Fix assertion failure when attempting to use IOC VFD directly

release_docs/RELEASE.txt

@@ -249,6 +249,17 @@ Bug Fixes since HDF5-1.14.0 release
 ===================================
  Library
  -------
+ - Fixed an assertion failure when attempting to use the Subfiling IOC
+ VFD directly
+
+ The Subfiling feature makes use of two Virtual File Drivers, the
+ Subfiling VFD and the IOC (I/O Concentrator) VFD. The two VFDs are
+ intended to be stacked together such that the Subfiling VFD sits
+ "on top" of the IOC VFD and routes I/O requests through it; using the
+ IOC VFD alone is currently unsupported. The IOC VFD has been fixed so
+ that an error message is displayed in this situation rather than causing
+ an assertion failure.
+
  - Fixed a potential bug when copying empty enum datatypes
 
  Copying an empty enum datatype (including implicitly, as when an enum

src/H5FDsubfiling/H5FDioc.c

@@ -819,6 +819,19 @@ H5FD__ioc_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
  /* Retrieve the HDF5 stub file ID for the current file */
  if (H5_subfiling_get_file_id_prop(plist_ptr, &file_ptr->file_id) < 0)
  H5_SUBFILING_GOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get stub file ID from FAPL");
+ if (file_ptr->file_id == UINT64_MAX) {
+ /* Since this VFD does no displaying of error stacks itself
+ * (it relies on the Subfiling VFD to do this), we must print
+ * the error stack here if we know it wasn't stacked under the
+ * Subfiling VFD.
+ */
+ H5_SUBFILING_DONE_ERROR(
+ H5E_PLIST, H5E_BADVALUE, NULL,
+ "subfiling stub file ID property was missing from FAPL - IOC VFD wasn't correctly stacked under "
+ "the Subfiling VFD and cannot currently be used alone");
+ PRINT_ERROR_STACK;
+ goto done;
+ }
 
  /*
  * Open the subfiles for this HDF5 file. A subfiling

testpar/CMakeTests.cmake

@@ -99,6 +99,7 @@ set (test_par_CLEANFILES
  MPItest.h5
  ShapeSameTest.h5
  test_subfiling_basic_create.h5
+ test_subfiling_only_ioc_fail.h5
  test_subfiling_config_file.h5
  test_subfiling_stripe_sizes.h5
  test_subfiling_selection_strategies.h5

testpar/t_subfiling_vfd.c

@@ -91,6 +91,7 @@ static hid_t create_subfiling_ioc_fapl(MPI_Comm comm, MPI_Info info, hbool_t cus
 
 /* Test functions */
 static void test_create_and_close(void);
+static void test_ioc_only_fail(void);
 static void test_config_file(void);
 static void test_stripe_sizes(void);
 static void test_selection_strategies(void);
@@ -102,6 +103,7 @@ static void test_subfiling_h5fuse(void);
 
 static test_func tests[] = {
  test_create_and_close,
+ test_ioc_only_fail,
  test_config_file,
  test_stripe_sizes,
  test_selection_strategies,
@@ -218,6 +220,45 @@ test_create_and_close(void)
 }
 #undef SUBF_FILENAME
 
+/*
+ * A simple test that ensures file creation fails when
+ * attempting to use the IOC VFD by itself, without it
+ * being stacked under the Subfiling VFD. This is
+ * currently unsupported.
+ */
+#define SUBF_FILENAME "test_subfiling_only_ioc_fail.h5"
+static void
+test_ioc_only_fail(void)
+{
+ hid_t file_id = H5I_INVALID_HID;
+ hid_t fapl_id = H5I_INVALID_HID;
+
+ curr_nerrors = nerrors;
+
+ if (MAINPROCESS)
+ TESTING_2("invalid use of IOC VFD by itself");
+
+ /* Setup a FAPL using only the IOC VFD */
+ fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+ VRFY((fapl_id >= 0), "H5Pcreate succeeded");
+
+ VRFY((H5Pset_mpi_params(fapl_id, comm_g, info_g) >= 0), "H5Pset_mpi_params succeeded");
+
+ VRFY((H5Pset_fapl_ioc(fapl_id, NULL) >= 0), "H5Pset_fapl_ioc succeeded");
+
+ H5E_BEGIN_TRY
+ {
+ file_id = H5Fcreate(SUBF_FILENAME, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
+ }
+ H5E_END_TRY;
+ VRFY((file_id < 0), "H5Fcreate failed successfully");
+
+ VRFY((H5Pclose(fapl_id) >= 0), "FAPL close succeeded");
+
+ CHECK_PASSED();
+}
+#undef SUBF_FILENAME
+
 /*
  * Test to check that Subfiling configuration file matches
  * what is expected for a given configuration