Am 24.12.24 um 12:07 schrieb Simon Kelley:
On 22/12/2024 10:44, Matthias Andree via Dnsmasq-discuss wrote:
Am 20.12.24 um 22:16 schrieb Simon Kelley:
On 12/20/24 12:27, Matthias Andree via Dnsmasq-discuss wrote:
Simon,
I cannot compile v2.91test1 on FreeBSD 14.2, errors below. (Neither
tarball nor Git compile.) (2nd to last shown errors). Patch attached,
should be fine with git-am.
Patch applied, thanks.
Adding multiple unions with variable size into some other aggregate
(union or struct) isn't portable, first shown warning below, might be
an error on other or strictly set compilers. This needs fixing not
covered by my patch.
If I've understood this right, then
https://thekelleys.org.uk/gitweb/?
p=dnsmasq.git;a=commit;h=4902807879c9b39db46c32e3e082a33266836d24
should fix it.
Thanks, but it's not sufficient, and my wording was unclear, sorry for
that.
I am attaching an incremental git-am ready patch to go on top your
Git HEAD,
to fix all sorts of issues and make this conforming C99 with default
options set,
and fix another load of warnings you receive when setting the compiler
to pick the nits,
-pedantic-errors -std=c99 (or c11, c18, c2x).
It changes many void * to uint8_t * to make the "increment by bytes"
explicit.
You can't do:
void *foo;
// ...
foo += 2.
Understood. There are few more instances of this in Linux-only code.
I'll see to those too.
IMPORTANT: please review the char data[1] in my patch, whether you want
to increase the size.
I see the six header warnings show below for practically all source
files compiled, and regarding the log message:
The warning is from FreeBSD 14.2's clang 18.1.6 compiler, not GCC, which
only shows them under -pedantic (I used GCC 13.3):
The root cause for these warnings appears to be the VLA char data[]
inside union all_addr's struct datablock, see line 342 of src/dnsmasq.h:
336 /* for arbitrary RR record small enough to go in addr.
337 NOTE: rrblock and rrdata are discriminated by the
F_KEYTAG bit
338 in the cache flags. */
339 struct datablock {
340 unsigned short rrtype;
341 unsigned char datalen; /* also length of SOA in negative
records. */
342 char data[];
343 } rrdata;
344 };
Declaring this as char data[1] or data[16] or whatever is suitable
should fix the warnings. data[0] is non-conforming and won't work
either.
I don't know what's a good size here, as I haven't read enough context
code to judge that. My patch sets it 1 because that's the minimum in
order not to bloat the structure.
data[1] will, I think, work fine.
The plan here is to to have a union tag that stores the rrtype and a
small length field and uses the rest of the space in the union to
store RR data when that's small enough. The size of the union is at
least 16 bytes, because it can store an IPv6 address, and I don't want
it to get any larger than that.
The line
#define RR_IMDATALEN (sizeof(union all_addr) - offsetof(struct
datablock, data))
calculates how much data will fit and is used in the code. This is
always 13 bytes at the moment. Sadly, the chicken-and-egg problem
prevents the use of that expression in the declaration of data[]
Declaring data[1] and then writing bytes up to data[12] clearly works
whilst struct rrdata is part of a union of size 16, but I wonder if it
will trip over array-overflow checking?
Maybe we should stop being clever,
#define RR_IMDATALEN 13
and declare data[RR_IMDATALEN];
That at least stays away from language definition areas I don't claim
to understand.
I think the previous RR_IMDATALEN expression is fine as long as you
#include <stddef.h> before its first use, and as along as you won't coin
your own version of offsetof, of which I don't know a
conforming/portable way.
The next thing you'll be missing is a _Static_assert to ensure
sizeof(data) <= 16. Which isn't C99. :-)
Could you also push the v2.91test3 tag to the public Git? Its HEAD is at
7c348a0, there is also a test3 tarball, but no Git tag, and my patches
still apply on top of it, so it's older, my guess is 3ac11cd.
Thanks in adavance.
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