[PATCH wayland 2/2] scanner: Generate all SINCE_VERSION macros for everyone

[Quentin Glidic]

On 08/08/2016 15:45, Pekka Paalanen wrote:
> On Tue,  5 Jul 2016 20:41:50 +0200
> Quentin Glidic <sardemff7+wayland at sardemff7.net> wrote:
>
>> From: Quentin Glidic <sardemff7+git at sardemff7.net>
>>
>> Practical example: a client supporting version 2 of wl_output will wait
>> for the wl_output.done event before starting wl_output-related
>> operations. However, if the server only supports version 1, no event
>> will ever come, and it must fallback to use the wl_output.geometry event
>> alone.
>> Without this macro, it cannot check for that in a nice way.
>>
>> Signed-off-by: Quentin Glidic <sardemff7+git at sardemff7.net>
>> ---
>>
>> I do not have a real world use-case for the request macro on the server-side,
>> but I guess you could do the same: wait the for a "commit" request if client is
>> new enough, otherwise use some older request as commit.
>>
>> Actually I think there was something like that somewhere, now that I write that,
>> but I do not remember where exactly.
>>
>>
>>  src/scanner.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/src/scanner.c b/src/scanner.c
>> index 4708cae..a4c1984 100644
>> --- a/src/scanner.c
>> +++ b/src/scanner.c
>> @@ -1544,10 +1544,12 @@ emit_header(struct protocol *protocol, enum side side)
>>  			emit_structs(&i->request_list, i, side);
>>  			emit_opcodes(&i->event_list, i);
>>  			emit_opcode_versions(&i->event_list, i);
>> +			emit_opcode_versions(&i->request_list, i);
>>  			emit_event_wrappers(&i->event_list, i);
>>  		} else {
>>  			emit_structs(&i->event_list, i, side);
>>  			emit_opcodes(&i->request_list, i);
>> +			emit_opcode_versions(&i->event_list, i);
>>  			emit_opcode_versions(&i->request_list, i);
>>  			emit_stubs(&i->request_list, i);
>>  		}
>
> Hi,
>
> I have just one question about this. Users must be able to include both
> server and client headers in the same compilation unit. Wouldn't this
> cause the same thing to be #defined in two different headers? More
> importantly, are we sure it won't cause problems?

At least with GCC, you can have twice the same #define (same name + same 
value) without issue. I do not know about the C standard take on that 
though.

If that would cause problems, it would be because a request and an event 
have the same name, and come from different versions. But if a user must 
be able to include both client and server headers, it is already an issue.

If you really want, I can make server-side define events + prefixed 
requests and the other way around.

server.h:
#define NAMESPACE_INTERFACE_SOMEEV_SINCE_VERSION 2
#define NAMESPACE_INTERFACE_REQUEST_SOMEREQ_SINCE_VERSION 3
client.h:
#define NAMESPACE_INTERFACE_EVENT_SOMEEV_SINCE_VERSION 2
#define NAMESPACE_INTERFACE_SOMEREQ_SINCE_VERSION 3


Cheers,

-- 

Quentin “Sardem FF7” Glidic