tree 0b4ac62ed3873b0c38dc47598fdbcaf18dc86048
parent 64764fd6debc749fd2025f2ea6e7c98c6758ccdd
author Andrew Jeffery <andrew@codeconstruct.com.au> 1713924722 +0930
committer Andrew Jeffery <andrew@codeconstruct.com.au> 1714391691 +0930

msgbuf: Enable pldm_msgbuf_extract() into packed members

`pldm_msgbuf_extract()` should work correctly regardless of whether the
`dst` argument is a member of a packed or padded struct.

To get there while still achieving type safety we have to jump through
some hoops. Commentary in the patch hopefully captures many of them, but
a side-effect of the hoop-jumping is a couple of changes to ergonomics
of the msgbuf API:

1. `pldm_msgbuf_extract()` no-longer requires that the `dst`
   argument be a pointer. Instead, it must be an lvalue, removing all
   the `&<lvalue>` noise from the call-sites.

2. However, unfortunately the generic extraction macro has been split in
   two. We now have:

   2.1 `pldm_msgbuf_extract()`, and
   2.2 `pldm_msgbuf_extract_p()`, for when the reference we already have
        for the `dst` object is a pointer and not an lvalue.

The split was necessary because I couldn't get GCC and Clang to play
nice with differences required in the assignment expression for lvalue
and pointer type-names in the one macro. Whilst it causes a bunch of
churn it isn't a great concern as the APIs are purely internal to the
library implementation.

Change-Id: Ifc5440a5b838a48bb84c881ec334d9e145365edb
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Signed-off-by: Thu Nguyen <thu@os.amperecomputing.com>