fixeria has posted comments on this change. (
https://gerrit.osmocom.org/c/libosmocore/+/31505 )
Change subject: gsm/{bsslap,bssmap_le}: zero-initialize structs using memset()
......................................................................
Patch Set 2:
(1 comment)
Patchset:
PS1:
> oh. Actually in API functions it is fine for padding bytes to be returned
> random.
Yes, it's fine. Because a regular user does not care about padding bytes in
structs. But the unit test does, because it uses `memcpy()` to compare the
whole chunk of memory.
> except if you are saying, a struct that has been memset(0) has its padding
> bytes overwritten randomly by *foo = (struct foo){} ... in my world so far
> that does not happen, but if zero padding does not stay zero, that would be a
> reason to memset(0) in the API implementation too, and that would change how
> I understand struct initialization.
This is exactly what I am saying and for me this was a new experience seeing
that valgrind reports (I was not able to reproduce this with ASAN)
uninitialized memory access, despite that part of memory has been explicitly
initialized in the unit test with `memset()`. The C11 standard is clear on this
though: "... the bytes of the object representation that correspond to any
padding bytes take unspecified values".
> I just find memset(0) looks ugly, and regression tests are allowed to look
> ugly, API implementations not so much.
Agreeing with Harald here. I see nothing wrong using it.
We should actually be careful with `{}`, as it's a non-standard GCC's extension.
https://stackoverflow.com/questions/17589533/is-an-empty-initializer-list-valid-c-code/54409687#54409687
--
To view, visit https://gerrit.osmocom.org/c/libosmocore/+/31505
To unsubscribe, or for help writing mail filters, visit
https://gerrit.osmocom.org/settings
Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Change-Id: Ib16964b16eb04315efc416164ed46c15b5dc7254
Gerrit-Change-Number: 31505
Gerrit-PatchSet: 2
Gerrit-Owner: fixeria <[email protected]>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <[email protected]>
Gerrit-Reviewer: neels <[email protected]>
Gerrit-Comment-Date: Sat, 25 Feb 2023 08:59:56 +0000
Gerrit-HasComments: Yes
Gerrit-Has-Labels: No
Comment-In-Reply-To: neels <[email protected]>
Comment-In-Reply-To: laforge <[email protected]>
Gerrit-MessageType: comment
