Re: [PATCH 2/2] Documentation Update.

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 2023-01-31 09:11, Qing Zhao wrote:
> Update documentation to clarify a GCC extension on structure with
> flexible array member being nested in another structure.
> 
> gcc/ChangeLog:
> 
> 	* doc/extend.texi: Document GCC extension on a structure containing
> 	a flexible array member to be a member of another structure.

Should this resolve pr#77650 since the proposed action there appears to 
be to document these semantics?

Thanks,
Sid

> ---
>   gcc/doc/extend.texi | 35 ++++++++++++++++++++++++++++++++++-
>   1 file changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> index 4a89a3eae7c..54e4baf49a9 100644
> --- a/gcc/doc/extend.texi
> +++ b/gcc/doc/extend.texi
> @@ -1748,7 +1748,40 @@ Flexible array members may only appear as the last member of a
>   A structure containing a flexible array member, or a union containing
>   such a structure (possibly recursively), may not be a member of a
>   structure or an element of an array.  (However, these uses are
> -permitted by GCC as extensions.)
> +permitted by GCC as extensions, see details below.)
> +@end itemize
> +
> +GCC extension accepts a structure containing a flexible array member, or
> +a union containing such a structure (possibly recursively) to be a member
> +of a structure.
> +
> +There are two situations:
> +
> +@itemize @bullet
> +@item
> +The structure with a flexible array member is the last field of another
> +structure, for example:
> +
> +@smallexample
> +struct flex  @{ int length; char data[]; @};
> +
> +struct out_flex @{ int m; struct flex flex_data; @};
> +@end smallexample
> +
> +In the above, @code{flex_data.data[]} is considered as a flexible array too.
> +
> +@item
> +The structure with a flexible array member is the middle field of another
> +structure, for example:
> +
> +@smallexample
> +struct flex  @{ int length; char data[]; @};
> +
> +struct mid_flex @{ int m; struct flex flex_data; int n; @};
> +@end smallexample
> +
> +In the above, @code{flex_data.data[]} is allowed to be extended flexibly to
> +the padding. E.g, up to 4 elements.
>   @end itemize
>   
>   Non-empty initialization of zero-length