Bug Fix: Segfault in H5CX_get_vol_wrap_ctx when H5VLwrap_register is called from an application (#2248)

* Jira HDFFV-10881: Segfault in H5CX_get_vol_wrap_ctx when H5VLwrap_register is called from an application.  A quick and simple fix to make it fail with a relevant error message.

* Format changes.

* Committing clang-format changes

* Minor change: split one condition check into two for clarity.

* Adding doxygen comment for H5VLwrap_register.

* Minor change: adding a little more detail to the Doxygen comment for H5VLwrap_register.

2 files changed, 35 insertions, 2 deletions

diff --git a/src/H5CX.c b/src/H5CX.c
index 24f10d9..95e824d 100644
--- a/src/H5CX.c
+++ b/src/H5CX.c
@@ -1621,12 +1621,20 @@ H5CX_get_vol_wrap_ctx(void **vol_wrap_ctx)
     H5CX_node_t **head      = NULL;    /* Pointer to head of API context list */
     herr_t        ret_value = SUCCEED; /* Return value */
 
-    FUNC_ENTER_NOAPI_NOERR
+    FUNC_ENTER_NOAPI(FAIL)
 
     /* Sanity check */
     HDassert(vol_wrap_ctx);
     head = H5CX_get_my_context(); /* Get the pointer to the head of the API context, for this thread */
-    HDassert(head && *head);
+
+    /* No error is expected at this point.  But in case an application calls H5VLwrap_register
+     * which doesn't reset the API context and there is no context, returns a relevant error here
+     */
+    if (!head)
+        HGOTO_ERROR(H5E_CONTEXT, H5E_UNINITIALIZED, FAIL, "the API context isn't available")
+
+    if (!(*head))
+        HGOTO_ERROR(H5E_CONTEXT, H5E_CANTGET, FAIL, "unable to get the current API context")
 
     /* Check for value that was set */
     if ((*head)->ctx.vol_wrap_ctx_valid)
@@ -1635,6 +1643,7 @@ H5CX_get_vol_wrap_ctx(void **vol_wrap_ctx)
     else
         *vol_wrap_ctx = NULL;
 
+done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5CX_get_vol_wrap_ctx() */
 
diff --git a/src/H5VLconnector_passthru.h b/src/H5VLconnector_passthru.h
index 079a869..68dd33a 100644
--- a/src/H5VLconnector_passthru.h
+++ b/src/H5VLconnector_passthru.h
@@ -56,6 +56,30 @@ extern "C" {
 
 /* Helper routines for VOL connector authors */
 H5_DLL herr_t H5VLcmp_connector_cls(int *cmp, hid_t connector_id1, hid_t connector_id2);
+/**
+ * \ingroup H5VL
+ *
+ * \brief Wrap an internal object with a "wrap context" and register an
+ *        hid_t for the resulting object.
+ *
+ * \param[in] obj  VOL object.
+ * \param[in] type VOL-managed object class. Allowable values are:
+ *                 - #H5I_FILE
+ *                 - #H5I_GROUP
+ *                 - #H5I_DATATYPE
+ *                 - #H5I_DATASET
+ *                 - #H5I_MAP
+ *                 - #H5I_ATTR
+ *
+ * \return \hid_t
+ *
+ * \note This routine is mainly targeted toward wrapping objects for
+ *       iteration routine callbacks (i.e. the callbacks from H5Aiterate*,
+ *       H5Literate* / H5Lvisit*, and H5Ovisit* ). Using it in an application
+ *       will return an error indicating the API context isn't available or
+ *       can't be retrieved.
+ *
+ */
 H5_DLL hid_t  H5VLwrap_register(void *obj, H5I_type_t type);
 H5_DLL herr_t H5VLretrieve_lib_state(void **state);
 H5_DLL herr_t H5VLstart_lib_state(void);