Squashed commit of the following:

commit 45b0cbc71929930a874e1c09e0770aa64d0ae697
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Thu Apr 23 13:14:56 2020 -0500

    Add C++ warnings treated as error for autotools builds.

commit 6debcddcc766601799d5bd661bd60946f951a07e
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Fri Jun 19 16:50:03 2020 -0500

    Remove tests for develop branch from testh5cc.sh.in.
    Add @H5_ECXXFLAGS@ to AM_CXXFLAGS.

commit fed497e7f207313b2a133d3b68c942b7d7104b90
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Fri Jun 12 15:06:39 2020 -0500

    Merge pull request #2646 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:develop to develop

    * commit '998c6470d78e14228695419c3b514c35ecf3d69e':
      Remove unnecessary version conditions for Clang compilers.

commit 92e52ce5c211bd1d3991a3b8bb67287ac7b652aa
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Wed Jun 10 18:53:45 2020 -0500

    Merge pull request #2639 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:develop to develop

    * commit 'a33667faf226f5d8c9633bf537893e8fce1bf1f6':
      Add c++ to --enable-sanitize-checks option.

commit 2e802534fb997b81fa98fdd1c7d97d4310898e0d
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Wed Jun 10 15:18:36 2020 -0500

    Merge pull request #2633 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:develop to develop

    * commit '20eab963899841c9a003baebead8e3bc07d9e127':
      Remove duplicate entries in MANIFEST.
      Make changes to CMake CompilerFlags.cmake files so extra flags are loaded for non-GNU compilers.
      Update new clang files to not pick up clang as vendor for pgCC. Add new files to MANIFEST Temporary demotion of 2 -Werror warning flags that fail on macos 10.12 Remove Production flag unknown to Apple clang.

commit 96ef60a58a23847a7da89a891f2415055ec2ab60
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Mon Jun 8 16:24:49 2020 -0500

    Merge pull request #2631 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:develop to develop

    * commit 'b942a4d8a3e27317cac50ce37ff5302d477664d8':
      Clean up code to get clang version in config/linux-gnulibc1

commit 8a7c687da568e8b50b38fa53da1ca63759be6ec4
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Mon Jun 8 11:42:37 2020 -0500

    Merge pull request #2623 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:develop to develop

    * commit 'c7626f79fdee4eee13925e240ef41e61f3367eab':
      Add flags from config/clang-warnings/*general files to H5 C and CXX flags for all versions of Clang and Clang++ compilers. Switched from cut to awk in testcheck_version.sh.in to avoid dependence on tab vs. " " in version definitions in H5public.h.
      Add files for adding warning flags for clang compilers in autotools configure.

commit db3ef7ff3c1ed79167cecef831501411cff8291f
Merge: 5a0f8d7 f9f1310
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Fri Jun 19 14:46:22 2020 -0500

    Merge branch 'hdf5_1_12' of https://bitbucket.hdfgroup.org/scm/~lrknox/hdf5_lrk into hdf5_1_12

commit 5a0f8d7940ae57b445f545a0abd7e303ce6924ee
Author: Larry Knox <lrknox@hdfgroup.org>
Date:   Wed Jun 10 20:15:41 2020 -0500

    Merge pull request #2636 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:HDFFV-11000-update-testh5cc.sh.in-for-version to develop

    * commit '5c0bd670d6e9919c463fbc05de99e2ba55b0761e':
      Add tests for all version to H5_NO_DEPRECATED_SYMBOLS section and to section for current version, with and without default API version flags.
      HDFFV-11000:  update-testh5cc.sh.in to test sample versioned functions in HDF5 1.10, 1.12 and develop.

10 files changed, 460 insertions, 56 deletions

diff --git a/config/apple b/config/apple
index 0b15dfe..aba48d1 100644
--- a/config/apple
+++ b/config/apple
@@ -49,6 +49,7 @@ fi
 
 # Figure out compiler flags
 . $srcdir/config/gnu-flags
+. $srcdir/config/clang-flags
 # temp patch: if GCC 4.2.1 is used in Lion or Mountain Lion systems, do not
 # use -O option as it causes failures in test/dt_arith.
 case "$host_os" in
@@ -155,11 +156,13 @@ esac
 # get c++ version info
 case $CXX in
     clang++)
+        . $srcdir/config/clang-cxxflags
         cxx_version_info=`$CXX $CXXFLAGS $H5_CXXFLAGS --version 2>&1 |\
             grep 'Apple' | sed 's/(.*//'`
         ;;
 
     *g++*)
+        . $srcdir/config/gnu-cxxflags
         cxx_version_info=`$CXX $CXXFLAGS $H5_CXXFLAGS --version 2>&1 |\
             grep 'GCC' | sed 's/.*\((GCC) [-a-z0-9\. ]*.*\)/\1/'`
         ;;
diff --git a/config/clang-cxxflags b/config/clang-cxxflags
new file mode 100644
index 0000000..edd62e7
--- /dev/null
+++ b/config/clang-cxxflags
@@ -0,0 +1,200 @@
+#                            -*- shell-script -*-
+#
+# Copyright by The HDF Group.
+# Copyright by the Board of Trustees of the University of Illinois.
+# All rights reserved.
+#
+# This file is part of HDF5.  The full HDF5 copyright notice, including
+# terms governing use, modification, and redistribution, is contained in
+# the COPYING file, which can be found at the root of the source code
+# distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.
+# If you do not have access to either file, you may request a copy from
+# help@hdfgroup.org.
+
+
+# This file should be sourced into configure if the compiler is the
+# Clang clang++ compiler or a derivative.  It is careful not to do anything
+# if the compiler is not Clang; otherwise 'cxx_flags_set' is set to 'yes'
+#
+
+#
+# For now, do not promote any warnings to errors.
+#
+PROMOTE_ERRORS_DFLT=no
+
+#
+# This filter rewrites -Werror= as -W, in that way demoting warnings
+# promoted to errors back to warnings, if PROMOTE_ERRORS is no.
+#
+demote_errors()
+{
+    if [ ${PROMOTE_ERRORS:-${PROMOTE_ERRORS_DFLT}} = no ]; then
+        sed 's,-Werror=,-W,g'
+    else
+        cat
+    fi
+}
+
+#
+# Prepend `$srcdir/config/clang-warnings/` to the filename suffix(es) given as
+# subroutine argument(s), remove comments starting with # and ending
+# at EOL, replace spans of whitespace (including newlines) with spaces,
+# and re-emit the file(s) thus filtered on the standard output stream.
+#
+load_clang_arguments()
+{
+    set -- $(for arg; do
+        sed 's,#.*$,,' $srcdir/config/clang-warnings/${arg}
+    done)
+    IFS=' ' echo "$*"
+}
+# Get the compiler version in a way that works for clang++
+# unless a compiler version is already known
+#
+#   cxx_vendor:    The compiler name: clang++
+#   cxx_version:   Version number: 6.0.0, 7.3.0, ... 10.0.1
+#
+if test "X-" = "X-$cxx_flags_set"; then
+    # clang++ -v will return version number following "clang" on Linux machines,
+    # but on Macs the version number will follow "Apple LLVM version"
+    cxx_version="`$CXX $CXXFLAGS $H5_CXXFLAGS -v 2>&1 |\
+        grep 'clang version' | sed 's/.*clang version \([-a-z0-9\.]*\).*/\1/'`"
+    if test -n "$cxx_version"; then
+        cxx_vendor="clang"
+    else
+        cxx_version="`$CXX $CXXFLAGS $H5_CXXFLAGS -v 2>&1 |\
+            grep 'Apple LLVM version' | sed 's/.*Apple LLVM version \([-a-z0-9\.]*\).*/\1/'`"
+        if test -n "$cxx_version"; then
+            cxx_vendor="Apple LLVM"
+        fi
+    fi
+    if test "X-" != "X-$cxx_version"; then
+
+        # Get the compiler version numbers
+        cxx_vers_major=`echo $cxx_version | cut -f1 -d.`
+        cxx_vers_minor=`echo $cxx_version | cut -f2 -d.`
+        cxx_vers_patch=`echo $cxx_version | cut -f3 -d.`
+        test -n "$cxx_vers_major" || cxx_vers_major=0
+        test -n "$cxx_vers_minor" || cxx_vers_minor=0
+        test -n "$cxx_vers_patch" || cxx_vers_patch=0
+    fi
+fi
+
+if test "X-clang" = "X-$cxx_vendor" -o "X-Apple LLVM" = "X-$cxx_vendor"; then
+    echo "compiler '$CXX' is $cxx_vendor-$cxx_version"
+    ###############################
+    # Architecture-specific flags #
+    ###############################
+
+    arch=
+    case "$host_os-$host_cpu" in
+        # FreeBSD sets the information from "uname -m" to the general machine
+        # architecture, not the specific CPU for the machine, so even our
+        # Pentium II Xeon server is set to "i386".  Once we know we are on a FreeBSD
+        # machine, use the "sysctl" command to get the CPU hardware model.
+        freebsd*-i386)
+            host_cpu_model=`sysctl -n hw.model`
+            case "$host_cpu_model" in
+                # Hmm.. this might not catch Celerons, but it won't hurt them either...
+                *Pro*|*II*|*III*|*IV*|*Athlon*)
+                    # architecture-specific optimizations cause problems
+                    # for some users who build binaries to be used on
+                    # multiple architectures.
+                    # arch="-march=i686"
+                ;;
+            esac
+            ;;
+
+        *-i686)
+                    # architecture-specific optimizations cause problems
+                    # for some users who build binaries to be used on
+                    # multiple architectures.
+                    # arch="-march=i686"
+            ;;
+    esac
+
+    case "$host_os-$host_cpu" in
+        # cygwin needs the "-std=c99" flag removed, so make
+        # a specific case for Cygwin without the flag and a default
+        # case to add the flag everywhere else
+        cygwin-*)
+            ;;
+
+        *)
+            H5_CXXFLAGS="$H5_CXXFLAGS -std=c++11"
+            ;;
+    esac
+
+    H5_CXXFLAGS="$H5_CXXFLAGS $arch"
+
+    ##############
+    # Production #
+    ##############
+
+    # NDEBUG is handled explicitly by the configure script
+    PROD_CXXFLAGS=
+
+    #########
+    # Debug #
+    #########
+
+    # NDEBUG is handled explicitly by the configure script
+    # -g is handled by the symbols flags
+    DEBUG_CXXFLAGS="-ftrapv -fno-common"
+
+    ###########
+    # Symbols #
+    ###########
+
+    NO_SYMBOLS_CXXFLAGS=
+    SYMBOLS_CXXFLAGS="-g -fno-omit-frame-pointer"
+
+    #############
+    # Profiling #
+    #############
+
+    PROFILE_CXXFLAGS="-pg"
+
+    ################
+    # Optimization #
+    ################
+
+    HIGH_OPT_CXXFLAGS="-O3"
+    DEBUG_OPT_CXXFLAGS="-g"
+    NO_OPT_CXXFLAGS="-O0"
+
+    ############
+    # Warnings #
+    ############
+
+    ###########
+    # General #
+    ###########
+
+    H5_CXXFLAGS="$H5_CXXFLAGS $(load_clang_arguments general)"
+    H5_ECXXFLAGS="$H5_ECXXFLAGS $(load_clang_arguments error-general)"
+
+    ######################
+    # Developer warnings #
+    ######################
+
+    NO_DEVELOPER_WARNING_CXXFLAGS=$(load_clang_arguments no-developer-general)
+    DEVELOPER_WARNING_CXXFLAGS=$(load_clang_arguments developer-general)
+
+    #############################
+    # Version-specific warnings #
+    #############################
+
+
+    #################
+    # Flags are set #
+    #################
+    cxx_flags_set=yes
+fi
+
+# Clear cxx info if no flags set
+if test "X$cxx_flags_set" = "X"; then
+    cxx_vendor=
+    cxx_version=
+fi
+
diff --git a/config/clang-flags b/config/clang-flags
new file mode 100644
index 0000000..b4f5e2e
--- /dev/null
+++ b/config/clang-flags
@@ -0,0 +1,200 @@
+#                            -*- shell-script -*-
+#
+# Copyright by The HDF Group.
+# Copyright by the Board of Trustees of the University of Illinois.
+# All rights reserved.
+#
+# This file is part of HDF5.  The full HDF5 copyright notice, including
+# terms governing use, modification, and redistribution, is contained in
+# the COPYING file, which can be found at the root of the source code
+# distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.
+# If you do not have access to either file, you may request a copy from
+# help@hdfgroup.org.
+
+
+# This file should be sourced into configure if the compiler is the
+# Clang compiler or a derivative.  It is careful not to do anything
+# if the compiler is not Clang; otherwise 'cc_flags_set' is set to 'yes'
+#
+
+#
+# For now, do not promote any warnings to errors.
+#
+PROMOTE_ERRORS_DFLT=no
+
+#
+# This filter rewrites -Werror= as -W, in that way demoting warnings
+# promoted to errors back to warnings, if PROMOTE_ERRORS is no.
+#
+demote_errors()
+{
+    if [ ${PROMOTE_ERRORS:-${PROMOTE_ERRORS_DFLT}} = no ]; then
+        sed 's,-Werror=,-W,g'
+    else
+        cat
+    fi
+}
+
+#
+# Prepend `$srcdir/config/clang-warnings/` to the filename suffix(es) given as
+# subroutine argument(s), remove comments starting with # and ending
+# at EOL, replace spans of whitespace (including newlines) with spaces,
+# and re-emit the file(s) thus filtered on the standard output stream.
+#
+load_clang_arguments()
+{
+    set -- $(for arg; do
+        sed 's,#.*$,,' $srcdir/config/clang-warnings/${arg}
+    done)
+    IFS=' ' echo "$*"
+}
+# Get the compiler version in a way that works for clang
+# unless a compiler version is already known
+#
+#   cc_vendor:    The compiler name: clang
+#   cc_version:   Version number: 6.0.0, 7.3.0, ... 10.0.1
+#
+if test "X-" = "X-$cc_flags_set"; then
+    # clang -v will return version number following "clang" on Linux machines,
+    # but on Macs the version number will follow "Apple LLVM version"
+    cc_version="`$CC $CFLAGS $H5_CFLAGS -v 2>&1 |\
+        grep 'clang version' | sed 's/.*clang version \([-a-z0-9\.]*\).*/\1/'`"
+    if test -n "$cc_version"; then
+        cc_vendor="clang"
+    else
+        cc_version="`$CC $CFLAGS $H5_CFLAGS -v 2>&1 |\
+            grep 'Apple LLVM version' | sed 's/.*Apple LLVM version \([-a-z0-9\.]*\).*/\1/'`"
+        if test -n "$cc_version"; then
+            cc_vendor="Apple LLVM"
+        fi
+    fi
+    if test "X-" != "X-$cc_version"; then
+
+        # Get the compiler version numbers
+        cc_vers_major=`echo $cc_version | cut -f1 -d.`
+        cc_vers_minor=`echo $cc_version | cut -f2 -d.`
+        cc_vers_patch=`echo $cc_version | cut -f3 -d.`
+        test -n "$cc_vers_major" || cc_vers_major=0
+        test -n "$cc_vers_minor" || cc_vers_minor=0
+        test -n "$cc_vers_patch" || cc_vers_patch=0
+    fi
+fi
+
+if test "X-clang" = "X-$cc_vendor" -o "X-Apple LLVM" = "X-$cc_vendor"; then
+    echo "compiler '$CC' is $cc_vendor-$cc_version"
+    ###############################
+    # Architecture-specific flags #
+    ###############################
+
+    arch=
+    case "$host_os-$host_cpu" in
+        # FreeBSD sets the information from "uname -m" to the general machine
+        # architecture, not the specific CPU for the machine, so even our
+        # Pentium II Xeon server is set to "i386".  Once we know we are on a FreeBSD
+        # machine, use the "sysctl" command to get the CPU hardware model.
+        freebsd*-i386)
+            host_cpu_model=`sysctl -n hw.model`
+            case "$host_cpu_model" in
+                # Hmm.. this might not catch Celerons, but it won't hurt them either...
+                *Pro*|*II*|*III*|*IV*|*Athlon*)
+                    # architecture-specific optimizations cause problems
+                    # for some users who build binaries to be used on
+                    # multiple architectures.
+                    # arch="-march=i686"
+                ;;
+            esac
+            ;;
+
+        *-i686)
+                    # architecture-specific optimizations cause problems
+                    # for some users who build binaries to be used on
+                    # multiple architectures.
+                    # arch="-march=i686"
+            ;;
+    esac
+
+    case "$host_os-$host_cpu" in
+        # cygwin needs the "-std=c99" flag removed, so make
+        # a specific case for Cygwin without the flag and a default
+        # case to add the flag everywhere else
+        cygwin-*)
+            ;;
+
+        *)
+            H5_CFLAGS="$H5_CFLAGS -std=c99"
+            ;;
+    esac
+
+    H5_CFLAGS="$H5_CFLAGS $arch"
+
+    ##############
+    # Production #
+    ##############
+
+    # NDEBUG is handled explicitly by the configure script
+    PROD_CFLAGS=
+
+    #########
+    # Debug #
+    #########
+
+    # NDEBUG is handled explicitly by the configure script
+    # -g is handled by the symbols flags
+    DEBUG_CFLAGS="-ftrapv -fno-common"
+
+    ###########
+    # Symbols #
+    ###########
+
+    NO_SYMBOLS_CFLAGS=
+    SYMBOLS_CFLAGS="-g"
+
+    #############
+    # Profiling #
+    #############
+
+    PROFILE_CFLAGS="-pg"
+
+    ################
+    # Optimization #
+    ################
+
+    HIGH_OPT_CFLAGS="-O3"
+    DEBUG_OPT_CFLAGS="-g"
+    NO_OPT_CFLAGS="-O0"
+
+    ############
+    # Warnings #
+    ############
+
+    ###########
+    # General #
+    ###########
+
+    H5_CFLAGS="$H5_CFLAGS $(load_clang_arguments general)"
+    H5_ECFLAGS="$H5_ECFLAGS $(load_clang_arguments error-general)"
+
+    ######################
+    # Developer warnings #
+    ######################
+
+    NO_DEVELOPER_WARNING_CFLAGS=$(load_clang_arguments no-developer-general)
+    DEVELOPER_WARNING_CFLAGS=$(load_clang_arguments developer-general)
+
+    #############################
+    # Version-specific warnings #
+    #############################
+
+
+    #################
+    # Flags are set #
+    #################
+    cc_flags_set=yes
+fi
+
+# Clear cc info if no flags set
+if test "X$cc_flags_set" = "X"; then
+    cc_vendor=
+    cc_version=
+fi
+
diff --git a/config/clang-warnings/developer-general b/config/clang-warnings/developer-general
index aa8c32e..74d8404 100644
--- a/config/clang-warnings/developer-general
+++ b/config/clang-warnings/developer-general
@@ -1,3 +1,4 @@
 -Wformat-nonliteral
 -Wmissing-noreturn
+-Wsometimes-uninitialized
 -Wswitch-enum
diff --git a/config/clang-warnings/error-general b/config/clang-warnings/error-general
index a9aa516..883dff7 100644
--- a/config/clang-warnings/error-general
+++ b/config/clang-warnings/error-general
@@ -8,10 +8,11 @@
 -Werror=missing-declarations
 -Werror=packed
 -Werror=shadow
--Werror=sometimes-uninitialized
 -Werror=switch
 #
-#-Werror=discarded-qualifiers
+# NOTE: Following files are not compatible with incompatible-pointer-types as errors
+#     src/H5Dchunk.c,src/H5Dint.c,src/H5Gint.c,src/H5HFcache.c,src/H5I.c,src/H5T.c
+-Wno-error=incompatible-pointer-types-discards-qualifiers
 #
 #
 # NOTE: File Driver files are not compatible with these warnings as errors
diff --git a/config/clang-warnings/no-developer-general b/config/clang-warnings/no-developer-general
index 2f4e0c5..2bf1703 100644
--- a/config/clang-warnings/no-developer-general
+++ b/config/clang-warnings/no-developer-general
@@ -1 +1 @@
--Wmissing-noreturn
+-Wno-missing-noreturn
diff --git a/config/cmake/HDFCXXCompilerFlags.cmake b/config/cmake/HDFCXXCompilerFlags.cmake
index 02bf5cd..6836707 100644
--- a/config/cmake/HDFCXXCompilerFlags.cmake
+++ b/config/cmake/HDFCXXCompilerFlags.cmake
@@ -40,7 +40,7 @@ if (HDF5_DISABLE_COMPILER_WARNINGS)
   # warning level is given, so remove it.
   if (MSVC)
     set (HDF5_WARNINGS_BLOCKED 1)
-    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_LOADED)
       string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
       set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W0")
     endif ()
@@ -51,7 +51,7 @@ if (HDF5_DISABLE_COMPILER_WARNINGS)
 
   # Most compilers use -w to suppress warnings.
   if (NOT HDF5_WARNINGS_BLOCKED)
-    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_LOADED)
       set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -w")
     endif ()
   endif ()
@@ -65,7 +65,7 @@ endif ()
 # CDash is configured to only allow 3000 warnings, so
 # break into groups (from the config/gnu-flags file)
 #-----------------------------------------------------------------------------
-if (NOT MSVC)
+if (NOT MSVC AND NOT MINGW)
   if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
     list (APPEND HDF5_CMAKE_CXX_FLAGS "-erroff=%none -DBSD_COMP")
   else ()
@@ -194,7 +194,9 @@ if (NOT MSVC)
     endif ()
   endif ()
 else ()
+  if (NOT MINGW)
     list (APPEND HDF5_CMAKE_CXX_FLAGS "/EHsc")
+    endif ()
 endif ()
 
 #-----------------------------------------------------------------------------
@@ -204,21 +206,19 @@ if (HDF5_ENABLE_ALL_WARNINGS)
   message (STATUS "....All Warnings are enabled")
   if (MSVC)
     if (HDF5_ENABLE_DEV_WARNINGS)
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+      if (CMAKE_CXX_COMPILER_LOADED)
         string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
         list (APPEND HDF5_CMAKE_CXX_FLAGS "/Wall /wd4668")
       endif ()
     else ()
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+      if (CMAKE_CXX_COMPILER_LOADED)
         string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
         list (APPEND HDF5_CMAKE_CXX_FLAGS "/W3")
       endif ()
     endif ()
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
-        list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS0} ${H5_CXXFLAGS1} ${H5_CXXFLAGS2} ${H5_CXXFLAGS3} ${H5_CXXFLAGS4})
-      endif ()
+    if (CMAKE_CXX_COMPILER_LOADED)
+      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS0} ${H5_CXXFLAGS1} ${H5_CXXFLAGS2} ${H5_CXXFLAGS3} ${H5_CXXFLAGS4})
     endif ()
   endif ()
 endif ()
@@ -229,15 +229,13 @@ endif ()
 if (HDF5_ENABLE_GROUPZERO_WARNINGS)
   message (STATUS "....Group Zero warnings are enabled")
   if (MSVC)
-    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_LOADED)
       string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
       list (APPEND HDF5_CMAKE_CXX_FLAGS "/W1")
     endif ()
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
-        list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS0})
-      endif ()
+    if (CMAKE_CXX_COMPILER_LOADED)
+      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS0})
     endif ()
   endif ()
 endif ()
@@ -248,15 +246,13 @@ endif ()
 if (HDF5_ENABLE_GROUPONE_WARNINGS)
   message (STATUS "....Group One warnings are enabled")
   if (MSVC)
-    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_LOADED)
       string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
       list (APPEND HDF5_CMAKE_CXX_FLAGS "/W2")
     endif ()
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
-        list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS1})
-      endif ()
+    if (CMAKE_CXX_COMPILER_LOADED)
+      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS1})
     endif ()
   endif ()
 endif ()
@@ -267,15 +263,13 @@ endif ()
 if (HDF5_ENABLE_GROUPTWO_WARNINGS)
   message (STATUS "....Group Two warnings are enabled")
   if (MSVC)
-    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_LOADED)
       string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
       list (APPEND HDF5_CMAKE_CXX_FLAGS "/W3")
     endif ()
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
-        list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS2})
-      endif ()
+    if (CMAKE_CXX_COMPILER_LOADED)
+      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS2})
     endif ()
   endif ()
 endif ()
@@ -286,15 +280,13 @@ endif ()
 if (HDF5_ENABLE_GROUPTHREE_WARNINGS)
   message (STATUS "....Group Three warnings are enabled")
   if (MSVC)
-    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_LOADED)
       string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
       list (APPEND HDF5_CMAKE_CXX_FLAGS "/W4")
     endif ()
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
-        list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS3})
-      endif ()
+    if (CMAKE_CXX_COMPILER_LOADED)
+      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS3})
     endif ()
   endif ()
 endif ()
@@ -305,10 +297,8 @@ endif ()
 if (HDF5_ENABLE_GROUPFOUR_WARNINGS)
   message (STATUS "....Group Four warnings are enabled")
   if (NOT MSVC)
-    if (CMAKE_COMPILER_IS_GNUCC)
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
-        list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS4})
-      endif ()
+    if (CMAKE_CXX_COMPILER_LOADED)
+      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS4})
     endif ()
   endif ()
 endif ()
diff --git a/config/cmake/HDFCompilerFlags.cmake b/config/cmake/HDFCompilerFlags.cmake
index cd4ab48..31af2f8 100644
--- a/config/cmake/HDFCompilerFlags.cmake
+++ b/config/cmake/HDFCompilerFlags.cmake
@@ -68,7 +68,7 @@ endif ()
 # CDash is configured to only allow 3000 warnings, so
 # break into groups (from the config/gnu-flags file)
 #-----------------------------------------------------------------------------
-if (NOT MSVC)
+if (NOT MSVC AND NOT MINGW)
   if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
     list (APPEND HDF5_CMAKE_C_FLAGS "-erroff=%none -DBSD_COMP")
   else ()
@@ -209,9 +209,7 @@ if (HDF5_ENABLE_ALL_WARNINGS)
       list (APPEND HDF5_CMAKE_C_FLAGS "/W3")
     endif ()
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS0} ${H5_CFLAGS1} ${H5_CFLAGS2} ${H5_CFLAGS3} ${H5_CFLAGS4})
-    endif ()
+    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS0} ${H5_CFLAGS1} ${H5_CFLAGS2} ${H5_CFLAGS3} ${H5_CFLAGS4})
   endif ()
 endif ()
 
@@ -225,9 +223,7 @@ if (HDF5_ENABLE_GROUPZERO_WARNINGS)
     string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
     list (APPEND HDF5_CMAKE_C_FLAGS "/W1")
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS0})
-    endif ()
+    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS0})
   endif ()
 endif ()
 
@@ -241,9 +237,7 @@ if (HDF5_ENABLE_GROUPONE_WARNINGS)
     string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
     list (APPEND HDF5_CMAKE_C_FLAGS "/W2")
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS1})
-    endif ()
+    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS1})
   endif ()
 endif ()
 
@@ -257,9 +251,7 @@ if (HDF5_ENABLE_GROUPTWO_WARNINGS)
     string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
     list (APPEND HDF5_CMAKE_C_FLAGS "/W3")
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS2})
-    endif ()
+    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS2})
   endif ()
 endif ()
 
@@ -273,9 +265,7 @@ if (HDF5_ENABLE_GROUPTHREE_WARNINGS)
     string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
     list (APPEND HDF5_CMAKE_C_FLAGS "/W4")
   else ()
-    if (CMAKE_COMPILER_IS_GNUCC)
-      list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS3})
-    endif ()
+    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS3})
   endif ()
 endif ()
 
@@ -286,9 +276,7 @@ option (HDF5_ENABLE_GROUPFOUR_WARNINGS "Enable group four warnings" OFF)
 if (HDF5_ENABLE_GROUPFOUR_WARNINGS)
   message (STATUS "....Group Four warnings are enabled")
   if (NOT MSVC)
-    if (CMAKE_COMPILER_IS_GNUCC)
-      list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS4})
-    endif ()
+    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS4})
   endif ()
 endif ()
 
diff --git a/config/commence.am b/config/commence.am
index 41e0f3f..6e3d9a9 100644
--- a/config/commence.am
+++ b/config/commence.am
@@ -72,7 +72,7 @@ H5CPP=${DESTDIR}$(bindir)/h5c++
 
 AM_CFLAGS=@AM_CFLAGS@ @H5_CFLAGS@ @H5_ECFLAGS@
 AM_FCFLAGS=@AM_FCFLAGS@ @H5_FCFLAGS@
-AM_CXXFLAGS=@AM_CXXFLAGS@ @H5_CXXFLAGS@
+AM_CXXFLAGS=@AM_CXXFLAGS@ @H5_CXXFLAGS@ @H5_ECXXFLAGS@
 AM_CPPFLAGS=@AM_CPPFLAGS@ @H5_CPPFLAGS@
 AM_LDFLAGS=@AM_LDFLAGS@ @H5_LDFLAGS@
 
diff --git a/config/linux-gnulibc1 b/config/linux-gnulibc1
index 39225e7..a6f81ff 100644
--- a/config/linux-gnulibc1
+++ b/config/linux-gnulibc1
@@ -42,6 +42,9 @@ fi
 # Figure out Intel C compiler flags
 . $srcdir/config/intel-flags
 
+# Figure out Clang C compiler flags
+. $srcdir/config/clang-flags
+
 # Use default Fortran 90 compiler according to what C compiler is used.
 if test "X-" = "X-$FC"; then
     case $CC_BASENAME in
@@ -61,6 +64,11 @@ if test "X-" = "X-$FC"; then
             FC=mpif90
             FC_BASENAME=mpif90
             ;;
+        clang*)
+            # clang has no fortran compiler. Use gfortran.
+            FC=gfortran
+            FC_BASENAME=gfortran
+            ;;
     esac
 else
     case $FC in
@@ -194,6 +202,9 @@ fi
 # Figure out GNU CXX compiler flags
 . $srcdir/config/gnu-cxxflags
 
+# Figure out Clang CXX compiler flags
+. $srcdir/config/clang-cxxflags
+
 # compiler version strings
 
 # check if the compiler_version_info is already set
@@ -223,6 +234,11 @@ case $CC in
             sed 's/\(Intel.* Compiler\).*\( Version [a-z0-9\.]*\).*\( Build [0-9]*\)/\1\2\3/'`
         ;;
 
+    *clang*)
+        cc_version_info="`$CC $CFLAGS $H5_CFLAGS --version 2>&1 |\
+            grep 'clang version' | sed 's/.*clang version \([-a-z0-9\.]*\).*/\1/'`"
+        ;;
+
     *)
         echo "No match to get cc_version_info for $CC"
         ;;
@@ -317,6 +333,11 @@ case $CXX in
         cxx_version_info=`echo $cxx_version_info`
         ;; 
 
+    *clang++*)
+        cxx_version_info="`$CXX $CXXFLAGS $H5_CXXFLAGS --version 2>&1 |\
+            grep 'clang version' | sed 's/.*clang version \([-a-z0-9\.]*\).*/\1/'`"
+        ;;
+
     *)
         echo "No match to get cxx_version_info for $CXX"
         ;;