Merge of recent develop work to 1.10 branch:

* H5FD_FEAT_DEFAULT_VFD_COMPATIBLE VFD feature flag (HDFFV-10214)
* H5FDdriver_query() API call (HDFFV-10215)
* Fix to skip SWMR tests that when the current VFD is not compatible
  with the default VFD (HDFFV-10197)
* Removed obsolete compiler versions from config/gnu-flags (HDFFV-9937)
* Many warning fixes

19 files changed, 241 insertions, 185 deletions

diff --git a/src/H5Dint.c b/src/H5Dint.c
index 1813ca6..08b3eb8 100644
--- a/src/H5Dint.c
+++ b/src/H5Dint.c
@@ -3004,10 +3004,10 @@ H5D__format_convert(H5D_t *dataset, hid_t dxpl_id)
 {
     H5D_chk_idx_info_t new_idx_info;    	/* Index info for the new layout */
     H5D_chk_idx_info_t idx_info;        	/* Index info for the current layout */
-    H5O_layout_t newlayout;			/* The new layout */
-    hbool_t init_new_index = FALSE;		/* Indicate that the new chunk index is initialized */
+    H5O_layout_t *newlayout = NULL;         /* The new layout */
+    hbool_t init_new_index = FALSE;         /* Indicate that the new chunk index is initialized */
     hbool_t delete_old_layout = FALSE;		/* Indicate that the old layout message is deleted */
-    hbool_t add_new_layout = FALSE;		/* Indicate that the new layout message is added */
+    hbool_t add_new_layout = FALSE;         /* Indicate that the new layout message is added */
     herr_t ret_value = SUCCEED;         	/* Return value */
 
     FUNC_ENTER_PACKAGE_TAG(dxpl_id, dataset->oloc.addr, FAIL)
@@ -3017,121 +3017,127 @@ H5D__format_convert(H5D_t *dataset, hid_t dxpl_id)
 
     switch(dataset->shared->layout.type) {
         case H5D_CHUNKED:
-	    HDassert(dataset->shared->layout.u.chunk.idx_type != H5D_CHUNK_IDX_BTREE);
-
-	    /* Set up the current index info */
-	    idx_info.f = dataset->oloc.file;
-	    idx_info.dxpl_id = dxpl_id;
-	    idx_info.pline = &dataset->shared->dcpl_cache.pline;
-	    idx_info.layout = &dataset->shared->layout.u.chunk;
-	    idx_info.storage = &dataset->shared->layout.storage.u.chunk;
-
-	    /* Copy the current layout info to the new layout */
-	    HDmemcpy(&newlayout, &dataset->shared->layout, sizeof(H5O_layout_t));
-
-	    /* Set up info for version 1 B-tree in the new layout */
-	    newlayout.version = H5O_LAYOUT_VERSION_3;
-	    newlayout.storage.u.chunk.idx_type = H5D_CHUNK_IDX_BTREE;
-	    newlayout.storage.u.chunk.idx_addr = HADDR_UNDEF;
-	    newlayout.storage.u.chunk.ops = H5D_COPS_BTREE;
-	    newlayout.storage.u.chunk.u.btree.shared = NULL;
-
-	    /* Set up the index info to version 1 B-tree */
-	    new_idx_info.f = dataset->oloc.file;
-	    new_idx_info.dxpl_id = dxpl_id;
-	    new_idx_info.pline = &dataset->shared->dcpl_cache.pline;
-	    new_idx_info.layout = &newlayout.u.chunk;
-	    new_idx_info.storage = &newlayout.storage.u.chunk;
-
-	    /* Initialize version 1 B-tree */
-	    if(new_idx_info.storage->ops->init && 
-              (new_idx_info.storage->ops->init)(&new_idx_info, dataset->shared->space, dataset->oloc.addr) < 0)
-		HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize indexing information")
-	    init_new_index = TRUE;
-
-	    /* If the current chunk index exists */
-	    if(H5F_addr_defined(idx_info.storage->idx_addr)) {
-
-		/* Create v1 B-tree chunk index */
-		if((new_idx_info.storage->ops->create)(&new_idx_info) < 0)
-		    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't create chunk index")
-
-		/* Iterate over the chunks in the current index and insert the chunk addresses 
-		 * into the version 1 B-tree chunk index */
-		if(H5D__chunk_format_convert(dataset, &idx_info, &new_idx_info) < 0)
-		    HGOTO_ERROR(H5E_DATASET, H5E_BADITER, FAIL, "unable to iterate/convert chunk index")
-	    } /* end if */
+            HDassert(dataset->shared->layout.u.chunk.idx_type != H5D_CHUNK_IDX_BTREE);
+
+            if(NULL == (newlayout = (H5O_layout_t *)H5MM_calloc(sizeof(H5O_layout_t))))
+                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate buffer")
+
+            /* Set up the current index info */
+            idx_info.f = dataset->oloc.file;
+            idx_info.dxpl_id = dxpl_id;
+            idx_info.pline = &dataset->shared->dcpl_cache.pline;
+            idx_info.layout = &dataset->shared->layout.u.chunk;
+            idx_info.storage = &dataset->shared->layout.storage.u.chunk;
+
+            /* Copy the current layout info to the new layout */
+            HDmemcpy(newlayout, &dataset->shared->layout, sizeof(H5O_layout_t));
+
+            /* Set up info for version 1 B-tree in the new layout */
+            newlayout->version = H5O_LAYOUT_VERSION_3;
+            newlayout->storage.u.chunk.idx_type = H5D_CHUNK_IDX_BTREE;
+            newlayout->storage.u.chunk.idx_addr = HADDR_UNDEF;
+            newlayout->storage.u.chunk.ops = H5D_COPS_BTREE;
+            newlayout->storage.u.chunk.u.btree.shared = NULL;
+
+            /* Set up the index info to version 1 B-tree */
+            new_idx_info.f = dataset->oloc.file;
+            new_idx_info.dxpl_id = dxpl_id;
+            new_idx_info.pline = &dataset->shared->dcpl_cache.pline;
+            new_idx_info.layout = &(newlayout->u).chunk;
+            new_idx_info.storage = &(newlayout->storage).u.chunk;
+
+            /* Initialize version 1 B-tree */
+            if(new_idx_info.storage->ops->init && (new_idx_info.storage->ops->init)(&new_idx_info, dataset->shared->space, dataset->oloc.addr) < 0)
+                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize indexing information")
+            init_new_index = TRUE;
+
+            /* If the current chunk index exists */
+            if(H5F_addr_defined(idx_info.storage->idx_addr)) {
+
+                /* Create v1 B-tree chunk index */
+                if((new_idx_info.storage->ops->create)(&new_idx_info) < 0)
+                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't create chunk index")
+
+                /* Iterate over the chunks in the current index and insert the chunk addresses 
+                 * into the version 1 B-tree chunk index
+                 */
+                if(H5D__chunk_format_convert(dataset, &idx_info, &new_idx_info) < 0)
+                    HGOTO_ERROR(H5E_DATASET, H5E_BADITER, FAIL, "unable to iterate/convert chunk index")
+            } /* end if */
 
-	    /* Delete the old "current" layout message */
-	    if(H5O_msg_remove(&dataset->oloc, H5O_LAYOUT_ID, H5O_ALL, FALSE, dxpl_id) < 0)
-		HGOTO_ERROR(H5E_SYM, H5E_CANTDELETE, FAIL, "unable to delete layout message")
+            /* Delete the old "current" layout message */
+            if(H5O_msg_remove(&dataset->oloc, H5O_LAYOUT_ID, H5O_ALL, FALSE, dxpl_id) < 0)
+                HGOTO_ERROR(H5E_SYM, H5E_CANTDELETE, FAIL, "unable to delete layout message")
 
-	    delete_old_layout = TRUE;
+            delete_old_layout = TRUE;
 
-	    /* Append the new layout message to the object header */
-	    if(H5O_msg_create(&dataset->oloc, H5O_LAYOUT_ID, 0, H5O_UPDATE_TIME, &newlayout, dxpl_id) < 0)
-		HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to update layout header message")
+            /* Append the new layout message to the object header */
+            if(H5O_msg_create(&dataset->oloc, H5O_LAYOUT_ID, 0, H5O_UPDATE_TIME, newlayout, dxpl_id) < 0)
+                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to update layout header message")
 
-	    add_new_layout = TRUE;
+            add_new_layout = TRUE;
 
-	    /* Release the old (current) chunk index */
-	    if(idx_info.storage->ops->dest && (idx_info.storage->ops->dest)(&idx_info) < 0)
-		HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "unable to release chunk index info")
+            /* Release the old (current) chunk index */
+            if(idx_info.storage->ops->dest && (idx_info.storage->ops->dest)(&idx_info) < 0)
+                HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "unable to release chunk index info")
 
-	    /* Copy the new layout to the dataset's layout */
-	    HDmemcpy(&dataset->shared->layout, &newlayout, sizeof(H5O_layout_t));
+            /* Copy the new layout to the dataset's layout */
+            HDmemcpy(&dataset->shared->layout, newlayout, sizeof(H5O_layout_t));
 
-	    break;
+            break;
 
-	case H5D_CONTIGUOUS:
+        case H5D_CONTIGUOUS:
         case H5D_COMPACT:
-	    HDassert(dataset->shared->layout.version > H5O_LAYOUT_VERSION_DEFAULT);
-	    dataset->shared->layout.version = H5O_LAYOUT_VERSION_DEFAULT;
-	    if(H5O_msg_write(&(dataset->oloc), H5O_LAYOUT_ID, 0, H5O_UPDATE_TIME, &(dataset->shared->layout), dxpl_id) < 0)
-		HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "unable to update layout message")
-	    break;
+            HDassert(dataset->shared->layout.version > H5O_LAYOUT_VERSION_DEFAULT);
+            dataset->shared->layout.version = H5O_LAYOUT_VERSION_DEFAULT;
+            if(H5O_msg_write(&(dataset->oloc), H5O_LAYOUT_ID, 0, H5O_UPDATE_TIME, &(dataset->shared->layout), dxpl_id) < 0)
+                HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "unable to update layout message")
+            break;
 
-	case H5D_VIRTUAL:
-	    HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "virtual dataset layout not supported")
+        case H5D_VIRTUAL:
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "virtual dataset layout not supported")
 
         case H5D_LAYOUT_ERROR:
         case H5D_NLAYOUTS:
-	    HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid dataset layout type")
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid dataset layout type")
 
-	default: 
-	    HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "unknown dataset layout type")
+        default: 
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "unknown dataset layout type")
     } /* end switch */
 
 done:
     if(ret_value < 0 && dataset->shared->layout.type == H5D_CHUNKED) {
-	/* Remove new layout message */
-	if(add_new_layout)
-	    if(H5O_msg_remove(&dataset->oloc, H5O_LAYOUT_ID, H5O_ALL, FALSE, dxpl_id) < 0)
-		HDONE_ERROR(H5E_SYM, H5E_CANTDELETE, FAIL, "unable to delete layout message")
-
-	/* Add back old layout message */
-	if(delete_old_layout)
-	    if(H5O_msg_create(&dataset->oloc, H5O_LAYOUT_ID, 0, H5O_UPDATE_TIME, &dataset->shared->layout, dxpl_id) < 0)
-		HDONE_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to add layout header message")
-
-	/* Clean up v1 b-tree chunk index */
-	if(init_new_index) {
-	    if(H5F_addr_defined(new_idx_info.storage->idx_addr)) {
-		/* Check for valid address i.e. tag */
-		if(!H5F_addr_defined(dataset->oloc.addr))
-		    HDONE_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL, "address undefined")
-
-		/* Expunge from cache all v1 B-tree type entries associated with tag */
-		if(H5AC_expunge_tag_type_metadata(dataset->oloc.file, dxpl_id, dataset->oloc.addr, H5AC_BT_ID, H5AC__NO_FLAGS_SET))
-		    HDONE_ERROR(H5E_DATASET, H5E_CANTEXPUNGE, FAIL, "unable to expunge index metadata")
-	    } /* end if */
+        /* Remove new layout message */
+        if(add_new_layout)
+            if(H5O_msg_remove(&dataset->oloc, H5O_LAYOUT_ID, H5O_ALL, FALSE, dxpl_id) < 0)
+                HDONE_ERROR(H5E_SYM, H5E_CANTDELETE, FAIL, "unable to delete layout message")
+
+        /* Add back old layout message */
+        if(delete_old_layout)
+            if(H5O_msg_create(&dataset->oloc, H5O_LAYOUT_ID, 0, H5O_UPDATE_TIME, &dataset->shared->layout, dxpl_id) < 0)
+                HDONE_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to add layout header message")
+
+        /* Clean up v1 b-tree chunk index */
+        if(init_new_index) {
+            if(H5F_addr_defined(new_idx_info.storage->idx_addr)) {
+                /* Check for valid address i.e. tag */
+                if(!H5F_addr_defined(dataset->oloc.addr))
+                    HDONE_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL, "address undefined")
+
+                /* Expunge from cache all v1 B-tree type entries associated with tag */
+                if(H5AC_expunge_tag_type_metadata(dataset->oloc.file, dxpl_id, dataset->oloc.addr, H5AC_BT_ID, H5AC__NO_FLAGS_SET))
+                    HDONE_ERROR(H5E_DATASET, H5E_CANTEXPUNGE, FAIL, "unable to expunge index metadata")
+            } /* end if */
 
-	    /* Delete v1 B-tree chunk index */
-	    if(new_idx_info.storage->ops->dest && (new_idx_info.storage->ops->dest)(&new_idx_info) < 0)
-		HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "unable to release chunk index info")
-	} /* end if */
+            /* Delete v1 B-tree chunk index */
+            if(new_idx_info.storage->ops->dest && (new_idx_info.storage->ops->dest)(&new_idx_info) < 0)
+                HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "unable to release chunk index info")
+        } /* end if */
     } /* end if */
 
+    if(newlayout != NULL)
+        newlayout = (H5O_layout_t *)H5MM_xfree(newlayout);
+
     FUNC_LEAVE_NOAPI_TAG(ret_value, FAIL)
 } /* end H5D__format_convert() */
 
diff --git a/src/H5Dio.c b/src/H5Dio.c
index 572e6cf..1766422 100644
--- a/src/H5Dio.c
+++ b/src/H5Dio.c
@@ -181,7 +181,6 @@ H5Dread(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
 
     if(direct_read) {
         unsigned u;
-        hsize_t  dims[H5O_LAYOUT_NDIMS];
         hsize_t  internal_offset[H5O_LAYOUT_NDIMS];
 
         if(H5D_CHUNKED != dset->shared->layout.type)
diff --git a/src/H5FD.c b/src/H5FD.c
index dcfaa6d..67cf963 100644
--- a/src/H5FD.c
+++ b/src/H5FD.c
@@ -62,7 +62,6 @@
 /********************/
 static herr_t H5FD_free_cls(H5FD_class_t *cls);
 static int H5FD_query(const H5FD_t *f, unsigned long *flags/*out*/);
-static int H5FD_driver_query(const H5FD_class_t *driver, unsigned long *flags/*out*/);
 
 /*********************/
 /* Package Variables */
@@ -790,7 +789,8 @@ H5FD_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
 	HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, NULL, "file driver has no `open' method")
 
     /* Query driver flag */
-    H5FD_driver_query(driver, &driver_flags);
+    if(H5FD_driver_query(driver, &driver_flags) < 0)
+        HGOTO_ERROR(H5E_VFL, H5E_BADVALUE, NULL, "can't query VFD flags")
 
     /* Get initial file image info */
     if(H5P_peek(plist, H5F_ACS_FILE_IMAGE_INFO_NAME, &file_image_info) < 0)
@@ -1085,42 +1085,6 @@ H5FD_query(const H5FD_t *f, unsigned long *flags/*out*/)
 
 
 /*-------------------------------------------------------------------------
-* Function:    H5FD_driver_query
-*
-* Purpose: Similar to H5FD_query(), but intended for cases when we don't
-*          have a file available (e.g. before one is opened). Since we
-*          can't use the file to get the driver, the driver is passed in
-*          as a parameter.
-*
-* Return:  Success:    non-negative
-*          Failure:    negative
-*
-* Programmer:  Jacob Gruber
-*              Wednesday, August 17, 2011
-*
-*-------------------------------------------------------------------------
-*/
-static int
-H5FD_driver_query(const H5FD_class_t *driver, unsigned long *flags/*out*/)
-{
-    int ret_value = 0;          /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT_NOERR
-
-    HDassert(driver);
-    HDassert(flags);
-
-    /* Check for the driver to query and then query it */
-    if(driver->query)
-        ret_value = (driver->query)(NULL, flags);
-    else 
-        *flags = 0;
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5FD_driver_query() */
-
-
-/*-------------------------------------------------------------------------
  * Function:	H5FDalloc
  *
  * Purpose:	Allocates SIZE bytes of memory from the FILE. The memory will
@@ -2076,3 +2040,42 @@ H5FD_set_paged_aggr(H5FD_t *file, hbool_t paged)
 
     FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5FD_set_paged_aggr() */
+
+
+/*-------------------------------------------------------------------------
+* Function: H5FDdriver_query
+*
+* Purpose:  Similar to H5FD_query(), but intended for cases when we don't
+*           have a file available (e.g. before one is opened). Since we
+*           can't use the file to get the driver, the driver ID is passed
+*           in as a parameter.
+*
+* Return:   SUCCEED/FAIL
+*
+* Programmer:  Jacob Gruber
+*              Wednesday, August 17, 2011
+*
+*-------------------------------------------------------------------------
+*/
+herr_t
+H5FDdriver_query(hid_t driver_id, unsigned long *flags/*out*/)
+{
+    H5FD_class_t *driver = NULL;            /* Pointer to VFD class struct  */
+    herr_t ret_value = SUCCEED;             /* Return value                 */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "ix", driver_id, flags);
+
+    if(NULL == flags)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "flags parameter cannot be NULL")
+
+    /* Check for the driver to query and then query it */
+    if (NULL == (driver = (H5FD_class_t *)H5I_object_verify(driver_id, H5I_VFL)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "not a VFL ID")
+    if (H5FD_driver_query(driver, flags) < 0)
+        HGOTO_ERROR(H5E_VFL, H5E_BADVALUE, FAIL, "driver flag query failed")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5FDdriver_query() */
+
diff --git a/src/H5FDcore.c b/src/H5FDcore.c
index d100a8b..b980b7e 100644
--- a/src/H5FDcore.c
+++ b/src/H5FDcore.c
@@ -982,9 +982,11 @@ H5FD__core_query(const H5FD_t * _file, unsigned long *flags /* out */)
         *flags |= H5FD_FEAT_ALLOW_FILE_IMAGE;               /* OK to use file image feature with this VFD                       */
         *flags |= H5FD_FEAT_CAN_USE_FILE_IMAGE_CALLBACKS;   /* OK to use file image callbacks with this VFD                     */
 
-        /* If the backing store is open, a POSIX file handle is available */
-        if(file && file->fd >= 0 && file->backing_store)
-            *flags |= H5FD_FEAT_POSIX_COMPAT_HANDLE; /* VFD handle is POSIX I/O call compatible */
+        /* These feature flags are only applicable if the backing store is enabled */
+        if(file && file->fd >= 0 && file->backing_store) {
+            *flags |= H5FD_FEAT_POSIX_COMPAT_HANDLE;        /* get_handle callback returns a POSIX file descriptor              */
+            *flags |= H5FD_FEAT_DEFAULT_VFD_COMPATIBLE;     /* VFD creates a file which can be opened with the default VFD      */
+        }
     } /* end if */
 
     FUNC_LEAVE_NOAPI(SUCCEED)
diff --git a/src/H5FDdirect.c b/src/H5FDdirect.c
index 1487cda..7a4c99c 100644
--- a/src/H5FDdirect.c
+++ b/src/H5FDdirect.c
@@ -698,6 +698,7 @@ H5FD_direct_query(const H5FD_t H5_ATTR_UNUSED * _f, unsigned long *flags /* out
         *flags |= H5FD_FEAT_ACCUMULATE_METADATA;    /* OK to accumulate metadata for faster writes                      */
         *flags |= H5FD_FEAT_DATA_SIEVE;             /* OK to perform data sieving for faster raw data reads & writes    */
         *flags |= H5FD_FEAT_AGGREGATE_SMALLDATA;    /* OK to aggregate "small" raw data allocations                     */
+        *flags |= H5FD_FEAT_DEFAULT_VFD_COMPATIBLE; /* VFD creates a file which can be opened with the default VFD      */
     }
 
     FUNC_LEAVE_NOAPI(SUCCEED)
diff --git a/src/H5FDint.c b/src/H5FDint.c
index bc322d6..52fbc23 100644
--- a/src/H5FDint.c
+++ b/src/H5FDint.c
@@ -433,3 +433,38 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5FD_get_eof() */
 
+
+/*-------------------------------------------------------------------------
+* Function:    H5FD_driver_query
+*
+* Purpose: Similar to H5FD_query(), but intended for cases when we don't
+*          have a file available (e.g. before one is opened). Since we
+*          can't use the file to get the driver, the driver is passed in
+*          as a parameter.
+*
+* Return:  SUCCEED/FAIL
+*
+* Programmer:  Jacob Gruber
+*              Wednesday, August 17, 2011
+*
+*-------------------------------------------------------------------------
+*/
+herr_t
+H5FD_driver_query(const H5FD_class_t *driver, unsigned long *flags/*out*/)
+{
+    herr_t ret_value = SUCCEED;          /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDassert(driver);
+    HDassert(flags);
+
+    /* Check for the driver to query and then query it */
+    if(driver->query)
+        ret_value = (driver->query)(NULL, flags);
+    else 
+        *flags = 0;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5FD_driver_query() */
+
diff --git a/src/H5FDlog.c b/src/H5FDlog.c
index 75333c2..7c6bbd4 100644
--- a/src/H5FDlog.c
+++ b/src/H5FDlog.c
@@ -895,8 +895,9 @@ H5FD_log_query(const H5FD_t *_file, unsigned long *flags /* out */)
         *flags |= H5FD_FEAT_ACCUMULATE_METADATA;    /* OK to accumulate metadata for faster writes                      */
         *flags |= H5FD_FEAT_DATA_SIEVE;             /* OK to perform data sieving for faster raw data reads & writes    */
         *flags |= H5FD_FEAT_AGGREGATE_SMALLDATA;    /* OK to aggregate "small" raw data allocations                     */
-        *flags |= H5FD_FEAT_POSIX_COMPAT_HANDLE;    /* VFD handle is POSIX I/O call compatible                          */
+        *flags |= H5FD_FEAT_POSIX_COMPAT_HANDLE;    /* get_handle callback returns a POSIX file descriptor              */
         *flags |= H5FD_FEAT_SUPPORTS_SWMR_IO;       /* VFD supports the single-writer/multiple-readers (SWMR) pattern   */
+        *flags |= H5FD_FEAT_DEFAULT_VFD_COMPATIBLE; /* VFD creates a file which can be opened with the default VFD      */
 
         /* Check for flags that are set by h5repart */
         if(file && file->fam_to_sec2)
diff --git a/src/H5FDmpio.c b/src/H5FDmpio.c
index ace91f8..f594d8e 100644
--- a/src/H5FDmpio.c
+++ b/src/H5FDmpio.c
@@ -1150,10 +1150,11 @@ H5FD_mpio_query(const H5FD_t H5_ATTR_UNUSED *_file, unsigned long *flags /* out
     /* Set the VFL feature flags that this driver supports */
     if(flags) {
         *flags=0;
-        *flags|=H5FD_FEAT_AGGREGATE_METADATA;  /* OK to aggregate metadata allocations */
-        *flags|=H5FD_FEAT_AGGREGATE_SMALLDATA; /* OK to aggregate "small" raw data allocations */
-        *flags|=H5FD_FEAT_HAS_MPI;             /* This driver uses MPI */
-        *flags|=H5FD_FEAT_ALLOCATE_EARLY;      /* Allocate space early instead of late */
+        *flags |= H5FD_FEAT_AGGREGATE_METADATA;     /* OK to aggregate metadata allocations                             */
+        *flags |= H5FD_FEAT_AGGREGATE_SMALLDATA;    /* OK to aggregate "small" raw data allocations                     */
+        *flags |= H5FD_FEAT_HAS_MPI;                /* This driver uses MPI                                             */
+        *flags |= H5FD_FEAT_ALLOCATE_EARLY;         /* Allocate space early instead of late                             */
+        *flags |= H5FD_FEAT_DEFAULT_VFD_COMPATIBLE; /* VFD creates a file which can be opened with the default VFD      */
     } /* end if */
 
     FUNC_LEAVE_NOAPI(SUCCEED)
diff --git a/src/H5FDprivate.h b/src/H5FDprivate.h
index 0fc2135..e758951 100644
--- a/src/H5FDprivate.h
+++ b/src/H5FDprivate.h
@@ -153,6 +153,7 @@ H5_DLL H5FD_t *H5FD_open(const char *name, unsigned flags, hid_t fapl_id,
 		  haddr_t maxaddr);
 H5_DLL herr_t H5FD_close(H5FD_t *file);
 H5_DLL int H5FD_cmp(const H5FD_t *f1, const H5FD_t *f2);
+H5_DLL herr_t H5FD_driver_query(const H5FD_class_t *driver, unsigned long *flags/*out*/);
 H5_DLL haddr_t H5FD_alloc(H5FD_t *file, hid_t dxpl_id, H5FD_mem_t type, 
     struct H5F_t *f, hsize_t size, haddr_t *frag_addr, hsize_t *frag_size);
 H5_DLL herr_t H5FD_free(H5FD_t *file, hid_t dxpl_id, H5FD_mem_t type, struct H5F_t *f,
diff --git a/src/H5FDpublic.h b/src/H5FDpublic.h
index 3032e8a..514d1bf 100644
--- a/src/H5FDpublic.h
+++ b/src/H5FDpublic.h
@@ -250,6 +250,14 @@ typedef enum H5F_mem_t	H5FD_mem_t;
      * This is specifically used for the multi/split driver.
      */
 #define H5FD_FEAT_PAGED_AGGR		0x00004000
+    /*
+     * Defining H5FD_FEAT_DEFAULT_VFD_COMPATIBLE for a VFL driver
+     * that creates a file which is compatible with the default VFD.
+     * Generally, this means that the VFD creates a single file that follows
+     * the canonical HDF5 file format.
+     */
+#define H5FD_FEAT_DEFAULT_VFD_COMPATIBLE        0x00008000
+
 
 /* Forward declaration */
 typedef struct H5FD_t H5FD_t;
@@ -376,6 +384,9 @@ H5_DLL herr_t H5FDtruncate(H5FD_t *file, hid_t dxpl_id, hbool_t closing);
 H5_DLL herr_t H5FDlock(H5FD_t *file, hbool_t rw);
 H5_DLL herr_t H5FDunlock(H5FD_t *file);
 
+/* Allows querying a VFD ID for features before the file is opened */
+H5_DLL herr_t H5FDdriver_query(hid_t driver_id, unsigned long *flags/*out*/);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/H5FDsec2.c b/src/H5FDsec2.c
index 26913e2..b6385fb 100644
--- a/src/H5FDsec2.c
+++ b/src/H5FDsec2.c
@@ -527,8 +527,9 @@ H5FD_sec2_query(const H5FD_t *_file, unsigned long *flags /* out */)
         *flags |= H5FD_FEAT_ACCUMULATE_METADATA;    /* OK to accumulate metadata for faster writes                      */
         *flags |= H5FD_FEAT_DATA_SIEVE;             /* OK to perform data sieving for faster raw data reads & writes    */
         *flags |= H5FD_FEAT_AGGREGATE_SMALLDATA;    /* OK to aggregate "small" raw data allocations                     */
-        *flags |= H5FD_FEAT_POSIX_COMPAT_HANDLE;    /* VFD handle is POSIX I/O call compatible                          */
+        *flags |= H5FD_FEAT_POSIX_COMPAT_HANDLE;    /* get_handle callback returns a POSIX file descriptor              */
         *flags |= H5FD_FEAT_SUPPORTS_SWMR_IO;       /* VFD supports the single-writer/multiple-readers (SWMR) pattern   */
+        *flags |= H5FD_FEAT_DEFAULT_VFD_COMPATIBLE; /* VFD creates a file which can be opened with the default VFD      */
 
         /* Check for flags that are set by h5repart */
         if(file && file->fam_to_sec2)
diff --git a/src/H5FDspace.c b/src/H5FDspace.c
index e451d6b..0af755f 100644
--- a/src/H5FDspace.c
+++ b/src/H5FDspace.c
@@ -99,9 +99,7 @@ H5FL_DEFINE(H5FD_free_t);
 static haddr_t
 H5FD_extend(H5FD_t *file, H5FD_mem_t type, hsize_t size)
 {
-    hsize_t orig_size = size;   /* Original allocation size */
     haddr_t eoa;                /* Address of end-of-allocated space */
-    hsize_t extra;        	/* Extra space to allocate, to align request */
     haddr_t ret_value = HADDR_UNDEF;    /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT
diff --git a/src/H5FDstdio.c b/src/H5FDstdio.c
index 5023af3..861c6a6 100644
--- a/src/H5FDstdio.c
+++ b/src/H5FDstdio.c
@@ -555,10 +555,11 @@ H5FD_stdio_query(const H5FD_t *_f, unsigned long /*OUT*/ *flags)
      */
     if(flags) {
         *flags = 0;
-        *flags|=H5FD_FEAT_AGGREGATE_METADATA; /* OK to aggregate metadata allocations */
-        *flags|=H5FD_FEAT_ACCUMULATE_METADATA; /* OK to accumulate metadata for faster writes */
-        *flags|=H5FD_FEAT_DATA_SIEVE;       /* OK to perform data sieving for faster raw data reads & writes */
-        *flags|=H5FD_FEAT_AGGREGATE_SMALLDATA; /* OK to aggregate "small" raw data allocations */
+        *flags |= H5FD_FEAT_AGGREGATE_METADATA;     /* OK to aggregate metadata allocations                             */
+        *flags |= H5FD_FEAT_ACCUMULATE_METADATA;    /* OK to accumulate metadata for faster writes                      */
+        *flags |= H5FD_FEAT_DATA_SIEVE;             /* OK to perform data sieving for faster raw data reads & writes    */
+        *flags |= H5FD_FEAT_AGGREGATE_SMALLDATA;    /* OK to aggregate "small" raw data allocations                     */
+        *flags |= H5FD_FEAT_DEFAULT_VFD_COMPATIBLE; /* VFD creates a file which can be opened with the default VFD      */
     }
 
     return 0;
diff --git a/src/H5Fint.c b/src/H5Fint.c
index fe532b2..e52d539 100644
--- a/src/H5Fint.c
+++ b/src/H5Fint.c
@@ -715,10 +715,6 @@ H5F_new(H5F_file_t *shared, unsigned flags, hid_t fcpl_id, hid_t fapl_id, H5FD_t
         if(!H5F_HAS_FEATURE(f, H5FD_FEAT_SUPPORTS_SWMR_IO) && (H5F_INTENT(f) & (H5F_ACC_SWMR_WRITE | H5F_ACC_SWMR_READ)))
             HGOTO_ERROR(H5E_FILE, H5E_BADVALUE, NULL, "must use a SWMR-compatible VFD when SWMR is specified")
 
-        /* Require a POSIX compatible VFD to use SWMR feature */
-        /* (It's reasonable to try to expand this to other VFDs eventually -QAK) */
-        if(!H5F_HAS_FEATURE(f, H5FD_FEAT_POSIX_COMPAT_HANDLE) && (H5F_INTENT(f) & (H5F_ACC_SWMR_WRITE | H5F_ACC_SWMR_READ)))
-            HGOTO_ERROR(H5E_FILE, H5E_BADVALUE, NULL, "must use POSIX compatible VFD with SWMR write access")
         if(H5FD_get_fs_type_map(lf, f->shared->fs_type_map) < 0)
             HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get free space type mapping from VFD")
         if(H5MF_init_merge_flags(f) < 0)
diff --git a/src/H5I.c b/src/H5I.c
index ce4ecdc..42edf58 100644
--- a/src/H5I.c
+++ b/src/H5I.c
@@ -888,7 +888,7 @@ H5I_subst(hid_t id, const void *new_object)
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end if */
+} /* end H5I_subst() */
 
 
 /*-------------------------------------------------------------------------
@@ -920,7 +920,7 @@ H5I_object(hid_t id)
     } /* end if */
 
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end if */
+} /* end H5I_object() */
 
 
 /*-------------------------------------------------------------------------
diff --git a/src/H5MFdbg.c b/src/H5MFdbg.c
index 49cfbfc..1ae902f 100644
--- a/src/H5MFdbg.c
+++ b/src/H5MFdbg.c
@@ -156,7 +156,7 @@ herr_t
 H5MF_sects_debug(H5F_t *f, hid_t dxpl_id, haddr_t fs_addr, FILE *stream, int indent, int fwidth)
 {
     herr_t      ret_value = SUCCEED;    /* Return value */
-    H5FD_mem_t 	type;                    /* Memory type for iteration */
+    H5F_mem_page_t type;                /* Memory type for iteration */
 
     FUNC_ENTER_NOAPI_TAG(dxpl_id, H5AC__FREESPACE_TAG, FAIL)
 
@@ -168,31 +168,31 @@ H5MF_sects_debug(H5F_t *f, hid_t dxpl_id, haddr_t fs_addr, FILE *stream, int ind
     HDassert(indent >= 0);
     HDassert(fwidth >= 0);
 
-    for(type = H5FD_MEM_DEFAULT; type < H5FD_MEM_NTYPES; H5_INC_ENUM(H5FD_mem_t, type))
-	if(H5F_addr_eq(f->shared->fs_addr[type], fs_addr)) {
-	    if(!f->shared->fs_man[type])
+    for(type = H5F_MEM_PAGE_DEFAULT; type < H5F_MEM_PAGE_NTYPES; H5_INC_ENUM(H5F_mem_page_t, type))
+        if(H5F_addr_eq(f->shared->fs_addr[type], fs_addr)) {
+            if(!f->shared->fs_man[type])
                 if(H5MF_open_fstype(f, dxpl_id, type) < 0)
-		    HGOTO_ERROR(H5E_RESOURCE, H5E_CANTINIT, FAIL, "can't initialize file free space")
-
-	    if(f->shared->fs_man[type]) {
-		H5MF_debug_iter_ud_t udata;        /* User data for callbacks */
-
-		/* Prepare user data for section iteration callback */
-		udata.fspace = f->shared->fs_man[type];
-		udata.stream = stream;
-		udata.indent = indent;
-		udata.fwidth = fwidth;
-
-		/* Iterate over all the free space sections */
-		if(H5FS_sect_iterate(f, dxpl_id, f->shared->fs_man[type], H5MF_sects_debug_cb, &udata) < 0)
-		    HGOTO_ERROR(H5E_HEAP, H5E_BADITER, FAIL, "can't iterate over heap's free space")
-
-		/* Close the free space information */
-		if(H5FS_close(f, dxpl_id, f->shared->fs_man[type]) < 0)
-		    HGOTO_ERROR(H5E_HEAP, H5E_CANTRELEASE, FAIL, "can't release free space info")
-	    } /* end if */
-	    break;
-	} /* end if */
+                    HGOTO_ERROR(H5E_RESOURCE, H5E_CANTINIT, FAIL, "can't initialize file free space")
+
+            if(f->shared->fs_man[type]) {
+                H5MF_debug_iter_ud_t udata;        /* User data for callbacks */
+
+                /* Prepare user data for section iteration callback */
+                udata.fspace = f->shared->fs_man[type];
+                udata.stream = stream;
+                udata.indent = indent;
+                udata.fwidth = fwidth;
+
+                /* Iterate over all the free space sections */
+                if(H5FS_sect_iterate(f, dxpl_id, f->shared->fs_man[type], H5MF_sects_debug_cb, &udata) < 0)
+                    HGOTO_ERROR(H5E_HEAP, H5E_BADITER, FAIL, "can't iterate over heap's free space")
+
+                /* Close the free space information */
+                if(H5FS_close(f, dxpl_id, f->shared->fs_man[type]) < 0)
+                    HGOTO_ERROR(H5E_HEAP, H5E_CANTRELEASE, FAIL, "can't release free space info")
+            } /* end if */
+            break;
+        } /* end if */
 
 done:
     FUNC_LEAVE_NOAPI_TAG(ret_value, FAIL)
diff --git a/src/H5MFsection.c b/src/H5MFsection.c
index 0dd26b3..02fc2d9 100644
--- a/src/H5MFsection.c
+++ b/src/H5MFsection.c
@@ -360,7 +360,7 @@ H5MF_sect_valid(const H5FS_section_class_t H5_ATTR_UNUSED *cls,
 static H5FS_section_info_t *
 H5MF_sect_split(H5FS_section_info_t *sect, hsize_t frag_size)
 {
-    H5MF_free_section_t *ret_value;     /* Return value */
+    H5MF_free_section_t *ret_value = NULL;      /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT
 
diff --git a/src/H5Ocache_image.c b/src/H5Ocache_image.c
index 29b2503..a427b49 100644
--- a/src/H5Ocache_image.c
+++ b/src/H5Ocache_image.c
@@ -323,7 +323,7 @@ H5O__mdci_delete(H5F_t *f, hid_t dxpl_id, H5O_t *open_oh, void *_mesg)
          * time constraints, I don't want to go there now.
          */
         if(H5F_FIRST_ALLOC_DEALLOC(f)) {
-            HDassert(HADDR_UNDEF !=H5F_EOA_PRE_FSM_FSALLOC(f));
+            HDassert(HADDR_UNDEF != H5F_EOA_PRE_FSM_FSALLOC(f));
             HDassert(H5F_addr_ge(mesg->addr, H5F_EOA_PRE_FSM_FSALLOC(f)));
             if(H5MF_tidy_self_referential_fsm_hack(f, dxpl_id) < 0)
                 HGOTO_ERROR(H5E_OHDR, H5E_CANTFREE, FAIL, "tidy of self referential fsm hack failed")
diff --git a/src/H5Ofsinfo.c b/src/H5Ofsinfo.c
index 89dc8ee..4d62f49 100644
--- a/src/H5Ofsinfo.c
+++ b/src/H5Ofsinfo.c
@@ -85,7 +85,7 @@ H5FL_DEFINE_STATIC(H5O_fsinfo_t);
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_fsinfo_decode(H5F_t *f, hid_t dxpl_id, H5O_t H5_ATTR_UNUSED *open_oh,
+H5O_fsinfo_decode(H5F_t *f, hid_t H5_ATTR_UNUSED dxpl_id, H5O_t H5_ATTR_UNUSED *open_oh,
     unsigned H5_ATTR_UNUSED mesg_flags, unsigned H5_ATTR_UNUSED *ioflags, const uint8_t *p)
 {
     H5O_fsinfo_t    *fsinfo = NULL;     /* File space info message */