New talloc_set for auto-cleanup.

[ccan] / ccan / talloc / talloc.h

diff --git a/ccan/talloc/talloc.h b/ccan/talloc/talloc.h
index 380009f380f8f16893019e33c178fe8eb575074a..54a702050e96d73409c8169e5ac58b11b359fc68 100644 (file)
--- a/ccan/talloc/talloc.h
+++ b/ccan/talloc/talloc.h
@@ -26,8 +26,8 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
+#include <ccan/typesafe_cb/typesafe_cb.h>
 #include "config.h"
-#include "typesafe_cb/typesafe_cb.h"
 
 /*
   this uses a little trick to allow __LINE__ to be stringified
@@ -87,6 +87,30 @@
  */
 #define talloc(ctx, type) (type *)talloc_named_const(ctx, sizeof(type), #type)
 
+/**
+ * talloc_set - allocate dynamic memory for a type, into a pointer
+ * @ptr: pointer to the pointer to assign.
+ * @ctx: context to be parent of this allocation, or NULL.
+ *
+ * talloc_set() does a talloc, but also adds a destructor which will make the
+ * pointer invalid when it is freed.  This can find many use-after-free bugs.
+ *
+ * Note that the destructor is chained off a zero-length allocation, and so
+ * is not affected by talloc_set_destructor().
+ *
+ * Example:
+ *     unsigned int *a;
+ *     a = talloc(NULL, unsigned int);
+ *     talloc_set(&b, a, unsigned int);
+ *     talloc_free(a);
+ *     *b = 1; // This will crash!
+ *
+ * See Also:
+ *     talloc.
+ */
+#define talloc_set(pptr, ctx) \
+       _talloc_set((pptr), (ctx), sizeof(&**(pptr)), __location__)
+
 /**
  * talloc_free - free talloc'ed memory and its children
  * @ptr: the talloced pointer to free
@@ -119,7 +143,7 @@
  * See Also:
  *     talloc_set_destructor, talloc_unlink
  */
-int talloc_free(void *ptr);
+int talloc_free(const void *ptr);
 
 /**
  * talloc_set_destructor: set a destructor for when this pointer is freed
@@ -917,6 +941,8 @@ void *talloc_find_parent_byname(const void *ctx, const char *name);
  * talloc_add_external - create an externally allocated node
  * @ctx: the parent
  * @realloc: the realloc() equivalent
+ * @lock: the call to lock before manipulation of external nodes
+ * @unlock: the call to unlock after manipulation of external nodes
  *
  * talloc_add_external() creates a node which uses a separate allocator.  All
  * children allocated from that node will also use that allocator.
@@ -924,32 +950,21 @@ void *talloc_find_parent_byname(const void *ctx, const char *name);
  * Note: Currently there is only one external allocator, not per-node,
  * and it is set with this function.
  *
+ * @lock is handed a pointer which was previous returned from your realloc
+ * function; you should use that to figure out which lock to get if you have
+ * multiple external pools.
+ *
  * The parent pointers in realloc is the talloc pointer of the parent, if any.
  */
 void *talloc_add_external(const void *ctx,
                          void *(*realloc)(const void *parent,
-                                          void *ptr, size_t));
-
-/**
- * talloc_locksafe - set locking for talloc on shared memory
- * @lock: function to use to lock memory
- * @unlock: function to use to unlock memory
- * @data: pointer to hand to @lock and @unlock
- *
- * If talloc is actually dealing with shared memory (threads or shared
- * memory using talloc_add_external()) then locking is required on
- * allocation and free to avoid corruption.
- *
- * These hooks allow a very course-grained locking scheme: @lock is
- * called before any internal alloc or free, and @unlock is called
- * after. */
-#define talloc_locksafe(lock, unlock, data)                    \
-       _talloc_locksafe(typesafe_cb(void, lock, data),         \
-                        typesafe_cb(void, unlock, data),       \
-                        data)
+                                          void *ptr, size_t),
+                         void (*lock)(const void *p),
+                         void (*unlock)(void));
 
 /* The following definitions come from talloc.c  */
 void *_talloc(const void *context, size_t size);
+void _talloc_set(void *ptr, const void *ctx, size_t size, const char *name);
 void _talloc_set_destructor(const void *ptr, int (*destructor)(void *));
 size_t talloc_reference_count(const void *ptr);
 void *_talloc_reference(const void *context, const void *ptr);
@@ -967,6 +982,5 @@ void *_talloc_realloc_array(const void *ctx, void *ptr, size_t el_size, unsigned
 void *talloc_realloc_fn(const void *context, void *ptr, size_t size);
 void talloc_show_parents(const void *context, FILE *file);
 int talloc_is_parent(const void *context, const void *ptr);
-void _talloc_locksafe(void (*lock)(void *), void (*unlock)(void *), void *);
 
 #endif /* CCAN_TALLOC_H */