On 3/25/22 12:45, David Malcolm wrote:
On Wed, 2022-03-23 at 17:52 +0100, Sebastian Huber wrote:
On 23/03/2022 17:31, Martin Sebor via Gcc-patches wrote:
The concern is that the constraints implied by atttributes access
and
nonnull are independent of each other. I would suggest to document
that without talking about dereferencing because that's not implied
by either of them. E.g., something like this (feel free to tweak
it
as you see fit):
Note that the @code{access} attribute doesn't imply the same
constraint as attribute @code{nonnull} (@pxref{Attribute
nonnull}).
The latter attribute should be used to annotate arguments that
must
never be null, regardless of the value of the size argument.
I would not give an advice on using the nonnull attribute here. This
attribute could have pretty dangerous effects in the function
definition
(removal of null pointer checks).
That's a fair point.
Here's a v3 of the patch, which tones down the advice, and mentions that
there are caveats when directing the reader to the "nonnull" attribute.
How does this look?
This version looks good to me.
Thanks
Martin
gcc/ChangeLog:
* doc/extend.texi (Common Function Attributes): Document that
'access' does not imply 'nonnull'.
Signed-off-by: David Malcolm <dmalc...@redhat.com>
---
gcc/doc/extend.texi | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index a4a25e86928..539dad7001d 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -2652,6 +2652,14 @@ The mode is intended to be used as a means to help
validate the expected
object size, for example in functions that call @code{__builtin_object_size}.
@xref{Object Size Checking}.
+Note that the @code{access} attribute merely specifies how an object
+referenced by the pointer argument can be accessed; it does not imply that
+an access @strong{will} happen. Also, the @code{access} attribute does not
+imply the attribute @code{nonnull}; it may be appropriate to add both
attributes
+at the declaration of a function that unconditionally manipulates a buffer via
+a pointer argument. See the @code{nonnull} attribute for more information and
+caveats.
+
@item alias ("@var{target}")
@cindex @code{alias} function attribute
The @code{alias} attribute causes the declaration to be emitted as an alias
