Organize and align compiler flags (#741)

* OESS-98 convert plugin option to FetchContent, add tests

* Fixes for pkcfg files because of plugin option

* OESS-98 fix tools test for plugins

* Keep doxygen comments under 100 chars long - format hint

* Whitespace

* HDFFV-11144 - Reclassify CMake messages

* HDFFV-11099/11100 added help text

* Reworked switch statement to compare string instead

* Fix typo

* Update CDash mode

* Correct name of threadsafe

* Correct option name

* Undo accidental commit

* Note LLVM 10 to 11 format default changes

* Update format plugin

* Undo clang-format version 11 changes

* One more correction

* Update supported platforms

* Revert whitespace changes

* Correct whitespace

* Changes from PR#3

* HDFFV-11213 added option to control gcc10 warnings diagnostics

* HDFFV-11212 Use the new references correctly in JNI utility and tests

* format source

* Fix typo

* Add new test file

* HDFFV-11212 - update test and remove unused arg

* Minor non-space formatting changes

* Use H5I_INVALID_ID instead of "-1"

* source formatting

* add missing testfile, update jni function

* Undo commit of debug code

* remove mislocated file

* Fix h5repack test for handling of fapls and id close

* Update h5diff test files usage text

* HDFFV-11212 add new ref tests for JNI export dataset

* src format update

* Remove blank line typo

* src format typo

* long double requires %Lg

* Another long double foramt specifer S.B. %Lg

* issue with t128bit test

* Windows issue with h5dump and type.

* Fix review issues

* refactor function nesting and fix error checks

* format fixes

* Remove untested functions and javadoc quiet comments

* Restore TRY block.

* Change string append errors to memory exception

* revert to H5_JNI_FATAL_ERROR - support functions need work

* Add assertion error for h5util functions

* remove duplicate function

* format fix

* Revert HD function error handling

* Update copyright comments

* GH #386 java folder copyright corrections

* Whitespace

* GH #359 implement and fix tools 1.6 API usage

* remove excessive comments

* Flip inits to correct ifdef section

* rework ifdef to be simpler

* format issue

* Reformat ifdef inits

* remove static attribute

* format compliance

* Update names

* Revert because logic relies on float not being int

* Changes noticed from creating merge of #412

* Double underscore change

* Correct compiler version variable used

* Remove header guard underscores

* Whitespace cleanup

* Split format source and commit changes on repo push

* remove pre-split setting

* Change windows TS to use older VS.

* correct window os name

* HDFFV-11212 JNI export util and Javadoc

* Suggested review changes

* Another change found

* Committing clang-format changes

* HDFFV-11113 long double in tools

* HDFFV-11113 add note

* Disable long double tests for now

* HDFFV-11228 remove arbitrary CMake warning groups.

* Make each flag a string

* Some Javadoc warning fixes

* Updated javadoc fixes

* # WARNING: head commit changed in the meantime

HDFFV-11229 Fix long double usage in tools and java

Changed h5dump and h5ls to just print 128-bit for long double type.
Added test and file for dataset and attributes with all three float
types.

* Committing clang-format changes

* HDFFV-11229 Add release note

* HDFFV-11229 windows testfile needed

* fix typo

* Remove non supported message text

* HDFFV-11229 - change ldouble test to check both native and general

* HDFFV-11229 add second file compare

* HDFFV-11229 fix reference file

* HDFFV-11229 autotools check two refs

* HDFFV-11229 revert back to removal of NATIVE_LDOUBLE in tools output

* Committing clang-format changes

* Update release note

* Update attribute type of ref file

* Change source of ninja for macs

* try port instead of brew

* Recommended is to use brew.

* Undo non long double changes

* remove unneeded file

* Fix perl and doxygen CMake code

* Add "option" command for clang options

* Rework CMake add_custom to use the BYPRODUCTS argument

* Add stamp files to BYPRODUCTS

* Only one copy of file exists

* Fix custom cmmand depends targets

* Fix fortran custom command DEPENDS

* Add LD_LIBRARY_PATH to tests

* Add custom target for DEPENDS

* Add h5detect conditionaly to generated target DEPENDS

* Correct DEPENDS targets

* Parallel builds need the mpi compiler for pkgconfig scripts.

* install only if MPI build

* Fortran target depends

* Remove incorrect source attribute

* doxygen adjustments

* doxygen build updates

* Correct version

* Correct function version - function has been merged to 1.12

* Correct version string for map functions

* Cleanup warnings for tools debug builds

* TRILAB-227 - fix indexing for h5diff selections

* Correct location of pos to index function call

* TRILAB-227 Enable test

* Quote subset args

* Use MATCHES because of AppleClang

* if blocks needed for build modes

* Update list of DT platforms

* VS2019 correctly displays float values

* revert VS2019 change

* Issue #669 remove version from pkgcfg filename

* remove version from h5cc script

* Java reference functions updated

enabled fortran in cmake gcc action yaml file
java reference test changed to correctly test refs
jni reference functions that create ids changed to use jni id logging

* Correct BYPRODUCTS argument

* Correct more genereated files BYPRODUCTS

* BYPRODUCTS must have unique locations

* Fix typo

* Fix fortran configure checks

* Rework H5_PAC_C_MAX_REAL_PRECISION setting logic

* Add note about fortran configure change

* Adds a quick for for some egregious chunk_info badness (#722)

* Fixes issue with ccmake that prevents building Fortran (#723)

ccmake runs iteratively, and the check_fortran_source_runs
macros were clobbering a single output file that did not
get updated on further configure iterations

* Fix conflicts with merge

* Move MAX_PRECISION back to HDF5UseFortran.cmake

* Use STREQUAL to test macro argument

* Move C language test to ConfigureChecks from HDF5UseFortran

* MAX_PRECISION defines must be defined

* Organize flags and align autotools and cmake

* Fix comment in no-error-general warnings files.

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Dana Robinson <43805+derobins@users.noreply.github.com>

15 files changed, 252 insertions, 89 deletions

diff --git a/MANIFEST b/MANIFEST
index 09209d6..2defb86 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -198,6 +198,9 @@
 ./config/gnu-warnings/noerror-5
 ./config/gnu-warnings/noerror-8
 ./config/gnu-warnings/noerror-general
+./config/intel-warnings/15
+./config/intel-warnings/18
+./config/intel-warnings/developer-general
 ./config/intel-warnings/ifort-general
 ./config/intel-warnings/general
 
diff --git a/config/clang-warnings/noerror-general b/config/clang-warnings/noerror-general
index ad50dfc..4690ebd 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/HDFCXXCompilerFlags.cmake b/config/cmake/HDFCXXCompilerFlags.cmake
index 260bbe0..bd14a0d 100644
--- a/config/cmake/HDFCXXCompilerFlags.cmake
+++ b/config/cmake/HDFCXXCompilerFlags.cmake
@@ -86,9 +86,11 @@ if (NOT MSVC AND NOT MINGW)
     # warnings that are emitted. If you need it, add it at configure time.
     if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
       ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/general")
+      if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 15.0)
+        ADD_H5_FLAGS (H5_CXXFLAGS "${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 "${HDF5_SOURCE_DIR}/config/intel-warnings/18")
       endif()
     elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
       if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED
@@ -117,21 +119,20 @@ if (NOT MSVC AND NOT MINGW)
   #-----------------------------------------------------------------------------
   if (HDF5_ENABLE_DEV_WARNINGS)
     message (STATUS "....HDF5 developer group warnings are enabled")
-    #  if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
-    #    list (APPEND H5_CXXFLAGS "-Winline -Wreorder -Wport -Wstrict-aliasing")
-    #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-      # autotools always add the C flags with the CXX flags
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${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 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
-  #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-  #    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
+    elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/developer-general")
     endif ()
   else ()
     if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-      # autotools always add the C flags with the CXX flags
+      # Use the C warnings as CXX warnings are the same
       ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-general")
-  #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-  #    ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
+    elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/no-developer-general")
     endif ()
   endif ()
 
@@ -139,14 +140,15 @@ if (NOT MSVC AND NOT MINGW)
     # 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
+      # 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 4.8+ knows about
     if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
-      ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.8")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${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")
@@ -155,8 +157,7 @@ if (NOT MSVC AND NOT MINGW)
 
     # 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 "${HDF5_SOURCE_DIR}/config/gnu-warnings/4.9")
+      # Use the C warnings as CXX warnings are the same
       ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-4.9")
     endif ()
 
@@ -173,16 +174,16 @@ if (NOT MSVC AND NOT MINGW)
 
     # 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
+      # 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 7.x+ knows about
     if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0)
-      # autotools always add the C flags with the CXX flags
+      # Use the C warnings as CXX warnings are the same
       ADD_H5_FLAGS (H5_CXxFLAGS2 "${HDF5_SOURCE_DIR}/config/gnu-warnings/7")
       if (HDF5_ENABLE_DEV_WARNINGS)
-        # autotools always add the C flags with the CXX flags
+      # Use the C warnings as CXX warnings are the same
         ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-7")
       #else ()
       #  ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/no-developer-7")
@@ -191,15 +192,15 @@ if (NOT MSVC AND NOT MINGW)
 
     # 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
+      # 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 "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-8")
-      #endif ()
+      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
+      else ()
+        ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/noerror-8")
+      endif ()
       if (HDF5_ENABLE_DEV_WARNINGS)
-        # autotools always add the C flags with the CXX flags
+        # Use the C warnings as CXX warnings are the same
         ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
       else ()
         # autotools always add the C flags with the CXX flags
@@ -209,15 +210,26 @@ if (NOT MSVC AND NOT MINGW)
 
     # Append more extra warning flags that only gcc 9.x+ knows 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_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/9")
+      # Use the C warnings as CXX warnings are the same
       ADD_H5_FLAGS (H5_CXXFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-9")
     endif ()
-  endif ()
-else ()
-  if (NOT MINGW)
-    list (APPEND HDF5_CMAKE_CXX_FLAGS "/EHsc")
+
+    # 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 ()
 endif ()
 
 #-----------------------------------------------------------------------------
diff --git a/config/cmake/HDFCompilerFlags.cmake b/config/cmake/HDFCompilerFlags.cmake
index 0775f59..e38a92b 100644
--- a/config/cmake/HDFCompilerFlags.cmake
+++ b/config/cmake/HDFCompilerFlags.cmake
@@ -108,14 +108,13 @@ 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 "${HDF5_SOURCE_DIR}/config/intel-warnings/general")
-      list (APPEND H5_CFLAGS "-Wcomment -Wdeprecated -Wmain -Wmissing-declarations -Wmissing-prototypes -Wp64 -Wpointer-arith")
-      list (APPEND H5_CFLAGS "-Wreturn-type -Wstrict-prototypes -Wuninitialized")
-      list (APPEND H5_CFLAGS "-Wunknown-pragmas -Wunused-function -Wunused-variable")
+      if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 15.0)
+        ADD_H5_FLAGS (H5_CFLAGS "${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 "${HDF5_SOURCE_DIR}/config/intel-warnings/18")
       endif()
     elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU")
       # Add general CFlags for GCC versions 4.8 and above
@@ -153,7 +152,7 @@ if (NOT MSVC AND NOT MINGW)
   if (HDF5_ENABLE_DEV_WARNINGS)
     message (STATUS "....HDF5 developer group warnings are enabled")
     if (CMAKE_C_COMPILER_ID STREQUAL "Intel")
-      list (APPEND H5_CFLAGS "-Winline -Wreorder -Wport -Wstrict-aliasing")
+      ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/intel-warnings/developer-general")
     elseif (CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
       ADD_H5_FLAGS (H5_CFLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-general")
     elseif (CMAKE_C_COMPILER_ID MATCHES "[Cc]lang")
diff --git a/config/gnu-cxxflags b/config/gnu-cxxflags
index 4fe5782..63cd952 100644
--- a/config/gnu-cxxflags
+++ b/config/gnu-cxxflags
@@ -183,7 +183,6 @@ if test "X-g++" = "X-$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
 
@@ -239,30 +240,45 @@ 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
+    if test $cc_vers_major -ge 10 -o $cc_vers_major -eq 9 -a $cc_vers_minor -ge 3; then
+        # do not use C warnings, $(load_gnu_arguments 9.3), no cxx warnings
+        # H5_CXXFLAGS="$H5_CXXFLAGS $(load_gnu_arguments cxx-9.3)"
+    fi
+
+    # gcc >= 10
+    if test $cc_vers_major -ge 10; then
+        # Use the C warnings as CXX warnings are the same
+        DEVELOPER_WARNING_CFLAGS="$DEVELOPER_WARNING_CFLAGS $(load_gnu_arguments developer-10)"
+    fi
+
     #################
     # Flags are set #
     #################
diff --git a/config/gnu-flags b/config/gnu-flags
index 01533de..3e4ceb2 100644
--- a/config/gnu-flags
+++ b/config/gnu-flags
@@ -207,9 +207,9 @@ if test "X-gcc" = "X-$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
index d897de2..8f843a4 100644
--- a/config/gnu-warnings/cxx-9
+++ b/config/gnu-warnings/cxx-9
@@ -1,2 +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/noerror-general b/config/gnu-warnings/noerror-general
index 31194d3..f49d89a 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
index 3ef172f..900bcb9 100644
--- a/config/intel-cxxflags
+++ b/config/intel-cxxflags
@@ -16,6 +16,20 @@
 # 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 "$*"
+}
+
 # Get the compiler version in a way that works for icpc
 # icpc unless a compiler version is already known
 #
@@ -88,14 +102,13 @@ if test "X-icpc" = "X-$cxx_vendor"; then
     # Symbols #
     ###########
 
-    SYMBOLS_CXXFLAGS="-g"
     NO_SYMBOLS_CXXFLAGS="-Wl,-s"
+    SYMBOLS_CXXFLAGS="-g"
 
     #############
     # Profiling #
     #############
 
-    # Use this for profiling with gprof
     PROFILE_CXXFLAGS="-p"
 
     ################
@@ -110,18 +123,49 @@ if test "X-icpc" = "X-$cxx_vendor"; then
     # Warnings #
     ############
 
+# First load the C warnings then add CXX warnings (if needed)
+
+    ###########
+    # General #
+    ###########
+
+    # Add various general warning flags in intel-warnings.
+    H5_CXXFLAGS="$H5_CXXFLAGS $(load_intel_arguments general)"
+
+    ######################
+    # Developer warnings #
+    ######################
+
+    #NO_DEVELOPER_WARNING_CXXFLAGS=$(load_intel_arguments no-developer-general)
+    #DEVELOPER_WARNING_CXXFLAGS=$(load_intel_arguments developer-general)
+
     #############################
     # Version-specific warnings #
     #############################
 
+    # intel == 8.0
+    if test $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"
+    fi
+
+    # intel == 10
+    if test $cc_vers_major -eq 10; then
+        HIGH_OPT_CFLAGS="-O1"
+    fi
+
+    # intel >= 15
+    if test $cc_vers_major -ge 15; then
+        H5_CXXFLAGS="$H5_CXXFLAGS $(load_intel_arguments 15)"
+    fi
+
     #################
     # Flags are set #
     #################
     cxx_flags_set=yes
-
 fi
 
-# Clear cc info if no flags set
+# Clear cxx info if no flags set
 if test "X-$cxx_flags_set" = "X-"; then
     cxx_vendor=
     cxx_version=
diff --git a/config/intel-fflags b/config/intel-fflags
index b759dfa..2dcd901 100644
--- a/config/intel-fflags
+++ b/config/intel-fflags
@@ -58,11 +58,16 @@ 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 +83,56 @@ 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 $(load_intel_arguments ifort-general)"
+
+    #############################
+    # Version-specific warnings #
+    #############################
+
+
     #################
     # Flags are set #
     #################
@@ -116,4 +145,3 @@ if test "X-$f9x_flags_set" = "X-"; then
   f9x_version=
 fi
 
-
diff --git a/config/intel-flags b/config/intel-flags
index 409ffe9..fa317ab 100644
--- a/config/intel-flags
+++ b/config/intel-flags
@@ -82,22 +82,36 @@ if test "X-icc" = "X-$cc_vendor"; then
     # Default to C99 standard.
     H5_CFLAGS="$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 +124,40 @@ 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
 
     #################
     # Flags are set #
     #################
     cc_flags_set=yes
-
 fi
 
 # Clear cc info if no flags set
@@ -143,3 +165,4 @@ if test "X-$cc_flags_set" = "X-"; then
     cc_vendor=
     cc_version=
 fi
+
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..565b47a
--- /dev/null
+++ b/config/intel-warnings/18
@@ -0,0 +1,8 @@
+-Wextra-tokens
+-Wformat
+-Wformat-security
+-Wic-pointer
+-Wshadow
+-Wsign-compare
+-Wtrigraphs
+-Wwrite-strings
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