From 664fc6af47e369152727ff66d68d8532feb0e210 Mon Sep 17 00:00:00 2001
From: Jacob Smith <jake.smith@hdfgroup.org>
Date: Wed, 8 Apr 2020 16:51:38 -0500
Subject: Add enable-mirror-vfd flag to configure options.

---
 config/cmake/ConfigureChecks.cmake | 16 +++++++++++-----
 configure.ac                       | 38 ++++++++++++++++++++++++++------------
 2 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index 1c3d5f9..5a401f7 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -175,11 +175,17 @@ endif ()
 # Check whether we can build the Mirror VFD 
 # Header-check flags set in config/cmake_ext_mod/ConfigureChecks.cmake
 # ----------------------------------------------------------------------
-if ( ${HDF_PREFIX}_HAVE_NETINET_IN_H AND
-     ${HDF_PREFIX}_HAVE_NETDB_H      AND
-     ${HDF_PREFIX}_HAVE_ARPA_INET_H  AND
-     ${HDF_PREFIX}_HAVE_SYS_SOCKET_H)
-    set (${HDF_PREFIX}_HAVE_MIRROR_VFD 1)
+option (HDF5_ENABLE_MIRROR_VFD "Build the Mirror Virtual File Driver" OFF)
+if (H5FD_ENABLE_MIRROR_VFD)
+  if ( ${HDF_PREFIX}_HAVE_NETINET_IN_H AND
+       ${HDF_PREFIX}_HAVE_NETDB_H      AND
+       ${HDF_PREFIX}_HAVE_ARPA_INET_H  AND
+       ${HDF_PREFIX}_HAVE_SYS_SOCKET_H AND
+       ${HDF_PREFIX}_HAVE_FORK)
+      set (${HDF_PREFIX}_HAVE_MIRROR_VFD 1)
+  else()
+    message(STATUS "The socket-based Mirror VFD was requested but cannot be built. System prerequisites are not met.")
+  endif()
 endif()
 
 #-----------------------------------------------------------------------------
diff --git a/configure.ac b/configure.ac
index e6d7535..81e985e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2849,24 +2849,38 @@ AM_CONDITIONAL([DIRECT_VFD_CONDITIONAL], [test "X$DIRECT_VFD" = "Xyes"])
 AC_SUBST([MIRROR_VFD])
 
 ## Default is no Mirror VFD
-MIRROR_VFD=yes
+MIRROR_VFD=no
 
-AC_CHECK_HEADERS([arpa/inet.h],, [unset MIRROR_VFD])
-AC_CHECK_HEADERS([netinet/in.h],, [unset MIRROR_VFD])
-AC_CHECK_HEADERS([netdb.h],, [unset MIRROR_VFD])
-AC_CHECK_HEADERS([sys/socket.h],, [unset MIRROR_VFD])
+AC_ARG_ENABLE([mirror-vfd],
+              [AS_HELP_STRING([--enable-mirror-vfd],
+                              [Build the socket-based Mirror virtual file driver (VFD).
+                               [default=no]])],
+              [MIRROR_VFD=$enableval], [MIRROR_VFD=no])
 
-AC_MSG_CHECKING([if the Mirror virtual file driver (VFD) can be built])
 if test "X$MIRROR_VFD" = "Xyes"; then
-    AC_DEFINE([HAVE_MIRROR_VFD], [1],
-            [Define whether the Mirror virtual file driver (VFD) will be compiled])
-    AC_MSG_RESULT([yes])
+
+    AC_CHECK_HEADERS([arpa/inet.h],, [unset MIRROR_VFD])
+    AC_CHECK_HEADERS([netinet/in.h],, [unset MIRROR_VFD])
+    AC_CHECK_HEADERS([netdb.h],, [unset MIRROR_VFD])
+    AC_CHECK_HEADERS([sys/socket.h],, [unset MIRROR_VFD])
+    AC_CHECK_FUNC([fork], [], [unset MIRROR_VFD])
+
+    AC_MSG_CHECKING([if the Mirror virtual file driver (VFD) can be built])
+    if test "X$MIRROR_VFD" = "Xyes"; then
+        AC_DEFINE([HAVE_MIRROR_VFD], [1],
+                [Define whether the Mirror virtual file driver (VFD) will be compiled])
+        AC_MSG_RESULT([yes])
+    else
+        AC_MSG_RESULT([no])
+        MIRROR_VFD=no
+        AC_MSG_ERROR([The Mirror VFD cannot be built.
+                      Missing one or more of: arpa/inet.h, netinet/in.h,
+                      netdb.h, sys/socket.h, fork().])
+    fi
 else
+    AC_MSG_CHECKING([if the Mirror virtual file driver (VFD) is enabled])
     AC_MSG_RESULT([no])
     MIRROR_VFD=no
-    AC_MSG_ERROR([The Mirror VFD cannot be built.
-                  Missing any of: arpa/inet.h, netinet/in.h, netdb.h,
-                  sys/socket.h.])
 fi
 
 ## Mirror VFD files built only if able.
-- 
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