Hdf5 1 10 merge warnings changes (#756)

* HDFFV-10865 - merge from dev, HDFArray perf fix.

* Remove duplicate setting

* Whitespace changes after clang format

* Undo version 11 clang format changes

* Merge CMake changes from develop

* test testing script merge from develop

* Update supported platforms

* PR#3 merge from develop

* Merge gcc 10 diagnostics option from develop

* Merge #318 OSX changes from develop

* Merge small changes from develop

* Minor non-space formatting changes

* #386 copyright corrections for java folder

* Merges from develop

#358 patches from vtk
#361 fix header guard spelling

* Merge updates

#358 patches from vtk
#361 fix header guard spelling

* format fix

* Fix missing underscore and make H5public.h closer to dev

* Merges from develop

#340 clang -Wformat-security warnings
#360 Fixed uninitialized warnings
header guard underscore cleanup
JNI cleanup

* format alignment

* Add missing test ref file

* Merge #380 from develop

* Finish java merges from develop

* Fix java issues with tests and javadoc

* Correct use of attribute access plist

* Remove debug code

* Remove unused variable

* Change file access to read only for java tests

* Split clang format operations.

* More javadoc comments

* Remove pre-split setting

* format source

* Change windows TS to use older VS.

* Mostly all javadoc fixes, one argument rename.

* synch file

* Merge of long double fix and compiler flags

* HDFFV-11229 merge changes from develop

* HDFFV-11229 correct test script

* HDFFV-11229 update autotools test script for two ref files

* HDFFV-11229 merge dev changes for long double display in tools

* Committing clang-format changes

* minor whitespace

* remove unneeded macro

* Committing clang-format changes

* Add "option" command for clang options

* Rework CMake add_custom to use the BYPRODUCTS argument

Update pkgconfig scripts for parallel builds.
Fix install COPYING file reference.
Remove unused round defines.
Change CMake default setting of BUILD_CPP to off.

* Fortran target depends

* Remove incorrect source attribute

* Revert define removal

* printf specifiers and VS2015 min changes

* Committing clang-format changes

* Add time struct

* TRILAB-227 and tools debug merges from develop

* Merge various changes from dev

* Issue #669 remove version from pkgcfg filename

* remove version from h5cc script

* doxygen changes merged from develop

* Committing clang-format changes

* Merge CMake fortran ninja changes from dev

* Enable fortran to gcc yaml

* Refactor Fortran CMake config tests and CMake test args

* Merge warnings files fixes from develop

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

MANIFEST

@@ -136,6 +136,7 @@
 ./config/cygwin
 ./config/ibm-aix
 ./config/ibm-flags
+./config/intel-cxxflags
 ./config/intel-fflags
 ./config/intel-flags
 ./config/libhdf5.pc.in
@@ -147,6 +148,7 @@
 ./config/lt_vers.am
 ./config/Makefile.am.blank
 ./config/netbsd
+./config/pgi-cxxflags
 ./config/pgi-fflags
 ./config/pgi-flags
 ./config/solaris
@@ -172,6 +174,7 @@
 ./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
@@ -196,8 +199,12 @@
 ./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/general-19
+./config/intel-warnings/ifort-general
 
 ./config/site-specific/BlankForm
 

config/clang-cxxflags

@@ -113,18 +113,6 @@ if test "X-clang" = "X-$cxx_vendor" -o "X-Apple LLVM" = "X-$cxx_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-*)
-            ;;
-
-        *)
-            H5_CXXFLAGS="$H5_CXXFLAGS -std=c++11"
-            ;;
-    esac
-
     H5_CXXFLAGS="$H5_CXXFLAGS $arch"
 
     ##############

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

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 "${HDF5_SOURCE_DIR}/config/intel-warnings/18")
       endif()
     elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
       if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_LOADED
@@ -117,36 +119,36 @@ if (NOT MSVC AND NOT MINGW)
   #-----------------------------------------------------------------------------
   if (HDF5_ENABLE_DEV_WARNINGS)
     message (STATUS "....HDF5 developer group warnings are enabled")
-  #  if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
-  #    list (APPEND H5_CXXFLAGS "-Winline -Wreorder -Wport -Wstrict-aliasing")
-  #  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-      # autotools always add the C flags with the CXX flags
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+      ADD_H5_FLAGS (H5_CXXFLAGS "${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 ()
 
   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
+      # 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
@@ -209,14 +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 ()
 
 #-----------------------------------------------------------------------------

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")

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
 
     #################

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)

config/gnu-warnings/cxx-4.9

@@ -1 +1,2 @@
+-Wdate-time
 -Wopenmp-simd

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

config/gnu-warnings/developer-10

@@ -1,6 +1,2 @@
 # New warning
 -Warith-conversion
-
-# Enable static analysis of program flow
--fanalyzer
--fdiagnostics-path-format=none

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