Re: [PATCH 2/6] Add returns_zero_on_success/failure attributes

On Mon, Nov 15, 2021 at 12:33:16PM +0530, Prathamesh Kulkarni wrote:

On Sun, 14 Nov 2021 at 02:07, David Malcolm via Gcc-patches

quoted

+/* Handle "returns_zero_on_failure" and "returns_zero_on_success" attributes;
+   arguments as in struct attribute_spec.handler.  */
+
+static tree
+handle_returns_zero_on_attributes (tree *node, tree name, tree, int,
+                                  bool *no_add_attrs)
+{
+  if (!INTEGRAL_TYPE_P (TREE_TYPE (*node)))
+    {
+      error ("%qE attribute on a function not returning an integral type",
+            name);
+      *no_add_attrs = true;
+    }
+  return NULL_TREE;

Hi David,
Just curious if a warning should be emitted if the function is marked
with the attribute but it's return value isn't actually 0 ?

There are other constants like -1 or 1 that are often used to indicate
error, so maybe tweak the attribute to
take the integer as an argument ?
Sth like returns_int_on_success(cst) / returns_int_on_failure(cst) ?

Also, would it make sense to extend it for pointers too for returning
NULL on success / failure ?

Please also consider that in Linux we use the 'last' page for error code
returns. That is, a function returning a pointer could return '(void
*)-EFAULT' also see linux/err.h