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authorAndrew Tridgell <tridge@samba.org>2009-07-01 14:53:01 +1000
committerAndrew Tridgell <tridge@samba.org>2009-07-01 15:15:37 +1000
commit5fe1d8dc1275e43d96da1297f5fb0d0088a1c3ab (patch)
treeca520776101c3ff64fa76d01d088c565ea265d5a
parent6a192020a230ab8e085f32b5559c0fe0d2f5c1a4 (diff)
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changes to remove the ambiguity in talloc_free() and talloc_steal()
These changes follow from the discussions on samba-technical. The changes are in several parts, and stem from the inherent ambiguity that was in talloc_free() and talloc_steal() when the pointer that is being changes has more than one parent, via references. The changes are: 1) when you call talloc_free() on a pointer with more than one parent the free will fail, and talloc will log an error to stderr like this: ERROR: talloc_free with references at some/foo.c:123 reference at other/bar.c:201 reference at other/foobar.c:641 2) Similarly, when you call talloc_steal() on a pointer with more than one parent, the steal will fail and talloc will log an error to stderr like this: ERROR: talloc_steal with references at some/foo.c:123 reference at other/bar.c:201 3) A new function talloc_reparent() has been added to change a parent in a controlled fashion. You need to supply both the old parent and the new parent. It handles the case whether either the old parent was a normal parent or a reference The use of stderr in the logging is ugly (and potentially dangerous), and will be removed in a future patch. We'll need to add a debug registration function to talloc.
-rw-r--r--lib/talloc/talloc.c119
-rw-r--r--lib/talloc/talloc.h16
2 files changed, 109 insertions, 26 deletions
diff --git a/lib/talloc/talloc.c b/lib/talloc/talloc.c
index 33cbfd7d26..bf2fb1f72e 100644
--- a/lib/talloc/talloc.c
+++ b/lib/talloc/talloc.c
@@ -107,6 +107,7 @@ static void *autofree_context;
struct talloc_reference_handle {
struct talloc_reference_handle *next, *prev;
void *ptr;
+ const char *location;
};
typedef int (*talloc_destructor_t)(void *);
@@ -465,7 +466,7 @@ static inline void *_talloc_named_const(const void *context, size_t size, const
same underlying data, and you want to be able to free the two instances separately,
and in either order
*/
-void *_talloc_reference(const void *context, const void *ptr)
+void *_talloc_reference(const void *context, const void *ptr, const char *location)
{
struct talloc_chunk *tc;
struct talloc_reference_handle *handle;
@@ -482,6 +483,7 @@ void *_talloc_reference(const void *context, const void *ptr)
own destructor on the context if they want to */
talloc_set_destructor(handle, talloc_reference_destructor);
handle->ptr = discard_const_p(void, ptr);
+ handle->location = location;
_TLIST_ADD(tc->refs, handle);
return handle->ptr;
}
@@ -490,7 +492,7 @@ void *_talloc_reference(const void *context, const void *ptr)
/*
internal talloc_free call
*/
-static inline int _talloc_free(void *ptr)
+static inline int _talloc_free_internal(void *ptr)
{
struct talloc_chunk *tc;
@@ -510,9 +512,9 @@ static inline int _talloc_free(void *ptr)
* pointer.
*/
is_child = talloc_is_parent(tc->refs, ptr);
- _talloc_free(tc->refs);
+ _talloc_free_internal(tc->refs);
if (is_child) {
- return _talloc_free(ptr);
+ return _talloc_free_internal(ptr);
}
return -1;
}
@@ -559,12 +561,12 @@ static inline int _talloc_free(void *ptr)
struct talloc_chunk *p = talloc_parent_chunk(tc->child->refs);
if (p) new_parent = TC_PTR_FROM_CHUNK(p);
}
- if (unlikely(_talloc_free(child) == -1)) {
+ if (unlikely(_talloc_free_internal(child) == -1)) {
if (new_parent == null_context) {
struct talloc_chunk *p = talloc_parent_chunk(ptr);
if (p) new_parent = TC_PTR_FROM_CHUNK(p);
}
- talloc_steal(new_parent, child);
+ _talloc_steal_internal(new_parent, child);
}
}
@@ -600,7 +602,7 @@ static inline int _talloc_free(void *ptr)
ptr on success, or NULL if it could not be transferred.
passing NULL as ptr will always return NULL with no side effects.
*/
-void *_talloc_steal(const void *new_ctx, const void *ptr)
+void *_talloc_steal_internal(const void *new_ctx, const void *ptr)
{
struct talloc_chunk *tc, *new_tc;
@@ -653,6 +655,66 @@ void *_talloc_steal(const void *new_ctx, const void *ptr)
}
+/*
+ move a lump of memory from one talloc context to another return the
+ ptr on success, or NULL if it could not be transferred.
+ passing NULL as ptr will always return NULL with no side effects.
+*/
+void *_talloc_steal(const void *new_ctx, const void *ptr, const char *location)
+{
+ struct talloc_chunk *tc;
+
+ if (unlikely(ptr == NULL)) {
+ return NULL;
+ }
+
+ tc = talloc_chunk_from_ptr(ptr);
+
+ if (unlikely(tc->refs != NULL) && talloc_parent(ptr) != new_ctx) {
+ struct talloc_reference_handle *h;
+ fprintf(stderr, "ERROR: talloc_steal with references at %s\n", location);
+ for (h=tc->refs; h; h=h->next) {
+ fprintf(stderr, "\treference at %s\n", h->location);
+ }
+ return NULL;
+ }
+
+ return _talloc_steal_internal(new_ctx, ptr);
+}
+
+/*
+ this is like a talloc_steal(), but you must supply the old
+ parent. This resolves the ambiguity in a talloc_steal() which is
+ called on a context that has more than one parent (via references)
+
+ The old parent can be either a reference or a parent
+*/
+void *talloc_reparent(const void *old_parent, const void *new_parent, const void *ptr)
+{
+ struct talloc_chunk *tc;
+ struct talloc_reference_handle *h;
+
+ if (unlikely(ptr == NULL)) {
+ return NULL;
+ }
+
+ if (old_parent == talloc_parent(ptr)) {
+ return _talloc_steal_internal(new_parent, ptr);
+ }
+
+ tc = talloc_chunk_from_ptr(ptr);
+ for (h=tc->refs;h;h=h->next) {
+ if (talloc_parent(h) == old_parent) {
+ if (_talloc_steal_internal(new_parent, h) != h) {
+ return NULL;
+ }
+ return ptr;
+ }
+ }
+
+ /* it wasn't a parent */
+ return NULL;
+}
/*
remove a secondary reference to a pointer. This undo's what
@@ -680,7 +742,7 @@ static inline int talloc_unreference(const void *context, const void *ptr)
return -1;
}
- return _talloc_free(h);
+ return _talloc_free_internal(h);
}
/*
@@ -717,7 +779,7 @@ 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_internal(ptr);
}
new_p = talloc_parent_chunk(tc_p->refs);
@@ -731,7 +793,7 @@ int talloc_unlink(const void *context, void *ptr)
return -1;
}
- talloc_steal(new_parent, ptr);
+ _talloc_steal_internal(new_parent, ptr);
return 0;
}
@@ -784,7 +846,7 @@ void *talloc_named(const void *context, size_t size, const char *fmt, ...)
va_end(ap);
if (unlikely(name == NULL)) {
- _talloc_free(ptr);
+ _talloc_free_internal(ptr);
return NULL;
}
@@ -882,7 +944,7 @@ void *talloc_init(const char *fmt, ...)
va_end(ap);
if (unlikely(name == NULL)) {
- _talloc_free(ptr);
+ _talloc_free_internal(ptr);
return NULL;
}
@@ -916,12 +978,12 @@ 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 (unlikely(_talloc_free(child) == -1)) {
+ if (unlikely(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);
}
- talloc_steal(new_parent, child);
+ _talloc_steal_internal(new_parent, child);
}
}
@@ -969,9 +1031,26 @@ void *talloc_named_const(const void *context, size_t size, const char *name)
will not be freed if the ref_count is > 1 or the destructor (if
any) returns non-zero
*/
-int talloc_free(void *ptr)
+int _talloc_free(void *ptr, const char *location)
{
- return _talloc_free(ptr);
+ struct talloc_chunk *tc;
+
+ if (unlikely(ptr == NULL)) {
+ return -1;
+ }
+
+ tc = talloc_chunk_from_ptr(ptr);
+
+ if (unlikely(tc->refs != NULL)) {
+ struct talloc_reference_handle *h;
+ fprintf(stderr, "ERROR: talloc_free with references at %s\n", location);
+ for (h=tc->refs; h; h=h->next) {
+ fprintf(stderr, "\treference at %s\n", h->location);
+ }
+ return -1;
+ }
+
+ return _talloc_free_internal(ptr);
}
@@ -988,7 +1067,7 @@ void *_talloc_realloc(const void *context, void *ptr, size_t size, const char *n
/* size zero is equivalent to free() */
if (unlikely(size == 0)) {
- _talloc_free(ptr);
+ talloc_free(ptr);
return NULL;
}
@@ -1085,7 +1164,7 @@ void *_talloc_realloc(const void *context, void *ptr, size_t size, const char *n
void *_talloc_move(const void *new_ctx, const void *_pptr)
{
const void **pptr = discard_const_p(const void *,_pptr);
- void *ret = _talloc_steal(new_ctx, *pptr);
+ void *ret = talloc_steal(new_ctx, *pptr);
(*pptr) = NULL;
return ret;
}
@@ -1306,7 +1385,7 @@ void talloc_enable_null_tracking(void)
*/
void talloc_disable_null_tracking(void)
{
- _talloc_free(null_context);
+ talloc_free(null_context);
null_context = NULL;
}
@@ -1688,7 +1767,7 @@ static int talloc_autofree_destructor(void *ptr)
static void talloc_autofree(void)
{
- _talloc_free(autofree_context);
+ talloc_free(autofree_context);
}
/*
diff --git a/lib/talloc/talloc.h b/lib/talloc/talloc.h
index a4b33c3ed4..9d1aa0df04 100644
--- a/lib/talloc/talloc.h
+++ b/lib/talloc/talloc.h
@@ -69,15 +69,15 @@ typedef void TALLOC_CTX;
} while(0)
/* this extremely strange macro is to avoid some braindamaged warning
stupidity in gcc 4.1.x */
-#define talloc_steal(ctx, ptr) ({ _TALLOC_TYPEOF(ptr) __talloc_steal_ret = (_TALLOC_TYPEOF(ptr))_talloc_steal((ctx),(ptr)); __talloc_steal_ret; })
+#define talloc_steal(ctx, ptr) ({ _TALLOC_TYPEOF(ptr) __talloc_steal_ret = (_TALLOC_TYPEOF(ptr))_talloc_steal((ctx),(ptr), __location__); __talloc_steal_ret; })
#else
#define talloc_set_destructor(ptr, function) \
_talloc_set_destructor((ptr), (int (*)(void *))(function))
#define _TALLOC_TYPEOF(ptr) void *
-#define talloc_steal(ctx, ptr) (_TALLOC_TYPEOF(ptr))_talloc_steal((ctx),(ptr))
+#define talloc_steal(ctx, ptr) (_TALLOC_TYPEOF(ptr))_talloc_steal((ctx),(ptr), __location__)
#endif
-#define talloc_reference(ctx, ptr) (_TALLOC_TYPEOF(ptr))_talloc_reference((ctx),(ptr))
+#define talloc_reference(ctx, ptr) (_TALLOC_TYPEOF(ptr))_talloc_reference((ctx),(ptr), __location__)
#define talloc_move(ctx, ptr) (_TALLOC_TYPEOF(*(ptr)))_talloc_move((ctx),(void *)(ptr))
/* useful macros for creating type checked pointers */
@@ -106,6 +106,8 @@ typedef void TALLOC_CTX;
#define talloc_get_type_abort(ptr, type) (type *)_talloc_get_type_abort(ptr, #type, __location__)
#define talloc_find_parent_bytype(ptr, type) (type *)talloc_find_parent_byname(ptr, #type)
+#define talloc_free(ctx) _talloc_free(ctx, __location__)
+
#if TALLOC_DEPRECATED
#define talloc_zero_p(ctx, type) talloc_zero(ctx, type)
@@ -124,7 +126,7 @@ void *talloc_pool(const void *context, size_t size);
void _talloc_set_destructor(const void *ptr, int (*_destructor)(void *));
int talloc_increase_ref_count(const void *ptr);
size_t talloc_reference_count(const void *ptr);
-void *_talloc_reference(const void *context, const void *ptr);
+void *_talloc_reference(const void *context, const void *ptr, const char *location);
int talloc_unlink(const void *context, void *ptr);
const char *talloc_set_name(const void *ptr, const char *fmt, ...) PRINTF_ATTRIBUTE(2,3);
void talloc_set_name_const(const void *ptr, const char *name);
@@ -137,10 +139,12 @@ void *_talloc_get_type_abort(const void *ptr, const char *name, const char *loca
void *talloc_parent(const void *ptr);
const char *talloc_parent_name(const void *ptr);
void *talloc_init(const char *fmt, ...) PRINTF_ATTRIBUTE(1,2);
-int talloc_free(void *ptr);
+int _talloc_free(void *ptr, const char *location);
void talloc_free_children(void *ptr);
void *_talloc_realloc(const void *context, void *ptr, size_t size, const char *name);
-void *_talloc_steal(const void *new_ctx, const void *ptr);
+void *_talloc_steal(const void *new_ctx, const void *ptr, const char *location);
+void *_talloc_steal_internal(const void *new_ctx, const void *ptr);
+void *talloc_reparent(const void *old_parent, const void *new_parent, const void *ptr);
void *_talloc_move(const void *new_ctx, const void *pptr);
size_t talloc_total_size(const void *ptr);
size_t talloc_total_blocks(const void *ptr);