRIES
  Affected: dcmdata
  Type of modification: Activates experimental or rarely used feature
  Explanation: When reading the data dictionary, duplicate entries (i.e. entries
    replacing an older entry in the dictionary) are reported on console if
    compiled with this macro.  Useful for testing a new dictionary version.

REJECT_FILE_IF_META_GROUP_LENGTH_ABSENT
  Affected: dcmdata
  Type of modification: Disables feature
  Explanation: When reading the a file that contains an incorrect meta header
    where meta header group length (0002,0000) is absent, DCMTK since release
    3.5.4 nevertheless tries to parse the file, unless this macro is enabled, in
    which case the behavior up to DCMTK 3.5.3 is retained.

RETAIN_ASSOCIATION
  Affected: dcmqrti
  Type of modification: Activates experimental or rarely used feature
  Explanation: Keeps association to remote Query SCP open after
    study/series/image listing.  Default behavior is to open a new association
    for each query.

REVERSE_OVERLAY_ORIGIN_ORDER
  Affected: dcmimgle
  Type of modification: Activates experimental or rarely used feature
  Explanation: When compiled with this macro, dcmimgle assumes that the values
    in Overlay Origin (60xx,0050) are in reverse order, i.e. X\Y instead of Y\X.

SITE_UID_ROOT
  Affected: dcmdata
  Type of modification: Site customization
  Explanation: dcmdata contains a routine that generates DICOM unique
    identifiers (UIDs).  By default, these are constructed from the OFFIS UID
    namespace, i.e. using the OFFIS UID Root "1.2.276.0.7230010.3".  Users who
    prefer to let the toolkit generate UIDs from their own UID namespace should
    compile DCMTK with SITE_UID_ROOT defined to their own UID root.  Please make
    sure that the resulting UIDs do not exceed the 64 characters limit!
    DCMTK may add a maximum of 44 characters to the UID root when generating
    UIDs.  Therefore, the root must not be longer than 20 characters in order to
    avoid UID truncation.

STARVIEW
  Affected: dcmimgle, dcmimage
  Type of modification: Activates experimental or rarely used feature
  Explanation: Enables support for old StarView 2 GUI class library from Star
    Division.

SUPPRESS_CREATE_STAMP
  Affected: dcmdata
  Type of modification: Activates experimental or rarely used feature
  Explanation: When defined, suppresses the creation of a time stamp comment
    when re-generating dcdeftag.h and dcdictbi.cc.

USE__LOCKING
  Affected: dcmnet
  Type of modification: Activates alternative implementation
  Explanation: Activates an alternative emulation of flock() on Win32 platforms
    using _locking().  This version should only be used on compilers where
    _get_osfhandle() is not available since it does not implement shared locks.

USE_BINARY_MODE_FOR_STDOUT_ON_WINDOWS
  Affected: dcmdata
  Type of modification: Activates experimental or rarely used feature
  Explanation: On Windows systems, the standard output (stdout) is opened in
    text mode by default.  Therefore, the binary output of tools like dcm2pnm
    to stdout does not work correctly (in contrast to Unix systems).  When
    this preprocessor macro is defined, the binary mode is enabled for stdout.
    However, this causes newlines in the textual output to be converted to LF
    only (instead of CR LF which would be the usual translation for Windows).

USE_NULL_SAFE_OFSTRING
  Affected: ofstd
  Type of modification: Activates feature
  Explanation: When this macro is defined, OFString(NULL) results in an empty
    string.  If this macro is not defined, OFString(NULL) causes a NULL pointer
    dereference.  This macro has no effect when HAVE_STL_STRING is also defined.
    Currently, this macro is always defined by DCMTK's Makefiles.  This will
    change in future releases.

USE_WIN32_CREATE_MUTEX
  Affected: ofstd
  Type of modification: Activates alternative implementation
  Explanation: Starting with DCMTK 3.6.2, the Win32 version of the OFMutex class
    uses critical sections instead of Win32 mutexes, because critical sections
    are much faster.  Their only drawback is that they cannot be shared across
    processes.  Users who want to revert to the behavior of older DCMTK releases
    can define this macro.

USE_WIN32_READ_WRITE_LOCK_HELPER
  Affected: ofstd
  Type of modification: Re-activated behavior of earlier DCMTK releases
  Explanation: Starting with DCMTK 3.6.4, the Win32 version of the
    OFReadWriteLock class uses Slim Reader/Writer (SRW) Locks, which are
    available since Windows Vista, instead of the older implementation based on
    a Mutex, a Semaphore and a counter, because SRW locks are much faster.
    Users who want to revert to the behavior of older DCMTK releases can define
    this macro.

USING_STD_NAMESPACE
  Affected: all modules
  Type of modification: Re-activated behavior of earlier DCMTK releases
  Explanation: DCMTK by default does not anymore pollute the default namespace
    by importing namespace std.  Earlier releases did this to simplify
    compatibility with older compilers where STL classes were not consistently
    defined in namespace std.  We now have configure macros which should care
    for this.  If user code still relies on namespace std to be included,
    compile with this macro defined.

WIDE_CHAR_FILE_IO_FUNCTIONS
  Affected: ofstd
  Type of modification: Activates feature
  Explanation: In addition to the standard file I/O functions, the OFFile class
    also defines the corresponding wide character functions from C99 standard.
    Since these functions are not yet supported by all compilers and the current
    implementation is Windows-specific, this feature is disabled by default.
    When using CMake, you can enable this macro by setting the CMake option
    DCMTK_WIDE_CHAR_FILE_IO_FUNCTIONS to "on".

WIDE_CHAR_MAIN_FUNCTION
  Affected: currently not used
  Type of modification: Activates experimental or rarely used feature
  Explanation: On Windows (at least for MSVC), a different main function has
    to be used in order to get the command line arguments with wide character
    encoding (UTF-16).  By defining this flag, the macro DCMTK_MAIN_FUNCTION
    expands to wmain() instead of main().  When using CMake, you can enable
    this macro by setting the CMake option DCMTK_WIDE_CHAR_MAIN_FUNCTION to
    "on".  Usually, WIDE_CHAR_FILE_IO_FUNCTIONS should also be enabled.

WIDE_CHAR_XML_PARSER
  Affected: ofstd
  Type of modification: Activates experimental or rarely used feature
  Explanation: The XML parser that is part of the DCMTK also supports a wide
    character API, at least on Windows systems.  By defining this macro, the
    type "wchar_t" is used for character strings instead of "char".  Please
    note, however, that some DCMTK tools and classes have not yet been adapted
    for the wide character API of the parser, e.g. cda2dcm and the underlying
    class DcmEncapsulatedDocument.  This is also the reason why there is no
    CMake option yet.

WRITE_VERY_LARGE_CHUNKS
  Affected: dcmdata
  Type of modification: Re-activated behavior of earlier DCMTK releases
  Explanation: On Windows (at least for some versions of MSVC), calls to
    fwrite() for more than 67,076,095 bytes (a bit less than 64 MByte) fail if
    we're writing to a network share.  See MSDN KB899149.  As a workaround, we
    always write in chunks of 32M which should hardly negatively affect
    performance.  This macro enables the behavior of earlier DCMTK releases,
    i.e. to always call fwrite with as much data as possible, which is known
    not to work correctly on Win32 but might offer very minor performance
    benefits on other platforms.

ZLIB_ENCODE_RFC1950_HEADER
  Affected: dcmdata
  Type of modification: Activates experimental or rarely used feature
  Explanation: When this macro is defined, the deflated ZLIB format is created
    instead of the deflated bitstream format (i.e. RFC 1950 instead of RFC
    1951). Please note that the resulting bitstream is not DICOM compliant.
    So, use only for testing, and use with care!
