path: root/release_docs/RELEASE.txt

HDF5 version 1.13.0 currently under development
================================================================================


INTRODUCTION

This document describes the differences between this release and the previous
HDF5 release. It contains information on the platforms tested and known
problems in this release. For more details check the HISTORY*.txt files in the
HDF5 source.

Note that documentation in the links below will be updated at the time of each
final release.

Links to HDF5 documentation can be found on The HDF5 web page:

     https://portal.hdfgroup.org/display/HDF5/HDF5

The official HDF5 releases can be obtained from:

     https://www.hdfgroup.org/downloads/hdf5/

Changes from Release to Release and New Features in the HDF5-1.13.x release series
can be found at:

     https://portal.hdfgroup.org/display/HDF5/HDF5+Application+Developer%27s+Guide

If you have any questions or comments, please send them to the HDF Help Desk:

     help@hdfgroup.org


CONTENTS

- New Features
- Support for new platforms and languages
- Bug Fixes since HDF5-1.10.3
- Bug Fixes since HDF5-1.10.2
- Supported Platforms
- Tested Configuration Features Summary
- More Tested Platforms
- Known Problems
- CMake vs. Autotools installations


New Features
============

    Configuration:
    -------------
    - CMake option to link the generated Fortran MOD files into the include
      directory.

      The Fortran generation of MOD files by a Fortran compile can produce
      different binary files between SHARED and STATIC compiles with different
      compilers and/or different platforms. Note that it has been found that
      different versions of Fortran compilers will produce incompatible MOD
      files. Currently, CMake will locate these MOD files in subfolders of
      the include directory and add that path to the Fortran library target
      in the CMake config file, which can be used by the CMake find library
      process. For other build systems using the binary from a CMake install,
      a new CMake configuration can be used to copy the pre-chosen version
      of the Fortran MOD files into the install include directory.

      The default will depend on the configuration of
      BUILD_STATIC_LIBS and BUILD_SHARED_LIBS:
            YES                   YES         Default to SHARED
            YES                   NO          Default to STATIC
            NO                    YES         Default to SHARED
            NO                    NO          Default to SHARED
      The defaults can be overriden by setting the config option
         HDF5_INSTALL_MOD_FORTRAN to one of NO, SHARED, or STATIC

      (ADB - 2020/07/9, HDFFV-11116)

    - CMake option to use AEC (open source SZip) library instead of SZip

      The open source AEC library is a replacement library for SZip. In
      order to use it for hdf5 the libaec CMake source was changed to add
      "-fPIC" and exclude test files. Autotools does not build the
      compression libraries within hdf5 builds. New option USE_LIBAEC is
      required to compensate for the different files produced by AEC build.

      (ADB - 2020/04/22, OESS-65)

    - CMake ConfigureChecks.cmake file now uses CHECK_STRUCT_HAS_MEMBER

      Some handcrafted tests in HDFTests.c has been removed and the CMake
      CHECK_STRUCT_HAS_MEMBER module has been used.

      (ADB - 2020/03/24, TRILAB-24)

    - Both build systems use same set of warnings flags

      GNU C, C++ and gfortran warnings flags were moved to files in a config
      sub-folder named gnu-warnings. Flags that only are available for a specific
      version of the compiler are in files named with that version.
      Clang C warnings flags were moved to files in a config sub-folder
      named clang-warnings.
      Intel C, Fortran warnings flags were moved to files in a config sub-folder
      named intel-warnings.

      There are flags in named "error-xxx" files with warnings that may
      be promoted to errors. Some source files may still need fixes.

      There are also pairs of files named "developer-xxx" and "no-developer-xxx"
      that are chosen by the CMake option:HDF5_ENABLE_DEV_WARNINGS or the
      configure option:--enable-developer-warnings.

      In addition, CMake no longer applies these warnings for examples.

      (ADB - 2020/03/24, TRILAB-192)

    - Added test script for file size compare

      if CMake minimum version is at least 3.14, the fileCompareTest.cmake
      script will compare file sizes.

      (ADB - 2020/02/24, HDFFV-11036)

    - Update CMake minimum version to 3.12

      Updated CMake minimum version to 3.12 and added version checks
      for Windows features.

      (ADB - 2020/02/05, TRILABS-142)

    - Fixed CMake include properties for Fortran libraries

      Corrected the library properties for Fortran to use the
      correct path for the Fortran module files.

      (ADB - 2020/02/04, HDFFV-11012)

    - Added common warnings files for gnu and intel

      Added warnings files to use one common set of flags
      during configure for both autotools and CMake build
      systems. The initial implementation only affects a
      general set of flags for gnu and intel compilers.

      (ADB - 2020/01/17)

    - Added new options to CMake for control of testing

      Added CMake options (default ON);
          HDF5_TEST_SERIAL AND/OR HDF5_TEST_PARALLEL
          combined with:
            HDF5_TEST_TOOLS
            HDF5_TEST_EXAMPLES
            HDF5_TEST_SWMR
            HDF5_TEST_FORTRAN
            HDF5_TEST_CPP
            HDF5_TEST_JAVA

      (ADB - 2020/01/15, HDFFV-11001)

    - Added Clang sanitizers to CMake for analyzer support if compiler is clang.

      Added CMake code and files to execute the Clang sanitizers if
      HDF5_ENABLE_SANITIZERS is enabled and the USE_SANITIZER option
      is set to one of the following:
          Address
          Memory
          MemoryWithOrigins
          Undefined
          Thread
          Leak
          'Address;Undefined'

      (ADB - 2019/12/12, TRILAB-135)

    - Update CMake for VS2019 support

      CMake added support for VS2019 in version 3.15. Changes to the CMake
      generator setting required changes to scripts. Also updated version
      references in CMake files as necessary.

      (ADB - 2019/11/18, HDFFV-10962)

    - Update CMake options to match new autotools options

      Add configure options (autotools - CMake):
            enable-asserts       HDF5_ENABLE_ASSERTS
            enable-symbols       HDF5_ENABLE_SYMBOLS
            enable-profiling     HDF5_ENABLE_PROFILING
            enable-optimization  HDF5_ENABLE_OPTIMIZATION
      In addition NDEBUG is no longer forced defined and relies on the CMake
      process.

      (ADB - 2019/10/07, HDFFV-100901, HDFFV-10637, TRILAB-97)

    - Update CMake tests to use FIXTURES

      CMake test fixtures allow setup/cleanup tests and other dependency
      requirements as properties for tests. This is more flexible for
      modern CMake code.

      (ADB - 2019/07/23, HDFFV-10529)

    - Windows PDB files are always installed

      There are build configuration or flag settings for Windows that may not
      generate PDB files. If those files are not generated then the install
      utility will fail because those PDB files are not found. An optional
      variable, DISABLE_PDB_FILES, was added to not install PDB files.

      (ADB - 2019/07/17, HDFFV-10424)

    - Add mingw CMake support with a toolchain file

      There has been a number of mingw issues that has been linked under
      HDFFV-10845. It has been decided to implement the CMake cross-compiling
      technique of toolchain files. We will use a linux platform with the mingw
      compiler stack for testing. Only the C language is fully supported, and
      the error tests are skipped. The C++ language works for static but shared
      builds has a shared library issue with the mingw Standard Exception Handling
      library, which is not available on Windows. Fortran has a common cross-compile
      problem with the fortran configure tests.

      (ADB - 2019/07/12, HDFFV-10845, HDFFV-10595)

    - Windows PDB files are installed incorrectly

      For static builds, the PDB files for windows should be installed next
      to the static libraries in the lib folder. Also the debug versions of
      libraries and PDB files are now correctly built using the default
      CMAKE_DEBUG_POSTFIX setting.

      (ADB - 2019/07/09, HDFFV-10581)

    - Add option to build only shared libs

      A request was made to prevent building static libraries and only build
      shared.  A new option was added to CMake, ONLY_SHARED_LIBS, which will
      skip building static libraries. Certain utility functions will build with
      static libs but are not published. Tests are adjusted to use the correct
      libraries depending on SHARED/STATIC settings.

      (ADB - 2019/06/12, HDFFV-10805)

    - Add options to enable or disable building tools and tests

      Configure options --enable-tests and --enable-tools were added for
      autotools configure.  These options are enabled by default, and can be
      disabled with either --disable-tests (or tools) or --enable-tests=no
      (or --enable-tools=no).  Build time is reduced ~20% when tools are
      disabled, 35% when tests are disabled, 45% when both are disabled.
      Reenabling them after the initial build requires running configure
      again with the option(s) enabled.

      (LRK - 2019/06/12, HDFFV-9976)

    - Change tools test that test the error stack

      There are some use cases which can cause the error stack of tools to be
      different then the expected output. These tests now use grepTest.cmake,
      this was changed to allow the error file to be searched for an expected string.

      (ADB - 2019/04/15, HDFFV-10741)

    - Keep stderr and stdout separate in tests

      Changed test handling of output capture. Tests now keep the stderr
      output separate from the stdout output. It is up to the test to decide
      which output to check against a reference. Also added the option
      to grep for a string in either output.

      (ADB - 2018/12/12, HDFFV-10632)

    - Add toolchain and cross-compile support

      Added info on using a toolchain file to INSTALL_CMAKE.txt. A
      toolchain file is also used in cross-compiling, which requires
      CMAKE_CROSSCOMPILING_EMULATOR to be set. To help with cross-compiling
      the fortran configure process, the HDF5UseFortran.cmake file macros
      were improved. Fixed a Fortran configure file issue that incorrectly
      used #cmakedefine instead of #define.

      (ADB - 2018/10/04, HDFFV-10594)

    - Add warning flags for Intel compilers

      Identified Intel compiler specific warnings flags that should be used
      instead of GNU flags.

      (ADB - 2018/10/04, TRILABS-21)

    - Add default rpath to targets

      Default rpaths should be set in shared executables and
      libraries to allow the use of loading dependent libraries
      without requiring LD_LIBRARY_PATH to be set. The default
      path should be relative using @rpath on osx and $ORIGIN
      on linux. Windows is not affected.

      (ADB - 2018/09/26, HDFFV-10594)

    - Add missing USE_110_API_DEFAULT option.

      Option USE_110_API_DEFAULT sets the default version of
      versioned APIs. The bin/makevers perl script did not set
      the maxidx variable correctly when the 1.10 branch was
      created. This caused the versioning process to always use
      the latest version of any API.

      (ADB - 2018/08/17, HDFFV-10552)

    - Added configuration checks for the following MPI functions:

      MPI_Mprobe - Used for the Parallel Compression feature
      MPI_Imrecv - Used for the Parallel Compression feature

      MPI_Get_elements_x - Used for the "big Parallel I/O" feature
      MPI_Type_size_x - Used for the "big Parallel I/O" feature

      (JTH - 2018/08/02, HDFFV-10512)

    - Added section to the libhdf5.settings file to indicate
      the status of the Parallel Compression and "big Parallel I/O"
      features.

      (JTH - 2018/08/02, HDFFV-10512)

    - Add option to execute swmr shell scripts from CMake.

      Option TEST_SHELL_SCRIPTS redirects processing into a
      separate ShellTests.cmake file for UNIX types. The tests
      execute the shell scripts if a SH program is found.

      (ADB - 2018/07/16)

    - Add file locking configure and CMake options

      HDF5 1.10.0 introduced a file locking scheme, primarily to help
      enforce SWMR setup. Formerly, the only user-level control of the scheme
      was via the HDF5_USE_FILE_LOCKING environment variable.

      This change introduces configure-time options that control whether
      or not file locking will be used and whether or not the library
      ignores errors when locking has been disabled on the file system
      (useful on some HPC Lustre installations).

      In both the Autotools and CMake, the settings have the effect of changing
      the default property list settings (see the H5Pset/get_file_locking()
      entry, below).

      The yes/no/best-effort file locking configure setting has also been
      added to the libhdf5.settings file.

      Autotools:

        An --enable-file-locking=(yes|no|best-effort) option has been added.

        yes:          Use file locking.
        no:           Do not use file locking.
        best-effort:  Use file locking and ignore "disabled" errors.

      CMake:

        Two self-explanatory options have been added:

        HDF5_USE_FILE_LOCKING
        HDF5_IGNORE_DISABLED_FILE_LOCKS

        Setting both of these to ON is the equivalent to the Autotools'
        best-effort setting.

      NOTE:
      The precedence order of the various file locking control mechanisms is:

        1) HDF5_USE_FILE_LOCKING environment variable (highest)

        2) H5Pset_file_locking()

        3) configure/CMake options (which set the property list defaults)

        4) library defaults (currently best-effort)

      (DER - 2020/07/30, HDFFV-11092)


    Library:
    --------
    - Add new public function H5Ssel_iter_reset

      This function resets a dataspace selection iterator back to an
      initial state so that it may be used for iteration once more.
      This can be useful when needing to iterate over a selection
      multiple times without having to repeatedly create/destroy
      a selection iterator for that dataspace selection.

      (JTH - 2020/09/18)

    - Remove HDFS VFD stubs

      The original implementation of the HDFS VFD included non-functional
      versions of the following public API calls when the HDFS VFD is
      not built as a part of the HDF5 library:

      * H5FD_hdfs_init()
      * H5Pget_fapl_hdfs()
      * H5Pset_fapl_hdfs()

      They will remain present in HDF5 1.10 and HDF5 1.12 releases
      for binary compatibility purposes but have been removed as of 1.14.0.

      Note that this has nothing to do with the real HDFS VFD API calls
      that are fully functional when the HDFS VFD is configured and built.

      We simply changed:

      #ifdef LIBHDFS
        <real API call>
      #else
        <useless stub>
      #endif

      to:

      #ifdef LIBHDFS
        <real API call>
      #endif

      Which is how the other optional VFDs are handled.

      (DER - 2020/08/27)

    - Add Mirror VFD

      Use TCP/IP sockets to perform write-only (W/O) file I/O on a remote
      machine. Must be used in conjunction with the Splitter VFD.

      (JOS - 2020/03/13, TBD)

    - Add Splitter VFD

      Maintain separate R/W and W/O channels for "concurrent" file writes
      to two files using a single HDF5 file handle.

     (JOS - 2020/03/13, TBD)

    - Refactored public exposure of haddr_t type in favor of "object tokens"

      To better accommodate HDF5 VOL connectors where "object addresses in a file"
      may not make much sense, the following changes were made to the library:

      * Introduced new H5O_token_t "object token" type, which represents a
        unique and permanent identifier for referencing an HDF5 object within
        a container; these "object tokens" are meant to replace object addresses.
        Along with the new type, a new H5Oopen_by_token API call was introduced
        to open an object by a token, similar to how object addresses were
        previously used with H5Oopen_by_addr.

      * Introduced new H5Lget_info2, H5Lget_info_by_idx2, H5Literate2, H5Literate_by_name2,
        H5Lvisit2 and H5Lvisit_by_name2 API calls, along with their associated H5L_info2_t
        struct and H5L_iterate2_t callback function, which work with the newly-introduced
        object tokens, instead of object addresses. The original functions have been
        renamed to version 1 functions and are deprecated in favor of the new version 2
        functions. The H5L_info_t and H5L_iterate_t types have been renamed to version 1
        types and are now deprecated in favor of their version 2 counterparts. For each of
        the functions and types, compatibility macros take place of the original symbols.

      * Introduced new H5Oget_info3, H5Oget_info_by_name3, H5Oget_info_by_idx3,
        H5Ovisit3 and H5Ovisit_by_name3 API calls, along with their associated H5O_info2_t
        struct and H5O_iterate2_t callback function, which work with the newly-introduced
        object tokens, instead of object addresses. The version 2 functions are now
        deprecated in favor of the version 3 functions. The H5O_info_t and H5O_iterate_t
        types have been renamed to version 1 types and are now deprecated in favor of their
        version 2 counterparts. For each, compatibility macros take place of the original
        symbols.

      * Introduced new H5Oget_native_info, H5Oget_native_info_by_name and
        H5Oget_native_info_by_idx API calls, along with their associated H5O_native_info_t
        struct, which are used to retrieve the native HDF5 file format-specific information
        about an object. This information (such as object header info and B-tree/heap info)
        has been removed from the new H5O_info2_t struct so that the more generic
        H5Oget_info(_by_name/_by_idx)3 routines will not try to retrieve it for non-native
        VOL connectors.

      * Added new H5Otoken_cmp, H5Otoken_to_str and H5Otoken_from_str routines to compare
        two object tokens, convert an object token into a nicely-readable string format and
        to convert an object token string back into a real object token, respectively.

      (DER, QAK, JTH - 2020/01/16)

    - Add new public function H5Sselect_adjust.

      This function shifts a dataspace selection by a specified logical offset
      within the dataspace extent.  This can be useful for VOL developers to
      implement chunked datasets.

      (NAF - 2019/11/18)

    - Add new public function H5Sselect_project_intersection.

      This function computes the intersection between two dataspace selections
      and projects that intersection into a third selection.  This can be useful
      for VOL developers to implement chunked or virtual datasets.

      (NAF - 2019/11/13, ID-148)

    - Add new public function H5VLget_file_type.

      This function returns a datatype equivalent to the supplied datatype but
      with the location set to be in the file.  This datatype can then be used
      with H5Tconvert to convert data between file and in-memory representation.
      This funcition is intended for use only by VOL connector developers.

      (NAF - 2019/11/08, ID-127)

    - Add S3 and HDFS VFDs to HDF5 maintenance

      Fix windows requirements and java tests. Windows requires CMake 3.13.
            Install openssl library (with dev files);
            from "Shining Light Productions". msi package preferred.

            PATH should have been updated with the installation dir.
            set ENV variable OPENSSL_ROOT_DIR to the installation dir.
            set ENV variable OPENSSL_CONF to the cfg file, likely %OPENSSL_ROOT_DIR%\bin\openssl.cfg
            Install libcurl library (with dev files);
            download the latest released version using git: https://github.com/curl/curl.git

            Open a Visual Studio Command prompt
            change to the libcurl root folder
            run the "buildconf.bat" batch file
            change to the winbuild directory
            nmake /f Makefile.vc mode=dll MACHINE=x64
            copy libcurl-vc-x64-release-dll-ipv6-sspi-winssl dir to C:\curl (installation dir)
            set ENV variable CURL_ROOT to C:\curl (installation dir)
            update PATH ENV variable to %CURL_ROOT%\bin (installation bin dir).
            the aws credentials file should be in %USERPROFILE%\.aws folder
            set the ENV variable "HDF5_ROS3_TEST_BUCKET_URL=https://s3.us-east-2.amazonaws.com/hdf5ros3"

      (ADB - 2019/09/12, HDFFV-10854)

    - Added new chunk query functions

      The following public functions were added to discover information about
      the chunks in an HDF5 file.
        herr_t H5Dget_num_chunks(dset_id, fspace_id, *nchunks)
        herr_t H5Dget_chunk_info_by_coord(dset_id, *coord, *filter_mask, *addr, *size)
        herr_t H5Dget_chunk_info(dset_id, fspace_id, index, *coord, *filter_mask, *addr, *size)

      (BMR - 2019/06/11, HDFFV-10677)

    - Improved the performance of virtual dataset I/O

      Refactored the internal dataspace routines used by the virtual dataset
      code to improve performance, especially when one of the selections
      involved is very long and non-contiguous.

      (NAF - 2019/05/31, HDFFV-10693)

    - Added the ability to open files with UTF-8 file names on Windows.

      The POSIX open(2) API call on Windows is limited to ASCII
      file names. The library has been updated to convert incoming file
      names to UTF-16 (via MultiByteToWideChar(CP_UTF8, ...) and use
      _wopen() instead.

     (DER - 2019/03/15, HDFFV-2714, HDFFV-3914, HDFFV-3895, HDFFV-8237, HDFFV-10413, HDFFV-10691)

    - Add new API H5M for map objects.  Currently not supported by native
      library, can be supported by VOL connectors.

      (NAF - 2019/03/01)

    - Add new H5R_ref_t type for object, dataset region and _attribute_
      references. This new type will deprecate the current hobj_ref_t
      and hdset_reg_ref_t types for references. Added H5T_REF datatype
      to read and write new reference types. As opposed to previous
      reference types, reference creation no longer modifies existing
      files. New reference types also now support references to external
      files.

      (JS - 2019/10/08)

    - Remove H5I_REFERENCE from the library

      This ID class was never used by the library and has been removed.

      (DER - 2018/12/08, HDFFV-10252)

    - Allow pre-generated H5Tinit.c and H5make_libsettings.c to be used.

      Rather than always running H5detect and generating H5Tinit.c and
      H5make_libsettings.c, supply a location for those files.

      (ADB - 2018/09/18, HDFFV-10332)

    - Fix shutdown failure when using H5VLregister_connector_by_name/value

      When using H5VLregister_connector_by_name/value to dynamically load a
      VOL connector plugin, the library can experience segmentation faults
      when the library is closed. This is due to the library unloading
      the plugin interface before the virtual object layer. Then, when the
      VOL shutdown occurs, it will attempt to close the VOL connector,
      however this will fail since the plugin will already have been unloaded.

      (DER - 2020/03/18, HDFFV-11057)

    - Add BEST_EFFORT value to HDF5_USE_FILE_LOCKING environment variable

      This change adds a BEST_EFFORT to the TRUE/FALSE, 1/0 settings that
      were previously accepted. This option turns on file locking but
      ignores locking errors when the library detects that file locking
      has been disabled on a file system (useful on some HPC Lustre
      installations).

      The capitalization of BEST_EFFORT is mandatory.

      See the configure option discussion for HDFFV-11092 (above) for more
      information on the file locking feature and how it's controlled.

      (DER - 2020/07/30, HDFFV-11092)


    - Add H5Pset/get_file_locking() API calls

      This change adds new API calls which can be used to set or get the
      file locking parameters. The single API call sets both the "use file
      locking" flag and the "ignore disabled file locking" flag.

      See the configure option discussion for HDFFV-11092 (above) for more
      information on the file locking feature and how it's controlled.

      (DER - 2020/07/30, HDFFV-11092)

    Parallel Library:
    -----------------
    - Changed the default behavior in parallel when reading the same dataset in its entirely
      (i.e. H5S_ALL dataset selection) which is being read by all the processes collectively.
      The dataset mush be contiguous, less than 2GB, and of an atomic datatype.
      The new behavior is the HDF5 library will use an MPI_Bcast to pass the data read from
      the disk by the root process to the remain processes in the MPI communicator associated
      with the HDF5 file.

      (MSB - 2019/01/02, HDFFV-10652)

    Fortran Library:
    ----------------
    - Added new Fortran derived type, c_h5o_info_t, which is interoperable with
      C's h5o_info_t. This is needed for callback functions which
      pass C's h5o_info_t data type definition.

      (MSB, 2019/01/08, HDFFV-10443)

    - Added new Fortran API, H5gmtime, which converts (C) 'time_t' structure
      to Fortran DATE AND TIME storage format.

      (MSB, 2019/01/08, HDFFV-10443)

    - Added new Fortran 'fields' optional parameter to: h5ovisit_f, h5oget_info_by_name_f,
      h5oget_info, h5oget_info_by_idx and h5ovisit_by_name_f.

      (MSB, 2019/01/08, HDFFV-10443)

    - Add wrappers for H5Pset/get_file_locking() API calls

      h5pget_file_locking_f()
      h5pset_file_locking_f()

      See the configure option discussion for HDFFV-11092 (above) for more
      information on the file locking feature and how it's controlled.

      (DER - 2020/07/30, HDFFV-11092)

    C++ Library:
    ------------
    - Added new wrappers for H5Pset/get_create_intermediate_group()
        LinkCreatPropList::getCreateIntermediateGroup()
        LinkCreatPropList::setCreateIntermediateGroup()

      (BMR - 2019/04/22, HDFFV-10622)

    - Added new wrapper for H5Ovisit2()
          H5Object::visit()

      (BMR - 2019/02/14, HDFFV-10532)

    - Add wrappers for H5Pset/get_file_locking() API calls

      FileAccPropList::setFileLocking()
      FileAccPropList::getFileLocking()

      See the configure option discussion for HDFFV-11092 (above) for more
      information on the file locking feature and how it's controlled.

      (DER - 2020/07/30, HDFFV-11092)


    Java Library:
    ----------------
    - Added ability to test java library with VOLs.

      Created new CMake script that combines the java and vol test scripts.

      (ADB - 2020/02/03, HDFFV-10996)

    - Tests fail for non-English locale.

      In the JUnit tests with a non-English locale, only the part before
      the decimal comma is replaced by XXXX and this leads to a comparison
      error. Changed the regex for the Time substitution.

      (ADB - 2020/01/09, HDFFV-10995)

    - Fix a failure in JUnit-TestH5P on 32-bit architectures

      (JTH - 2019/04/30)

    - Duplicate the data read/write functions of Datasets for Attributes.

      Region references could not be displayed for attributes as they could
      for datasets. Datasets had overloaded read and write functions for different
      datatypes that were not available for attributes. After adding similar
      functions, attribute region references work normally.

      (ADB - 2018/12/12, HDFVIEW-4)

    - Removed H5I_REFERENCE from the Java wrappers

      This ID class was never used by the library and has been removed
      from the Java wrappers.

      (DER - 2018/12/08, HDFFV-10252)

    - Add wrappers for H5Pset/get_file_locking() API calls

      H5Pset_file_locking()
      H5Pget_use_file_locking()
      H5Pget_ignore_disabled_file_locking()

      Unlike the C++ and Fortran wrappers, there are separate getters for the
      two file locking settings, each of which returns a boolean value.

      See the configure option discussion for HDFFV-11092 (above) for more
      information on the file locking feature and how it's controlled.

      (DER - 2020/07/30, HDFFV-11092)


    Tools:
    ------
    - h5repack added options to control how external links are handled.

      Currently h5repack preserves external links and cannot copy and merge
      data from the external files. Two options, merge and prune, were added to
      control how to merge data from an external link into the resulting file.
       --merge             Follow external soft link recursively and merge data.
       --prune             Do not follow external soft links and remove link.
       --merge --prune     Follow external link, merge data and remove dangling link.

      (ADB - 2020/08/05, HDFFV-9984)

    - h5repack was fixed to repack the reference attributes properly.
      The code line that checks if the update of reference inside a compound
      datatype is misplaced outside the code block loop that carries out the
      check. In consequence, the next attribute that is not the reference
      type was repacked again as the reference type and caused the failure of
      repacking. The fix is to move the corresponding code line to the correct
      code block.

      (KY -2020/02/07, HDFFV-11014)

    - h5diff was updated to use the new reference APIs.

      h5diff uses the new reference APIs to compare references.
      Attribute references can also be compared.

      (ADB - 2019/12/19, HDFFV-10980)

    - h5dump and h5ls were updated to use the new reference APIs.

      The tools library now use the new reference APIs to inspect a
      file. Also the DDL spec was updated to reflect the format
      changes produced with the new APIs. The export API and support
      functions in the JNI were updated to match.

      (ADB - 2019/12/06, HDFFV-10876 and HDFFV-10877)

    - h5repack was fixed to repack datasets with external storage
      to other types of storage.

      New test added to repack files and verify the correct data using h5diff.

      (JS - 2019/09/25, HDFFV-10408)
      (ADB - 2019/10/02, HDFFV-10918)

    - h5dump was fixed for 128-bit floats, but was missing a test.

      New test greps for the first 15 numbers of the 128-bit value.

      (ADB - 2019/06/23, HDFFV-9407)


    High-Level APIs:
    ---------------
    - 

    C Packet Table API
    ------------------
    -

    Internal header file
    --------------------
    -

    Documentation
    -------------
    -

Support for new platforms, languages and compilers.
=======================================
    -

Bug Fixes since HDF5-1.10.3 release
==================================

    Library
    -------
    - Creation of dataset with optional filter

      When the combination of type, space, etc doesn't work for filter
      and the filter is optional, it was supposed to be skipped but it was
      not skipped and the creation failed.

      Allowed the creation of the dataset in such situation.

      (BMR - 2020/8/13, HDFFV-10933)

    - Explicitly declared dlopen to use RTLD_LOCAL

      dlopen documentation states that if neither RTLD_GLOBAL nor
      RTLD_LOCAL are specified, then the default behavior is unspecified.
      The default on linux is usually RTLD_LOCAL while macos will default
      to RTLD_GLOBAL.

      (ADB - 2020/08/12, HDFFV-11127)

    - Fixed issues CVE-2018-13870 and CVE-2018-13869

      When a buffer overflow occurred because a name length was corrupted
      and became very large, h5dump crashed on memory access violation.

      A check for reading pass the end of the buffer was added to multiple
      locations to prevent the crashes and h5dump now simply fails with an
      error message when this error condition occurs.

      (BMR - 2020/07/22, HDFFV-11120 and HDFFV-11121)

    - Fixed the segmentation fault when reading attributes with multiple threads

      It was reported that the reading of attributes with variable length string
      datatype will crash with segmentation fault particularly when the number of
      threads is high (>16 threads).  The problem was due to the file pointer that
      was set in the variable length string datatype for the attribute.  That file
      pointer was already closed when the attribute was accessed.

      The problem was fixed by setting the file pointer to the current opened file pointer
      when the attribute was accessed.  Similar patch up was done before when reading
      dataset with variable length string datatype.

      (VC - 2020/07/13, HDFFV-11080)

    - Fixed CVE-2020-10810

      The tool h5clear produced a segfault during an error recovery in
      the superblock decoding.  An internal pointer was reset to prevent
      further accessing when it is not assigned with a value.

      (BMR - 2020/6/29, HDFFV-11053)

    - Fixed CVE-2018-17435

      The tool h52gif produced a segfault when the size of an attribute
      message was corrupted and caused a buffer overflow.

      The problem was fixed by verifying the attribute message's size
      against the buffer size before accessing the buffer.  h52gif was
      also fixed to display the failure instead of silently exiting
      after the segfault was eliminated.

      (BMR - 2020/6/19, HDFFV-10591)

    - Improved peformance when creating a large number of small datasets by
      retrieving default property values from the API context instead of doing
      skip list searches.

      (CJH - 2019/12/10, HDFFV-10658)

    - Fixed user-created data access properties not existing in the property list
      returned by H5Dget_access_plist. Thanks to Steven Varga for submitting a
      reproducer and a patch.

      (CJH - 2019/12/9, HDFFV-10934)

    - Fixed an assertion failure in the parallel library when collectively
      filling chunks. As it is required that chunks be written in
      monotonically non-decreasing order of offset in the file, this assertion
      was being triggered when the list of chunk file space allocations being
      passed to the collective chunk filling routine was not sorted according
      to this particular requirement.

      The addition of a sort of the out of order chunks trades a bit of
      performance for the elimination of this assertion and of any complaints
      from MPI implementations about the file offsets used being out of order.

      (JTH - 2019/10/07, HDFFV-10792)

    - Fixed the iteration error in test_versionbounds() in test/dtypes.c

      The test was supposed to loop through all valid combinations of
      low and high bounds in the array versions[], but they were set to
      H5F_LIBVER_EARLIEST always without changing.

      The problem was fixed by indexing low and high into the array versions[].

      (VC - 2019/09/30)

    - Fixed the slowness of regular hyperslab selection in a chunked dataset

      It was reported that the selection of every 10th element from a 20G
      chunked dataset was extremely slow and sometimes could hang the system.
      The problem was due to the iteration and the building of the span tree
      for all the selected elements in file space.

      As the selected elements are going to a 1-d contiguous single block
      memory space, the problem was fixed by building regular hyperslab selections
      in memory space for the selected elements in file space.

      (VC - 2019/09/26, HDFFV-10585)

    - Fixed a bug caused by bad tag value when condensing object header
      messages

      There was an assertion failure when moving meessages from running a
      user test program with library release hdf5.1.10.4. It was because
      the tag value (object header's address) was not set up when entering
      the library routine H5O__chunk_update_idx(), which will eventually
      verifies the metadata tag value when protecting the object header.

      The problem was fixed by replacing FUNC_ENTER_PACKAGE in H5O__chunk_update_idx()
      with FUNC_ENTER_PACKAGE_TAG(oh->cache_info.addr) to set up the metadata tag.

      (VC - 2019/08/23, HDFFV-10873)

    - Fixed the test failure from test_metadata_read_retry_info() in
      test/swmr.c

      The test failure is due to the incorrect number of bins returned for
      retry info (info.nbins).  The # of bins expected for 101 read attempts
      is 3 instead of 2.  The routine H5F_set_retries() in src/H5Fint.c
      calculates the # of bins by first obtaining the log10 value for
      (read attempts - 1).  For PGI/19, the log10 value for 100 read attempts
      is 1.9999999999999998 instead of 2.00000.  When casting the log10 value
      to unsigned later on, the decimal part is chopped off causing the test
      failure.

      This was fixed by obtaining the rounded integer value (HDceil) for the
      log10 value of read attempts first before casting the result to unsigned.

      (VC - 2019/8/14, HDFFV-10813)

    - Fixed an issue where creating a file with non-default file space info
      together with library high bound setting to H5F_LIBVER_V18.

      When setting non-default file space info in fcpl via
      H5Pset_file_space_strategy() and then creating a file with
      both high and low library bounds set to
      H5F_LIBVER_V18 in fapl, the library succeeds in creating the file.
      File creation should fail because the feature of setting non-default
      file space info does not exist in library release 1.8 or earlier.

      This was fixed by setting and checking the proper version in the
      file space info message based on the library low and high bounds
      when creating and opening the HDF5 file.

      (VC - 2019/6/25, HDFFV-10808)

    - When iterating over an old-style group (i.e., when not using the latest
      file format) of size 0, a NULL pointer representing the empty links
      table would be sent to qsort(3) for sorting, which is undefined behavior.

      Iterating over an empty group is explicitly tested in the links test.
      This has not caused any failures to date and was flagged by gcc's
      -fsanitize=undefined.

      The library no longer attempts to sort an empty array.

      (DER - 2019/06/18, HDFFV-10829)

    - Fixed an issue where copying a version 1.8 dataset between files using
      H5Ocopy fails due to an incompatible fill version

      When using the HDF5 1.10.x H5Ocopy() API call to copy a version 1.8
      dataset to a file created with both high and low library bounds set to
      H5F_LIBVER_V18, the H5Ocopy() call will fail with the error stack indicating
      that the fill value version is out of bounds.

      This was fixed by changing the fill value message version to H5O_FILL_VERSION_3
      (from H5O_FILL_VERSION_2) for H5F_LIBVER_V18.

      (VC - 2019/6/14, HDFFV-10800)

    - Some oversights in the index iterating area of the library caused
      a callback function to continue iterating even though it's supposed
      to stop.

      Added the returned value check to the for loop's conditions in
      H5EA_iterate(), H5FA_iterate(), and H5D__none_idx_iterate().  The
      iteration now stops when it should.

      (BMR - 2019/06/11, HDFFV-10661)

    - Fixed a bug that would cause an error or cause fill values to be
      incorrectly read from a chunked dataset using the "single chunk" index if
      the data was held in cache and there was no data on disk.

      (NAF - 2019/03/06)

    - Fixed a bug that could cause an error or cause fill values to be
      incorrectly read from a dataset that was written to using H5Dwrite_chunk
      if the dataset was not closed after writing.

      (NAF - 2019/03/06, HDFFV-10716)

    - Fixed memory leak in scale offset filter

      In a special case where the MinBits is the same as the number of bits in
      the datatype's precision, the filter's data buffer was not freed, causing
      the memory usage to grow. In general the buffer was freed correctly.  The
      Minbits are the minimal number of bits to store the data values.  Please
      see the reference manual for H5Pset_scaleoffset for the detail.

      (RL - 2019/3/4, HDFFV-10705)

    - Fix hangs with collective metadata reads during chunked dataset I/O

      In the parallel library, it was discovered that when a particular
      sequence of operations following a pattern of:

      "write to chunked dataset" -> "flush file" -> "read from dataset"

      occurred with collective metadata reads enabled, hangs could be
      observed due to certain MPI ranks not participating in the collective
      metadata reads.

      To fix the issue, collective metadata reads are now disabled during
      chunked dataset raw data I/O.

      (JTH - 2019/02/11, HDFFV-10563, HDFFV-10688)

    - Performance issue when closing an object

      The slow down is due to the search of the "tag_list" to find
      out the "corked" status of an object and "uncork" it if so.

      Improve porformance by skipping the search of the "tag_list"
      if there are no "corked" objects when closing an object.

      (VC - 2019/2/6)

    - Fixed a potential invalid memory access and failure that could occur when
      decoding an unknown object header message (from a future version of the
      library).

      (NAF - 2019/01/07)

    - Deleting attributes in dense storage

      The library aborts with "infinite loop closing library" after
      attributes in dense storage are created and then deleted.

      When deleting the attribute nodes from the name index v2 B-tree,
      if an attribute is found in the intermediate B-tree nodes,
      which may be merged/redistributed in the process, we need to
      free the dynamically allocated spaces for the intermediate
      decoded attribute.

      (VC - 2018/12/26, HDFFV-10659)

    - Allow H5detect and H5make_libsettings to take a file as an argument.

      Rather than only writing to stdout, add a command argument to name
      the file that H5detect and H5make_libsettings will use for output.
      Without an argument, stdout is still used, so backwards compatibility
      is maintained.

      (ADB - 2018/09/05, HDFFV-9059)

    - A bug was discovered in the parallel library where an application
      would hang if a collective read/write of a chunked dataset occurred
      when collective metadata reads were enabled and some of the ranks
      had no selection in the dataset's dataspace. The ranks which had no
      selection in the dataset's dataspace called H5D__chunk_addrmap() to
      retrieve the lowest chunk address in the dataset. This is because we
      require reads/writes to be performed in strictly non-decreasing order
      of chunk address in the file.

      When the chunk index used was a version 1 or 2 B-tree, these
      non-participating ranks would issue a collective MPI_Bcast() call
      that the participating ranks would not issue, causing the hang. Since
      the non-participating ranks are not actually reading/writing anything,
      the H5D__chunk_addrmap() call can be safely removed and the address used
      for the read/write can be set to an arbitrary number (0 was chosen).

      (JTH - 2018/08/25, HDFFV-10501)

    - fcntl(2)-based file locking incorrectly passed the lock argument struct
      instead of a pointer to the struct, causing errors on systems where
      flock(2) is not available.

      File locking is used when files are opened to enforce SWMR semantics. A
      lock operation takes place on all file opens unless the
      HDF5_USE_FILE_LOCKING environment variable is set to the string "FALSE".
      flock(2) is preferentially used, with fcntl(2) locks as a backup if
      flock(2) is unavailable on a system (if neither is available, the lock
      operation fails). On these systems, the file lock will often fail, which
      causes HDF5 to not open the file and report an error.

      This bug only affects POSIX systems. Win32 builds on Windows use a no-op
      locking call which always succeeds. Systems which exhibit this bug will
      have H5_HAVE_FCNTL defined but not H5_HAVE_FLOCK in the configure output.

      This bug affects HDF5 1.10.0 through 1.10.5.

      fcntl(2)-based file locking now correctly passes the struct pointer.

      (DER - 2019/08/27, HDFFV-10892)

    - Torn pread/pwrite I/O would result in read and write corruption.

      In the sec2, log, and core (with backing store) virtual file drivers
      (VFDs), the read and write calls incorrectly reset the offset parameter
      on torn pread and pwrite operations (i.e., I/O operations which fail to
      be written atomically by the OS). For this bug to occur, pread/pwrite
      have to be configured (this is the default if they are present on the
      system) and the pread/pwrite operation has to fail to transfer all
      the bytes, resulting in a multiple pread/pwrite calls.

      This feature was initially enabled in HDF5 1.10.5 so the bug is
      limited to that version.

      (DER - 2019/12/09, HDFFV-10945)

    - H5Sset_extent_none() sets the dataspace class to H5S_NO_CLASS which
      causes asserts/errors when passed to other dataspace API calls.

      H5S_NO_CLASS is an internal class value that should not have been
      exposed via a public API call.

      In debug builds of the library, this can cause asserts to trip. In
      non-debug builds, it will produce normal library errors.

      The new library behavior is for H5Sset_extent_none() to convert
      the dataspace into one of type H5S_NULL, which is better handled
      by the library and easier for developers to reason about.

      (DER - 2020/07/27, HDFFV-11027)


    Java Library:
    ----------------
    - JNI native library dependencies

      The build for the hdf5_java native library used the wrong
      hdf5 target library for CMake builds. Correcting the hdf5_java
      library to build with the shared hdf5 library required testing
      paths to change also.

      (ADB - 2018/08/31, HDFFV-10568)
     - Java iterator callbacks

      Change global callback object to a small stack structure in order
      to fix a runtime crash. This crash was discovered when iterating
      through a file with nested group members. The global variable
      visit_callback is overwritten when recursion starts. When recursion
      completes, visit_callback will be pointing to the wrong callback method.

      (ADB - 2018/08/15, HDFFV-10536)

    - Java HDFLibraryException class

      Change parent class from Exception to RuntimeException.

      (ADB - 2018/07/30, HDFFV-10534)

    - JNI Read and Write

      Refactored variable-length functions, H5DreadVL and H5AreadVL,
      to correct dataset and attribute reads. New write functions,
      H5DwriteVL and H5AwriteVL, are under construction.

      (ADB - 2018/06/02, HDFFV-10519)

    Configuration
    -------------
    - Correct option for default API version

      CMake options for default API version are not mutually exclusive.
      Change the multiple BOOL options to a single STRING option with the
      strings; v16, v18, v110, v112.

      (ADB - 2019/08/12, HDFFV-10879)

    Performance
    -------------
    -

    Fortran
    --------
    - Added symbolic links libhdf5_hl_fortran.so to libhdf5hl_fortran.so and
      libhdf5_hl_fortran.a to libhdf5hl_fortran.a in hdf5/lib directory for
      autotools installs.  These were added to match the name of the files
      installed by cmake and the general pattern of hl lib files.  We will
      change the names of the installed lib files to the matching name in
      the next major release.

      (LRK - 2019/01/04, HDFFV-10596)

    - Made Fortran specific subroutines PRIVATE in generic procedures.

      Effected generic procedures were functions in H5A, H5D, H5P, H5R and H5T.

      (MSB, 2018/12/04, HDFFV-10511)

    - Fixed issue with Fortran not returning h5o_info_t field values
      meta_size%attr%index_size and  meta_size%attr%heap_size.

      (MSB, 2018/1/8, HDFFV-10443)

    - Corrected INTERFACE INTENT(IN) to INTENT(OUT) for buf_size in h5fget_file_image_f.

      (MSB - 2020/2/18, HDFFV-11029)

    Tools
    -----
    - The tools library was updated by standardizing the error stack process.

      General sequence is:
          h5tools_setprogname(PROGRAMNAME);
          h5tools_setstatus(EXIT_SUCCESS);
          h5tools_init();
          ... process the command-line (check for error-stack enable) ...
          h5tools_error_report();
          ... (do work) ...
          h5diff_exit(ret);

      (ADB - 2020/07/20, HDFFV-11066)

    - h5diff fixed a command line parsing error.

      h5diff would ignore the argument to -d (delta) if it is smaller than DBL_EPSILON.
      The macro H5_DBL_ABS_EQUAL was removed and a direct value comparision was used.

      (ADB - 2020/07/20, HDFFV-10897)

    - h5diff added a command line option to ignore attributes.

      h5diff would ignore all objects with a supplied path if the exclude-path argument is used.
      Adding the exclude-attribute argument will only eclude attributes, with the supplied path,
      from comparision.

      (ADB - 2020/07/20, HDFFV-5935)

    - h5diff added another level to the verbose argument to print filenames.

      Added verbose level 3 that is level 2 plus the filenames. The levels are:
          0 : Identical to '-v' or '--verbose'
          1 : All level 0 information plus one-line attribute status summary
          2 : All level 1 information plus extended attribute status report
          3 : All level 2 information plus file names

      (ADB - 2020/07/20, HDFFV-10005)

    High-Level APIs:
    ------
    - The H5DSis_scale function was updated to return "not a dimension scale" (0)
      instead of failing (-1), when CLASS or DIMENSION_SCALE attributes are 
      not written according to Dimension Scales Specification. 

     (EIP - 2020/08/12, HDFFV-10436)

    Fortran High-Level APIs:
    ------
    -

    Documentation
    -------------
    -

    F90 APIs
    --------
    -

    C++ APIs
    --------
    -

    Testing
    -------
    - Stopped java/test/junit.sh.in installing libs for testing under ${prefix}

      Lib files needed are now copied to a subdirectory in the java/test
      directory, and on Macs the loader path for libhdf5.xxxs.so is changed
      in the temporary copy of libhdf5_java.dylib.

      (LRK, 2020/7/2, HDFFV-11063)

    - Fixed a test failure in testpar/t_dset.c caused by
      the test trying to use the parallel filters feature
      on MPI-2 implementations.

      (JTH, 2019/2/7)

Bug Fixes since HDF5-1.10.2 release
==================================

    Library
    -------
    - Java HDF5LibraryException class

      The error minor and major values would be lost after the
      constructor executed.

      Created two local class variables to hold the values obtained during
      execution of the constructor. Refactored the class functions to retrieve
      the class values rather then calling the native functions.
      The native functions were renamed and called only during execution
      of the constructor.
      Added error checking to calling class constructors in JNI classes.

      (ADB - 2018/08/06, HDFFV-10544)

    - Added checks of the defined MPI_VERSION to guard against usage of
      MPI-3 functions in the Parallel Compression and "big Parallel I/O"
      features when HDF5 is built with MPI-2. Previously, the configure
      step would pass but the build itself would fail when it could not
      locate the MPI-3 functions used.

      As a result of these new checks, HDF5 can again be built with MPI-2,
      but the Parallel Compression feature will be disabled as it relies
      on the MPI-3 functions used.

      (JTH - 2018/08/02, HDFFV-10512)

    - User's patches: CVEs

      The following patches have been applied:

      CVE-2018-11202 - NULL pointer dereference was discovered in
                       H5S_hyper_make_spans in H5Shyper.c (HDFFV-10476)
        https://security-tracker.debian.org/tracker/CVE-2018-11202
        https://cve.mitre.org/cgi-bin/cvename.cgi?name=3DCVE-2018-11202

      CVE-2018-11203 - A division by zero was discovered in
                       H5D__btree_decode_key in H5Dbtree.c (HDFFV-10477)
        https://security-tracker.debian.org/tracker/CVE-2018-11203
        https://cve.mitre.org/cgi-bin/cvename.cgi?name=3DCVE-2018-11203

      CVE-2018-11204 - A NULL pointer dereference was discovered in
                       H5O__chunk_deserialize in H5Ocache.c (HDFFV-10478)
        https://security-tracker.debian.org/tracker/CVE-2018-11204
        https://cve.mitre.org/cgi-bin/cvename.cgi?name=3DCVE-2018-11204

      CVE-2018-11206 - An out of bound read was discovered in
                       H5O_fill_new_decode and H5O_fill_old_decode in H5Ofill.c
                       (HDFFV-10480)
        https://security-tracker.debian.org/tracker/CVE-2018-11206
        https://cve.mitre.org/cgi-bin/cvename.cgi?name=3DCVE-2018-11206

      CVE-2018-11207 - A division by zero was discovered in
                       H5D__chunk_init in H5Dchunk.c  (HDFFV-10481)
        https://security-tracker.debian.org/tracker/CVE-2018-11207
        https://cve.mitre.org/cgi-bin/cvename.cgi?name=3DCVE-2018-11207

      (BMR - 2018/7/22, PR#s: 1134 and 1139,
       HDFFV-10476, HDFFV-10477, HDFFV-10478, HDFFV-10480, HDFFV-10481)

    - H5Adelete

      H5Adelete failed when deleting the last "large" attribute that
      is stored densely via fractal heap/v2 b-tree.

      After removing the attribute, update the ainfo message.  If the
      number of attributes goes to zero, remove the message.

      (VC - 2018/07/20, HDFFV-9277)

    - A bug was discovered in the parallel library which caused partial
      parallel reads of filtered datasets to return incorrect data. The
      library used the incorrect dataspace for each chunk read, causing
      the selection used in each chunk to be wrong.

      The bug was not caught during testing because all of the current
      tests which do parallel reads of filtered data read all of the data
      using an H5S_ALL selection. Several tests were added which exercise
      partial parallel reads.

      (JTH - 2018/07/16, HDFFV-10467)

    - A bug was discovered in the parallel library which caused parallel
      writes of filtered datasets to trigger an assertion failure in the
      file free space manager.

      This occurred when the filter used caused chunks to repeatedly shrink
      and grow over the course of several dataset writes. The previous chunk
      information, such as the size of the chunk and the offset in the file,
      was being cached and not updated after each write, causing the next write
      to the chunk to retrieve the incorrect cached information and run into
      issues when reallocating space in the file for the chunk.

      (JTH - 2018/07/16, HDFFV-10509)

    - A bug was discovered in the parallel library which caused the
      H5D__mpio_array_gatherv() function to allocate too much memory.

      When the function is called with the 'allgather' parameter set
      to a non-true value, the function will receive data from all MPI
      ranks and gather it to the single rank specied by the 'root'
      parameter. However, the bug in the function caused memory for
      the received data to be allocated on all MPI ranks, not just the
      singular rank specified as the receiver. In some circumstances,
      this would cause an application to fail due to the large amounts
      of memory being allocated.

      (JTH - 2018/07/16, HDFFV-10467)

    - Error checks in h5stat and when decoding messages

      h5stat exited with seg fault/core dumped when
      errors are encountered in the internal library.

      Add error checks and --enable-error-stack option to h5stat.
      Add range checks when decoding messages: old fill value, old
      layout and refcount.

      (VC - 2018/07/11, HDFFV-10333)

    - If an HDF5 file contains a malformed compound datatype with a
      suitably large offset, the type conversion code can run off
      the end of the type conversion buffer, causing a segmentation
      fault.

      This issue was reported to The HDF Group as issue #CVE-2017-17507.

      NOTE: The HDF5 C library cannot produce such a file. This condition
            should only occur in a corrupt (or deliberately altered) file
            or a file created by third-party software.

      THE HDF GROUP WILL NOT FIX THIS BUG AT THIS TIME

      Fixing this problem would involve updating the publicly visible
      H5T_conv_t function pointer typedef and versioning the API calls
      which use it. We normally only modify the public API during
      major releases, so this bug will not be fixed at this time.

      (DER - 2018/02/26, HDFFV-10356)

    - Inappropriate linking with deprecated MPI C++ libraries

      HDF5 does not define *_SKIP_MPICXX in the public headers, so applications
      can inadvertently wind up linking to the deprecated MPI C++ wrappers.

      MPICH_SKIP_MPICXX and OMPI_SKIP_MPICXX have both been defined in H5public.h
      so this should no longer be an issue. HDF5 makes no use of the deprecated
      MPI C++ wrappers.

      (DER - 2019/09/17, HDFFV-10893)



    Configuration
    -------------
    - Applied patches to address Cywin build issues

      There were three issues for Cygwin builds:
      - Shared libs were not built.
      - The -std=c99 flag caused a SIG_SETMASK undeclared error.
      - Undefined errors when buildbing test shared libraries.

      Patches to address these issues were received and incorporated in this version.

      (LRK - 2018/07/18, HDFFV-10475)

    - Moved the location of gcc attribute.

      The gcc attribute(no_sanitize), named as the macro HDF_NO_UBSAN,
      was located after the function name. Builds with GCC 7 did not
      indicate any problem, but GCC 8 issued errors. Moved the
      attribute before the function name, as required.

      (ADB - 2018/05/22, HDFFV-10473)

    - Reworked java test suite into individual JUnit tests.

      Testing the whole suite of java unit tests in a single JUnit run
      made it difficult to determine actual failures when tests would fail.
      Running each file set of tests individually, allows individual failures
      to be diagnosed easier. A side benefit is that tests for optional components
      of the library can be disabled if not configured.

      (ADB - 2018/05/16, HDFFV-9739)

    - Converted CMake global commands ADD_DEFINITIONS and INCLUDE_DIRECTORIES
      to use target_* type commands. This change modernizes the CMake usage
      in the HDF5 library.

      In addition, there is the intention to convert to generator expressions,
      where possible. The exception is Fortran FLAGS on Windows Visual Studio.
      The HDF macros TARGET_C_PROPERTIES and TARGET_FORTRAN_PROPERTIES have
      been removed with this change in usage.

      The additional language (C++ and Fortran) checks have also been localized
      to only be checked when that language is enabled.

      (ADB - 2018/05/08)

    Performance
    -------------
    -

    Fortran
    --------
    -

    Tools
    -----
    -

    High-Level APIs:
    ------
    -

    Fortran High-Level APIs:
    ------
    -

    Documentation
    -------------
    -

    F90 APIs
    --------
    -

    C++ APIs
    --------
    - Adding default arguments to existing functions

      Added the following items:
      + Two more property list arguments are added to H5Location::createDataSet:
        const DSetAccPropList& dapl = DSetAccPropList::DEFAULT
        const LinkCreatPropList& lcpl = LinkCreatPropList::DEFAULT

      + One more property list argument is added to H5Location::openDataSet:
        const DSetAccPropList& dapl = DSetAccPropList::DEFAULT

      (BMR - 2018/07/21, PR# 1146)

    - Improvement C++ documentation

      Replaced the table in main page of the C++ documentation from mht to htm format
      for portability.

      (BMR - 2018/07/17, PR# 1141)

    Testing
    -------
    - The dt_arith test failed on IBM Power8 and Power9 machines when testing
      conversions from or to long double types, especially when special values
      such as infinity or NAN were involved.  In some cases the results differed
      by extremely small amounts from those on other machines, while some other
      tests resulted in segmentation faults.  These conversion tests with long
      double types have been disabled for ppc64 machines until the problems are
      better understood and can be properly addressed.

      (SRL - 2019/01/07, TRILAB-98)

Supported Platforms
===================

    Linux 2.6.32-696.16.1.el6.ppc64 gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-18)
    #1 SMP ppc64 GNU/Linux        g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-18)
    (ostrich)                     GNU Fortran (GCC) 4.4.7 20120313 (Red Hat 4.4.7-18)
                                  IBM XL C/C++ V13.1
                                  IBM XL Fortran V15.1

    Linux 3.10.0-327.10.1.el7   GNU C (gcc), Fortran (gfortran), C++ (g++)
    #1 SMP x86_64 GNU/Linux       compilers:
    (kituo/moohan)                Version 4.8.5 20150623 (Red Hat 4.8.5-4)
                                    Version 4.9.3, Version 5.2.0,
                                  Intel(R) C (icc), C++ (icpc), Fortran (icc)
                                  compilers:
                                     Version 17.0.0.098 Build 20160721
                                  MPICH 3.1.4 compiled with GCC 4.9.3

    SunOS 5.11 32- and 64-bit     Sun C 5.12 SunOS_sparc
    (emu)                         Sun Fortran 95 8.6 SunOS_sparc
                                  Sun C++ 5.12 SunOS_sparc

    Windows 7 x64                 Visual Studio 2015 w/ Intel C, Fortran 2018 (cmake)
                                  Visual Studio 2015 w/ MSMPI 10 (cmake)

    Windows 10 x64                Visual Studio 2015 w/ Intel Fortran 18 (cmake)
                                  Visual Studio 2017 w/ Intel Fortran 19 (cmake)
                                  Visual Studio 2019 w/ Intel Fortran 19 (cmake)

    Mac OS X Yosemite 10.10.5     Apple clang/clang++ version 6.1 from Xcode 7.0
    64-bit                        gfortran GNU Fortran (GCC) 4.9.2
    (osx1010dev/osx1010test)      Intel icc/icpc/ifort version 15.0.3

    Mac OS X El Capitan 10.11.6   Apple clang/clang++ version 7.3.0 from Xcode 7.3
    64-bit                        gfortran GNU Fortran (GCC) 5.2.0
    (osx1011dev/osx1011test)      Intel icc/icpc/ifort version 16.0.2

    Mac OS Sierra 10.12.6         Apple LLVM version 8.1.0 (clang/clang++-802.0.42)
    64-bit                        gfortran GNU Fortran (GCC) 7.1.0
    (swallow/kite)                Intel icc/icpc/ifort version 17.0.2


Tested Configuration Features Summary
=====================================

    In the tables below
          y   = tested
          n   = not tested in this release
          C   = Cluster
          W   = Workstation
          x   = not working in this release
          dna = does not apply
          ( ) = footnote appears below second table
          <blank> = testing incomplete on this feature or platform

Platform                              C         F90/   F90      C++  zlib  SZIP
                                      parallel  F2003  parallel
Solaris2.11 32-bit                      n        y/y    n        y    y     y
Solaris2.11 64-bit                      n        y/n    n        y    y     y
Windows 7                               y        y/y    n        y    y     y
Windows 7 x64                           y        y/y    y        y    y     y
Windows 7 Cygwin                        n        y/n    n        y    y     y
Windows 7 x64 Cygwin                    n        y/n    n        y    y     y
Windows 10                              y        y/y    n        y    y     y
Windows 10 x64                          y        y/y    n        y    y     y
Mac OS X Mountain Lion 10.8.5 64-bit    n        y/y    n        y    y     y
Mac OS X Mavericks 10.9.5 64-bit        n        y/y    n        y    y     ?
Mac OS X Yosemite 10.10.5 64-bit        n        y/y    n        y    y     ?
Mac OS X El Capitan 10.11.6 64-bit      n        y/y    n        y    y     ?
CentOS 6.7 Linux 2.6.18 x86_64 GNU      n        y/y    n        y    y     y
CentOS 6.7 Linux 2.6.18 x86_64 Intel    n        y/y    n        y    y     y
CentOS 6.7 Linux 2.6.32 x86_64 PGI      n        y/y    n        y    y     y
CentOS 7.2 Linux 2.6.32 x86_64 GNU      y        y/y    y        y    y     y
CentOS 7.2 Linux 2.6.32 x86_64 Intel    n        y/y    n        y    y     y
Linux 2.6.32-573.18.1.el6.ppc64         n        y/n    n        y    y     y


Platform                                 Shared  Shared    Shared    Thread-
                                         C libs  F90 libs  C++ libs  safe
Solaris2.11 32-bit                         y       y         y         y
Solaris2.11 64-bit                         y       y         y         y
Windows 7                                  y       y         y         y
Windows 7 x64                              y       y         y         y
Windows 7 Cygwin                           n       n         n         y
Windows 7 x64 Cygwin                       n       n         n         y
Windows 10                                 y       y         y         y
Windows 10 x64                             y       y         y         y
Mac OS X Mountain Lion 10.8.5 64-bit       y       n         y         y
Mac OS X Mavericks 10.9.5 64-bit           y       n         y         y
Mac OS X Yosemite 10.10.5 64-bit           y       n         y         y
Mac OS X El Capitan 10.11.6 64-bit         y       n         y         y
CentOS 6.7 Linux 2.6.18 x86_64 GNU         y       y         y         y
CentOS 6.7 Linux 2.6.18 x86_64 Intel       y       y         y         n
CentOS 6.7 Linux 2.6.32 x86_64 PGI         y       y         y         n
CentOS 7.2 Linux 2.6.32 x86_64 GNU         y       y         y         n
CentOS 7.2 Linux 2.6.32 x86_64 Intel       y       y         y         n
Linux 2.6.32-573.18.1.el6.ppc64            y       y         y         n

Compiler versions for each platform are listed in the preceding
"Supported Platforms" table.


More Tested Platforms
=====================
The following platforms are not supported but have been tested for this release.

    Linux 2.6.32-573.22.1.el6    GNU C (gcc), Fortran (gfortran), C++ (g++)
    #1 SMP x86_64 GNU/Linux       compilers:
    (mayll/platypus)                 Version 4.4.7 20120313
                                     Version 4.9.3, 5.3.0, 6.2.0
                                  PGI C, Fortran, C++ for 64-bit target on
                                  x86-64;
                                      Version 17.10-0
                                  Intel(R) C (icc), C++ (icpc), Fortran (icc)
                                  compilers:
                                     Version 17.0.4.196 Build 20170411
                                  MPICH 3.1.4 compiled with GCC 4.9.3

    Linux 3.10.0-327.18.2.el7     GNU C (gcc) and C++ (g++) compilers
    #1 SMP x86_64 GNU/Linux          Version 4.8.5 20150623 (Red Hat 4.8.5-4)
    (jelly)                       with NAG Fortran Compiler Release 6.1(Tozai)
                                  GCC Version 7.1.0
                                  OpenMPI 3.0.0-GCC-7.2.0-2.29
                                  Intel(R) C (icc) and C++ (icpc) compilers
                                     Version 17.0.0.098 Build 20160721
                                  with NAG Fortran Compiler Release 6.1(Tozai)

    Linux 3.10.0-327.10.1.el7     MPICH 3.2 compiled with GCC 5.3.0
    #1 SMP x86_64 GNU/Linux
    (moohan)

    Linux 2.6.32-573.18.1.el6.ppc64  MPICH mpich 3.1.4 compiled with
    #1 SMP ppc64 GNU/Linux           IBM XL C/C++ for Linux, V13.1
    (ostrich)                        and IBM XL Fortran for Linux, V15.1

   Fedora30 5.3.11-200.fc30.x86_64
   #1 SMP x86_64  GNU/Linux          GNU gcc (GCC) 9.2.1 20190827 (Red Hat 9.2.1 20190827)
                                     GNU Fortran (GCC) 9.2.1 20190827 (Red Hat 9.2.1 20190827)
                                     (cmake and autotools)


Known Problems
==============
    CMake files do not behave correctly with paths containing spaces.
    Do not use spaces in paths because the required escaping for handling spaces
    results in very complex and fragile build files.
    ADB - 2019/05/07

    At present, metadata cache images may not be generated by parallel
    applications.  Parallel applications can read files with metadata cache
    images, but since this is a collective operation, a deadlock is possible
    if one or more processes do not participate.

    Known problems in previous releases can be found in the HISTORY*.txt files
    in the HDF5 source. Please report any new problems found to
    help@hdfgroup.org.


CMake vs. Autotools installations
=================================
While both build systems produce similar results, there are differences.
Each system produces the same set of folders on linux (only CMake works
on standard Windows); bin, include, lib and share. Autotools places the
COPYING and RELEASE.txt file in the root folder, CMake places them in
the share folder.

The bin folder contains the tools and the build scripts. Additionally, CMake
creates dynamic versions of the tools with the suffix "-shared". Autotools
installs one set of tools depending on the "--enable-shared" configuration
option.
  build scripts
  -------------
  Autotools: h5c++, h5cc, h5fc
  CMake: h5c++, h5cc, h5hlc++, h5hlcc

The include folder holds the header files and the fortran mod files. CMake
places the fortran mod files into separate shared and static subfolders,
while Autotools places one set of mod files into the include folder. Because
CMake produces a tools library, the header files for tools will appear in
the include folder.

The lib folder contains the library files, and CMake adds the pkgconfig
subfolder with the hdf5*.pc files used by the bin/build scripts created by
the CMake build. CMake separates the C interface code from the fortran code by
creating C-stub libraries for each Fortran library. In addition, only CMake
installs the tools library. The names of the szip libraries are different
between the build systems.

The share folder will have the most differences because CMake builds include
a number of CMake specific files for support of CMake's find_package and support
for the HDF5 Examples CMake project.