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.

1 files changed, 10 insertions, 6 deletions

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);