[Libguestfs] [PATCH libnbd v3 1/6] lib/opt: Don't use NULL for an empty StringList

[Richard W.M. Jones]

StringList parameters (char ** in C) will be marked with
__attribute__((nonnull)).  To pass an empty list you have to use a
list containing a single NULL element, not a NULL pointer.

nbd_internal_set_querylist has also been adjusted.

Fixes: commit e33762a86cd5f064e5ef841520baa5fe7361d2c2
---
 generator/states-newstyle-opt-meta-context.c |  4 +++-
 lib/opt.c                                    | 16 ++++++++++++----
 lib/utils.c                                  |  4 ++--
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/generator/states-newstyle-opt-meta-context.c 
b/generator/states-newstyle-opt-meta-context.c
index 46fee15be1..a60aa66f3b 100644
--- a/generator/states-newstyle-opt-meta-context.c
+++ b/generator/states-newstyle-opt-meta-context.c
@@ -65,12 +65,14 @@  NEWSTYLE.OPT_META_CONTEXT.START:
     }
   }
   if (opt != h->opt_current) {
+    char *empty[] = { NULL };
+
     if (!h->request_meta || !h->structured_replies ||
         h->request_meta_contexts.len == 0) {
       SET_NEXT_STATE (%^OPT_GO.START);
       return 0;
     }
-    if (nbd_internal_set_querylist (h, NULL) == -1) {
+    if (nbd_internal_set_querylist (h, empty) == -1) {
       SET_NEXT_STATE (%.DEAD);
       return 0;
     }
diff --git a/lib/opt.c b/lib/opt.c
index 1b18920fdb..e323d7b1b0 100644
--- a/lib/opt.c
+++ b/lib/opt.c
@@ -224,7 +224,9 @@ int
 nbd_unlocked_opt_list_meta_context (struct nbd_handle *h,
                                     nbd_context_callback *context)
 {
-  return nbd_unlocked_opt_list_meta_context_queries (h, NULL, context);
+  char *empty[] = { NULL };
+
+  return nbd_unlocked_opt_list_meta_context_queries (h, empty, context);
 }
 
 /* Issue NBD_OPT_LIST_META_CONTEXT and wait for the reply. */
@@ -255,7 +257,9 @@ int
 nbd_unlocked_opt_set_meta_context (struct nbd_handle *h,
                                    nbd_context_callback *context)
 {
-  return nbd_unlocked_opt_set_meta_context_queries (h, NULL, context);
+  char *empty[] = { NULL };
+
+  return nbd_unlocked_opt_set_meta_context_queries (h, empty, context);
 }
 
 /* Issue NBD_OPT_SET_META_CONTEXT and wait for the reply. */
@@ -371,7 +375,9 @@ nbd_unlocked_aio_opt_list_meta_context (struct nbd_handle 
*h,
                                         nbd_context_callback *context,
                                         nbd_completion_callback *complete)
 {
-  return nbd_unlocked_aio_opt_list_meta_context_queries (h, NULL, context,
+  char *empty[] = { NULL };
+
+  return nbd_unlocked_aio_opt_list_meta_context_queries (h, empty, context,
                                                          complete);
 }
 
@@ -407,7 +413,9 @@ nbd_unlocked_aio_opt_set_meta_context (struct nbd_handle *h,
                                        nbd_context_callback *context,
                                        nbd_completion_callback *complete)
 {
-  return nbd_unlocked_aio_opt_set_meta_context_queries (h, NULL, context,
+  char *empty[] = { NULL };
+
+  return nbd_unlocked_aio_opt_set_meta_context_queries (h, empty, context,
                                                         complete);
 }
 
diff --git a/lib/utils.c b/lib/utils.c
index c1d633fea1..b4043aa3bc 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -100,7 +100,7 @@ nbd_internal_set_querylist (struct nbd_handle *h, char 
**queries)
 {
   size_t i;
 
-  if (queries) {
+  if (queries[0] != NULL /* non-empty list */) {
     if (nbd_internal_copy_string_list (&h->querylist, queries) == -1) {
       set_error (errno, "realloc");
       return -1;
@@ -109,7 +109,7 @@ nbd_internal_set_querylist (struct nbd_handle *h, char 
**queries)
     assert (h->querylist.len > 0);
     string_vector_remove (&h->querylist, h->querylist.len - 1);
   }
-  else {
+  else /* empty list */ {
     string_vector_reset (&h->querylist);
     for (i = 0; i < h->request_meta_contexts.len; ++i) {
       char *copy = strdup (h->request_meta_contexts.ptr[i]);
-- 
2.37.0.rc2

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