[openbeos] Re: broken struct mouse_map in InterfaceDefs.h
- From: "Andrew Bachmann" <shatty@xxxxxxxxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Mon, 12 Jan 2004 01:08:33 -0800 PST
Oops,
Looks like I lose in at least 2 ways:
Way #1: no R5 compiler supports anonymous structs as union members.
Way #2: anonymous unions in structs are C++ feature and will not
compile in C
So, for future reference all: no anonymous unions in structs in any
headers that are supposed to be C friendly.
In my searchings on this issue I also found a warning about interchanging
access to union members. (that is to say, using a union as a reinterpretation
of the members.) Apparently the spec doesn't require such things to work
in the way you expect. Even on a C++ compiler that supported what I
wrote earlier, for example, middle could be mapped to button[0] instead
of button[2] as one might expect.
I think we have to use separate structs. Any other suggestions?
Andrew
"Andrew Bachmann" <shatty@xxxxxxxxxxxxx> wrote:
[snip]
> I think this is at least a source compatible version:
>
> struct mouse_map {
> union {
> struct {
> uint32 left;
> uint32 right;
> uint32 middle;
> };
> uint32 button[B_MAX_MOUSE_BUTTONS];
> };
> };
>
> This still has a binary compat problem. A better alternative
> would seem to be to use a new struct.
>
> Andrew
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