1.8 Merge config changes from dev (#1032)

* Merge config changes from dev

* Revert added git file changes

* Merge MS clang needs EHsc flag #1035

37 files changed, 958 insertions, 441 deletions

diff --git a/MANIFEST b/MANIFEST
index 65ba64c..ad51e01 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -129,6 +129,7 @@
 ./config/cygwin
 ./config/ibm-aix
 ./config/ibm-flags
+./config/intel-cxxflags
 ./config/intel-fflags
 ./config/intel-flags
 ./config/libhdf5.pc.in
@@ -140,6 +141,7 @@
 ./config/lt_vers.am
 ./config/Makefile.am.blank
 ./config/netbsd
+./config/pgi-cxxflags
 ./config/pgi-fflags
 ./config/pgi-flags
 ./config/solaris
@@ -165,6 +167,7 @@
 ./config/gnu-warnings/cxx-4.8
 ./config/gnu-warnings/cxx-4.9
 ./config/gnu-warnings/cxx-5
+./config/gnu-warnings/cxx-9
 ./config/gnu-warnings/cxx-error-5
 ./config/gnu-warnings/cxx-error-general
 ./config/gnu-warnings/cxx-noerror-5
@@ -189,8 +192,13 @@
 ./config/gnu-warnings/noerror-5
 ./config/gnu-warnings/noerror-8
 ./config/gnu-warnings/noerror-general
-./config/intel-warnings/ifort-general
+./config/intel-warnings/15
+./config/intel-warnings/18
+./config/intel-warnings/developer-general
 ./config/intel-warnings/general
+./config/intel-warnings/win-developer-general
+./config/intel-warnings/win-general
+./config/intel-warnings/ifort-general
 
 ./config/site-specific/BlankForm
 
diff --git a/config/clang-warnings/noerror-general b/config/clang-warnings/noerror-general
index b570b23..f90c812 100644
--- a/config/clang-warnings/noerror-general
+++ b/config/clang-warnings/noerror-general
@@ -1,6 +1,8 @@
 #
-# HDF5 code should not trigger the following warnings under any
-# circumstances, so ask the compiler to treat them as errors:
+# These warnings will be treated as errors, using the error-general file,
+# when HDF5_ENABLE_WARNINGS_AS_ERRORS is set to true for CMake or
+# the --enable-warnings-as-errors option is specified for configure.
+#   Otherwise this file will be used to treat them as warnings.
 #
 -Wbad-function-cast
 -Wimplicit-function-declaration
diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index b437266..729fff8 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -148,7 +148,7 @@ if (NOT WINDOWS)
         OUTPUT_VARIABLE OUTPUT
     )
     if (TEST_DIRECT_VFD_WORKS_COMPILE)
-      if (TEST_DIRECT_VFD_WORKS_RUN MATCHES 0)
+      if (TEST_DIRECT_VFD_WORKS_RUN EQUAL "0")
         HDF_FUNCTION_TEST (HAVE_DIRECT)
         set (CMAKE_REQUIRED_DEFINITIONS "${CMAKE_REQUIRED_DEFINITIONS} -D_GNU_SOURCE")
         add_definitions ("-D_GNU_SOURCE")
@@ -201,7 +201,7 @@ macro (H5ConversionTests TEST msg)
         OUTPUT_VARIABLE OUTPUT
     )
     if (${TEST}_COMPILE)
-      if (${TEST}_RUN MATCHES 0)
+      if (${TEST}_RUN EQUAL "0")
         set (${TEST} 1 CACHE INTERNAL ${msg})
         if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
           message (VERBOSE "${msg}... yes")
diff --git a/config/cmake/H5pubconf.h.in b/config/cmake/H5pubconf.h.in
index a41e862..82d9f5f 100644
--- a/config/cmake/H5pubconf.h.in
+++ b/config/cmake/H5pubconf.h.in
@@ -72,7 +72,7 @@
 #cmakedefine H5_HAVE_CODESTACK @H5_HAVE_CODESTACK@
 
 /* Define to 1 if you have the <curl/curl.h> header file. */
-#cmakedefine H5_HAVE_CURL_H @H5_HAVE_CURL_H@
+#cmakedefine H5_HAVE_CURL_CURL_H @H5_HAVE_CURL_H@
 
 /* Define if Darwin or Mac OS X */
 #cmakedefine H5_HAVE_DARWIN @H5_HAVE_DARWIN@
@@ -307,7 +307,7 @@
 /* Define to 1 if you have the `stat64' function. */
 #cmakedefine H5_HAVE_STAT64 @H5_HAVE_STAT64@
 
-/* Define if `struct stat' has the `st_blocks' field */
+/* Define if struct stat has the st_blocks field */
 #cmakedefine H5_HAVE_STAT_ST_BLOCKS @H5_HAVE_STAT_ST_BLOCKS@
 
 /* Define to 1 if you have the <stddef.h> header file. */
diff --git a/config/cmake/HDF5_Examples_options.cmake b/config/cmake/HDF5_Examples_options.cmake
index d318aac..4df9301 100644
--- a/config/cmake/HDF5_Examples_options.cmake
+++ b/config/cmake/HDF5_Examples_options.cmake
@@ -40,17 +40,21 @@
 
 ### enable FILTERS builds
 #set(ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF_BUILD_FILTERS:BOOL=ON")
+### default HDF5_PLUGIN_PATH to where the filter libraries are located
+#set(ENV{HDF5_PLUGIN_PATH} "${INSTALLDIR}/lib/plugin")
 
 #############################################################################################
 ### enable parallel program builds
 #set(ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF_ENABLE_PARALLEL:BOOL=ON")
 
+#############################################################################################
+### match the hdf5 library namespace
+set(ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF5_NAMESPACE:STRING=hdf5::")
 
 #############################################################################################
 ### enable threadsafe program builds
 #set(ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DHDF_ENABLE_THREADSAFE:BOOL=ON")
 
-
 #############################################################################################
 ### enable test program builds, requires reference files in testfiles subdirectory
 #set(ADD_BUILD_OPTIONS "${ADD_BUILD_OPTIONS} -DBUILD_TESTING:BOOL=ON")
diff --git a/config/cmake/HDFCXXCompilerFlags.cmake b/config/cmake/HDFCXXCompilerFlags.cmake
index 8bcfb14..f06ffb0 100644
--- a/config/cmake/HDFCXXCompilerFlags.cmake
+++ b/config/cmake/HDFCXXCompilerFlags.cmake
@@ -9,17 +9,46 @@
 # If you do not have access to either file, you may request a copy from
 # help@hdfgroup.org.
 #
-set(CMAKE_CXX_STANDARD 98)
-set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
-set(CMAKE_CXX_EXTENSIONS OFF)
+set (CMAKE_CXX_STANDARD 98)
+set (CMAKE_CXX_STANDARD_REQUIRED TRUE)
+
+set (CMAKE_CXX_EXTENSIONS OFF)
 
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_SANITIZER_FLAGS} ${CMAKE_CXX_FLAGS}")
 if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
-  message (VERBOSE "Warnings Configuration: CXX default:  ${CMAKE_CXX_FLAGS}")
+  message (VERBOSE "Warnings Configuration: CXX default: ${CMAKE_CXX_FLAGS}")
 endif ()
 #-----------------------------------------------------------------------------
 # Compiler specific flags : Shouldn't there be compiler tests for these
 #-----------------------------------------------------------------------------
+if (WIN32 AND CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+  set (_INTEL_WINDOWS 1)
+endif ()
+
+if (WIN32 AND CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang" AND "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
+  set (_CLANG_MSVC_WINDOWS 1)
+endif()
+
+# MSVC 14.28 enables C5105, but the Windows SDK 10.0.18362.0 triggers it.
+if ((_CLANG_MSVC_WINDOWS OR CMAKE_CXX_COMPILER_ID STREQUAL "MSVC") AND CMAKE_CXX_COMPILER_LOADED)
+  set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHsc")
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 19.28)
+    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -wd5105")
+  endif ()
+endif ()
+
+if (CMAKE_CXX_COMPILER_ID STREQUAL SunPro AND CMAKE_CXX_COMPILER_LOADED)
+  if (NOT DEFINED CMAKE_CXX${CMAKE_CXX_STANDARD}_STANDARD_COMPILE_OPTION)
+    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.13)
+      if (NOT CMAKE_CXX_STANDARD OR CMAKE_CXX_STANDARD EQUAL 98)
+        set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++03")
+      endif ()
+    else ()
+      set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -library=stlport4")
+    endif ()
+  endif ()
+endif ()
+
 if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED)
   set (CMAKE_CXX_FLAGS "${CMAKE_ANSI_CFLAGS} ${CMAKE_CXX_FLAGS}")
   if (${HDF_CFG_NAME} MATCHES "Debug")
@@ -71,152 +100,169 @@ endif ()
 # HDF5 library compile options
 #-----------------------------------------------------------------------------
 
-if (NOT MSVC AND NOT MINGW)
-  if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
-    list (APPEND HDF5_CMAKE_CXX_FLAGS "-erroff=%none -DBSD_COMP")
-  else ()
-    # General flags
-    #
-    # Note that some of the flags listed here really should be developer
-    # flags (listed in a separate variable, below) but we put them here
-    # because they are not raised by the current code and we'd like to
-    # know if they do start showing up.
-    #
-    # NOTE: Don't add -Wpadded here since we can't/won't fix the (many)
-    # warnings that are emitted. If you need it, add it at configure time.
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+  list (APPEND HDF5_CMAKE_CXX_FLAGS "-erroff=%none -DBSD_COMP")
+else ()
+  # General flags
+  #
+  # Note that some of the flags listed here really should be developer
+  # flags (listed in a separate variable, below) but we put them here
+  # because they are not raised by the current code and we'd like to
+  # know if they do start showing up.
+  #
+  # NOTE: Don't add -Wpadded here since we can't/won't fix the (many)
+  # warnings that are emitted. If you need it, add it at configure time.
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+    if (_INTEL_WINDOWS)
+      ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/win-general")
+    else ()
       ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/general")
+    endif()
+    if (NOT _INTEL_WINDOWS)
+      if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 15.0)
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/15")
+      endif()
       if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 18.0)
-        list (APPEND H5_CXXFLAGS "-Wextra-tokens -Wformat -Wformat-security -Wic-pointer -Wshadow")
-        list (APPEND H5_CXXFLAGS "-Wsign-compare -Wtrigraphs -Wwrite-strings")
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/18")
       endif()
-    elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-      if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED
-          AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
-        # add the general CXX flags for g++ compiler versions 4.8 and above.
-        ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-general")
-        if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-          ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-general")
-        else ()
-          ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-noerror-general")
-        endif ()
+    endif()
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED
+        AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
+      # add the general CXX flags for g++ compiler versions 4.8 and above.
+      ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-general")
+      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-general")
+      else ()
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-noerror-general")
       endif ()
-    elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-      ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/general")
-    elseif (CMAKE_CXX_COMPILER_ID STREQUAL "PGI")
-      list (APPEND HDF5_CMAKE_CXX_FLAGS "-Minform=inform")
-    endif ()
-    if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
-      message (VERBOSE "CMAKE_CXX_FLAGS_GENERAL=${HDF5_CMAKE_CXX_FLAGS}")
     endif ()
+  elseif (CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+    ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/general")
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "PGI")
+    list (APPEND HDF5_CMAKE_CXX_FLAGS "-Minform=inform")
   endif ()
-
-  #-----------------------------------------------------------------------------
-  # Option to allow the user to enable developer warnings
-  # Developer warnings (suggestions from gcc, not code problems)
-  #-----------------------------------------------------------------------------
-  if (HDF5_ENABLE_DEV_WARNINGS)
-    message (STATUS "....HDF5 developer group warnings are enabled")
-  #  if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
-  #    list (APPEND H5_CXXFLAGS "-Winline -Wreorder -Wport -Wstrict-aliasing")
-  #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
-  #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-  #    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
-    endif ()
-  else ()
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
-  #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-  #    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
-    endif ()
+  if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
+    message (VERBOSE "CMAKE_CXX_FLAGS_GENERAL=${HDF5_CMAKE_CXX_FLAGS}")
   endif ()
+endif ()
 
+#-----------------------------------------------------------------------------
+# Option to allow the user to enable developer warnings
+# Developer warnings (suggestions from gcc, not code problems)
+#-----------------------------------------------------------------------------
+if (HDF5_ENABLE_DEV_WARNINGS)
+  message (STATUS "....HDF5 developer group warnings are enabled")
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/developer-general")
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
+  elseif (CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
+  endif ()
+else ()
   if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    # Technically, variable-length arrays are part of the C99 standard, but
-    #   we should approach them a bit cautiously... Only needed for gcc 4.X
-    if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0 AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
-    endif ()
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
+  elseif (CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
+  endif ()
+endif ()
 
-    # Append more extra warning flags that only gcc 4.8+ knows about
-    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
-      if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
-      else ()
-        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
-      endif ()
-    endif ()
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  # Technically, variable-length arrays are part of the C99 standard, but
+  #   we should approach them a bit cautiously... Only needed for gcc 4.X
+  if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0 AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
+  endif ()
 
-    # Append more extra warning flags that only gcc 4.9+ knows about
-    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9)
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.9")
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-4.9")
+  # Append more extra warning flags that only gcc 4.8+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-4.8")
+    if (HDF5_ENABLE_DEV_WARNINGS)
+      # Use the C warnings as CXX warnings are the same
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
+    else ()
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
     endif ()
+  endif ()
 
-    # Append more extra warning flags that only gcc 5.1+ knows about
-    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-5")
-      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-5")
-      else ()
-        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-noerror-5")
-      endif ()
-    endif ()
+  # Append more extra warning flags that only gcc 4.9+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9)
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-4.9")
+  endif ()
 
-    # Append more extra warning flags that only gcc 6.x+ knows about
-    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.0)
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
+  # Append more extra warning flags that only gcc 5.1+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)
+    # autotools always add the C flags with the CXX flags
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-5")
+    if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-5")
+    else ()
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-noerror-5")
     endif ()
+  endif ()
 
-    # Append more extra warning flags that only gcc 7.x+ knows about
-    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0)
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXxFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
-      if (HDF5_ENABLE_DEV_WARNINGS)
-        # autotools always add the C flags with the CXX flags
-        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
-      #else ()
-      #  ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
-      endif ()
-    endif ()
+  # Append more extra warning flags that only gcc 6.x+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.0)
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
+  endif ()
 
-    # Append more extra warning flags that only gcc 8.x+ knows about
-    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 8.0)
-      # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/8")
-      #if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-      #  ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
-      #else ()
-      #  ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-8")
-      #endif ()
-      if (HDF5_ENABLE_DEV_WARNINGS)
-        # autotools always add the C flags with the CXX flags
-        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
-      else ()
-        # autotools always add the C flags with the CXX flags
-        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
-      endif ()
+  # Append more extra warning flags that only gcc 7.x+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0)
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXxFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
+    if (HDF5_ENABLE_DEV_WARNINGS)
+    # Use the C warnings as CXX warnings are the same
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
+    #else ()
+    #  ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
     endif ()
+  endif ()
 
-    # Append more extra warning flags that only gcc 9.x+ knows about
-    if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+  # Append more extra warning flags that only gcc 8.x+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 8.0)
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/8")
+    if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
+    else ()
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-8")
+    endif ()
+    if (HDF5_ENABLE_DEV_WARNINGS)
+      # Use the C warnings as CXX warnings are the same
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
+    else ()
       # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
     endif ()
   endif ()
-else ()
-  if (NOT MINGW)
-    list (APPEND HDF5_CMAKE_CXX_FLAGS "/EHsc")
+
+  # Append more extra warning flags that only gcc 9.x+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+    # Use the C warnings as CXX warnings are the same
+    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-9")
+  endif ()
+
+  # Append more extra warning flags that only gcc 9.3+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.3)
+    # do not use C warnings, gnu-warnings 9.3, no cxx warniings
+    # ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9.3")
+  endif ()
+
+  # Append more extra warning flags that only gcc 10.x+ knows about
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10.0)
+    if (HDF5_ENABLE_DEV_WARNINGS)
+      # Use the C warnings as CXX warnings are the same
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-10")
+    #else ()
+    #  ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-10")
     endif ()
+  endif ()
 endif ()
 
 #-----------------------------------------------------------------------------
@@ -256,17 +302,17 @@ endif ()
 # This option will force/override the default setting for all configurations
 #-----------------------------------------------------------------------------
 if (HDF5_ENABLE_SYMBOLS MATCHES "YES")
-  if(CMAKE_CXX_COMPILER_LOADED)
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+  if (CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel" AND NOT _INTEL_WINDOWS)
       set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g")
     elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
       set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g")
     endif ()
   endif ()
 elseif (HDF5_ENABLE_SYMBOLS MATCHES "NO")
-  if(CMAKE_CXX_COMPILER_LOADED)
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
-      set (CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS} -Wl,-s")
+  if (CMAKE_CXX_COMPILER_LOADED)
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel" AND NOT _INTEL_WINDOWS)
+      set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,-s")
     elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
       set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s")
     endif ()
@@ -278,7 +324,7 @@ endif ()
 # This option will force/override the default setting for all configurations
 #-----------------------------------------------------------------------------
 if (HDF5_ENABLE_PROFILING)
-  if(CMAKE_CXX_COMPILER_LOADED)
+  if (CMAKE_CXX_COMPILER_LOADED)
     list (APPEND HDF5_CMAKE_CXX_FLAGS "${PROFILE_CXXFLAGS}")
   endif ()
 endif ()
@@ -288,7 +334,7 @@ endif ()
 # This option will force/override the default setting for all configurations
 #-----------------------------------------------------------------------------
 if (HDF5_ENABLE_OPTIMIZATION)
-  if(CMAKE_CXX_COMPILER_LOADED)
+  if (CMAKE_CXX_COMPILER_LOADED)
     list (APPEND HDF5_CMAKE_CXX_FLAGS "${OPTIMIZE_CXXFLAGS}")
   endif ()
 endif ()
diff --git a/config/cmake/HDFCompilerFlags.cmake b/config/cmake/HDFCompilerFlags.cmake
index 0775f59..210e475 100644
--- a/config/cmake/HDFCompilerFlags.cmake
+++ b/config/cmake/HDFCompilerFlags.cmake
@@ -14,14 +14,42 @@ set(CMAKE_C_STANDARD_REQUIRED TRUE)
 
 set (CMAKE_C_FLAGS "${CMAKE_C99_STANDARD_COMPILE_OPTION} ${CMAKE_C_FLAGS}")
 set (CMAKE_C_FLAGS "${CMAKE_C_SANITIZER_FLAGS} ${CMAKE_C_FLAGS}")
-set (CMAKE_CXX_FLAGS "${CMAKE_CXX_SANITIZER_FLAGS} ${CMAKE_CXX_FLAGS}")
-
 if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
-  message (VERBOSE "Warnings Configuration: default: ${CMAKE_C_FLAGS} : ${CMAKE_CXX_FLAGS}")
+  message (VERBOSE "Warnings Configuration: C default: ${CMAKE_C_FLAGS}")
 endif ()
 #-----------------------------------------------------------------------------
 # Compiler specific flags : Shouldn't there be compiler tests for these
 #-----------------------------------------------------------------------------
+if(WIN32 AND CMAKE_C_COMPILER_ID STREQUAL "Intel")
+  set(_INTEL_WINDOWS 1)
+endif()
+
+if(WIN32 AND CMAKE_C_COMPILER_ID MATCHES "[Cc]lang" AND "x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
+  set(_CLANG_MSVC_WINDOWS 1)
+endif()
+
+# Disable deprecation warnings for standard C functions.
+# really only needed for newer versions of VS, but should
+# not hurt other versions, and this will work into the
+# future
+if(MSVC OR _INTEL_WINDOWS OR _CLANG_MSVC_WINDOWS)
+  add_definitions(-D_CRT_SECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE)
+else()
+endif()
+
+if(MSVC)
+  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stack:10000000")
+endif()
+
+# MSVC 14.28 enables C5105, but the Windows SDK 10.0.18362.0 triggers it.
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC" AND NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 19.28)
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -wd5105")
+endif()
+
+if(_CLANG_MSVC_WINDOWS AND "x${CMAKE_C_COMPILER_FRONTEND_VARIANT}" STREQUAL "xGNU")
+  set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Xlinker -stack:20000000")
+endif()
+
 if (CMAKE_COMPILER_IS_GNUCC)
   set (CMAKE_C_FLAGS "${CMAKE_ANSI_CFLAGS} ${CMAKE_C_FLAGS}")
   if (${HDF_CFG_NAME} MATCHES "Debug")
@@ -81,169 +109,176 @@ endif ()
 # HDF5 library compile options
 #-----------------------------------------------------------------------------
 
-if (NOT MSVC AND NOT MINGW)
-  #-----------------------------------------------------------------------------
-  # Option to allow the user to interpret certain warnings as errors
-  #
-  # This should NOT be on by default as it can cause a lot of conflicts with
-  # new operating systems and compiler versions. Header files that are out of
-  # our control (MPI, HDFS, etc.) can also raise warnings.
-  #-----------------------------------------------------------------------------
-  option (HDF5_ENABLE_WARNINGS_AS_ERRORS "Interpret some warnings as errors" OFF)
-  if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-    message (STATUS "...some warnings will be interpreted as errors")
-  endif ()
+#-----------------------------------------------------------------------------
+# Option to allow the user to interpret certain warnings as errors
+#
+# This should NOT be on by default as it can cause a lot of conflicts with
+# new operating systems and compiler versions. Header files that are out of
+# our control (MPI, HDFS, etc.) can also raise warnings.
+#-----------------------------------------------------------------------------
+option (HDF5_ENABLE_WARNINGS_AS_ERRORS "Interpret some warnings as errors" OFF)
+if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+  message (STATUS "...some warnings will be interpreted as errors")
+endif ()
 
-  if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
-    list (APPEND HDF5_CMAKE_C_FLAGS "-erroff=%none -DBSD_COMP")
-  else ()
-    # General flags
-    #
-    # Note that some of the flags listed here really should be developer
-    # flags (listed in a separate variable, below) but we put them here
-    # because they are not raised by the current code and we'd like to
-    # know if they do start showing up.
-    #
-    # NOTE: Don't add -Wpadded here since we can't/won't fix the (many)
-    # warnings that are emitted. If you need it, add it at configure time.
-    if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
+if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+  list (APPEND HDF5_CMAKE_C_FLAGS "-erroff=%none -DBSD_COMP")
+else ()
+  # General flags
+  #
+  # Note that some of the flags listed here really should be developer
+  # flags (listed in a separate variable, below) but we put them here
+  # because they are not raised by the current code and we'd like to
+  # know if they do start showing up.
+  #
+  # NOTE: Don't add -Wpadded here since we can't/won't fix the (many)
+  # warnings that are emitted. If you need it, add it at configure time.
+  if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
+    if (_INTEL_WINDOWS)
+      ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/win-general")
+    else ()
       ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/general")
-      list (APPEND H5_CFLAGS "-Wcomment -Wdeprecated -Wmain -Wmissing-declarations -Wmissing-prototypes -Wp64 -Wpointer-arith")
-      list (APPEND H5_CFLAGS "-Wreturn-type -Wstrict-prototypes -Wuninitialized")
-      list (APPEND H5_CFLAGS "-Wunknown-pragmas -Wunused-function -Wunused-variable")
+    endif()
+    if (NOT _INTEL_WINDOWS)
+      if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 15.0)
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/15")
+      endif()
       # this is just a failsafe
       list (APPEND H5_CFLAGS "-finline-functions")
       if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 18.0)
-        list (APPEND H5_CFLAGS "-Wextra-tokens -Wformat -Wformat-security -Wic-pointer -Wshadow")
-        list (APPEND H5_CFLAGS "-Wsign-compare -Wtrigraphs -Wwrite-strings")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/18")
       endif()
-    elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU")
-      # Add general CFlags for GCC versions 4.8 and above
-      if (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
-        ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/general")
-        if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-          ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-general")
-        else ()
-          ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-general")
-        endif ()
-      endif ()
-      # gcc automatically inlines based on the optimization level
-      # this is just a failsafe
-      list (APPEND H5_CFLAGS "-finline-functions")
-    elseif (CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
-      ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/general")
+    endif()
+  elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    # Add general CFlags for GCC versions 4.8 and above
+    if (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
+      ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/general")
       if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/error-general")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-general")
       else ()
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/noerror-general")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-general")
       endif ()
-    elseif (CMAKE_C_COMPILER_ID STREQUAL "PGI")
-      list (APPEND HDF5_CMAKE_C_FLAGS "-Minform=inform")
     endif ()
-    if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
-      message (VERBOSE "CMAKE_C_FLAGS_GENERAL=${HDF5_CMAKE_C_FLAGS}")
+    # gcc automatically inlines based on the optimization level
+    # this is just a failsafe
+    list (APPEND H5_CFLAGS "-finline-functions")
+  elseif (CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
+    ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/general")
+    if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/error-general")
+    else ()
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/noerror-general")
     endif ()
+  elseif (CMAKE_C_COMPILER_ID STREQUAL "PGI")
+    list (APPEND HDF5_CMAKE_C_FLAGS "-Minform=inform")
+  endif ()
+  if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
+    message (VERBOSE "CMAKE_C_FLAGS_GENERAL=${HDF5_CMAKE_C_FLAGS}")
   endif ()
+endif ()
 
-  #-----------------------------------------------------------------------------
-  # Option to allow the user to enable developer warnings
-  # Developer warnings (suggestions from gcc, not code problems)
-  #-----------------------------------------------------------------------------
-  option (HDF5_ENABLE_DEV_WARNINGS "Enable HDF5 developer group warnings" OFF)
-  if (HDF5_ENABLE_DEV_WARNINGS)
-    message (STATUS "....HDF5 developer group warnings are enabled")
-    if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
-      list (APPEND H5_CFLAGS "-Winline -Wreorder -Wport -Wstrict-aliasing")
-    elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
-    elseif (CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
-    endif ()
-  else ()
-    if (CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
-    elseif (CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
+#-----------------------------------------------------------------------------
+# Option to allow the user to enable developer warnings
+# Developer warnings (suggestions from gcc, not code problems)
+#-----------------------------------------------------------------------------
+option (HDF5_ENABLE_DEV_WARNINGS "Enable HDF5 developer group warnings" OFF)
+if (HDF5_ENABLE_DEV_WARNINGS)
+  message (STATUS "....HDF5 developer group warnings are enabled")
+  if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
+    if (_INTEL_WINDOWS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/win-developer-general")
+    else ()
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/developer-general")
     endif ()
+  elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
+  elseif (CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
+  endif ()
+else ()
+  if (CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
+  elseif (CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
   endif ()
+endif ()
 
-  if (CMAKE_C_COMPILER_ID STREQUAL "GNU")
-    # Technically, variable-length arrays are part of the C99 standard, but
-    #   we should approach them a bit cautiously... Only needed for gcc 4.X
-    if (CMAKE_C_COMPILER_VERSION VERSION_LESS 5.0 AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
-    endif ()
+if (CMAKE_C_COMPILER_ID STREQUAL "GNU")
+  # Technically, variable-length arrays are part of the C99 standard, but
+  #   we should approach them a bit cautiously... Only needed for gcc 4.X
+  if (CMAKE_C_COMPILER_VERSION VERSION_LESS 5.0 AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
+  endif ()
 
-    # Append more extra warning flags that only gcc 4.8+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.8)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
-      if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
-      else ()
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
-      endif ()
+  # Append more extra warning flags that only gcc 4.8+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.8)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
+    if (HDF5_ENABLE_DEV_WARNINGS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
+    else ()
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
     endif ()
+  endif ()
 
-    # Append more extra warning flags that only gcc 4.9+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.9)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.9")
-    endif ()
+  # Append more extra warning flags that only gcc 4.9+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.9)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.9")
+  endif ()
 
-    # Append more extra warning flags that only gcc 5.x+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 5.0)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/5")
-      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-5")
-      else ()
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-5")
-      endif ()
+  # Append more extra warning flags that only gcc 5.x+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 5.0)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/5")
+    if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-5")
+    else ()
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-5")
     endif ()
+  endif ()
 
-    # Append more extra warning flags that only gcc 6.x+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 6.0)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
-    endif ()
+  # Append more extra warning flags that only gcc 6.x+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 6.0)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
+  endif ()
 
-    # Append more extra warning flags that only gcc 7.x+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 7.0)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
-      if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
-      #else ()
-      #  ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
-      endif ()
+  # Append more extra warning flags that only gcc 7.x+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 7.0)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
+    if (HDF5_ENABLE_DEV_WARNINGS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
+    #else ()
+    #  ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
     endif ()
+  endif ()
 
-    # Append more extra warning flags that only gcc 8.x+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 8.0)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/8")
-      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
-      endif ()
-      if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
-      else ()
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
-      endif ()
+  # Append more extra warning flags that only gcc 8.x+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 8.0)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/8")
+    if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
     endif ()
-
-    # Append more extra warning flags that only gcc 9.x+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.0)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
+    if (HDF5_ENABLE_DEV_WARNINGS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
+    else ()
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
     endif ()
+  endif ()
 
-    # Append more extra warning flags that only gcc 9.3+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.3)
-      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9.3")
-    endif ()
+  # Append more extra warning flags that only gcc 9.x+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.0)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
+  endif ()
 
-    # Append more extra warning flags that only gcc 10.x+ knows about
-    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 10.0)
-      if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-10")
-      #else ()
-      #  ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-10")
-      endif ()
+  # Append more extra warning flags that only gcc 9.3+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.3)
+    ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9.3")
+  endif ()
+
+  # Append more extra warning flags that only gcc 10.x+ knows about
+  if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 10.0)
+    if (HDF5_ENABLE_DEV_WARNINGS)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-10")
+    #else ()
+    #  ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-10")
     endif ()
   endif ()
 endif ()
@@ -298,13 +333,13 @@ MARK_AS_ADVANCED (HDF5_ENABLE_ASSERTS)
 set (HDF5_ENABLE_SYMBOLS "OFF" CACHE STRING "Add debug symbols to the library independent of the build mode and optimization level (OFF NO YES)")
 set_property (CACHE HDF5_ENABLE_SYMBOLS PROPERTY STRINGS OFF NO YES)
 if (HDF5_ENABLE_SYMBOLS MATCHES "YES")
-  if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
+  if (CMAKE_C_COMPILER_ID STREQUAL "Intel" AND NOT _INTEL_WINDOWS)
     set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g")
   elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU")
     set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g -fno-omit-frame-pointer")
   endif ()
 elseif (HDF5_ENABLE_SYMBOLS MATCHES "NO")
-  if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
+  if (CMAKE_C_COMPILER_ID STREQUAL "Intel" AND NOT _INTEL_WINDOWS)
     set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wl,-s")
   elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU")
     set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -s")
diff --git a/config/cmake/HDFFortranCompilerFlags.cmake b/config/cmake/HDFFortranCompilerFlags.cmake
index 18ab621..94c40aa 100644
--- a/config/cmake/HDFFortranCompilerFlags.cmake
+++ b/config/cmake/HDFFortranCompilerFlags.cmake
@@ -91,9 +91,10 @@ if (NOT MSVC AND NOT MINGW)
     #endif ()
 
     # Append more extra warning flags that only gcc 5.x+ knows about
-    if (NOT CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 5.0)
-      ADD_H5_FLAGS (HDF5_CMAKE_Fortran_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/gfort-5")
-    endif ()
+    # do not include -Wuse-without-only
+    #if (NOT CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 5.0)
+    #  ADD_H5_FLAGS (HDF5_CMAKE_Fortran_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/gfort-5")
+    #endif ()
 
     # Append more extra warning flags that only gcc 6.x+ knows about
     if (NOT CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 6.0)
diff --git a/config/cmake/hdf5-config-version.cmake.in b/config/cmake/hdf5-config-version.cmake.in
index 8e93dc6..20ce630 100644
--- a/config/cmake/hdf5-config-version.cmake.in
+++ b/config/cmake/hdf5-config-version.cmake.in
@@ -33,7 +33,7 @@ else()
   endif()
 
   if((PACKAGE_FIND_VERSION_MAJOR STREQUAL CVF_VERSION_MAJOR) AND
-     (PACKAGE_FIND_VERSION_MINOR STREQUAL CVF_VERSION_MINOR))
+     (PACKAGE_FIND_VERSION_MINOR STRLESS_EQUAL CVF_VERSION_MINOR))
     set(PACKAGE_VERSION_COMPATIBLE TRUE)
   else()
     set(PACKAGE_VERSION_COMPATIBLE FALSE)
diff --git a/config/cmake/libh5cc.in b/config/cmake/libh5cc.in
index c98d9ca..ecdd13e 100644
--- a/config/cmake/libh5cc.in
+++ b/config/cmake/libh5cc.in
@@ -29,4 +29,4 @@ printf 'dir is %s\n' "$dir"
 
 export PKG_CONFIG_PATH=$dir/lib/pkgconfig
 
-@_PKG_CONFIG_COMPILER@ `pkg-config --define-variable=prefix=$dir --cflags --libs @_PKG_CONFIG_LIBNAME@` $@
+@_PKG_CONFIG_COMPILER@ $@ `pkg-config --define-variable=prefix=$dir --cflags --libs @_PKG_CONFIG_LIBNAME@`
diff --git a/config/cmake/scripts/HDF5config.cmake b/config/cmake/scripts/HDF5config.cmake
index b89b915..5a44cde 100755
--- a/config/cmake/scripts/HDF5config.cmake
+++ b/config/cmake/scripts/HDF5config.cmake
@@ -11,7 +11,7 @@
 #
 #############################################################################################
 ### ${CTEST_SCRIPT_ARG} is of the form OPTION=VALUE                                       ###
-### BUILD_GENERATOR required [Unix, VS2017, VS201764, VS2015, VS201564, VS2013, VS201364] ###
+### BUILD_GENERATOR required [Unix, VS2019, VS201964, VS2017, VS201764, VS2015, VS201564] ###
 ### ctest -S HDF518config.cmake,BUILD_GENERATOR=VS201764 -C Release -VV -O hdf518.log     ###
 #############################################################################################
 
@@ -68,7 +68,7 @@ endif ()
 
 # build generator must be defined
 if (NOT DEFINED BUILD_GENERATOR)
-  message (FATAL_ERROR "BUILD_GENERATOR must be defined - Unix, VS2017, or VS201764, VS2015, VS201564, VS2013, VS201364")
+  message (FATAL_ERROR "BUILD_GENERATOR must be defined - Unix, VS2019, VS201964, VS2017, or VS201764, VS2015, VS201564")
 endif ()
 
 ###################################################################
@@ -105,7 +105,7 @@ endif ()
 #########       Following describes compiler           ############
 if (NOT DEFINED HPC)
   if (NOT DEFINED BUILD_GENERATOR)
-    message (FATAL_ERROR "BUILD_GENERATOR must be defined - Unix, VS2017, or VS201764, VS2015, VS201564, VS2013, VS201364")
+    message (FATAL_ERROR "BUILD_GENERATOR must be defined - Unix, VS2019, VS201964, VS2017, or VS201764, VS2015, VS201564")
   endif ()
   if (WIN32 AND NOT MINGW)
     set (SITE_OS_NAME "Windows")
diff --git a/config/cmake_ext_mod/ConfigureChecks.cmake b/config/cmake_ext_mod/ConfigureChecks.cmake
index 61a47be..e89d91e 100644
--- a/config/cmake_ext_mod/ConfigureChecks.cmake
+++ b/config/cmake_ext_mod/ConfigureChecks.cmake
@@ -396,15 +396,13 @@ HDF_CHECK_TYPE_SIZE (uint_least64_t ${HDF_PREFIX}_SIZEOF_UINT_LEAST64_T)
 HDF_CHECK_TYPE_SIZE (int_fast64_t   ${HDF_PREFIX}_SIZEOF_INT_FAST64_T)
 HDF_CHECK_TYPE_SIZE (uint_fast64_t  ${HDF_PREFIX}_SIZEOF_UINT_FAST64_T)
 
-if (NOT APPLE)
-  HDF_CHECK_TYPE_SIZE (size_t       ${HDF_PREFIX}_SIZEOF_SIZE_T)
-  HDF_CHECK_TYPE_SIZE (ssize_t      ${HDF_PREFIX}_SIZEOF_SSIZE_T)
-  if (NOT ${HDF_PREFIX}_SIZEOF_SSIZE_T)
-    set (${HDF_PREFIX}_SIZEOF_SSIZE_T 0)
-  endif ()
-  if (MINGW OR NOT WINDOWS)
-    HDF_CHECK_TYPE_SIZE (ptrdiff_t    ${HDF_PREFIX}_SIZEOF_PTRDIFF_T)
-  endif ()
+HDF_CHECK_TYPE_SIZE (size_t       ${HDF_PREFIX}_SIZEOF_SIZE_T)
+HDF_CHECK_TYPE_SIZE (ssize_t      ${HDF_PREFIX}_SIZEOF_SSIZE_T)
+if (NOT ${HDF_PREFIX}_SIZEOF_SSIZE_T)
+  set (${HDF_PREFIX}_SIZEOF_SSIZE_T 0)
+endif ()
+if (MINGW OR NOT WINDOWS)
+  HDF_CHECK_TYPE_SIZE (ptrdiff_t    ${HDF_PREFIX}_SIZEOF_PTRDIFF_T)
 endif ()
 
 HDF_CHECK_TYPE_SIZE (off_t          ${HDF_PREFIX}_SIZEOF_OFF_T)
diff --git a/config/cmake_ext_mod/HDFUseCXX.cmake b/config/cmake_ext_mod/HDFUseCXX.cmake
index 28e7f8a..63101bb 100644
--- a/config/cmake_ext_mod/HDFUseCXX.cmake
+++ b/config/cmake_ext_mod/HDFUseCXX.cmake
@@ -43,6 +43,9 @@ if (${HDF_PREFIX}_HAVE_STDINT_H AND CMAKE_CXX_COMPILER_LOADED)
   endif ()
 endif ()
 
+#Always define
+set (${HDF_PREFIX}_CXX_HAVE_OFFSETOF 1)
+
 # For other CXX specific tests, use this MACRO.
 macro (HDF_CXX_FUNCTION_TEST OTHER_TEST)
   if (NOT DEFINED ${OTHER_TEST})
@@ -108,7 +111,6 @@ if (CMAKE_CXX_COMPILER_LOADED)
       HDF_NO_STD
       BOOL_NOTDEFINED
       NO_STATIC_CAST
-      CXX_HAVE_OFFSETOF
   )
     HDF_CXX_FUNCTION_TEST (${cxx_test})
   endforeach ()
diff --git a/config/commence.am b/config/commence.am
index 385da06..7f20ae9 100644
--- a/config/commence.am
+++ b/config/commence.am
@@ -44,7 +44,7 @@ LIBH5CPP_HL=$(top_builddir)/hl/c++/src/libhdf5_hl_cpp.la
 docdir = $(exec_prefix)/doc
 
 # Note that in svn revision 19400 the '/' after DESTDIR in H5* variables below
-# has been removed. According to the official description of DESTDIR by Gnu at
+# has been removed. According to the official description of DESTDIR by GNU at
 # http://www.gnu.org/prep/standards/html_node/DESTDIR.html, DESTDIR is
 # prepended to the normal and complete install path that it precedes for the
 # purpose of installing in a temporary directory which is useful for building
diff --git a/config/gnu-cxxflags b/config/gnu-cxxflags
index cba8298..b2ba08d 100644
--- a/config/gnu-cxxflags
+++ b/config/gnu-cxxflags
@@ -183,7 +183,6 @@ if test "X-g++" = "X-$cxx_vendor"; then
     # Warnings #
     ############
 
-# First load the C warnings then add CXX warnings (if needed)
 
     ###########
     # General #
@@ -199,6 +198,7 @@ if test "X-g++" = "X-$cxx_vendor"; then
         # Developer warnings #
         ######################
 
+        # Use the C warnings as CXX warnings are the same
         NO_DEVELOPER_WARNING_CXXFLAGS=$(load_gnu_arguments no-developer-general)
         DEVELOPER_WARNING_CXXFLAGS=$(load_gnu_arguments developer-general)
 
@@ -210,6 +210,7 @@ if test "X-g++" = "X-$cxx_vendor"; then
 
     # GCC 4.8 through the end of GCC 4 series
     if test $cxx_vers_major -eq 4 -a $cxx_vers_minor -ge 8; then
+        # Use the C warnings as CXX warnings are the same
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments 4.8-4.last)"
     fi
 
@@ -220,13 +221,13 @@ if test "X-g++" = "X-$cxx_vendor"; then
     # gcc >= 4.8
     if test $cxx_vers_major -ge 5 -o $cxx_vers_major -eq 4 -a $cxx_vers_minor -ge 8; then
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments cxx-4.8)"
+        # Use the C warnings as CXX warnings are the same
         DEVELOPER_WARNING_CXXFLAGS="$DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments developer-4.8)"
         NO_DEVELOPER_WARNING_CXXFLAGS="$NO_DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments no-developer-4.8)"
     fi
 
     # gcc >= 4.9
     if test $cxx_vers_major -ge 5 -o $cxx_vers_major -eq 4 -a $cxx_vers_minor -ge 9; then
-        H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments 4.9)"
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments cxx-4.9)"
     fi
 
@@ -239,27 +240,40 @@ if test "X-g++" = "X-$cxx_vendor"; then
 
     # gcc >= 6
     if test $cxx_vers_major -ge 6; then
+        # Use the C warnings as CXX warnings are the same
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments 6)"
     fi
 
     # gcc >= 7
     if test $cxx_vers_major -ge 7; then
+        # Use the C warnings as CXX warnings are the same
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments 7)"
         DEVELOPER_WARNING_CXXFLAGS="$DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments developer-7)"
     fi
 
     # gcc 8
     if test $cxx_vers_major -ge 8; then
+        # Use the C warnings as CXX warnings are the same
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments 8)"
         #H5_ECXXFLAGS="$H5_ECXXFLAGS $(load_gnu_arguments error-8)"
         #H5_NECXXFLAGS="$H5_NECXXFLAGS $(load_gnu_arguments noerror-8)"
+        # Use the C warnings as CXX warnings are the same
         DEVELOPER_WARNING_CXXFLAGS="$DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments developer-8)"
         NO_DEVELOPER_WARNING_CXXFLAGS="$NO_DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments no-developer-8)"
     fi
 
     # gcc 9
     if test $cxx_vers_major -ge 9; then
-        H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments 9)"
+        H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments cxx-9)"
+    fi
+
+    # gcc >= 9.3
+        # no cxx warnings, do NOT use C warnings
+
+    # gcc >= 10
+    if test $cxx_vers_major -ge 10; then
+        # Use the C warnings as CXX warnings are the same
+        DEVELOPER_WARNING_CFLAGS="$DEVELOPER_WARNING_CFLAGS $(load_gnu_arguments developer-10)"
     fi
 
     #################
diff --git a/config/gnu-fflags b/config/gnu-fflags
index ec4fcab..ce12561 100644
--- a/config/gnu-fflags
+++ b/config/gnu-fflags
@@ -161,10 +161,10 @@ if test "X-gfortran" = "X-$f9x_vendor"; then
 
     # gfortran 4.9 (nothing new)
 
-    # gfortran >= 5
-    if test $f9x_vers_major -ge 5; then
-        H5_FCFLAGS="$H5_FCFLAGS $(load_gnu_arguments gfort-5)"
-    fi
+    # gfortran >= 5 (do not include -Wuse-without-only)
+    #if test $f9x_vers_major -ge 5; then
+    #    H5_FCFLAGS="$H5_FCFLAGS $(load_gnu_arguments gfort-5)"
+    #fi
 
     # gfortran >= 6
     if test $f9x_vers_major -ge 6; then
diff --git a/config/gnu-flags b/config/gnu-flags
index 01533de..3e4ceb2 100644
--- a/config/gnu-flags
+++ b/config/gnu-flags
@@ -207,9 +207,9 @@ if test "X-gcc" = "X-$cc_vendor"; then
         H5_ECFLAGS="$H5_ECFLAGS $(load_gnu_arguments error-general)"
         H5_NECFLAGS="$H5_NECFLAGS $(load_gnu_arguments noerror-general)"
 
-    ######################
-    # Developer warnings #
-    ######################
+        ######################
+        # Developer warnings #
+        ######################
 
         NO_DEVELOPER_WARNING_CFLAGS=$(load_gnu_arguments no-developer-general)
         DEVELOPER_WARNING_CFLAGS=$(load_gnu_arguments developer-general)
diff --git a/config/gnu-warnings/cxx-4.9 b/config/gnu-warnings/cxx-4.9
index 046d6db..30553bd 100644
--- a/config/gnu-warnings/cxx-4.9
+++ b/config/gnu-warnings/cxx-4.9
@@ -1 +1,2 @@
+-Wdate-time
 -Wopenmp-simd
diff --git a/config/gnu-warnings/cxx-9 b/config/gnu-warnings/cxx-9
new file mode 100644
index 0000000..8f843a4
--- /dev/null
+++ b/config/gnu-warnings/cxx-9
@@ -0,0 +1,4 @@
+-Wattribute-alias=2
+-Wmissing-profile
+# Turn this on when the C++ wrappers obey the Rule of Five
+-Wno-deprecated-copy
diff --git a/config/gnu-warnings/developer-10 b/config/gnu-warnings/developer-10
index fcd460d..022c97f 100644
--- a/config/gnu-warnings/developer-10
+++ b/config/gnu-warnings/developer-10
@@ -1,6 +1,2 @@
 # New warning
 -Warith-conversion
-
-# Enable static analysis of program flow
--fanalyzer
--fdiagnostics-path-format=none
diff --git a/config/gnu-warnings/noerror-general b/config/gnu-warnings/noerror-general
index f5b4afb..80c1975 100644
--- a/config/gnu-warnings/noerror-general
+++ b/config/gnu-warnings/noerror-general
@@ -1,6 +1,8 @@
 #
-# HDF5 code should not trigger the following warnings under any
-# circumstances, so ask the compiler to treat them as errors:
+# These warnings will be treated as errors, using the error-general file,
+# when HDF5_ENABLE_WARNINGS_AS_ERRORS is set to true for CMake or
+# the --enable-warnings-as-errors option is specified for configure.
+#   Otherwise this file will be used to treat them as warnings.
 #
 -Wbad-function-cast
 -Wimplicit-function-declaration
diff --git a/config/intel-cxxflags b/config/intel-cxxflags
new file mode 100644
index 0000000..484100f
--- /dev/null
+++ b/config/intel-cxxflags
@@ -0,0 +1,184 @@
+#                            -*- shell-script -*-
+#
+# Copyright by The HDF Group.
+# 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://www.hdfgroup.org/licenses.
+# 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
+# Intel icpc compiler or a derivative.  It is careful not to do anything
+# if the compiler is not Intel; otherwise `cxx_flags_set' is set to `yes'
+#
+
+#
+# Prepend `$srcdir/config/intel-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_intel_arguments()
+{
+    set -- $(for arg; do
+        sed 's,#.*$,,' $srcdir/config/intel-warnings/${arg}
+    done)
+    IFS=' ' echo "$*"
+}
+
+# Get the compiler version in a way that works for icpc
+# icpc unless a compiler version is already known
+#
+#   cxx_vendor:    The compiler name: icpc
+#   cxx_version:   Version number: 8.0
+#
+if test X = "X$cxx_flags_set"; then
+    cxx_version="`$CXX $CXXFLAGS $H5_CXXFLAGS -V 2>&1 |grep 'Version'`"
+    if test X != "X$cxx_version"; then
+        cxx_vendor=icpc
+        cxx_version=`echo $cxx_version |sed 's/.*Version \([-a-z0-9\.\-]*\).*/\1/'`
+        echo "compiler '$CXX' is Intel $cxx_vendor-$cxx_version"
+
+        # Some version numbers
+        # Intel version numbers are of the form: "major.minor"
+        cxx_vers_major=`echo $cxx_version | cut -f1 -d.`
+        cxx_vers_minor=`echo $cxx_version | cut -f2 -d.`
+        #cxx_vers_patch=`echo $cxx_version | cut -f2 -d.`
+        test -n "$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
+        cxx_vers_all=`expr $cxx_vers_major '*' 1000000 + $cxx_vers_minor '*' 1000 + $cxx_vers_patch`
+    fi
+fi
+
+# Common Intel flags for various situations
+if test "X-icpc" = "X-$cxx_vendor"; then
+    # Insert section about version specific problems from compiler flags here,
+    # if necessary.
+
+    arch=
+    # Architecture-specific flags
+    # Nothing currently. (Uncomment code below and modify to add any)
+    #case "$host_os-$host_cpu" in
+    #    *-i686)
+    #        arch="-march=i686"
+    #        ;;
+    #esac
+
+    # Host-specific flags
+    # Nothing currently. (Uncomment code below and modify to add any)
+    #case "`hostname`" in
+    #    sleipnir.ncsa.uiuc.edu)
+    #        arch="$arch -pipe"
+    #        ;;
+    #esac
+
+    ###########
+    # General #
+    ###########
+
+    H5_CXXFLAGS="$H5_CXXFLAGS $arch"
+
+    ##############
+    # Production #
+    ##############
+
+    PROD_CXXFLAGS=
+
+    #########
+    # Debug #
+    #########
+
+    # NDEBUG is handled explicitly in configure
+    # -g is handled by the symbols flags
+    DEBUG_CXXFLAGS=
+
+    ###########
+    # Symbols #
+    ###########
+
+    NO_SYMBOLS_CXXFLAGS="-Wl,-s"
+    SYMBOLS_CXXFLAGS="-g"
+
+    #############
+    # Profiling #
+    #############
+
+    PROFILE_CXXFLAGS="-p"
+
+    ################
+    # Optimization #
+    ################
+
+    HIGH_OPT_CXXFLAGS="-O3"
+    DEBUG_OPT_CXXFLAGS="-O0"
+    NO_OPT_CXXFLAGS="-O0"
+
+    ############
+    # Warnings #
+    ############
+
+    ###########
+    # General #
+    ###########
+
+    # Add various general warning flags in intel-warnings.
+    # Use the C warnings as CXX warnings are the same
+    H5_CXXFLAGS="$H5_CXXFLAGS $(load_intel_arguments general)"
+
+    ######################
+    # Developer warnings #
+    ######################
+
+    # Use the C warnings as CXX warnings are the same
+    #NO_DEVELOPER_WARNING_CXXFLAGS=$(load_intel_arguments no-developer-general)
+    #DEVELOPER_WARNING_CXXFLAGS=$(load_intel_arguments developer-general)
+
+    #############################
+    # Version-specific warnings #
+    #############################
+
+    # intel == 8.0
+    if test $cxx_vers_major -eq 8 -a $cxx_vers_minor -eq 0; then
+        # v8.0 -O3 infinite loops when compiling test/tselect.c. Use -O2.
+        HIGH_OPT_CFLAGS="-O2"
+    fi
+
+    # intel == 10
+    if test $cxx_vers_major -eq 10; then
+        HIGH_OPT_CFLAGS="-O1"
+    fi
+
+    # intel >= 15
+    if test $cxx_vers_major -ge 15; then
+        # Use the C warnings as CXX warnings are the same
+        H5_CXXFLAGS="$H5_CXXFLAGS $(load_intel_arguments 15)"
+    fi
+
+    # intel >= 18
+    if test $cxx_vers_major -ge 18; then
+        # Use the C warnings as CXX warnings are the same
+        H5_CXXFLAGS="$H5_CXXFLAGS $(load_intel_arguments 18)"
+    fi
+
+    # intel <= 19
+    if test $cxx_vers_major -le 19; then
+        # Use the C warnings as CXX warnings are the same
+        H5_CXXFLAGS="$H5_CXXFLAGS $(load_intel_arguments general-19)"
+    fi
+
+    #################
+    # Flags are set #
+    #################
+    cxx_flags_set=yes
+fi
+
+# Clear cxx info if no flags set
+if test "X-$cxx_flags_set" = "X-"; then
+    cxx_vendor=
+    cxx_version=
+fi
diff --git a/config/intel-fflags b/config/intel-fflags
index b759dfa..42c1781 100644
--- a/config/intel-fflags
+++ b/config/intel-fflags
@@ -56,13 +56,17 @@ if test X = "X$f9x_flags_set"; then
     fi
 fi
 
-# Common Intel flags for various situations
 if test "X-ifort" = "X-$f9x_vendor"; then
-    # Insert section about version specific problems from compiler flags here,
-    # if necessary.
+
+    FC_BASENAME=ifort
+    F9XSUFFIXFLAG=""
+    FSEARCH_DIRS=""
+
+    ###############################
+    # Architecture-specific flags #
+    ###############################
 
     arch=
-    # Architecture-specific flags
     # Nothing currently. (Uncomment code below and modify to add any)
     #case "$host_os-$host_cpu" in
     #    *-i686)
@@ -78,32 +82,55 @@ if test "X-ifort" = "X-$f9x_vendor"; then
     #        ;;
     #esac
 
-    # General
-    FC_BASENAME=ifort
-    F9XSUFFIXFLAG=""
-    FSEARCH_DIRS=""
-    H5_FCFLAGS="$H5_FCFLAGS -stand:f03 -free"
-    H5_FCFLAGS="$H5_FCFLAGS $(load_intel_arguments ifort-general)"
+    ##############
+    # Production #
+    ##############
 
-    # Production
     PROD_FCFLAGS=
 
-    # Debug
+    #########
+    # Debug #
+    #########
+
     DEBUG_FCFLAGS="-check all"
 
-    # Symbols
-    SYMBOLS_FCFLAGS="-g"
+    ###########
+    # Symbols #
+    ###########
+
     NO_SYMBOLS_FCFLAGS=
+    SYMBOLS_FCFLAGS="-g"
+
+    #############
+    # Profiling #
+    #############
 
-    # Profiling
-    # Use this for profiling with gprof
     PROFILE_FCFLAGS="-p"
 
-    # Optimization
+    ################
+    # Optimization #
+    ################
+
     HIGH_OPT_FCFLAGS="-O3"
     DEBUG_OPT_FCFLAGS=
     NO_OPT_FCFLAGS=
 
+    ############
+    # Warnings #
+    ############
+
+    ###########
+    # General #
+    ###########
+
+    H5_FCFLAGS="$H5_FCFLAGS -stand:f03 -free"
+    H5_FCFLAGS="$H5_FCFLAGS $(load_intel_arguments ifort-general)"
+
+    #############################
+    # Version-specific warnings #
+    #############################
+
+
     #################
     # Flags are set #
     #################
@@ -116,4 +143,3 @@ if test "X-$f9x_flags_set" = "X-"; then
   f9x_version=
 fi
 
-
diff --git a/config/intel-flags b/config/intel-flags
index 409ffe9..f46da0a 100644
--- a/config/intel-flags
+++ b/config/intel-flags
@@ -78,26 +78,43 @@ if test "X-icc" = "X-$cc_vendor"; then
     #        ;;
     #esac
 
-    # General
+    ###########
+    # General #
+    ###########
+
     # Default to C99 standard.
     H5_CFLAGS="$H5_CFLAGS $arch -std=c99"
 
-    # Production
+    ##############
+    # Production #
+    ##############
+
     PROD_CFLAGS=
 
-    # Debug
+    #########
+    # Debug #
+    #########
+
     # NDEBUG is handled explicitly in configure
     DEBUG_CFLAGS=
 
-    # Symbols
-    SYMBOLS_CFLAGS="-g"
+    ###########
+    # Symbols #
+    ###########
+
     NO_SYMBOLS_CFLAGS="-Wl,-s"
+    SYMBOLS_CFLAGS="-g"
+
+    #############
+    # Profiling #
+    #############
 
-    # Profiling
-    # Use this for profiling with gprof
     PROFILE_CFLAGS="-p"
 
-    # Optimization
+    ################
+    # Optimization #
+    ################
+
     HIGH_OPT_CFLAGS="-O3"
     DEBUG_OPT_CFLAGS="-O0"
     NO_OPT_CFLAGS="-O0"
@@ -110,32 +127,51 @@ if test "X-icc" = "X-$cc_vendor"; then
     # General #
     ###########
 
+    # Add various general warning flags in intel-warnings.
     H5_CFLAGS="$H5_CFLAGS $(load_intel_arguments general)"
 
+    ######################
+    # Developer warnings #
+    ######################
+
+    #NO_DEVELOPER_WARNING_CFLAGS=$(load_intel_arguments no-developer-general)
+    #DEVELOPER_WARNING_CFLAGS=$(load_intel_arguments developer-general)
+
     #############################
     # Version-specific warnings #
     #############################
 
-case "$cc_vendor-$cc_version" in
-    icc-1[5-6]*)
-        H5_CFLAGS="$H5_CFLAGS -Wcomment -Wdeprecated -Wextra-tokens -Wformat -Wformat-security -Wmain -Wmissing-declarations -Wmissing-prototypes -Wp64 -Wpointer-arith -Wreturn-type -Wshadow -Wstrict-prototypes -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function -Wunused-variable -Wwrite-strings"
-        ;;
-    icc-10*)
-        HIGH_OPT_CFLAGS="-O1"
-        ;;
-    icc-8.0*)
+    # intel == 8.0
+    if test $cc_vers_major -eq 8 -a $cc_vers_minor -eq 0; then
         # v8.0 -O3 infinite loops when compiling test/tselect.c. Use -O2.
         HIGH_OPT_CFLAGS="-O2"
-        ;;
-    icc-*)
-        ;;
-esac
+    fi
+
+    # intel == 10
+    if test $cc_vers_major -eq 10; then
+        HIGH_OPT_CFLAGS="-O1"
+    fi
+
+    # intel >= 15
+    if test $cc_vers_major -ge 15; then
+        H5_CFLAGS="$H5_CFLAGS $(load_intel_arguments 15)"
+    fi
+
+    # intel >= 18
+    if test $cc_vers_major -ge 18; then
+        H5_CFLAGS="$H5_CFLAGS $(load_intel_arguments 18)"
+    fi
+
+    # intel <= 19
+    # this file has warnings only available before oneapi versions
+    if test $cc_vers_major -le 19; then
+        H5_CFLAGS="$H5_CFLAGS $(load_intel_arguments general-19)"
+    fi
 
     #################
     # Flags are set #
     #################
     cc_flags_set=yes
-
 fi
 
 # Clear cc info if no flags set
diff --git a/config/intel-warnings/15 b/config/intel-warnings/15
new file mode 100644
index 0000000..6746f97
--- /dev/null
+++ b/config/intel-warnings/15
@@ -0,0 +1,19 @@
+-Wcomment
+-Wdeprecated
+-Wextra-tokens
+-Wformat
+-Wformat-security
+-Wmain
+-Wmissing-declarations
+-Wmissing-prototypes
+-Wp64
+-Wpointer-arith
+-Wreturn-type
+-Wshadow
+-Wstrict-prototypes
+-Wtrigraphs
+-Wuninitialized
+-Wunknown-pragmas
+-Wunused-function
+-Wunused-variable
+-Wwrite-strings
diff --git a/config/intel-warnings/18 b/config/intel-warnings/18
new file mode 100644
index 0000000..02bcdea
--- /dev/null
+++ b/config/intel-warnings/18
@@ -0,0 +1,2 @@
+-Wic-pointer
+-Wsign-compare
diff --git a/config/intel-warnings/developer-general b/config/intel-warnings/developer-general
new file mode 100644
index 0000000..fae56f0
--- /dev/null
+++ b/config/intel-warnings/developer-general
@@ -0,0 +1,4 @@
+-Winline
+-Wreorder
+-Wport
+-Wstrict-aliasing
diff --git a/config/intel-warnings/general b/config/intel-warnings/general
index d0b2e25..bd866b6 100644
--- a/config/intel-warnings/general
+++ b/config/intel-warnings/general
@@ -1,2 +1 @@
 -Wall
--Wcheck
\ No newline at end of file
diff --git a/config/intel-warnings/win-developer-general b/config/intel-warnings/win-developer-general
new file mode 100644
index 0000000..6cd7ed7
--- /dev/null
+++ b/config/intel-warnings/win-developer-general
@@ -0,0 +1 @@
+/Wport
diff --git a/config/intel-warnings/win-general b/config/intel-warnings/win-general
new file mode 100644
index 0000000..ef54b2b
--- /dev/null
+++ b/config/intel-warnings/win-general
@@ -0,0 +1 @@
+/Wall
diff --git a/config/linux-gnulibc1 b/config/linux-gnulibc1
index 0fef161..d952c4e 100644
--- a/config/linux-gnulibc1
+++ b/config/linux-gnulibc1
@@ -199,9 +199,16 @@ if test -z "$CXX"; then
   CXX_BASENAME=g++
 fi
 
+# Figure out Intel CXX compiler flags
+# Do this ahead of GNU to avoid icpc being detected as g++
+. $srcdir/config/intel-cxxflags
+
 # Figure out GNU CXX compiler flags
 . $srcdir/config/gnu-cxxflags
 
+# Figure out PGI CXX compiler flags
+. $srcdir/config/pgi-cxxflags
+
 # Figure out Clang CXX compiler flags
 . $srcdir/config/clang-cxxflags
 
@@ -314,6 +321,9 @@ fi
 # check if the compiler_version_info is already set
 if test -z "$cxx_version_info"; then
 case $CXX in
+    *pgc++*)
+        cxx_version_info=`$CXX $CXXFLAGS $H5_CXXFLAGS -V 2>&1 | grep 'pgc++'`
+        ;;
     *g++*)
         cxx_version_info=`$CXX $CXXFLAGS $H5_CXXFLAGS --version 2>&1 |\
             grep 'GCC' | sed 's/\(.*(GCC) [-a-z0-9\. ]*\).*/\1/'`
@@ -322,10 +332,6 @@ case $CXX in
         cxx_version_info=`$CXX $CXXFLAGS $H5_CXXFLAGS -V 2>&1 | grep 'Version' |\
             sed 's/\(Intel.* Compiler\).*\( Version [a-z0-9\.]*\).*\( Build [0-9]*\)/\1\2\3/'`
         ;;
-    *pgCC*)
-        cxx_version_info=`$CXX $CXXFLAGS $H5_CXXFLAGS -V 2>&1 | grep 'pgCC'`
-        ;;
-
     *mpicxx*)
         cxx_version_info=`$CXX $CXXFLAGS $H5_CXXFLAGS -v 2>&1 | grep 'version' |\
             sed 's/^[a-z0-9]* for //' |\
diff --git a/config/pgi-cxxflags b/config/pgi-cxxflags
new file mode 100644
index 0000000..5fc74ae
--- /dev/null
+++ b/config/pgi-cxxflags
@@ -0,0 +1,100 @@
+#                            -*- shell-script -*-
+#
+# Copyright by The HDF Group.
+# All rights reserved.
+#
+# This file is part of HDF5.  The full HDF5 copyright notice, including
+# terms governing use, modification, and redistribution, is contained in
+# the COPYING file, which can be found at the root of the source code
+# distribution tree, or in https://www.hdfgroup.org/licenses.
+# If you do not have access to either file, you may request a copy from
+# help@hdfgroup.org.
+
+
+# This file should be sourced into configure if the compiler is the
+# PGI pgc++ compiler or a derivative.  It is careful not to do anything
+# if the compiler is not PGI; otherwise `cxx_flags_set' is set to `yes'
+#
+
+# Get the compiler version in a way that works for pgc++
+# pgc++ unless a compiler version is already known
+#
+#   cxx_vendor:    The compiler name: pgc++
+#   cxx_version:   Version number: 5.0-2, 5.2-2
+#
+if test X = "X$cxx_flags_set"; then
+    cxx_version="`$CXX $CXXFLAGS -V 2>&1 |grep '^pgc++ '`"
+    if test X != "X$cxx_version"; then
+        cxx_vendor=`echo $cxx_version |sed 's/\([a-z]*++\).*/\1/'`
+        cxx_version=`echo $cxx_version |sed 's/pgc++ \([-a-z0-9\.\-]*\).*/\1/'`
+        echo "compiler '$CXX' is PGI $cxx_vendor-$cxx_version"
+
+        # Some version numbers
+        # PGI version numbers are of the form: "major.minor-patch"
+        cxx_vers_major=`echo $cxx_version | cut -f1 -d.`
+        cxx_vers_minor=`echo $cxx_version | cut -f2 -d. | cut -f1 -d-`
+        cxx_vers_patch=`echo $cxx_version | cut -f2 -d. | cut -f2 -d-`
+        test -n "$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
+        cxx_vers_all=`expr $cxx_vers_major '*' 1000000 + $cxx_vers_minor '*' 1000 + $cxx_vers_patch`
+    fi
+fi
+
+# Common PGI flags for various situations
+if test "X-pgc++" = "X-$cxx_vendor"; then
+
+    ###########
+    # General #
+    ###########
+
+    H5_CXXFLAGS="$H5_CXXFLAGS -Minform=warn"
+
+    ##############
+    # Production #
+    ##############
+
+    PROD_CXXFLAGS=
+
+    #########
+    # Debug #
+    #########
+
+    # NDEBUG is handled explicitly in configure
+    # -g is handled by the symbols flags
+    DEBUG_CXXFLAGS="-Mbounds"
+
+    ###########
+    # Symbols #
+    ###########
+
+    NO_SYMBOLS_CXXFLAGS="-s"
+    SYMBOLS_CXXFLAGS="-g"
+
+    #############
+    # Profiling #
+    #############
+
+    PROFILE_CXXFLAGS="-Mprof=func,line"
+    # Use this for profiling with gprof
+    #PROFILE_CXXFLAGS="-pg"
+
+    ################
+    # Optimization #
+    ################
+
+    HIGH_OPT_CXXFLAGS="-O4"
+    DEBUG_OPT_CXXFLAGS="-gopt -O2"
+    NO_OPT_CXXFLAGS="-O0"
+
+    #################
+    # Flags are set #
+    #################
+    cxx_flags_set=yes
+fi
+
+# Clear cxx info if no flags set
+if test "X-$cxx_flags_set" = "X-"; then
+    cxx_vendor=
+    cxx_version=
+fi
diff --git a/config/pgi-fflags b/config/pgi-fflags
index 3171695..6401d8d 100644
--- a/config/pgi-fflags
+++ b/config/pgi-fflags
@@ -1,4 +1,4 @@
-#							-*- shell-script -*-
+#                            -*- shell-script -*-
 #
 # Copyright by The HDF Group.
 # Copyright by the Board of Trustees of the University of Illinois.
@@ -45,11 +45,12 @@ fi
 
 # Common PGI flags for various situations
 if test "X-pgf90" = "X-$f9x_vendor"; then
-    # Insert section about version specific problems from gnu-flags here, if
-    # necessary.
+
+    ###############################
+    # Architecture-specific flags #
+    ###############################
 
     arch=
-    # Architecture-specific flags
     # Nothing currently. (Uncomment code below and modify to add any)
     #case "$host_os-$host_cpu" in
     #    *-i686)
@@ -65,15 +66,10 @@ if test "X-pgf90" = "X-$f9x_vendor"; then
     #        ;;
     #esac
 
-    # General
-    FC_BASENAME=pgf90
-    Fortran_COMPILER_ID=PGI
-    F9XSUFFIXFLAG=""
-    FSEARCH_DIRS=""
-    # Uncomment the following to add something specific for FCFLAGS.
-    #FCFLAGS="$FCFLAGS"
+    ##############
+    # Production #
+    ##############
 
-    # Production
     # Check for MPI wrapper being used and tweak down compiler options
     # Comment out the Tweaking since it caused problems to mpich1.2.6.
     # Need to investigate the reasons to tweak.
@@ -84,24 +80,55 @@ if test "X-pgf90" = "X-$f9x_vendor"; then
     #fi
     PROD_FCFLAGS="-fast -Mnoframe"
 
-    # Debug
+    #########
+    # Debug #
+    #########
+
     DEBUG_FCFLAGS="-Mbounds -Mchkptr -Mdclchk"
 
-    # Symbols
-    SYMBOLS_FCFLAGS="-g"
+    ###########
+    # Symbols #
+    ###########
+
     NO_SYMBOLS_FCFLAGS="-s"
+    SYMBOLS_FCFLAGS="-g"
+
+    #############
+    # Profiling #
+    #############
 
-    # Profiling
     PROFILE_FCFLAGS="-Mprof=func,line"
     # Use this for profiling with gprof
     #PROFILE_FCFLAGS="-pg"
 
-    # Optimization
+    ################
+    # Optimization #
+    ################
+
     HIGH_OPT_FCFLAGS=
     DEBUG_OPT_FCFLAGS=
     NO_OPT_FCFLAGS=
 
-    # Flags are set
+    ############
+    # Warnings #
+    ############
+
+    ###########
+    # General #
+    ###########
+
+    FC_BASENAME=pgf90
+    Fortran_COMPILER_ID=PGI
+    F9XSUFFIXFLAG=""
+    FSEARCH_DIRS=""
+    # Uncomment the following to add something specific for FCFLAGS.
+    #FCFLAGS="$FCFLAGS"
+
+
+
+    #################
+    # Flags are set #
+    #################
     f9x_flags_set=yes
 fi
 
@@ -111,4 +138,3 @@ if test "X-$f9x_flags_set" = "X-"; then
   f9x_version=
 fi
 
-
diff --git a/config/pgi-flags b/config/pgi-flags
index e1bec00..b197a1c 100644
--- a/config/pgi-flags
+++ b/config/pgi-flags
@@ -1,4 +1,4 @@
-#							-*- shell-script -*-
+#                            -*- shell-script -*-
 #
 # Copyright by The HDF Group.
 # Copyright by the Board of Trustees of the University of Illinois.
@@ -45,8 +45,8 @@ fi
 
 # Common PGI flags for various situations
 if test "X-pgcc" = "X-$cc_vendor"; then
-    # Insert section about version specific problems from gnu-flags here, if
-    # necessary.
+    # Insert section about version specific problems from compiler flags here,
+    # if necessary.
 
     arch=
     # Architecture-specific flags
@@ -65,58 +65,59 @@ if test "X-pgcc" = "X-$cc_vendor"; then
     #        ;;
     #esac
 
-    # General
-    H5_CFLAGS="$H5_CFLAGS $arch -c99 -Minform=inform"
-
-    # Production
-    case "$cc_vendor-$cc_version" in
-      pgcc-10.6*)
-        PROD_CFLAGS=
-        ;;
-      pgcc-9.*)
-        PROD_CFLAGS=
-        ;;
-      *)
-        PROD_CFLAGS="-fast"
-        ;;
-    esac
-
-    # Debug
+    ###########
+    # General #
+    ###########
+
+    # Default to C99 standard.
+    H5_CFLAGS="$H5_CFLAGS $arch -c99 -Minform=warn"
+
+    ##############
+    # Production #
+    ##############
+
+    # NDEBUG is handled explicitly by the configure script
+    PROD_CFLAGS="-fast"
+
+    #########
+    # Debug #
+    #########
+
     # NDEBUG is handled explicitly by the configure script
+    # -g is handled by the symbols flags
     DEBUG_CFLAGS="-Mbounds"
 
-    # Symbols
-    SYMBOLS_CFLAGS="-g"
+    ###########
+    # Symbols #
+    ###########
+
     NO_SYMBOLS_CFLAGS="-s"
+    SYMBOLS_CFLAGS="-g"
+
+    #############
+    # Profiling #
+    #############
 
-    # Profiling
     PROFILE_CFLAGS="-Mprof=func,line"
     # Use this for profiling with gprof
     #PROFILE_CFLAGS="-pg"
 
-    # Optimization
-    case "$cc_vendor-$cc_version" in
-      # Tweak down compiler optimizations for v10.6, it has a bug
-      pgcc-10.6*)
-        HIGH_OPT_CFLAGS="-O1"
-        ;;
-      # Tweak down compiler optimizations for v9.x
-      pgcc-9.*)
-        HIGH_OPT_CFLAGS="-O1"
-        ;;
-      *)
-        HIGH_OPT_CFLAGS=
-        ;;
-    esac
-    DEBUG_OPT_CFLAGS=
-    NO_OPT_CFLAGS=
-
-    # Flags are set
+    ################
+    # Optimization #
+    ################
+
+    HIGH_OPT_CFLAGS="-O4"
+    DEBUG_OPT_CFLAGS="-gopt -O2"
+    NO_OPT_CFLAGS="-O0"
+
+    #################
+    # 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=
+    cc_vendor=
+    cc_version=
 fi
diff --git a/config/sanitizer/code-coverage.cmake b/config/sanitizer/code-coverage.cmake
index 8d765f7..c79aeac 100644
--- a/config/sanitizer/code-coverage.cmake
+++ b/config/sanitizer/code-coverage.cmake
@@ -99,8 +99,7 @@ if(CODE_COVERAGE AND NOT CODE_COVERAGE_ADDED)
             ${CMAKE_COVERAGE_OUTPUT_DIRECTORY}
     DEPENDS ccov-clean)
 
-  if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang"
-     OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+  if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
     # Messages
     message(STATUS "Building with llvm Code Coverage Tools")
 
@@ -206,8 +205,7 @@ function(target_code_coverage TARGET_NAME)
   if(CODE_COVERAGE)
 
     # Add code coverage instrumentation to the target's linker command
-    if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang"
-       OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+    if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
       target_compile_options(${TARGET_NAME} PRIVATE -fprofile-instr-generate
                                                     -fcoverage-mapping)
       set_property(
@@ -229,8 +227,7 @@ function(target_code_coverage TARGET_NAME)
 
     # Add shared library to processing for 'all' targets
     if(target_type STREQUAL "SHARED_LIBRARY" AND target_code_coverage_ALL)
-      if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang"
-         OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+      if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
         add_custom_target(
           ccov-run-${TARGET_NAME}
           COMMAND echo "-object=$<TARGET_FILE:${TARGET_NAME}>" >>
@@ -250,8 +247,7 @@ function(target_code_coverage TARGET_NAME)
 
     # For executables add targets to run and produce output
     if(target_type STREQUAL "EXECUTABLE")
-      if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang"
-         OR CMAKE_CXX_COMPILER_ID MATCHES "(Apple)?Cc]lang")
+      if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "(Apple)?Cc]lang")
 
         # If there are shared objects to also work with, generate the string to
         # add them here
@@ -409,8 +405,7 @@ endfunction()
 # any subdirectories. To add coverage instrumentation to only specific targets,
 # use `target_code_coverage`.
 function(add_code_coverage)
-  if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang"
-     OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+  if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
     add_compile_options(-fprofile-instr-generate -fcoverage-mapping)
     add_link_options(-fprofile-instr-generate -fcoverage-mapping)
   elseif(CMAKE_C_COMPILER_ID MATCHES "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "GNU")
@@ -435,8 +430,7 @@ function(add_code_coverage_all_targets)
                         "${multi_value_keywords}" ${ARGN})
 
   if(CODE_COVERAGE)
-    if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang"
-       OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
+    if(CMAKE_C_COMPILER_ID MATCHES "[Cc]lang" OR CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang")
 
       # Merge the profile data for all of the run executables
       add_custom_target(
diff --git a/config/sanitizer/sanitizers.cmake b/config/sanitizer/sanitizers.cmake
index 0803279..8bf1d5b 100644
--- a/config/sanitizer/sanitizers.cmake
+++ b/config/sanitizer/sanitizers.cmake
@@ -30,13 +30,13 @@ endfunction()
 
 message(STATUS "USE_SANITIZER=${USE_SANITIZER}, CMAKE_C_COMPILER_ID=${CMAKE_C_COMPILER_ID}")
 if(USE_SANITIZER)
-  if(INTEL_CLANG OR "${CMAKE_C_COMPILER_ID}" MATCHES "Clang")
+  if(INTEL_CLANG OR CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
     set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-    append("-fno-omit-frame-pointer" CMAKE_C_SANITIZER_FLAGS CMAKE_CXX_SANITIZER_FLAGS)
-    message(STATUS "Building with sanitize, base flags=${CMAKE_C_SANITIZER_FLAGS}")
-
     if(UNIX)
+      append("-fno-omit-frame-pointer" CMAKE_C_SANITIZER_FLAGS CMAKE_CXX_SANITIZER_FLAGS)
+      message(STATUS "Building with sanitize, base flags=${CMAKE_C_SANITIZER_FLAGS}")
+
       if(uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
         append("-O1" CMAKE_C_SANITIZER_FLAGS CMAKE_CXX_SANITIZER_FLAGS)
       endif()
@@ -83,7 +83,7 @@ if(USE_SANITIZER)
     elseif(MSVC)
       if(USE_SANITIZER MATCHES "([Aa]ddress)")
         message(STATUS "Building with Address sanitizer")
-        append("-fsanitize=address" CMAKE_C_SANITIZER_FLAGS CMAKE_CXX_SANITIZER_FLAGS)
+        append("/fsanitize=address" CMAKE_C_SANITIZER_FLAGS CMAKE_CXX_SANITIZER_FLAGS)
       else()
         message(FATAL_ERROR "This sanitizer not yet supported in the MSVC environment: ${USE_SANITIZER}")
       endif()
diff --git a/config/toolchain/clang.cmake b/config/toolchain/clang.cmake
index 5e3b13a..af176aa 100644
--- a/config/toolchain/clang.cmake
+++ b/config/toolchain/clang.cmake
@@ -3,8 +3,13 @@
 
 set(CMAKE_COMPILER_VENDOR "clang")
 
-set(CMAKE_C_COMPILER clang)
-set(CMAKE_CXX_COMPILER clang++)
+if(WIN32)
+  set(CMAKE_C_COMPILER clang-cl)
+  set(CMAKE_CXX_COMPILER clang-cl)
+else()
+  set(CMAKE_C_COMPILER clang)
+  set(CMAKE_CXX_COMPILER clang++)
+endif()
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 # the following is used if cross-compiling