From c2577ddbbcbaf3cd367bc36dac4e5413d6da84cc Mon Sep 17 00:00:00 2001
From: Dana Robinson <derobins@hdfgroup.org>
Date: Sat, 16 Mar 2024 00:26:05 -0700
Subject: [PATCH] Clean up CMake direct VFD handling

There's no need to build and run programs, or even check the operating
system. We just need to check for O_DIRECT and posix_memalign().
---
 config/cmake/ConfigureChecks.cmake     | 48 ++++++++------------------
 config/cmake/HDFTests.c                | 23 ------------
 config/cmake/libhdf5.settings.cmake.in |  2 +-
 3 files changed, 16 insertions(+), 57 deletions(-)

diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index 668739e7074..62c053f49a2 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -653,38 +653,20 @@ unset (CMAKE_EXTRA_INCLUDE_FILES)
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
-#  Check if Direct I/O driver works
-#-----------------------------------------------------------------------------
-if (NOT WINDOWS)
-  option (HDF5_ENABLE_DIRECT_VFD "Build the Direct I/O Virtual File Driver" OFF)
-  if (HDF5_ENABLE_DIRECT_VFD)
-    set (msg "Performing TEST_DIRECT_VFD_WORKS")
-    set (MACRO_CHECK_FUNCTION_DEFINITIONS "-DTEST_DIRECT_VFD_WORKS -D_GNU_SOURCE ${CMAKE_REQUIRED_FLAGS}")
-    TRY_RUN (TEST_DIRECT_VFD_WORKS_RUN   TEST_DIRECT_VFD_WORKS_COMPILE
-        ${CMAKE_BINARY_DIR}
-        ${HDF_RESOURCES_DIR}/HDFTests.c
-        CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_FUNCTION_DEFINITIONS}
-        OUTPUT_VARIABLE OUTPUT
-    )
-    if (TEST_DIRECT_VFD_WORKS_COMPILE)
-      if (TEST_DIRECT_VFD_WORKS_RUN EQUAL "0")
-        HDF_FUNCTION_TEST (HAVE_DIRECT)
-        set (CMAKE_REQUIRED_DEFINITIONS "${CMAKE_REQUIRED_DEFINITIONS} -D_GNU_SOURCE")
-        add_definitions ("-D_GNU_SOURCE")
-      else ()
-        set (TEST_DIRECT_VFD_WORKS "" CACHE INTERNAL ${msg})
-        message (VERBOSE "${msg}... no")
-        file (APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeError.log
-              "Test TEST_DIRECT_VFD_WORKS Run failed with the following output and exit code:\n ${OUTPUT}\n"
-        )
-      endif ()
-    else ()
-      set (TEST_DIRECT_VFD_WORKS "" CACHE INTERNAL ${msg})
-      message (VERBOSE "${msg}... no")
-      file (APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeError.log
-          "Test TEST_DIRECT_VFD_WORKS Compile failed with the following output:\n ${OUTPUT}\n"
-      )
-    endif ()
+# Check whether we can build the direct VFD
+#-----------------------------------------------------------------------------
+option (HDF5_ENABLE_DIRECT_VFD "Build the Direct I/O Virtual File Driver" OFF)
+if (HDF5_ENABLE_DIRECT_VFD)
+  # The direct VFD is tied to POSIX direct I/O as enabled by the O_DIRECT
+  # flag. No other form of direct I/O is supported. This feature also
+  # requires posix_memalign().
+  check_symbol_exists(O_DIRECT "fcntl.h" HAVE_O_DIRECT)
+  check_symbol_exists(posix_memalign "stdlib.h" HAVE_POSIX_MEMALIGN)
+
+  if (HAVE_O_DIRECT AND HAVE_POSIX_MEMALIGN)
+    set (${HDF_PREFIX}_HAVE_DIRECT 1)
+  else ()
+      message (FATAL_ERROR "The direct VFD was requested but cannot be built.\nIt requires O_DIRECT flag support and posix_memalign()")
   endif ()
 endif ()
 
@@ -705,7 +687,7 @@ option (HDF5_ENABLE_ROS3_VFD "Build the ROS3 Virtual File Driver" OFF)
 endif ()
 
 # ----------------------------------------------------------------------
-# Check whether we can build the Mirror VFD
+# Check whether we can build the mirror VFD
 # ----------------------------------------------------------------------
 option (HDF5_ENABLE_MIRROR_VFD "Build the Mirror Virtual File Driver" OFF)
 if (HDF5_ENABLE_MIRROR_VFD)
diff --git a/config/cmake/HDFTests.c b/config/cmake/HDFTests.c
index 3d16721346c..bcfec284299 100644
--- a/config/cmake/HDFTests.c
+++ b/config/cmake/HDFTests.c
@@ -89,29 +89,6 @@ int main ()
 
 #endif /* DEV_T_IS_SCALAR */
 
-#ifdef TEST_DIRECT_VFD_WORKS
-
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-
-int main(void)
-{
-    int fid;
-
-    if ((fid = open("tst_file", O_CREAT | O_TRUNC | O_DIRECT, 0755)) < 0)
-        return 1;
-    close(fid);
-    remove("tst_file");
-
-    return 0;
-}
-#endif
-
-#ifdef HAVE_DIRECT
-       SIMPLE_TEST(posix_memalign());
-#endif
-
 #ifdef HAVE_DEFAULT_SOURCE
 /* Check default source */
 #include <features.h>
diff --git a/config/cmake/libhdf5.settings.cmake.in b/config/cmake/libhdf5.settings.cmake.in
index f60f0def177..abf33c734f2 100644
--- a/config/cmake/libhdf5.settings.cmake.in
+++ b/config/cmake/libhdf5.settings.cmake.in
@@ -79,7 +79,7 @@ Dimension scales w/ new references: @DIMENSION_SCALES_WITH_NEW_REF@
     With deprecated public symbols: @HDF5_ENABLE_DEPRECATED_SYMBOLS@
             I/O filters (external): @EXTERNAL_FILTERS@
                      Map (H5M) API: @H5_HAVE_MAP_API@
-                        Direct VFD: @H5_HAVE_DIRECT@
+                        Direct VFD: @HDF5_ENABLE_DIRECT_VFD@
                         Mirror VFD: @H5_HAVE_MIRROR_VFD@
                      Subfiling VFD: @H5_HAVE_SUBFILING_VFD@
                 (Read-Only) S3 VFD: @H5_HAVE_ROS3_VFD@