r2718: - added a talloc_unreference() function as requested by metze.

- added documentation for talloc_unreference()

- made the abandoned child logic in talloc_free() clearer and more consistent
(This used to be commit a87584c8e3fb06cd3ff29a918f681b5c6c32b9ff)

3 files changed, 175 insertions, 19 deletions

diff --git a/source4/lib/talloc.c b/source4/lib/talloc.c
index d0056d7b2a..bb2ed9449c 100644
--- a/source4/lib/talloc.c
+++ b/source4/lib/talloc.c
@@ -170,6 +170,34 @@ void *talloc_reference(const void *context, const void *ptr)
 	return handle->ptr;
 }
 
+/*
+  remove a secondary reference to a pointer. This undo's what
+  talloc_reference() has done. The context and pointer arguments
+  must match those given to a talloc_reference()
+*/
+void *talloc_unreference(const void *context, const void *ptr)
+{
+	struct talloc_chunk *tc = talloc_chunk_from_ptr(ptr);
+	struct talloc_reference_handle *h;
+
+	if (context == NULL) {
+		context = null_context;
+	}
+
+	for (h=tc->refs;h;h=h->next) {
+		struct talloc_chunk *tc2 = talloc_chunk_from_ptr(h);
+		const void *parent = tc2->parent?tc2->parent+1:null_context;
+		if (parent == context) break;
+	}
+	if (h == NULL) {
+		return NULL;
+	}
+
+	talloc_set_destructor(h, NULL);
+	DLIST_REMOVE(tc->refs, h);
+	talloc_free(h);
+	return discard_const(ptr);
+}
 
 /*
   add a name to an existing pointer - va_list version
@@ -318,8 +346,21 @@ int talloc_free(void *ptr)
 	}
 
 	while (tc->child) {
-		talloc_free(talloc_steal(tc->parent?tc->parent+1:null_context, 
-					 tc->child+1));
+		/* we need to work out who will own an abandoned child
+		   if it cannot be freed. In priority order, the first
+		   choice is owner of any remaining reference to this
+		   pointer, the second choice is our parent, and the
+		   final choice is the null context. */
+		void *child = tc->child+1;
+		const void *new_parent = null_context;
+		if (tc->child->refs) {
+			struct talloc_chunk *ref = talloc_chunk_from_ptr(tc->child->refs);
+			if (ref->parent) new_parent = ref->parent+1;
+		}
+		if (new_parent == null_context && tc->parent) {
+			new_parent = tc->parent+1;
+		}
+		talloc_free(talloc_steal(new_parent, child));
 	}
 
 	if (tc->parent) {
diff --git a/source4/torture/local/talloc.c b/source4/torture/local/talloc.c
index 4c353ecbbd..9f518eabf2 100644
--- a/source4/torture/local/talloc.c
+++ b/source4/torture/local/talloc.c
@@ -22,20 +22,6 @@
 
 #include "includes.h"
 
-static struct timeval tp1,tp2;
-
-static void start_timer(void)
-{
-	gettimeofday(&tp1,NULL);
-}
-
-static double end_timer(void)
-{
-	gettimeofday(&tp2,NULL);
-	return((tp2.tv_sec - tp1.tv_sec) + 
-	       (tp2.tv_usec - tp1.tv_usec)*1.0e-6);
-}
-
 /*
   test references 
 */
@@ -68,7 +54,7 @@ static BOOL test_ref1(void)
 	talloc_report_full(NULL, stdout);
 
 	if (talloc_total_size(NULL) != 0) {
-		printf("non-zero total size\n");
+		printf("failed: non-zero total size\n");
 		return False;
 	}
 
@@ -93,21 +79,134 @@ static BOOL test_ref2(void)
 	r1 = talloc_named_const(NULL, 1, "r1");	
 	ref = talloc_reference(r1, p2);
 	talloc_report_full(NULL, stdout);
+
 	printf("Freeing ref\n");
 	talloc_free(ref);
 	talloc_report_full(NULL, stdout);
+
 	printf("Freeing p2\n");
 	talloc_free(p2);
 	talloc_report_full(NULL, stdout);
+
 	printf("Freeing p1\n");
 	talloc_free(p1);
 	talloc_report_full(NULL, stdout);
+
 	printf("Freeing r1\n");
 	talloc_free(r1);
 	talloc_report_full(NULL, stdout);
 
 	if (talloc_total_size(NULL) != 0) {
-		printf("non-zero total size\n");
+		printf("failed: non-zero total size\n");
+		return False;
+	}
+
+	return True;
+}
+
+/*
+  test references 
+*/
+static BOOL test_ref3(void)
+{
+	void *p1, *p2, *ref, *r1;
+
+	printf("TESTING PARENT REFERENCE FREE\n");
+
+	p1 = talloc_named_const(NULL, 1, "p1");
+	p2 = talloc_named_const(NULL, 1, "p2");
+
+	r1 = talloc_named_const(p1, 1, "r1");
+
+	ref = talloc_reference(p2, r1);
+
+	talloc_report_full(NULL, stdout);
+
+	printf("Freeing p1\n");
+	talloc_free(p1);
+	talloc_report_full(NULL, stdout);
+
+	printf("Freeing p2\n");
+	talloc_free(p2);
+	talloc_report_full(NULL, stdout);
+
+	if (talloc_total_size(NULL) != 0) {
+		printf("failed: non-zero total size\n");
+		return False;
+	}
+
+	return True;
+}
+
+/*
+  test references 
+*/
+static BOOL test_ref4(void)
+{
+	void *p1, *p2, *ref, *r1;
+
+	printf("TESTING REFERRER REFERENCE FREE\n");
+
+	p1 = talloc_named_const(NULL, 1, "p1");
+	talloc_named_const(p1, 1, "x1");
+	talloc_named_const(p1, 1, "x2");
+	talloc_named_const(p1, 1, "x3");
+	p2 = talloc_named_const(p1, 1, "p2");
+
+	r1 = talloc_named_const(NULL, 1, "r1");	
+	ref = talloc_reference(r1, p2);
+	talloc_report_full(NULL, stdout);
+
+	printf("Freeing r1\n");
+	talloc_free(r1);
+	talloc_report_full(NULL, stdout);
+
+	printf("Freeing p2\n");
+	talloc_free(p2);
+	talloc_report_full(NULL, stdout);
+
+	printf("Freeing p1\n");
+	talloc_free(p1);
+	talloc_report_full(NULL, stdout);
+
+	if (talloc_total_size(NULL) != 0) {
+		printf("failed: non-zero total size\n");
+		return False;
+	}
+
+	return True;
+}
+
+
+/*
+  test references 
+*/
+static BOOL test_unref1(void)
+{
+	void *p1, *p2, *ref, *r1;
+
+	printf("TESTING UNREFERENCE\n");
+
+	p1 = talloc_named_const(NULL, 1, "p1");
+	talloc_named_const(p1, 1, "x1");
+	talloc_named_const(p1, 1, "x2");
+	talloc_named_const(p1, 1, "x3");
+	p2 = talloc_named_const(p1, 1, "p2");
+
+	r1 = talloc_named_const(p1, 1, "r1");	
+	ref = talloc_reference(r1, p2);
+	talloc_report_full(NULL, stdout);
+
+	printf("Unreferencing r1\n");
+	talloc_unreference(r1, p2);
+	talloc_report_full(NULL, stdout);
+
+	printf("Freeing p1\n");
+	talloc_free(p1);
+	talloc_report_full(NULL, stdout);
+
+	if (talloc_total_size(NULL) != 0) {
+		printf("failed: non-zero total size\n");
 		return False;
 	}
 
@@ -137,6 +236,8 @@ static BOOL test_speed(void)
 
 	printf("talloc: %.0f ops/sec\n", count/end_timer());
 
+	talloc_free(ctx);
+
 	start_timer();
 	count = 0;
 	do {
@@ -164,7 +265,10 @@ BOOL torture_local_talloc(int dummy)
 
 	ret &= test_ref1();
 	ret &= test_ref2();
+	ret &= test_ref3();
+	ret &= test_ref4();
+	ret &= test_unref1();
 	ret &= test_speed();
 
-	return True;
+	return ret;
 }
diff --git a/talloc_guide.txt b/talloc_guide.txt
index ed3f7713aa..6920ea16f1 100644
--- a/talloc_guide.txt
+++ b/talloc_guide.txt
@@ -125,6 +125,17 @@ ways:
 
 
 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+void *talloc_unreference(const void *context, const void *ptr);
+
+The talloc_unreference() function removes a reference added by
+talloc_reference(). It must be called with exactly the same arguments
+as talloc_reference().
+
+Note that if the reference has already been removed using
+talloc_free() then this function will fail and will return NULL.
+
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 void talloc_set_destructor(const void *ptr, int (*destructor)(void *));
 
 The function talloc_set_destructor() sets the "destructor" for the