docs: deprecated.rst: Update zero-length/one-element arrays section

Update information in the zero-length and one-element arrays section
and illustrate how to make use of the new flex_array_size() helper,
together with struct_size() and a flexible-array member.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200901010949.GA21398@embeddedor
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Gustavo A. R. Silva 2020-08-31 20:09:49 -05:00 committed by Jonathan Corbet
parent 9334e34fe1
commit 17dca05023

View File

@ -304,7 +304,8 @@ to allocate for a structure containing an array of this kind as a member::
In the example above, we had to remember to calculate ``count - 1`` when using
the struct_size() helper, otherwise we would have --unintentionally-- allocated
memory for one too many ``items`` objects. The cleanest and least error-prone way
to implement this is through the use of a `flexible array member`::
to implement this is through the use of a `flexible array member`, together with
struct_size() and flex_array_size() helpers::
struct something {
size_t count;
@ -316,5 +317,4 @@ to implement this is through the use of a `flexible array member`::
instance = kmalloc(struct_size(instance, items, count), GFP_KERNEL);
instance->count = count;
size = sizeof(instance->items[0]) * instance->count;
memcpy(instance->items, source, size);
memcpy(instance->items, source, flex_array_size(instance, items, instance->count));