[riot-notifications] [RIOT-OS/RIOT] gnrc/ipv6_auto_subnets: relax topology requirements (#16750)

benpicco notifications at github.com
Tue Sep 28 16:32:11 CEST 2021

@benpicco commented on this pull request.

> +    uint8_t version : 4;    /**< version number, should be 0 */
+    uint8_t flags   : 4;    /**< flags, unused, should be 0 */

> **If enough space remains**, a bit-field that immediately follows another bit-field in a structure shall be **packed into adjacent bits of the same unit**. If **insufficient space remains**, whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is implementation-defined.

This is only an issue if you write

struct foo {
    uint8_t version : 4; 
    uint8_t flags   : 6;
} _auto_subnets_request_t;

Now `flags` could either use some bits of the first byte or entirely occupy the second byte.

If the bits add up to a whole byte, there should be no ambiguity. 

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