Adds a configure/CMake option to control -Werror behavior (#119)

* Works in both Autotools and CMake
* OFF by default
* Reverts "always on" -Werror behavior released in 1.10.7

6 files changed, 95 insertions, 19 deletions

diff --git a/config/cmake/HDFCXXCompilerFlags.cmake b/config/cmake/HDFCXXCompilerFlags.cmake
index 7bbebbc..8443bbd 100644
--- a/config/cmake/HDFCXXCompilerFlags.cmake
+++ b/config/cmake/HDFCXXCompilerFlags.cmake
@@ -89,7 +89,9 @@ if (NOT MSVC AND NOT MINGW)
           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_CXXFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-general")
+        endif ()
       endif ()
     elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
       ADD_H5_FLAGS (HDF5_CMAKE_CXX_FLAGS "${HDF5_SOURCE_DIR}/config/clang-warnings/general")
@@ -152,7 +154,9 @@ if (NOT MSVC AND NOT MINGW)
     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")
+      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+        ADD_H5_FLAGS (H5_CXXFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/cxx-error-5")
+      endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 6.x+ know about
@@ -177,7 +181,9 @@ if (NOT MSVC AND NOT MINGW)
     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")
+      #if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+      #  ADD_H5_FLAGS (H5_CXXFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
+      #endif ()
       if (HDF5_ENABLE_DEV_WARNINGS)
         # autotools always add the C flags with the CXX flags
         ADD_H5_FLAGS (H5_CXXFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
diff --git a/config/cmake/HDFCompilerFlags.cmake b/config/cmake/HDFCompilerFlags.cmake
index 31af2f8..456db36 100644
--- a/config/cmake/HDFCompilerFlags.cmake
+++ b/config/cmake/HDFCompilerFlags.cmake
@@ -69,6 +69,18 @@ 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 (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
     list (APPEND HDF5_CMAKE_C_FLAGS "-erroff=%none -DBSD_COMP")
   else ()
@@ -96,14 +108,18 @@ if (NOT MSVC AND NOT MINGW)
       # Add general CFlags for GCC versions 4.8 and above
       if (CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 4.8)
         ADD_H5_FLAGS (HDF5_CMAKE_C_FLAGS "${HDF5_SOURCE_DIR}/config/gnu-warnings/general")
-        ADD_H5_FLAGS (H5_CFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-general")
+        if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+          ADD_H5_FLAGS (H5_CFLAGS0 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-general")
+        endif ()
       endif ()
       # gcc automatically inlines based on the optimization level
       # this is just a failsafe
       list (APPEND H5_CFLAGS0 "-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_CFLAGS0 "${HDF5_SOURCE_DIR}/config/clang-warnings/error-general")
+      endif ()
     elseif (CMAKE_C_COMPILER_ID STREQUAL "PGI")
       list (APPEND HDF5_CMAKE_C_FLAGS "-Minform=inform")
     endif ()
@@ -132,7 +148,6 @@ if (NOT MSVC AND NOT MINGW)
     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
@@ -158,7 +173,9 @@ if (NOT MSVC AND NOT MINGW)
     # 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")
+      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+        ADD_H5_FLAGS (H5_CFLAGS1 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-5")
+      endif ()
     endif ()
 
     # Append more extra warning flags that only gcc 6.x+ know about
@@ -179,7 +196,9 @@ if (NOT MSVC AND NOT MINGW)
     # 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")
+      if (HDF5_ENABLE_WARNINGS_AS_ERRORS)
+        ADD_H5_FLAGS (H5_CFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/error-8")
+      endif ()
       if (HDF5_ENABLE_DEV_WARNINGS)
         ADD_H5_FLAGS (H5_CFLAGS3 "${HDF5_SOURCE_DIR}/config/gnu-warnings/developer-8")
       else ()
diff --git a/config/commence.am b/config/commence.am
index e73352c..f47d704 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/configure.ac b/configure.ac
index f6b8423..2a02109 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 $DEVELOPER_WARNING_CFLAGS"
@@ -2267,6 +2259,43 @@ case "X-$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)
+    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])
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 1b6a097..67fbe51 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -47,6 +47,28 @@ New Features
 
     Configuration:
     -------------
+    - 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.
diff --git a/src/libhdf5.settings.in b/src/libhdf5.settings.in
index 98390b8..4fddbc8 100644
--- a/src/libhdf5.settings.in
+++ b/src/libhdf5.settings.in
@@ -39,7 +39,7 @@ Languages:
                     H5_CPPFLAGS: @H5_CPPFLAGS@
                     AM_CPPFLAGS: @AM_CPPFLAGS@
                         C Flags: @CFLAGS@
-                     H5 C Flags: @H5_CFLAGS@ @H5_ECFLAGS@
+                     H5 C Flags: @H5_CFLAGS@
                      AM C Flags: @AM_CFLAGS@
                Shared C Library: @enable_shared@
                Static C Library: @enable_static@