path: root/release_docs/RELEASE.txt

HDF5 version 1.8.23-1 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 HDF5-1.8.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, Languages, and Compilers
- Bug Fixes since HDF5-1.8.22
- Supported Platforms
- Supported Configuration Features Summary
- More Tested Platforms
- Known Problems
- CMake vs. Autotools installations


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

    Configuration:
    -------------
    - Add new CMake configuration variable HDF5_USE_GNU_DIRS

      HDF5_USE_GNU_DIRS (default OFF) selects the use of GNU Coding Standard install
      directory variables by including the CMake module, GNUInstallDirs(see CMake
      documentation for details). The HDF_DIR_PATHS macro in the HDFMacros.cmake file
      sets various PATH variables for use during the build, test and install processes.
      By default, the historical settings for these variables will be used.

      (ADB - 2022/10/21, GH-2175, GH-1716)

    - Correct the usage of CMAKE_Fortran_MODULE_DIRECTORY and where to
      install Fortran mod files.

      The Fortran modules files, ending in .mod are files describing a
      Fortran 90 (and above) module API and ABI. These are not like C
      header files describing an API, they are compiler dependent and
      arch dependent, and not easily readable by a human being. They are
      nevertheless searched for in the includes directories by gfortran
      (in directories specified with -I).

      Autotools configure uses the -fmoddir option to specify the folder.
      CMake will use "mod" folder by default unless overridden by the CMake
      variable; HDF5_INSTALL_MODULE_DIR.

      (ADB - 2022/07/21)

    - Added new option to the h5cc scripts produced by CMake.

      Add -showconfig option to h5cc scripts to cat the 
      libhdf5-settings to the standard output.

      (ADB - 2022/03/11)

    - Changed autotools and CMake configurations to derive both
      compilation warnings-as-errors and warnings-only-warn configurations
      from the same files, 'config/*/*error*'.  Removed redundant files
      'config/*/*noerror*'.

      (DCY - 2021/09/29)

    - Added new option to control the build of High-Level tools
      that default ON/enabled.

      Add configure options (autotools - CMake):
            enable-hltools       HDF5_BUILD_HL_TOOLS

      (ADB - 2021/09/16, HDFFV-11266)

    - CMake no longer builds the C++ library by default

      HDF5_BUILD_CPP_LIB now defaults to OFF, which is in line with the
      Autotools build defaults.

      (DER - 2021/04/20)

    - Add CMake variable HDF5_LIB_INFIX

      This infix is added to all library names after 'hdf5'.
      e.g. the infix '_openmpi' results in the library name 'libhdf5_openmpi.so'
      This name is used in packages on debian based systems.
      (see https://packages.debian.org/jessie/amd64/libhdf5-openmpi-8/filelist)

      (barcode - 2021/03/22)

    - On macOS, Universal Binaries can now be built, allowing native execution on
      both Intel and Apple Silicon (ARM) based Macs.

      To do so, set CMAKE_OSX_ARCHITECTURES="x86_64;arm64"

      (SAM - 2021/02/07, https://github.com/HDFGroup/hdf5/issues/311)

    - Added a configure-time option to control certain compiler warnings
      diagnostics

      A new configure-time option was added that allows some compiler warnings
      diagnostics to have the default operation. This is mainly intended for
      library developers and currently only works for gcc 10 and above. The
      diagnostics flags apply to C, C++ and Fortran compilers and will appear
      in "H5 C Flags", H5 C++ Flags" and H5 Fortran Flags, respectively. They
      will NOT be exported to h5cc, etc.

      The default is OFF, which will disable the warnings URL and color attributes
      for the warnings output. ON will not add the flags and allow default behavior.

      Autotools:    --enable-diags

      CMake:        HDF5_ENABLE_BUILD_DIAGS

      (ADB - 2021/02/05, HDFFV-11213)

    - FreeBSD Autotools configuration now defaults to 'cc' and 'c++' compilers

      On FreeBSD, the autotools defaulted to 'gcc' as the C compiler and did
      not process C++ options. Since FreeBSD 10, the default compiler has
      been clang (via 'cc').

      The default compilers have been set to 'cc' for C and 'c++' for C++,
      which will pick up clang and clang++ respectively on FreeBSD 10+.
      Additionally, clang options are now set correctly for both C and C++
      and g++ options will now be set if that compiler is being used (an
      omission from the former functionality).

      (DER - 2021/02/16, HDFFV-11193)

    - Fixed POSIX problems when building w/ gcc on Solaris

      When building on Solaris using gcc, the POSIX symbols were not
      being set correctly, which could lead to issues like clock_gettime()
      not being found.

      The standard is now set to gnu99 when building with gcc on Solaris,
      which allows POSIX things to be #defined and linked correctly. This
      differs slightly from the gcc norm, where we set the standard to c99
      and manually set POSIX #define symbols.

      (DER - 2021/02/16, HDFFV-11191)

    - Added a configure-time option to consider certain compiler warnings
      as errors

      A new configure-time option was added that converts some compiler warnings
      to errors. This is mainly intended for library developers and currently
      only works for gcc and clang. The warnings that are considered errors
      will appear in the generated libhdf5.settings file. These warnings apply
      to C and C++ code and will appear in "H5 C Flags" and H5 C++ Flags",
      respectively. They will NOT be exported to h5cc, etc.

      The default is OFF. Building with this option may fail when compiling
      on operating systems and with compiler versions not commonly used by
      the library developers. Compilation may also fail when headers not
      under the control of the library developers (e.g., mpi.h, hdfs.h) raise
      warnings.

      Autotools:    --enable-warnings-as-errors

      CMake:        HDF5_ENABLE_WARNINGS_AS_ERRORS

      (DER - 2021/02/16, HDFFV-11189)


    Library:
    --------
    - H5Epush_ret() now requires a trailing semi-colon

        H5Epush_ret() is a function-like macro that has been changed to
        contain a `do {} while(0)` loop. Consequently, a trailing semi-colon
        is now required to end the `while` statement. Previously, a trailing
        semi would work, but was not mandatory. This change was made to allow
        clang-format to correctly format the source code.

        (SAM - 2021/03/03)


    Fortran Library:
    ----------------
    - H5Fget_name_f fixed to handle correctly trailing whitespaces and
      newly allocated buffers.

      (MSB - 2021/08/30, github-826,972)


    C++ Library:
    ------------
    -


    Parallel Library:
    ----------------
    - None


    Tools:
    ------
    - h5repack added help text for user-defined filters.

        Added help text line that states the valid values of the filter flag
        for user-defined filters;
            filter_flag: 1 is OPTIONAL or 0 is MANDATORY

        (ADB - 2021/02/16, HDFFV-11099)

    - 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 - 2021/02/16, HDFFV-9984)


    High-Level APIs:
    ---------------
    - None


    Documentation
    -------------
    - None


Support for New Platforms, Languages, and Compilers
===================================================
    - None



Bug Fixes since HDF5-1.8.22
===========================

    Configuration
    -------------
    - Move MPI libraries link from PRIVATE to PUBLIC

      The install dependencies were not including the need for MPI libraries when
      an application or library was built with the C library. Also updated the
      CMake target link command to use the newer style MPI::MPI_C link variable.

      (ADB - 2022/20/27)

    - Reworked corrected path searched by CMake find_package command

      The install path for cmake find_package files had been changed to use
        "share/cmake"
      for all platforms. However setting the HDF5_ROOT variable failed to locate
      the configuration files. The build variable HDF5_INSTALL_CMAKE_DIR is now
      set to the <INSTALL_DIR>/cmake folder. The location of the configuration 
      files can still be specified by the "HDF5_DIR" variable.

      (ADB - 2022/03/11)

    - Corrected path searched by CMake find_package command

      The install path for cmake find_package files had been changed to use
        "share/cmake"
      for all platforms. However the trailing "hdf5" directory was not removed.
      This "hdf5" additional directory has been removed.

      (ADB - 2021/09/27)

    - Corrected pkg-config compile script

      It was discovered that the position of the "$@" argument for the command
      in the compile script may fail on some platforms and configurations. The
      position of the "$@"command argument was moved before the pkg-config sub command.

      (ADB - 2021/08/30)

    - Fixed CMake C++ compiler flags

      A recent refactoring of the C++ configure files accidently removed the
      file that executed the enable_language command for C++ needed by the
      HDFCXXCompilerFlags.cmake file. Also updated the intel warnings files,
      including adding support for windows platforms.

      (ADB - 2021/08/10)

    - Remove arbitrary warning flag groups from CMake builds

      The arbitrary groups were created to reduce the quantity of warnings being
      reported that overwhelmed testing report systems. Considerable work has
      been accomplished to reduce the warning count and these arbitrary groups
      are no longer needed.
      Also the default for all warnings, HDF5_ENABLE_ALL_WARNINGS, is now ON.

      Visual Studio warnings C4100, C4706, and C4127 have been moved to
      developer warnings, HDF5_ENABLE_DEV_WARNINGS, and are disabled for normal builds.

      (ADB - 2021/03/22, HDFFV-11228)

    - Reclassify CMake messages, to allow new modes and --log-level option

      CMake message commands have a mode argument. By default, STATUS mode
      was chosen for any non-error message. CMake version 3.15 added additional
      modes, NOTICE, VERBOSE, DEBUG and TRACE. All message commands with a mode
      of STATUS were reviewed and most were reclassified as VERBOSE. The new
      mode was protected by a check for a CMake version of at least 3.15. If CMake
      version 3.17 or above is used, the user can use the command line option
      of "--log-level" to further restrict which message commands are displayed.

      (ADB - 2021/02/16, HDFFV-11144)

    - Fixes Autotools determination of the stat struct having an st_blocks field

      A missing parenthesis in an autoconf macro prevented building the test
      code used to determine if the stat struct contains the st_blocks field.
      Now that the test functions correctly, the H5_HAVE_STAT_ST_BLOCKS #define
      found in H5pubconf.h will be defined correctly on both the Autotools and
      CMake. This #define is only used in the tests and does not affect the
      HDF5 C library.

      (DER - 2021/02/16, HDFFV-11201)


    Library
    -------
    - Fixed an issue with variable length attributes

      Previously, if a variable length attribute was held open while its file
      was opened through another handle, the same attribute was opened through
      the second file handle, and the second file and attribute handles were
      closed, attempting to write to the attribute through the first handle
      would cause an error.

      (NAF - 2022/10/24)

    - Fixed an issue with attribute type conversion with compound datatypes

      Previously, when performing type conversion for attribute I/O with a
      compound datatype, the library would not fill the background buffer with
      the contents of the destination, potentially causing data to be lost when
      only writing to a subset of the compound fields.

      (NAF - 2022/09/12, GitHub #2016)

    - Issue #1436 identified a problem with the H5_VERS_RELEASE check in the
      H5check_version function.

      Investigating the original fix, #812, we discovered some inconsistencies
      with a new block added to check H5_VERS_RELEASE for incompatibilities.
      This new block was not using the new warning text dealing with the
      H5_VERS_RELEASE check and would cause the warning to be duplicated.

      By removing the H5_VERS_RELEASE argument in the first check for 
      H5_VERS_MAJOR and H5_VERS_MINOR, the second check would only check
      the H5_VERS_RELEASE for incompatible release versions. This adheres
      to the statement that except for the develop branch, all release versions
      in a major.minor maintenance branch should be compatible. The prerequisite
      is that an application will not use any APIs not present in all release versions.

      (ADB - 2022/03/11, #1438)



    Performance
    -----------
    - None


    Tools
    -----
    - Changed how h5dump and h5ls identify long double.

        Long double support is not consistent across platforms. Tools will always
        identify long double as 128-bit [little/big]-endian float nn-bit precision.
        New test file created for datasets with attributes for float, double and
        long double. In addition any unknown integer or float datatype will now
        also show the number of bits for precision.
        These files are also used in the java tests.

        (ADB - 2021/03/24, HDFFV-11229)

    - Fixed tools argument parsing.

        Tools parsing used the length of the option from the long array to match
        the option from the command line. This incorrectly matched a shorter long
        name option that happened to be a subset of another long option.
        Changed to match whole names.

        (ADB - 2021/02/16, HDFFV-11106)

    - 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 - 2021/02/16, 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 - 2021/02/16, 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 - 2021/02/16, 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 - 2021/02/16, HDFFV-10005)

    - 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 -2021/02/16, HDFFV-11014)


    Fortran API
    -----------
    - None


    C++ API
    -------
    - None


    High-Level APIs:
    ---------------
    - None


    Packet Table APIs:
    ------------------
    - Fixed HL_test_packet, test for packet table vlen of vlen.

      Incorrect length assignment.

        (ADB - 2021/10/14)


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

    Linux 3.10.0-1127.10.1.el7    gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39)
    #1 SMP ppc64 GNU/Linux        g++ (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39)
    (echidna)                     GNU Fortran (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39)

    Linux 2.6.32-573.18.1.el6     IBM XL C/C++ V13.1
    #1 SMP ppc64 GNU/Linux        IBM XL Fortran V15.1
    (ostrich)

    Linux 3.10.0-327.10.1.el7     GNU C (gcc), Fortran (gfortran), C++ (g++)
    #1 SMP x86_64 GNU/Linux       compilers:
    (jelly/kituo/moohan)          Version 4.8.5 20150623 (Red Hat 4.8.5-39)
                                     Versions 4.9.3, 5.3.0, 6.3.0, 7.2.0
                                              8.3.0, 9.1.0, 10.1.0
                                  Intel(R) C (icc), C++ (icpc), Fortran (icc)
                                  compilers:
                                     Version 17.0.0.098 Build 20160721
                                  MPICH 3.3 compiled with GCC 7.2.0
                                  OpenMPI 4.0.0 compiled with GCC 7.2.0
                                  NAG Fortran Compiler Release 7.0(Yurakuchho) Build 7011

    SunOS 5.11 11.4.5.12.5.0      Sun C 5.15 SunOS_sparc 2017/05/30
    32- and 64-bit                Studio 12.6 Fortran 95 8.8 SunOS_sparc 2017/05/30
    (hedgehog)                    Sun C++ 5.15 SunOS_sparc 2017/05/30

    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)
                                  Visual Studio 2019 w/ MSMPI 10.1 (cmake)



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
SunOS 5.11 32-bit                       n        y/y    n        y    y     y
SunOS 5.11 64-bit                       n        y/y    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 El Capitan 10.11.6 64-bit      n        y/y    n        y    y     y
Mac OS Sierra 10.12.6 64-bit            n        y/y    n        y    y     y
Mac OS X High Sierra 10.13.6 64-bit     n        y/y    n        y    y     y
Mac OS X Mojave 10.14.6 64-bit          n        y/y    n        y    y     y
CentOS 7.2 Linux 2.10.0 x86_64 PGI      n        y/y    n        y    y     y
CentOS 7.1 Linux 3.10.0 x86_64 GNU      y        y/y    y        y    y     y
CentOS 7.1 Linux 3.10.0 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
SunOS 5.11 32-bit                          y       y         y         y
SunOS 5.11 64-bit                          y       y         y         y
Windows 10                                 y       y         y         y
Windows 10 x64                             y       y         y         y
Mac OS X El Capitan 10.11.6 64-bit         y       n         y         y
Mac OS Sierra 10.12.6 64-bit               y       n         y         y
Mac OS X High Sierra 10.13.6 64-bit        y       n         y         y
Mac OS X Mojave 10.14.6 64-bit             y       n         y         y
CentOS 7.2 Linux 3.10.0 x86_64 PGI         y       y         y         y
CentOS 7.2 Linux 3.10.0 x86_64 GNU         y       y         y         y
CentOS 7.2 Linux 3.10.0 x86_64 Intel       y       y         y         y
Linux 2.6.32-573.18.1.el6.ppc64            y       y         y         y

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:
    (platypus)                    Version 4.4.7 20120313
                                     Versions 4.9.3, 5.3.0, 6.2.0
                                  PGI C, Fortran, C++ for 64-bit target on
                                  x86-64;
                                      Version 16.10-0
                                  Intel(R) C (icc), C++ (icpc), Fortran (icc)
                                  compilers:
                                     Version 17.0.0.196 Build 20160721
                                  MPICH 3.1.4 compiled with GCC 4.9.3
                                  OpenMPI 2.0.1 compiled with GCC 4.9.3

    Linux 2.6.32-573.18.1.el6     gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-16)
    #1 SMP ppc64 GNU/Linux        g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-16)
    (ostrich)                     GNU Fortran (GCC) 4.4.7 20120313 (Red Hat 4.4.7-16)

    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 2.1.6-GCC-7.2.0-2.29,
                                     3.1.3-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 3.1.4 compiled with GCC 4.9.3
    #1 SMP x86_64 GNU/Linux
    (moohan)

    Linux-3.10.0-1127.0.0.1chaos  openmpi-4.0.0
    #1 SMP x86_64 GNU/Linux           clang/3.9.0, 8.0.1
    (quartz)                          gcc/7.3.0, 8.1.0
                                      intel/16.0.4

    Linux-4.14.0-115.10.1.1       spectrum-mpi/rolling-release
    #1 SMP ppc64le GNU/Linux          clang/coral-2018.08.08
    (lassen)                          gcc/7.3.1
                                      xl/2019.02.07

    Linux-4.12.14-150.52-default  cray-mpich/7.7.10
    #1 SMP x86_64 GNU/Linux           gcc/7.3.0, 8.2.0
    (cori)                            intel/19.0.3

    Linux-4.4.180-94.107-default  cray-mpich/7.7.6
    # 1SMP x86_64 GNU/Linux           gcc/7.2.0, 8.2.0
    (mutrino)                         intel/17.0.4, 18.0.2, 19.0.4

    Fedora33 5.10.10-200.fc33.x86_64
    #1 SMP x86_64  GNU/Linux         GNU gcc (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9)
                                     GNU Fortran (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9)
                                     clang version 11.0.0 (Fedora 11.0.0-2.fc33)
                                     (cmake and autotools)

    Ubuntu20.10 5.8.0-41-generic-x86_64
    #46-Ubuntu SMP x86_64  GNU/Linux GNU gcc (GCC) 10.2.0-13ubuntu1
                                     GNU Fortran (GCC) 10.2.0-13ubuntu1
                                     (cmake and autotools)

    SUSE15sp2 5.3.18-22-default
    #1 SMP x86_64  GNU/Linux         GNU gcc (SUSE Linux) 7.5.0
                                     GNU Fortran (SUSE Linux) 7.5.0
                                     clang version 7.0.1 (tags/RELEASE_701/final 349238)
                                     (cmake and autotools)

    Mac OS X El Capitan 10.11.6   Apple LLVM version 7.3.0 (clang-703.0.29)
    64-bit                        gfortran GNU Fortran (GCC) 5.2.0
    (VM osx1011dev/osx1011test)   Intel icc/icpc/ifort version 16.0.2

    Mac OS Sierra 10.12.6         Apple LLVM version 8.1 (clang-802.0.42)
    64-bit                        gfortran GNU Fortran (GCC) 7.4.0
    (kite)                        Intel icc/icpc/ifort version 17.0.2

    SunOS 5.11 11.3               Sun C 5.15 SunOS_sparc
    32- and 64-bit                Sun Fortran 95 8.8 SunOS_sparc
    (emu)

Known Problems
==============
    HDF5-1.8.22 binaries can replace the previous HDF5 version to run with
    applications compiled and linked with HDF5-1.8.21 and possibly HDF5 versions
    as early as 1.8.15.  However, HDF5 checks versions in lib files against
    versions in header files used to compile the application and will cause the
    application to abort when they do not match.  An environment variable
    HDF5_DISABLE_VERSION_CHECK can be set to 2 to skip the check, to 1 to warn
    but not abort, or to 0 for the default behavior, aborting when the HDF5
    version in the lib files does not match the version in the header files.
    LRK - 2020/02/02

    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

    The dynamically loaded plugin test libraries require undefined references
    to HDF5 functions to be resolved at runtime in order to function properly.
    With autotools on CYGWIN this results in build errors, and we have not
    found a solution that satisfies both.  Therefore the dynamically loaded
    plugin tests have been disabled on CYGWIN.

    Mac OS X 10.13 added additional subdirectory structure in .libs for shared
    libraries.  Consequently "make check" will fail testing java and dynamically
    loaded plugin test libraries attempting to copy files from the previous
    locations in .libs directories.  This will be addressed in the next release
    when support for the Mac OS X 10.13 platform is added.

    CPP ptable test fails on both VS2017 and VS2019 with Intel compiler, JIRA
    issue: HDFFV-10628.  This test will pass with VS2015 with Intel compiler.

    The subsetting option in ph5diff currently will fail and should be avoided.
    The subsetting option works correctly in serial h5diff.

    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.