Brings the 'warnings-as-errors' changes from develop

22 files changed, 456 insertions, 234 deletions

diff --git a/config/clang-cxxflags b/config/clang-cxxflags
index bd8ce2d..e7ab6d8 100644
--- a/config/clang-cxxflags
+++ b/config/clang-cxxflags
@@ -173,6 +173,7 @@ if test "X-clang" = "X-$cxx_vendor" -o "X-Apple LLVM" = "X-$cxx_vendor"; then
 
     H5_CXXFLAGS="$H5_CXXFLAGS $(load_clang_arguments general)"
     H5_ECXXFLAGS="$H5_ECXXFLAGS $(load_clang_arguments error-general)"
+    H5_NECXXFLAGS="$H5_NECXXFLAGS $(load_clang_arguments noerror-general)"
 
     ######################
     # Developer warnings #
diff --git a/config/clang-flags b/config/clang-flags
index 5a6d9c2..92a8973 100644
--- a/config/clang-flags
+++ b/config/clang-flags
@@ -163,9 +163,16 @@ if test "X-clang" = "X-$cc_vendor" -o "X-Apple LLVM" = "X-$cc_vendor"; then
     ################
 
     HIGH_OPT_CFLAGS="-O3"
-    DEBUG_OPT_CFLAGS="-g"
     NO_OPT_CFLAGS="-O0"
 
+    # -Og is only understood by clang 4+ and Xcode 9+
+    # Otherwise use -O1 (which is what -Og usually equates to)
+    if test "X-clang" = "X-$cc_vendor" -a $cc_vers_major -ge 4 -o "X-Apple LLVM" = "X-$cc_vendor" -a $cc_vers_major -ge 9; then
+        DEBUG_OPT_CFLAGS="-Og"
+    else
+        DEBUG_OPT_CFLAGS="-O1"
+    fi
+
     ############
     # Warnings #
     ############
@@ -176,6 +183,7 @@ if test "X-clang" = "X-$cc_vendor" -o "X-Apple LLVM" = "X-$cc_vendor"; then
 
     H5_CFLAGS="$H5_CFLAGS $(load_clang_arguments general)"
     H5_ECFLAGS="$H5_ECFLAGS $(load_clang_arguments error-general)"
+    H5_NECFLAGS="$H5_NECFLAGS $(load_clang_arguments noerror-general)"
 
     ######################
     # Developer warnings #
diff --git a/config/clang-warnings/noerror-general b/config/clang-warnings/noerror-general
new file mode 100644
index 0000000..ad50dfc
--- /dev/null
+++ b/config/clang-warnings/noerror-general
@@ -0,0 +1,80 @@
+#
+# HDF5 code should not trigger the following warnings under any
+# circumstances, so ask the compiler to treat them as errors:
+#
+-Wbad-function-cast
+-Wimplicit-function-declaration
+-Wincompatible-pointer-types
+-Wmissing-declarations
+-Wpacked
+-Wshadow
+-Wswitch
+#
+# 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
+#     H5FDdirect.c,H5FDmpio.c,H5FDros3.c,
+#       -Werror=unused-function
+#
+-Wunused-function
+#
+#     H5FDdrvr_module.h
+#       -Werror=unused-variable
+#
+-Wunused-variable
+#
+#     H5VLpassthru.c
+#       -Werror=unused-parameter
+#
+-Wunused-parameter
+#
+#
+#
+# NOTE: Tools files are not compatible with these warnings as errors
+#     lib/h5tools.c
+#       -Werror=cast-align
+#
+-Wcast-align
+#
+#     lib/h5tools_utils.c
+#       -Werror=unused-parameter
+#
+#
+# NOTE: JNI files are not compatible with these warnings as errors
+#     jni/h5pDCPLImp.c,jni/nativeData.c,jni/h5util.c,jni/h5rImp.c
+#     jni/h5sImp.c,jni/h5tImp.c
+#       -Werror=cast-align
+#     jni/h5util.c
+#       -Werror=format(-overflow)
+#
+-Wformat
+#
+#
+#Examples and tests do not use the same set of extensive warning flags as libraries
+# Here is a list of tests and examples that have issues with the stricter warnings as error
+#
+# NOTE: Test files are not compatible with these warnings as errors
+#     thread_id.c,
+#       -Werror=unused-function
+#     dsets.c
+#       -Werror=unused-parameter
+#
+#
+# NOTE: Examples files are not compatible with these warnings as errors
+#     h5_vds-eiger.c,h5_vds-exclim.c,h5_vds.c,h5_vds-exc.c,h5_vds-percival-unlim-maxmin.c
+#     h5_vds-percival.c,h5_read.c,h5_rdwt.c,h5_mount.c,h5_extend.c,h5_extend_write.c
+#     h5_write.c,h5_vds-simpleIO.c,h5_ref2reg_deprec.c,h5_crtgrp.c,h5_select.c
+#     h5_vds-percival-unlim.c,h5_crtatt.c,h5_group.c,h5_attribute.c,h5_crtdat.c
+#     h5_reference_deprec.c
+#     h5_rdwt.c,h5_crtgrp.c,h5_crtatt.c,h5_crtdat.c
+#       -Werror=strict-prototypes
+#     h5_rdwt.c,h5_crtgrp.c,h5_crtatt.c,h5_crtdat.c
+#       -Werror=old-style-definition
+#     h5_vds-exclim.c,h5_vds.c,h5_vds-exc.c,
+#       -Werror=unused-variable
+#     h5_elink_unix2win.c,h5_extlink.c,h5_attribute.c
+#       -Werror=unused-parameter
+
diff --git a/config/cmake/HDFCXXCompilerFlags.cmake b/config/cmake/HDFCXXCompilerFlags.cmake
index b0f9e23..ef06090 100644
--- a/config/cmake/HDFCXXCompilerFlags.cmake
+++ b/config/cmake/HDFCXXCompilerFlags.cmake
@@ -14,7 +14,9 @@ set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_SANITIZER_FLAGS} ${CMAKE_CXX_FLAGS}")
-message (STATUS "Warnings Configuration: CXX default:  ${CMAKE_CXX_FLAGS}")
+if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
+  message (VERBOSE "Warnings Configuration: CXX default:  ${CMAKE_CXX_FLAGS}")
+endif ()
 #-----------------------------------------------------------------------------
 # Compiler specific flags : Shouldn't there be compiler tests for these
 #-----------------------------------------------------------------------------
@@ -81,22 +83,28 @@ if (NOT MSVC AND NOT MINGW)
     if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
       ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/general")
       if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 18.0)
-        list (APPEND H5_CXXFLAGS0 "-Wextra-tokens -Wformat -Wformat-security -Wic-pointer -Wshadow")
-        list (APPEND H5_CXXFLAGS0 "-Wsign-compare -Wtrigraphs -Wwrite-strings")
+        list (APPEND H5_CXXFLAGS "-Wextra-tokens -Wformat -Wformat-security -Wic-pointer -Wshadow")
+        list (APPEND H5_CXXFLAGS "-Wsign-compare -Wtrigraphs -Wwrite-strings")
       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 "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-general")
-        ADD_H5_FLAGS (H5_CXXFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-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 "Clang")
       ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/general")
     elseif (CMAKE_CXX_COMPILER_ID STREQUAL "PGI")
       list (APPEND HDF5_CMAKE_CXX_FLAGS "-Minform=inform")
     endif ()
-    message (STATUS "CMAKE_CXX_FLAGS_GENERAL=${HDF5_CMAKE_CXX_FLAGS}")
+    if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
+      message (VERBOSE "CMAKE_CXX_FLAGS_GENERAL=${HDF5_CMAKE_CXX_FLAGS}")
+    endif ()
   endif ()
 
   #-----------------------------------------------------------------------------
@@ -106,20 +114,20 @@ if (NOT MSVC AND NOT MINGW)
   if (HDF5_ENABLE_DEV_WARNINGS)
     message (STATUS "....HDF5 developer group warnings are enabled")
   #  if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
-  #    list (APPEND H5_CXXFLAGS0 "-Winline -Wreorder -Wport -Wstrict-aliasing")
+  #    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_CXXFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
   #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-  #    ADD_H5_FLAGS (H5_CXXFLAGS0 "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
+  #    ADD_H5_FLAGS (H5_CXXFLAGS "${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_CXXFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
   #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-  #    ADD_H5_FLAGS (H5_CXXFLAGS0 "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
+  #    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
     endif ()
   endif ()
 
@@ -128,37 +136,41 @@ if (NOT MSVC AND NOT MINGW)
     #   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_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
     endif ()
 
     # Append more extra warning flags that only gcc 4.8+ know about
     if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
-      ADD_H5_FLAGS (H5_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
       if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
       else ()
-        ADD_H5_FLAGS (H5_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
       endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 4.9+ know 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_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.9")
-      ADD_H5_FLAGS (H5_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-4.9")
+      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")
     endif ()
 
     # Append more extra warning flags that only gcc 5.1+ know 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_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-5")
-      ADD_H5_FLAGS (H5_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-5")
+      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 6.x+ know 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_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
     endif ()
 
     # Append more extra warning flags that only gcc 7.x+ know about
@@ -167,30 +179,34 @@ if (NOT MSVC AND NOT MINGW)
       ADD_H5_FLAGS (H5_CXxFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
       if (HDF5_ENABLE_DEV_WARNINGS)
         # autotools always add the C flags with the CXX flags
-        ADD_H5_FLAGS (H5_CXXFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
       #else ()
-      #  ADD_H5_FLAGS (H5_CXXFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
+      #  ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
       endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 8.x+ know 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_CXXFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/8")
-      #ADD_H5_FLAGS (H5_CXXFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
+      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 "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-8")
+      #endif ()
       if (HDF5_ENABLE_DEV_WARNINGS)
         # autotools always add the C flags with the CXX flags
-        ADD_H5_FLAGS (H5_CXXFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
       else ()
         # autotools always add the C flags with the CXX flags
-        ADD_H5_FLAGS (H5_CXXFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
       endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 9.x+ know about
     if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
       # autotools always add the C flags with the CXX flags
-      ADD_H5_FLAGS (H5_CXXFLAGS4 "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
     endif ()
   endif ()
 else ()
@@ -208,97 +224,17 @@ if (HDF5_ENABLE_ALL_WARNINGS)
     if (HDF5_ENABLE_DEV_WARNINGS)
       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")
+        list (APPEND HDF5_CMAKE_CXX_FLAGS "/Wall" "/wd4668")
       endif ()
     else ()
       if (CMAKE_CXX_COMPILER_LOADED)
         string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
-        list (APPEND HDF5_CMAKE_CXX_FLAGS "/W3")
+        list (APPEND HDF5_CMAKE_CXX_FLAGS "/W3" "/wd4100" "/wd4706" "/wd4127")
       endif ()
     endif ()
   else ()
     if (CMAKE_CXX_COMPILER_LOADED)
-      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS0} ${H5_CXXFLAGS1} ${H5_CXXFLAGS2} ${H5_CXXFLAGS3} ${H5_CXXFLAGS4})
-    endif ()
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-if (HDF5_ENABLE_GROUPZERO_WARNINGS)
-  message (STATUS "....Group Zero warnings are enabled")
-  if (MSVC)
-    if (CMAKE_CXX_COMPILER_LOADED)
-      string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
-      list (APPEND HDF5_CMAKE_CXX_FLAGS "/W1")
-    endif ()
-  else ()
-    if (CMAKE_CXX_COMPILER_LOADED)
-      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS0})
-    endif ()
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-if (HDF5_ENABLE_GROUPONE_WARNINGS)
-  message (STATUS "....Group One warnings are enabled")
-  if (MSVC)
-    if (CMAKE_CXX_COMPILER_LOADED)
-      string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
-      list (APPEND HDF5_CMAKE_CXX_FLAGS "/W2")
-    endif ()
-  else ()
-    if (CMAKE_CXX_COMPILER_LOADED)
-      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS1})
-    endif ()
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-if (HDF5_ENABLE_GROUPTWO_WARNINGS)
-  message (STATUS "....Group Two warnings are enabled")
-  if (MSVC)
-    if (CMAKE_CXX_COMPILER_LOADED)
-      string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
-      list (APPEND HDF5_CMAKE_CXX_FLAGS "/W3")
-    endif ()
-  else ()
-    if (CMAKE_CXX_COMPILER_LOADED)
-      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS2})
-    endif ()
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-if (HDF5_ENABLE_GROUPTHREE_WARNINGS)
-  message (STATUS "....Group Three warnings are enabled")
-  if (MSVC)
-    if (CMAKE_CXX_COMPILER_LOADED)
-      string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_CXX_FLAGS "${HDF5_CMAKE_CXX_FLAGS}")
-      list (APPEND HDF5_CMAKE_CXX_FLAGS "/W4")
-    endif ()
-  else ()
-    if (CMAKE_CXX_COMPILER_LOADED)
-      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS3})
-    endif ()
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-if (HDF5_ENABLE_GROUPFOUR_WARNINGS)
-  message (STATUS "....Group Four warnings are enabled")
-  if (NOT MSVC)
-    if (CMAKE_CXX_COMPILER_LOADED)
-      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS4})
+      list (APPEND HDF5_CMAKE_CXX_FLAGS ${H5_CXXFLAGS})
     endif ()
   endif ()
 endif ()
diff --git a/config/cmake/HDFCompilerFlags.cmake b/config/cmake/HDFCompilerFlags.cmake
index e4808d2..18f8d01 100644
--- a/config/cmake/HDFCompilerFlags.cmake
+++ b/config/cmake/HDFCompilerFlags.cmake
@@ -15,7 +15,10 @@ set(CMAKE_C_STANDARD_REQUIRED TRUE)
 set (CMAKE_C_FLAGS "${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}")
-message (STATUS "Warnings Configuration: default: ${CMAKE_C_FLAGS} : ${CMAKE_CXX_FLAGS}")
+
+if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
+  message (VERBOSE "Warnings Configuration: default: ${CMAKE_C_FLAGS} : ${CMAKE_CXX_FLAGS}")
+endif ()
 #-----------------------------------------------------------------------------
 # Compiler specific flags : Shouldn't there be compiler tests for these
 #-----------------------------------------------------------------------------
@@ -69,6 +72,18 @@ endif ()
 # break into groups (from the config/gnu-flags file)
 #-----------------------------------------------------------------------------
 if (NOT MSVC AND NOT MINGW)
+  #-----------------------------------------------------------------------------
+  # Option to allow the user to interpret certain warnings as errors
+  #
+  # This should NOT be on by default as it can cause a lot of conflicts with
+  # new operating systems and compiler versions. Header files that are out of
+  # our control (MPI, HDFS, etc.) can also raise warnings.
+  #-----------------------------------------------------------------------------
+  option (HDF5_ENABLE_WARNINGS_AS_ERRORS "Interpret some warnings as errors" OFF)
+  if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+    message (STATUS "...some warnings will be interpreted as errors")
+  endif ()
+
   if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
     list (APPEND HDF5_CMAKE_C_FLAGS "-erroff=%none -DBSD_COMP")
   else ()
@@ -83,31 +98,41 @@ if (NOT MSVC AND NOT MINGW)
     # warnings that are emitted. If you need it, add it at configure time.
     if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
       ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/general")
-      list (APPEND H5_CFLAGS0 "-Wcomment -Wdeprecated -Wmain -Wmissing-declarations -Wmissing-prototypes -Wp64 -Wpointer-arith")
-      list (APPEND H5_CFLAGS0 "-Wreturn-type -Wstrict-prototypes -Wuninitialized")
-      list (APPEND H5_CFLAGS0 "-Wunknown-pragmas -Wunused-function -Wunused-variable")
+      list (APPEND H5_CFLAGS "-Wcomment -Wdeprecated -Wmain -Wmissing-declarations -Wmissing-prototypes -Wp64 -Wpointer-arith")
+      list (APPEND H5_CFLAGS "-Wreturn-type -Wstrict-prototypes -Wuninitialized")
+      list (APPEND H5_CFLAGS "-Wunknown-pragmas -Wunused-function -Wunused-variable")
       # this is just a failsafe
-      list (APPEND H5_CFLAGS0 "-finline-functions")
+      list (APPEND H5_CFLAGS "-finline-functions")
       if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 18.0)
-        list (APPEND H5_CFLAGS0 "-Wextra-tokens -Wformat -Wformat-security -Wic-pointer -Wshadow")
-        list (APPEND H5_CFLAGS0 "-Wsign-compare -Wtrigraphs -Wwrite-strings")
+        list (APPEND H5_CFLAGS "-Wextra-tokens -Wformat -Wformat-security -Wic-pointer -Wshadow")
+        list (APPEND H5_CFLAGS "-Wsign-compare -Wtrigraphs -Wwrite-strings")
       endif()
     elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU")
       # Add general CFlags for GCC versions 4.8 and above
       if (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
         ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/general")
-        ADD_H5_FLAGS (H5_CFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-general")
+        if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+          ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-general")
+        else ()
+          ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-general")
+        endif ()
       endif ()
       # gcc automatically inlines based on the optimization level
       # this is just a failsafe
-      list (APPEND H5_CFLAGS0 "-finline-functions")
+      list (APPEND H5_CFLAGS "-finline-functions")
     elseif (CMAKE_C_COMPILER_ID STREQUAL "Clang")
       ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/general")
-      ADD_H5_FLAGS (H5_CFLAGS0 "${HDF5_SOURCE_DIR}/config/clang-warnings/error-general")
+      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/error-general")
+      else ()
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/noerror-general")
+      endif ()
     elseif (CMAKE_C_COMPILER_ID STREQUAL "PGI")
       list (APPEND HDF5_CMAKE_C_FLAGS "-Minform=inform")
     endif ()
-    message (STATUS "CMAKE_C_FLAGS_GENERAL=${HDF5_CMAKE_C_FLAGS}")
+    if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.15.0")
+      message (VERBOSE "CMAKE_C_FLAGS_GENERAL=${HDF5_CMAKE_C_FLAGS}")
+    endif ()
   endif ()
 
   #-----------------------------------------------------------------------------
@@ -118,78 +143,97 @@ if (NOT MSVC AND NOT MINGW)
   if (HDF5_ENABLE_DEV_WARNINGS)
     message (STATUS "....HDF5 developer group warnings are enabled")
     if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
-      list (APPEND H5_CFLAGS0 "-Winline -Wreorder -Wport -Wstrict-aliasing")
+      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_CFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
     elseif (CMAKE_C_COMPILER_ID STREQUAL "Clang")
-      ADD_H5_FLAGS (H5_CFLAGS0 "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
+      ADD_H5_FLAGS (H5_CFLAGS "${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_CFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
     elseif (CMAKE_C_COMPILER_ID STREQUAL "Clang")
-      ADD_H5_FLAGS (H5_CFLAGS0 "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
+      ADD_H5_FLAGS (H5_CFLAGS "${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_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8-4.last")
     endif ()
 
     # Append more extra warning flags that only gcc 4.8+ know about
     if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.8)
-      ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
       if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-4.8")
       else ()
-        ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-4.8")
       endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 4.9+ know about
     if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.9)
-      ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.9")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.9")
     endif ()
 
     # Append more extra warning flags that only gcc 5.x+ know about
     if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 5.0)
-      ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/5")
-      ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-5")
+      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+ know about
     if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 6.0)
-      ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/6")
     endif ()
 
     # Append more extra warning flags that only gcc 7.x+ know about
     if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 7.0)
-      ADD_H5_FLAGS (H5_CFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
       if (HDF5_ENABLE_DEV_WARNINGS)
-        ADD_H5_FLAGS (H5_CFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
       #else ()
-      #  ADD_H5_FLAGS (H5_CFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
+      #  ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
       endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 8.x+ know about
     if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 8.0)
-      ADD_H5_FLAGS (H5_CFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/8")
-      ADD_H5_FLAGS (H5_CFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
+      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_CFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
       else ()
-        ADD_H5_FLAGS (H5_CFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-8")
       endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 9.x+ know about
     if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.0)
-      ADD_H5_FLAGS (H5_CFLAGS4 "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
+    endif ()
+
+    # Append more extra warning flags that only gcc 9.3+ know about
+    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 9.3)
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9.3")
+    endif ()
+
+    # Append more extra warning flags that only gcc 10.x+ know about
+    if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 10.0)
+      if (HDF5_ENABLE_DEV_WARNINGS)
+        ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-10")
+      #else ()
+      #  ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-10")
+      endif ()
     endif ()
   endif ()
 endif ()
@@ -197,86 +241,19 @@ endif ()
 #-----------------------------------------------------------------------------
 # Option to allow the user to enable all warnings
 #-----------------------------------------------------------------------------
-option (HDF5_ENABLE_ALL_WARNINGS "Enable all warnings" OFF)
+option (HDF5_ENABLE_ALL_WARNINGS "Enable all warnings" ON)
 if (HDF5_ENABLE_ALL_WARNINGS)
   message (STATUS "....All Warnings are enabled")
   if (MSVC)
     if (HDF5_ENABLE_DEV_WARNINGS)
       string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
-      list (APPEND HDF5_CMAKE_C_FLAGS "/Wall /wd4668")
+      list (APPEND HDF5_CMAKE_C_FLAGS "/Wall" "/wd4668")
     else ()
       string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
-      list (APPEND HDF5_CMAKE_C_FLAGS "/W3")
+      list (APPEND HDF5_CMAKE_C_FLAGS "/W3" "/wd4100" "/wd4706" "/wd4127")
     endif ()
   else ()
-    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS0} ${H5_CFLAGS1} ${H5_CFLAGS2} ${H5_CFLAGS3} ${H5_CFLAGS4})
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-option (HDF5_ENABLE_GROUPZERO_WARNINGS "Enable group zero warnings" OFF)
-if (HDF5_ENABLE_GROUPZERO_WARNINGS)
-  message (STATUS "....Group Zero warnings are enabled")
-  if (MSVC)
-    string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
-    list (APPEND HDF5_CMAKE_C_FLAGS "/W1")
-  else ()
-    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS0})
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-option (HDF5_ENABLE_GROUPONE_WARNINGS "Enable group one warnings" OFF)
-if (HDF5_ENABLE_GROUPONE_WARNINGS)
-  message (STATUS "....Group One warnings are enabled")
-  if (MSVC)
-    string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
-    list (APPEND HDF5_CMAKE_C_FLAGS "/W2")
-  else ()
-    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS1})
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-option (HDF5_ENABLE_GROUPTWO_WARNINGS "Enable group two warnings" OFF)
-if (HDF5_ENABLE_GROUPTWO_WARNINGS)
-  message (STATUS "....Group Two warnings are enabled")
-  if (MSVC)
-    string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
-    list (APPEND HDF5_CMAKE_C_FLAGS "/W3")
-  else ()
-    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS2})
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-option (HDF5_ENABLE_GROUPTHREE_WARNINGS "Enable group three warnings" OFF)
-if (HDF5_ENABLE_GROUPTHREE_WARNINGS)
-  message (STATUS "....Group Three warnings are enabled")
-  if (MSVC)
-    string (REGEX REPLACE "(^| )([/-])W[0-9]( |$)" " " HDF5_CMAKE_C_FLAGS "${HDF5_CMAKE_C_FLAGS}")
-    list (APPEND HDF5_CMAKE_C_FLAGS "/W4")
-  else ()
-    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS3})
-  endif ()
-endif ()
-
-#-----------------------------------------------------------------------------
-# Option to allow the user to enable warnings by groups
-#-----------------------------------------------------------------------------
-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)
-    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS4})
+    list (APPEND HDF5_CMAKE_C_FLAGS ${H5_CFLAGS})
   endif ()
 endif ()
 
diff --git a/config/commence.am b/config/commence.am
index 5ddbc72..486dea7 100644
--- a/config/commence.am
+++ b/config/commence.am
@@ -70,9 +70,9 @@ H5CPP=${DESTDIR}$(bindir)/h5c++
 # instead of CFLAGS, as CFLAGS is reserved solely for the user to define.
 # This applies to FCFLAGS, CXXFLAGS, CPPFLAGS, and LDFLAGS as well.
 
-AM_CFLAGS=@AM_CFLAGS@ @H5_CFLAGS@ @H5_ECFLAGS@
+AM_CFLAGS=@AM_CFLAGS@ @H5_CFLAGS@
 AM_FCFLAGS=@AM_FCFLAGS@ @H5_FCFLAGS@
-AM_CXXFLAGS=@AM_CXXFLAGS@ @H5_CXXFLAGS@ @H5_ECXXFLAGS@
+AM_CXXFLAGS=@AM_CXXFLAGS@ @H5_CXXFLAGS@
 AM_CPPFLAGS=@AM_CPPFLAGS@ @H5_CPPFLAGS@
 AM_LDFLAGS=@AM_LDFLAGS@ @H5_LDFLAGS@
 
diff --git a/config/gnu-cxxflags b/config/gnu-cxxflags
index b8cac77..67f925c 100644
--- a/config/gnu-cxxflags
+++ b/config/gnu-cxxflags
@@ -184,10 +184,11 @@ if test "X-g++" = "X-$cxx_vendor"; then
     if test $cxx_vers_major -eq 4 -a $cxx_vers_minor -ge 8 -o $cxx_vers_major -ge 5; then
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments cxx-general)"
         H5_ECXXFLAGS="$H5_ECXXFLAGS $(load_gnu_arguments cxx-error-general)"
+        H5_NECXXFLAGS="$H5_NECXXFLAGS $(load_gnu_arguments cxx-noerror-general)"
 
-    ######################
-    # Developer warnings #
-    ######################
+        ######################
+        # Developer warnings #
+        ######################
 
         NO_DEVELOPER_WARNING_CXXFLAGS=$(load_gnu_arguments no-developer-general)
         DEVELOPER_WARNING_CXXFLAGS=$(load_gnu_arguments developer-general)
@@ -209,7 +210,7 @@ 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 $(load_gnu_arguments 4.8)"
+        H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments cxx-4.8)"
         DEVELOPER_WARNING_CXXFLAGS="$DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments developer-4.8)"
         NO_DEVELOPER_WARNING_CXXFLAGS="$NO_DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments no-developer-4.8)"
     fi
@@ -224,6 +225,7 @@ if test "X-g++" = "X-$cxx_vendor"; then
     if test $cxx_vers_major -ge 5; then
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments cxx-5)"
         H5_ECXXFLAGS="$H5_ECXXFLAGS $(load_gnu_arguments cxx-error-5)"
+        H5_NECXXFLAGS="$H5_NECXXFLAGS $(load_gnu_arguments cxx-noerror-5)"
     fi
 
     # gcc >= 6
@@ -241,6 +243,7 @@ if test "X-g++" = "X-$cxx_vendor"; then
     if test $cxx_vers_major -ge 8; then
         H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments 8)"
         #H5_ECXXFLAGS="$H5_ECXXFLAGS $(load_gnu_arguments error-8)"
+        #H5_NECXXFLAGS="$H5_NECXXFLAGS $(load_gnu_arguments noerror-8)"
         DEVELOPER_WARNING_CXXFLAGS="$DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments developer-8)"
         NO_DEVELOPER_WARNING_CXXFLAGS="$NO_DEVELOPER_WARNING_CXXFLAGS $(load_gnu_arguments no-developer-8)"
     fi
diff --git a/config/gnu-flags b/config/gnu-flags
index 9a09022..89d27d6 100644
--- a/config/gnu-flags
+++ b/config/gnu-flags
@@ -20,7 +20,7 @@
 #
 # For now, do not promote any warnings to errors.
 #
-PROMOTE_ERRORS_DFLT=yes
+PROMOTE_ERRORS_DFLT=no
 
 #
 # This filter rewrites -Werror= as -W, in that way demoting warnings
@@ -118,12 +118,16 @@ if test "X-gcc" = "X-$cc_vendor"; then
     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 needs the "-std=c99" flag removed.
         cygwin-*)
             ;;
-
+        # On Solaris, gcc needs the gnu99 standard to pick up certain POSIX
+        # things. Do NOT use this as the gcc norm as this encourages the use
+        # of non-standard gcc extensions.
+        *solaris*)
+            H5_CFLAGS="$H5_CFLAGS -std=gnu99"
+            ;;
+        # Everybody else gets c99 as the standard.
         *)
             H5_CFLAGS="$H5_CFLAGS -std=c99"
             ;;
@@ -192,8 +196,7 @@ if test "X-gcc" = "X-$cc_vendor"; then
     if test $cc_vers_major -eq 4 -a $cc_vers_minor -ge 8 -o $cc_vers_major -gt 4; then
         H5_CFLAGS="$H5_CFLAGS $(load_gnu_arguments general)"
         H5_ECFLAGS="$H5_ECFLAGS $(load_gnu_arguments error-general)"
-
-    H5_CFLAGS="$H5_CFLAGS -Wno-c++-compat"
+        H5_NECFLAGS="$H5_NECFLAGS $(load_gnu_arguments noerror-general)"
 
     ######################
     # Developer warnings #
@@ -233,6 +236,7 @@ if test "X-gcc" = "X-$cc_vendor"; then
     if test $cc_vers_major -ge 5; then
         H5_CFLAGS="$H5_CFLAGS $(load_gnu_arguments 5)"
         H5_ECFLAGS="$H5_ECFLAGS $(load_gnu_arguments error-5)"
+        H5_NECFLAGS="$H5_NECFLAGS $(load_gnu_arguments noerror-5)"
     fi
 
     # gcc >= 6
@@ -250,6 +254,7 @@ if test "X-gcc" = "X-$cc_vendor"; then
     if test $cc_vers_major -ge 8; then
         H5_CFLAGS="$H5_CFLAGS $(load_gnu_arguments 8)"
         H5_ECFLAGS="$H5_ECFLAGS $(load_gnu_arguments error-8)"
+        H5_NECFLAGS="$H5_NECFLAGS $(load_gnu_arguments noerror-8)"
         DEVELOPER_WARNING_CFLAGS="$DEVELOPER_WARNING_CFLAGS $(load_gnu_arguments developer-8)"
         NO_DEVELOPER_WARNING_CFLAGS="$NO_DEVELOPER_WARNING_CFLAGS $(load_gnu_arguments no-developer-8)"
     fi
@@ -259,6 +264,16 @@ if test "X-gcc" = "X-$cc_vendor"; then
         H5_CFLAGS="$H5_CFLAGS $(load_gnu_arguments 9)"
     fi
 
+    # gcc >= 9.3
+    if test $cc_vers_major -ge 10 -o $cc_vers_major -eq 9 -a $cc_vers_minor -ge 3; then
+        H5_CFLAGS="$H5_CFLAGS $(load_gnu_arguments 9.3)"
+    fi
+
+    # gcc >= 10
+    if test $cc_vers_major -ge 10; then
+        DEVELOPER_WARNING_CFLAGS="$DEVELOPER_WARNING_CFLAGS $(load_gnu_arguments developer-10)"
+    fi
+
     #################
     # Flags are set #
     #################
diff --git a/config/gnu-warnings/4.8 b/config/gnu-warnings/4.8
index c7e3dd1..fa678ff 100644
--- a/config/gnu-warnings/4.8
+++ b/config/gnu-warnings/4.8
@@ -10,6 +10,10 @@
 # warning flag added for GCC >= 4.5
 -Wstrict-overflow=5
 
+# This warning can only be truly addressed using the gcc extension of
+# using D to indicate doubles (e.g., 1.23D).
+-Wno-unsuffixed-float-constants
+
 # warning flags added for GCC >= 4.6
 -Wdouble-promotion
 -Wtrampolines
diff --git a/config/gnu-warnings/7 b/config/gnu-warnings/7
index 266f5c1..9d5b44d 100644
--- a/config/gnu-warnings/7
+++ b/config/gnu-warnings/7
@@ -3,5 +3,4 @@
 -Wduplicated-branches
 -Wformat-overflow=2
 -Wformat-truncation=1
--Wimplicit-fallthrough=5
 -Wrestrict
diff --git a/config/gnu-warnings/9.3 b/config/gnu-warnings/9.3
new file mode 100644
index 0000000..f37fdd6
--- /dev/null
+++ b/config/gnu-warnings/9.3
@@ -0,0 +1 @@
+-Wc11-c2x-compat
diff --git a/config/gnu-warnings/cxx-4.8 b/config/gnu-warnings/cxx-4.8
new file mode 100644
index 0000000..744ebdc
--- /dev/null
+++ b/config/gnu-warnings/cxx-4.8
@@ -0,0 +1,26 @@
+# warning flags added for GCC >= 4.3
+-Wlarger-than=2560
+-Wlogical-op
+
+# warning flags added for GCC >= 4.4
+-Wframe-larger-than=16384
+-Wpacked-bitfield-compat
+-Wsync-nand
+
+# warning flag added for GCC >= 4.5
+-Wstrict-overflow=5
+
+# warning flags added for GCC >= 4.6
+-Wdouble-promotion
+-Wtrampolines
+
+# warning flag added for GCC >= 4.7
+#
+# -Wstack-usage=8192 warnings need to be swept up on a branch so
+# that we can stop burdening the whole development team.
+#
+-Wstack-usage=8192
+
+# warning flag added for GCC >= 4.8
+-Wmaybe-uninitialized
+
diff --git a/config/gnu-warnings/cxx-noerror-5 b/config/gnu-warnings/cxx-noerror-5
new file mode 100644
index 0000000..7bce3e8
--- /dev/null
+++ b/config/gnu-warnings/cxx-noerror-5
@@ -0,0 +1,11 @@
+#
+# In GCC 4.4.7, the compiler gripes about shadowed global
+# declarations when a local variable uses the name of a
+# function that's in a system header file.  For some reason,
+# later versions of GCC (e.g., 5.2.0) don't complain about
+# the shadowed globals.  Maybe later versions are less fussy?
+# Anyway, the shadowing seems to be harmless, and GCC 4.4.7
+# is not a supported compiler, so let us promote shadowed globals
+# warnings to errors only for GCC 5 and later.
+#
+-Wshadow
diff --git a/config/gnu-warnings/cxx-noerror-general b/config/gnu-warnings/cxx-noerror-general
new file mode 100644
index 0000000..8cc1d94
--- /dev/null
+++ b/config/gnu-warnings/cxx-noerror-general
@@ -0,0 +1,32 @@
+#
+# HDF5 code should not trigger the following warnings under any
+# circumstances, so ask the compiler to treat them as errors:
+#
+# NOTE: c++/test files are not compatible with these warnings as errors
+#     c++/test/tcompound.cpp
+#       -Werror=cast-align
+-Wcast-align
+# NOTE: c++/src files are not compatible with these warnings as errors
+#     c++/src/H5Object.cpp
+#       -Werror=missing-declarations
+-Wmissing-declarations
+-Wpacked
+-Wredundant-decls
+-Wswitch
+# NOTE: c++/test files are not compatible with these warnings as errors
+#     c++/test/tattr.cpp
+#       -Werror=unused-but-set-variable
+-Wunused-but-set-variable
+-Wunused-function
+-Wunused-variable
+# NOTE: c++/src files are not compatible with these warnings as errors
+#     c++/src/H5Object.cpp,c++/src/H5StrType.cpp,c++/src/H5PredType.cpp
+#       -Werror=unused-parameter
+-Wunused-parameter
+#
+# Other files not compatible
+# NOTE: c++/test files are not compatible with these warnings as errors
+#     c++/test/titerate.cpp,c++/test/tarray.cpp
+#       -Werror=missing-declarations
+#     c++/test/titerate.cpp,c++/test/tarray.cpp,c++/test/tlinks.cpp,c++/test/ttypes.cpp,c++/test/dsets.cpp
+#       -Werror=unused-parameter
diff --git a/config/gnu-warnings/developer-10 b/config/gnu-warnings/developer-10
new file mode 100644
index 0000000..fcd460d
--- /dev/null
+++ b/config/gnu-warnings/developer-10
@@ -0,0 +1,6 @@
+# New warning
+-Warith-conversion
+
+# Enable static analysis of program flow
+-fanalyzer
+-fdiagnostics-path-format=none
diff --git a/config/gnu-warnings/developer-4.8 b/config/gnu-warnings/developer-4.8
index fd76f6c..bfd15a1 100644
--- a/config/gnu-warnings/developer-4.8
+++ b/config/gnu-warnings/developer-4.8
@@ -5,7 +5,6 @@
 # the variable is never *used* before it has been initialized?
 #
 -Wjump-misses-init
--Wunsuffixed-float-constants
 
 # developer warning flag added for GCC >= 4.6
 -Wsuggest-attribute=const
diff --git a/config/gnu-warnings/error-5 b/config/gnu-warnings/error-5
index 000f218..f7e1138 100644
--- a/config/gnu-warnings/error-5
+++ b/config/gnu-warnings/error-5
@@ -10,4 +10,3 @@
 # warnings to errors only for GCC 5 and later.
 #
 -Werror=shadow
--Werror=int-conversion
diff --git a/config/gnu-warnings/error-general b/config/gnu-warnings/error-general
index 28e8ae9..4358b20 100644
--- a/config/gnu-warnings/error-general
+++ b/config/gnu-warnings/error-general
@@ -5,9 +5,7 @@
 -Werror=bad-function-cast
 -Werror=declaration-after-statement
 -Werror=implicit-function-declaration
--Werror=int-to-pointer-cast
 -Werror=missing-declarations
--Werror=missing-field-initializers
 -Werror=missing-prototypes
 -Werror=nested-externs
 -Werror=old-style-definition
@@ -61,7 +59,7 @@
 #     jni/h5util.c
 #       -Werror=format(-overflow)
 #
--Wformat
+-Werror=format
 #
 #
 #Examples and tests do not use the same set of extensive warning flags as libraries
diff --git a/config/gnu-warnings/no-developer-4.8 b/config/gnu-warnings/no-developer-4.8
index 1e29c78..09a9a96 100644
--- a/config/gnu-warnings/no-developer-4.8
+++ b/config/gnu-warnings/no-developer-4.8
@@ -1,6 +1,5 @@
 # no-developer warning flag added for GCC >= 4.5
 -Wno-jump-misses-init
--Wno-unsuffixed-float-constants
 
 # no-developer warning flag added for GCC >= 4.6
 -Wno-suggest-attribute=const
diff --git a/config/gnu-warnings/noerror-5 b/config/gnu-warnings/noerror-5
new file mode 100644
index 0000000..a7d40dd
--- /dev/null
+++ b/config/gnu-warnings/noerror-5
@@ -0,0 +1,12 @@
+-Wincompatible-pointer-types
+#
+# In GCC 4.4.7, the compiler gripes about shadowed global
+# declarations when a local variable uses the name of a
+# function that's in a system header file.  For some reason,
+# later versions of GCC (e.g., 5.2.0) don't complain about
+# the shadowed globals.  Maybe later versions are less fussy?
+# Anyway, the shadowing seems to be harmless, and GCC 4.4.7
+# is not a supported compiler, so let us promote shadowed globals
+# warnings to errors only for GCC 5 and later.
+#
+-Wshadow
diff --git a/config/gnu-warnings/noerror-8 b/config/gnu-warnings/noerror-8
new file mode 100644
index 0000000..2f54a4d
--- /dev/null
+++ b/config/gnu-warnings/noerror-8
@@ -0,0 +1,25 @@
+# NOTE: src/ files are not compatible with these warnings as errors
+#     src/H5Dchunk.c
+#       -Werror=cast-function-type
+-Wcast-function-type
+#
+# For GCC 8, promote maybe-initialized warnings to an error.  GCC 8
+# reports 0 maybe-uninitialized warnings where earlier versions
+# make many false reports.  GCC 8 seems to analyze calls to static
+# in order to detect initializations that occur there.  It's possible
+# that GCC 8 only performs that analysis at -O3, though.
+#
+#
+# NOTE: File Driver files are not compatible with these warnings as errors
+#     H5FDlog.c,
+#       -Werror=maybe-uninitialized
+-Wmaybe-uninitialized
+# NOTE: src/ files are not compatible with these warnings as errors
+#     src/H5Shyper.c,src/H5SL.c,src/H5Shyper.c
+#       -Werror=maybe-uninitialized
+# NOTE: Test files are not compatible with these warnings as errors
+#     test/cache_common.c,
+#       -Werror=maybe-uninitialized
+# NOTE: hl/src/ files are not compatible with these warnings as errors
+#     hl/src/H5DS.c,
+#       -Werror=maybe-uninitialized
diff --git a/config/gnu-warnings/noerror-general b/config/gnu-warnings/noerror-general
new file mode 100644
index 0000000..e19014f
--- /dev/null
+++ b/config/gnu-warnings/noerror-general
@@ -0,0 +1,91 @@
+#
+# HDF5 code should not trigger the following warnings under any
+# circumstances, so ask the compiler to treat them as errors:
+#
+-Wbad-function-cast
+-Wdeclaration-after-statement
+-Wimplicit-function-declaration
+-Wmissing-declarations
+-Wmissing-prototypes
+-Wnested-externs
+-Wold-style-definition
+-Wpacked
+-Wpointer-sign
+-Wpointer-to-int-cast
+-Wredundant-decls
+-Wstrict-prototypes
+-Wswitch
+#
+#-Werror=discarded-qualifiers
+#
+#
+# NOTE: File Driver files are not compatible with these warnings as errors
+#     H5FDdirect.c,H5FDmpio.c,H5FDros3.c,
+#       -Werror=unused-function
+#
+-Wunused-function
+#
+#     H5FDdrvr_module.h
+#       -Werror=unused-variable
+#
+-Wunused-variable
+#
+#     H5VLpassthru.c
+#       -Werror=unused-parameter
+#
+-Wunused-parameter
+#
+#
+#
+# NOTE: Tools files are not compatible with these warnings as errors
+#     lib/h5tools.c
+#       -Werror=cast-align
+#
+-Wcast-align
+#
+#     lib/h5diff_array.c
+#       -Werror=unused-but-set-variable
+#
+-Wunused-but-set-variable
+#
+#     lib/h5tools_utils.c
+#       -Werror=unused-parameter
+#
+#
+# NOTE: JNI files are not compatible with these warnings as errors
+#     jni/h5pDCPLImp.c,jni/nativeData.c,jni/h5util.c,jni/h5rImp.c
+#     jni/h5sImp.c,jni/h5tImp.c
+#       -Werror=cast-align
+#     jni/h5util.c
+#       -Werror=format(-overflow)
+#
+-Wformat
+#
+#
+#Examples and tests do not use the same set of extensive warning flags as libraries
+# Here is a list of tests and examples that have issues with the stricter warnings as error
+#
+# NOTE: Test files are not compatible with these warnings as errors
+#     thread_id.c,
+#       -Werror=unused-function
+#     dsets.c
+#       -Werror=unused-parameter
+#     external.c,perform/sio_engine.c
+#       -Werror=format(-truncation)
+#
+#
+# NOTE: Examples files are not compatible with these warnings as errors
+#     h5_vds-eiger.c,h5_vds-exclim.c,h5_vds.c,h5_vds-exc.c,h5_vds-percival-unlim-maxmin.c
+#     h5_vds-percival.c,h5_read.c,h5_rdwt.c,h5_mount.c,h5_extend.c,h5_extend_write.c
+#     h5_write.c,h5_vds-simpleIO.c,h5_ref2reg_deprec.c,h5_crtgrp.c,h5_select.c
+#     h5_vds-percival-unlim.c,h5_crtatt.c,h5_group.c,h5_attribute.c,h5_crtdat.c
+#     h5_reference_deprec.c
+#     h5_rdwt.c,h5_crtgrp.c,h5_crtatt.c,h5_crtdat.c
+#       -Werror=strict-prototypes
+#     h5_rdwt.c,h5_crtgrp.c,h5_crtatt.c,h5_crtdat.c
+#       -Werror=old-style-definition
+#     h5_vds-exclim.c,h5_vds.c,h5_vds-exc.c,
+#       -Werror=unused-variable
+#     h5_elink_unix2win.c,h5_extlink.c,h5_attribute.c
+#       -Werror=unused-parameter
+