sys/net/gnrc_pktbuf_static: add double free detection

[benpicco]

Contribution description

The basic idea is: all free data is filled with CANARY bytes, once data is allocated this is overwritten with ~CANARY.
When data is freed we now check if the chunk is only set to CANARY - if this happens, it was already freed.

Testing procedure

Set CONFIG_GNRC_PKTBUF_CHECK_USE_AFTER_FREE to 1.

Issues/PRs references

[riot-ci]

Murdock results

✔️ PASSED

982af61 sys/net/gnrc_pktbuf_static: make hexdump optional

Success	Failures	Total	Runtime
10250	0	10251	18m:04s

Artifacts

• Documentation preview

[maribu]

Looks like the Murdock queue and the Github queue got out of sync. If the current Murdock build of this succeeds but this PR will not get merged due to the sync issue, I'll requeue it without compile-testing to not waste another 4 h.

[maribu]

The Murdock run failed (probably bogus), but let's have a full run again.

[maribu]

This did just pass the CI: https://ci.riot-os.org/details/0e58eacd8ce441bab5074592a9f1b431

Because of a timeout in the merge queue, it did not get merged. I'll requeue without compile test now and add it to the head of the queue, so that everything is as if it were merged after passing the CI.

[maribu]

so that everything is as if it were merged after passing the CI.

The PR that changes the README.md ended up getting queued first. So it is not exactly as if it this PR got merged right after the test. But I feel confident that a README.md change will not break builds.

[maribu]

OK, now other stuff got merged as well. Let's have a full CI run again.