Warnings merge 110 (#300)

* 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

* Merge dev warnings refactor from develop

1 files changed, 39 insertions, 8 deletions

diff --git a/configure.ac b/configure.ac
index e91f06f..9296080 100644
--- a/configure.ac
+++ b/configure.ac
@@ -104,14 +104,10 @@ AC_SUBST([AR_FLAGS])
 ## H5_CFLAGS (and company) are for CFLAGS that should be used on HDF5, but
 ## not exported to h5cc (or h5fc, etc.)
 ##
-## H5_ECFLAGS (and company) are for warnings that should be treated as errors.
-##
 AC_SUBST([H5_CFLAGS])
-AC_SUBST([H5_ECFLAGS])
 AC_SUBST([H5_CPPFLAGS])
 AC_SUBST([H5_FCFLAGS])
 AC_SUBST([H5_CXXFLAGS])
-AC_SUBST([H5_ECXXFLAGS])
 AC_SUBST([H5_JNIFLAGS])
 AC_SUBST([H5_JAVACFLAGS])
 AC_SUBST([H5_JAVAFLAGS])
@@ -2248,10 +2244,6 @@ if test "X-$DEV_WARNINGS" = X- ; then
   DEV_WARNINGS=no
 fi
 
-## Allow this variable to be substituted in
-## other files (src/libhdf5.settings.in, etc.)
-AC_SUBST([DEV_WARNINGS])
-
 case "X-$DEV_WARNINGS" in
   X-yes)
     H5_CFLAGS="$H5_CFLAGS $DEVELOPER_WARNING_CFLAGS"
@@ -2267,6 +2259,45 @@ case "X-$DEV_WARNINGS" in
 esac
 
 ## ----------------------------------------------------------------------
+## Check if we should consider certain compiler warnings as errors
+##
+## These should NOT be on by default as the risk of breakage is high
+## when compiling HDF5 on new (or new versions) of platforms and
+## compilers. It can also cause failures when header files we have no
+## control over (e.g. MPI, HDFS) raise warnings.
+##
+AC_MSG_CHECKING([enable warnings as errors])
+AC_ARG_ENABLE([warnings-as-errors],
+              [AS_HELP_STRING([--enable-warnings-as-errors],
+                              [Determines whether certain warnings will be
+                               considered errors. This is mainly for use
+                               by HDF5 library developers.
+                               [default=no]
+                               ])],
+              [WARNINGS_AS_ERRORS=$enableval])
+
+## Set default
+if test "X-$WARNINGS_AS_ERRORS" = X- ; then
+  WARNINGS_AS_ERRORS=no
+fi
+
+case "X-$WARNINGS_AS_ERRORS" in
+  X-yes)
+    H5_CFLAGS="$H5_CFLAGS $H5_ECFLAGS"
+    H5_CXXFLAGS="$H5_CXXFLAGS $H5_ECXXFLAGS"
+    AC_MSG_RESULT([yes])
+    ;;
+  X-no)
+    H5_CFLAGS="$H5_CFLAGS $H5_NECFLAGS"
+    H5_CXXFLAGS="$H5_CXXFLAGS $H5_NECXXFLAGS"
+    AC_MSG_RESULT([no])
+    ;;
+  *)
+    AC_MSG_ERROR([Unrecognized value: $WARNINGS_AS_ERRORS])
+    ;;
+esac
+
+## ----------------------------------------------------------------------
 ## Check if the compiler should use profiling flags/settings
 ##
 AC_MSG_CHECKING([profiling])