X-Git-Url: http://git.ozlabs.org/?a=blobdiff_plain;f=ccan%2Ftalloc%2Ftalloc.c;h=63423a50f5ec05e73aa1816910fdc82860fbb2d0;hb=1e962ba9b5808dafc0be9cc562b25e3ae068ca5d;hp=ed958a8e5f25fdbeebf83f30b1ea8fef82d018bc;hpb=76ae790f2cc2cb1e46bb0b9e5002c7feb6a79df1;p=ccan

diff --git a/ccan/talloc/talloc.c b/ccan/talloc/talloc.c
index ed958a8e..63423a50 100644
--- a/ccan/talloc/talloc.c
+++ b/ccan/talloc/talloc.c
@@ -538,13 +538,28 @@ static inline int _talloc_free(const void *ptr)
 		   final choice is the null context. */
 		void *child = TC_PTR_FROM_CHUNK(tc->child);
 		const void *new_parent = null_context;
+		struct talloc_chunk *old_parent = NULL;
 		if (unlikely(tc->child->refs)) {
 			struct talloc_chunk *p = talloc_parent_chunk(tc->child->refs);
 			if (p) new_parent = TC_PTR_FROM_CHUNK(p);
 		}
+		/* finding the parent here is potentially quite
+		   expensive, but the alternative, which is to change
+		   talloc to always have a valid tc->parent pointer,
+		   makes realloc more expensive where there are a
+		   large number of children.
+
+		   The reason we need the parent pointer here is that
+		   if _talloc_free_internal() fails due to references
+		   or a failing destructor we need to re-parent, but
+		   the free call can invalidate the prev pointer.
+		*/
+		if (new_parent == null_context && (tc->child->refs || tc->child->destructor)) {
+			old_parent = talloc_parent_chunk(ptr);
+		}
 		if (unlikely(_talloc_free(child) == -1)) {
 			if (new_parent == null_context) {
-				struct talloc_chunk *p = talloc_parent_chunk(ptr);
+				struct talloc_chunk *p = old_parent;
 				if (p) new_parent = TC_PTR_FROM_CHUNK(p);
 			}
 			__talloc_steal(new_parent, child);
@@ -664,7 +679,7 @@ int talloc_unlink(const void *context, void *ptr)
 /*
   add a name to an existing pointer - va_list version
 */
-static inline const char *talloc_set_name_v(const void *ptr, const char *fmt, va_list ap) PRINTF_ATTRIBUTE(2,0);
+static inline const char *talloc_set_name_v(const void *ptr, const char *fmt, va_list ap) PRINTF_FMT(2,0);
 
 static inline const char *talloc_set_name_v(const void *ptr, const char *fmt, va_list ap)
 {
@@ -801,21 +816,25 @@ static int talloc_destroy_pointer(void ***pptr)
 void _talloc_set(void *ptr, const void *ctx, size_t size, const char *name)
 {
 	void ***child;
-	void **pptr = ptr;
+	void *p;
 
-	*pptr = talloc_named_const(ctx, size, name);
-	if (unlikely(!*pptr))
-		return;
+	p = talloc_named_const(ctx, size, name);
+	if (unlikely(!p))
+		goto set_ptr;
 
-	child = talloc(*pptr, void **);
+	child = talloc(p, void **);
 	if (unlikely(!child)) {
-		talloc_free(*pptr);
-		*pptr = NULL;
-		return;
+		talloc_free(p);
+		p = NULL;
+		goto set_ptr;
 	}
-	*child = pptr;
+	*child = ptr;
 	talloc_set_name_const(child, "talloc_set destructor");
 	talloc_set_destructor(child, talloc_destroy_pointer);
+
+set_ptr:
+	/* memcpy rather than cast avoids aliasing problems. */
+	memcpy(ptr, &p, sizeof(p));
 }
 
 /*