lib: Allow static analyzers to check for t_pop() leaks.

They should be able to detect the missing free() call from code paths
missing a t_pop().

src/lib/data-stack.c

@@ -67,13 +67,13 @@ struct stack_frame_block {
 #endif
 };
 
-#ifdef DEBUG
+#ifdef STATIC_CHECKER
 struct data_stack_frame {
-	int dummy;
+	unsigned int id;
 };
 #endif
 
-data_stack_frame_t data_stack_frame = 0;
+unsigned int data_stack_frame_id = 0;
 
 static bool data_stack_initialized = FALSE;
 static data_stack_frame_t root_frame_id;
@@ -184,7 +184,13 @@ data_stack_frame_t t_push(const char *marker)
 	(void)marker; /* only used for debugging */
 #endif
 
-	return data_stack_frame++;
+#ifndef STATIC_CHECKER
+	return data_stack_frame_id++;
+#else
+	struct data_stack_frame *frame = i_new(struct data_stack_frame, 1);
+	frame->id = data_stack_frame_id++;
+	return frame;
+#endif
 }
 
 data_stack_frame_t t_push_named(const char *format, ...)
@@ -314,9 +320,17 @@ bool t_pop(data_stack_frame_t *id)
 		frame_block->prev = unused_frame_blocks;
 		unused_frame_blocks = frame_block;
 	}
-	if (unlikely(--data_stack_frame != *id))
+#ifndef STATIC_CHECKER
+	if (unlikely(--data_stack_frame_id != *id))
 		return FALSE;
 	*id = 0;
+#else
+	unsigned int frame_id = (*id)->id;
+	i_free_and_null(*id);
+
+	if (unlikely(--data_stack_frame_id != frame_id))
+		return FALSE;
+#endif
 	return TRUE;
 }
 
@@ -577,7 +591,7 @@ void data_stack_init(void)
 		return;
 	}
 	data_stack_initialized = TRUE;
-	data_stack_frame = (data_stack_frame_t)1;
+	data_stack_frame_id = 1;
 
 	outofmem_area.block.size = outofmem_area.block.left =
 		sizeof(outofmem_area) - sizeof(outofmem_area.block);

src/lib/data-stack.h

@@ -31,13 +31,13 @@
       overflows.
 */
 
-#ifndef DEBUG
+#ifndef STATIC_CHECKER
 typedef unsigned int data_stack_frame_t;
 #else
 typedef struct data_stack_frame *data_stack_frame_t;
 #endif
 
-extern data_stack_frame_t data_stack_frame;
+extern unsigned int data_stack_frame_id;
 
 /* All t_..() allocations between t_push*() and t_pop() are freed after t_pop()
    is called. Returns the current stack frame number, which can be used

src/lib/mempool-datastack.c

@@ -40,7 +40,7 @@ struct datastack_pool {
 	struct pool pool;
 	int refcount;
 
-	data_stack_frame_t data_stack_frame;
+	unsigned int data_stack_frame;
 };
 
 pool_t pool_datastack_create(void)
@@ -50,7 +50,7 @@ pool_t pool_datastack_create(void)
 	dpool = t_new(struct datastack_pool, 1);
 	dpool->pool = static_data_stack_pool;
 	dpool->refcount = 1;
-	dpool->data_stack_frame = data_stack_frame;
+	dpool->data_stack_frame = data_stack_frame_id;
 	return &dpool->pool;
 }
 
@@ -63,7 +63,7 @@ static void pool_data_stack_ref(pool_t pool)
 {
 	struct datastack_pool *dpool = (struct datastack_pool *) pool;
 
-	if (unlikely(dpool->data_stack_frame != data_stack_frame))
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
 		i_panic("pool_data_stack_ref(): stack frame changed");
 
 	dpool->refcount++;
@@ -73,7 +73,7 @@ static void pool_data_stack_unref(pool_t *pool)
 {
 	struct datastack_pool *dpool = (struct datastack_pool *)*pool;
 
-	if (unlikely(dpool->data_stack_frame != data_stack_frame))
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
 		i_panic("pool_data_stack_unref(): stack frame changed");
 
 	dpool->refcount--;
@@ -89,7 +89,7 @@ static void *pool_data_stack_malloc(pool_t pool ATTR_UNUSED, size_t size)
 	if (unlikely(size == 0 || size > SSIZE_T_MAX))
 		i_panic("Trying to allocate %"PRIuSIZE_T" bytes", size);
 
-	if (unlikely(dpool->data_stack_frame != data_stack_frame))
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
 		i_panic("pool_data_stack_malloc(): stack frame changed");
 
 	return t_malloc0(size);
@@ -99,7 +99,7 @@ static void pool_data_stack_free(pool_t pool, void *mem ATTR_UNUSED)
 {
 	struct datastack_pool *dpool = (struct datastack_pool *) pool;
 
-	if (unlikely(dpool->data_stack_frame != data_stack_frame))
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
 		i_panic("pool_data_stack_free(): stack frame changed");
 }
 
@@ -113,7 +113,7 @@ static void *pool_data_stack_realloc(pool_t pool, void *mem,
 	if (unlikely(new_size == 0 || new_size > SSIZE_T_MAX))
 		i_panic("Trying to allocate %"PRIuSIZE_T" bytes", new_size);
 
-	if (unlikely(dpool->data_stack_frame != data_stack_frame))
+	if (unlikely(dpool->data_stack_frame != data_stack_frame_id))
 		i_panic("pool_data_stack_realloc(): stack frame changed");
 
 	if (mem == NULL)