[PATCH 03/20] 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.

Change that by renaming talloc_free() to _talloc_free() in talloc.c and
adding a wrapper to talloc.c.

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

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 tools/xenstore/talloc.c         | 25 ++++++++++++++++++-------
 tools/xenstore/xenstored_core.c |  2 --
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/tools/xenstore/talloc.c b/tools/xenstore/talloc.c
index d7edcf3a93..5fbefdf091 100644
--- a/tools/xenstore/talloc.c
+++ b/tools/xenstore/talloc.c
@@ -103,6 +103,8 @@ struct talloc_chunk {
        unsigned flags;
 };
 
+static int _talloc_free(void *ptr);
+
 /* 16 byte alignment seems to keep everyone happy */
 #define TC_HDR_SIZE ((sizeof(struct talloc_chunk)+15)&~15)
 #define TC_PTR_FROM_CHUNK(tc) ((void *)(TC_HDR_SIZE + (char*)tc))
@@ -245,7 +247,7 @@ static int talloc_reference_destructor(void *ptr)
                tc1->destructor = NULL;
        }
        _TLIST_REMOVE(tc2->refs, handle);
-       talloc_free(handle);
+       _talloc_free(handle);
        return 0;
 }
 
@@ -311,7 +313,7 @@ static int talloc_unreference(const void *context, const 
void *ptr)
 
        talloc_set_destructor(h, NULL);
        _TLIST_REMOVE(tc->refs, h);
-       talloc_free(h);
+       _talloc_free(h);
        return 0;
 }
 
@@ -349,7 +351,7 @@ int talloc_unlink(const void *context, void *ptr)
        tc_p = talloc_chunk_from_ptr(ptr);
 
        if (tc_p->refs == NULL) {
-               return talloc_free(ptr);
+               return _talloc_free(ptr);
        }
 
        new_p = talloc_parent_chunk(tc_p->refs);
@@ -521,7 +523,7 @@ static void talloc_free_children(void *ptr)
                        struct talloc_chunk *p = 
talloc_parent_chunk(tc->child->refs);
                        if (p) new_parent = TC_PTR_FROM_CHUNK(p);
                }
-               if (talloc_free(child) == -1) {
+               if (_talloc_free(child) == -1) {
                        if (new_parent == null_context) {
                                struct talloc_chunk *p = 
talloc_parent_chunk(ptr);
                                if (p) new_parent = TC_PTR_FROM_CHUNK(p);
@@ -539,7 +541,7 @@ static void talloc_free_children(void *ptr)
    will not be freed if the ref_count is > 1 or the destructor (if
    any) returns non-zero
 */
-int talloc_free(void *ptr)
+static int _talloc_free(void *ptr)
 {
        struct talloc_chunk *tc;
 
@@ -597,7 +599,16 @@ int talloc_free(void *ptr)
        return 0;
 }
 
+int talloc_free(void *ptr)
+{
+       int ret;
+       int saved_errno = errno;
 
+       ret = _talloc_free(ptr);
+       errno = saved_errno;
+
+       return ret;
+}
 
 /*
   A talloc version of realloc. The context argument is only used if
@@ -610,7 +621,7 @@ void *_talloc_realloc(const void *context, void *ptr, 
size_t size, const char *n
 
        /* size zero is equivalent to free() */
        if (size == 0) {
-               talloc_free(ptr);
+               _talloc_free(ptr);
                return NULL;
        }
 
@@ -1243,7 +1254,7 @@ void *talloc_realloc_fn(const void *context, void *ptr, 
size_t size)
 
 static void talloc_autofree(void)
 {
-       talloc_free(cleanup_context);
+       _talloc_free(cleanup_context);
        cleanup_context = NULL;
 }
 
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 476d5c6d51..5a174b9881 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