Bug 101618

Summary:	wl_array_for_each is not C++ compliant
Product:	Wayland	Reporter:	msisov <msisov>
Component:	wayland	Assignee:	Wayland bug list <wayland-bugs>
Status:	RESOLVED MOVED	QA Contact:
Severity:	trivial
Priority:	medium	CC:	tonikitoo
Version:	unspecified
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description msisov 2017-06-28 06:40:18 UTC

Hi,

We've faced an issue, when we used wl_array_for_each in our C++ wayland client implementation.

The problem is that one can't use wl_array_for_each(pos, array) when 
pos is passed as uint32_t*, for example, and array->data is assigned to it. In C++, one cannot just convert void* to other pointer type implicitly as in C.

Is it possible to modify the macro defined to have explicit type cast?

#define wl_array_for_each(pos, array)	\
	for (pos = (uint32_t*) (array)->data; \

or maybe intptr_t before (array)->data ??. 

I'm not sure which one would be better, but it is to you to decide.

Br,
msisov

Comment 1 Daniel Stone 2017-06-28 09:22:20 UTC

It cannot be cast to uint32_t as the type is not known in advance; for example, the modifiers_map request from the text_input protocol uses an array of uint8_t.

Is it possible to do the cast with typeof(*pos)? Every time I think I remember how type-casting works in C++ I'm wrong, so maybe it wouldn't work.

Comment 2 msisov 2017-06-28 12:05:50 UTC

Well, (typeof(pos)) works well, IIRC, C++ doesn't have such a thing like typeof. decltype is used instead. Of course, one can use typeof with C++, but it's rather a compile extension rather than the feature of the language.

Comment 3 msisov 2017-06-28 12:06:16 UTC

Sorry,

s/Well, (typeof(pos)) works well, IIRC,/Well, (typeof(pos)) works well, BUT IIRC,/

Comment 4 GitLab Migration User 2018-06-08 23:49:48 UTC

-- GitLab Migration Automatic Message --

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