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, 49 insertions, 0 deletions

diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 2c65384..d2d6914 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -64,6 +64,55 @@ New Features
 
         (ADB - 2020/12/10, OESS-98)
 
+    - FreeBSD Autotools configuration now defaults to 'cc' and 'c++' compilers
+
+      On FreeBSD, the autotools defaulted to 'gcc' as the C compiler and did
+      not process C++ options. Since FreeBSD 10, the default compiler has
+      been clang (via 'cc').
+
+      The default compilers have been set to 'cc' for C and 'c++' for C++,
+      which will pick up clang and clang++ respectively on FreeBSD 10+.
+      Additionally, clang options are now set correctly for both C and C++
+      and g++ options will now be set if that compiler is being used (an
+      omission from the former functionality).
+
+      (DER - 2020/11/28, HDFFV-11193)
+
+    - Fixed POSIX problems when building w/ gcc on Solaris
+
+      When building on Solaris using gcc, the POSIX symbols were not
+      being set correctly, which could lead to issues like clock_gettime()
+      not being found.
+
+      The standard is now set to gnu99 when building with gcc on Solaris,
+      which allows POSIX things to be #defined and linked correctly. This
+      differs slightly from the gcc norm, where we set the standard to c99
+      and manually set POSIX #define symbols.
+
+      (DER - 2020/11/25, HDFFV-11191)
+
+    - Added a configure-time option to consider certain compiler warnings
+      as errors
+
+      A new configure-time option was added that converts some compiler warnings
+      to errors. This is mainly intended for library developers and currently
+      only works for gcc and clang. The warnings that are considered errors
+      will appear in the generated libhdf5.settings file. These warnings apply
+      to C and C++ code and will appear in "H5 C Flags" and H5 C++ Flags",
+      respectively. They will NOT be exported to h5cc, etc.
+
+      The default is OFF. Building with this option may fail when compiling
+      on operating systems and with compiler versions not commonly used by
+      the library developers. Compilation may also fail when headers not
+      under the control of the library developers (e.g., mpi.h, hdfs.h) raise
+      warnings.
+
+      Autotools:    --enable-warnings-as-errors
+
+      CMake:        HDF5_ENABLE_WARNINGS_AS_ERRORS
+
+      (DER - 2020/11/23, HDFFV-11189)
+
     - Autotools and CMake target added to produce doxygen generated documentation
 
         The default is OFF or disabled.