[PATCH v4 01/17] tools/xenstore: let talloc_free() preserve errno

[Juergen Gross <jgross@xxxxxxxx>]

Today talloc_free() is not guaranteed to preserve errno, especially in
case a custom destructor is being used.

So preserve errno in talloc_free().

This allows to remove some errno saving outside of talloc.c.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
V2:
- drop wrapper (Julien Grall)
---
 tools/xenstore/talloc.c         | 21 +++++++++++++--------
 tools/xenstore/xenstored_core.c |  2 --
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/tools/xenstore/talloc.c b/tools/xenstore/talloc.c
index d7edcf3a93..23c3a23b19 100644
--- a/tools/xenstore/talloc.c
+++ b/tools/xenstore/talloc.c
@@ -541,38 +541,39 @@ static void talloc_free_children(void *ptr)
 */
 int talloc_free(void *ptr)
 {
+       int saved_errno = errno;
        struct talloc_chunk *tc;
 
        if (ptr == NULL) {
-               return -1;
+               goto err;
        }
 
        tc = talloc_chunk_from_ptr(ptr);
 
        if (tc->null_refs) {
                tc->null_refs--;
-               return -1;
+               goto err;
        }
 
        if (tc->refs) {
                talloc_reference_destructor(tc->refs);
-               return -1;
+               goto err;
        }
 
        if (tc->flags & TALLOC_FLAG_LOOP) {
                /* we have a free loop - stop looping */
-               return 0;
+               goto success;
        }
 
        if (tc->destructor) {
                talloc_destructor_t d = tc->destructor;
                if (d == (talloc_destructor_t)-1) {
-                       return -1;
+                       goto err;
                }
                tc->destructor = (talloc_destructor_t)-1;
                if (d(ptr) == -1) {
                        tc->destructor = d;
-                       return -1;
+                       goto err;
                }
                tc->destructor = NULL;
        }
@@ -594,10 +595,14 @@ int talloc_free(void *ptr)
        tc->flags |= TALLOC_FLAG_FREE;
 
        free(tc);
+ success:
+       errno = saved_errno;
        return 0;
-}
-
 
+ err:
+       errno = saved_errno;
+       return -1;
+}
 
 /*
   A talloc version of realloc. The context argument is only used if
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 78a3edaa4e..1650821922 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -771,9 +771,7 @@ struct node *read_node(struct connection *conn, const void 
*ctx,
        return node;
 
  error:
-       err = errno;
        talloc_free(node);
-       errno = err;
        return NULL;
 }
 
-- 
2.35.3