[Dnsmasq-discuss] Three v2.92test8 findings (one regression from d1008215 made 2025 May 14)

[Matthias Andree]

Hi Simon,

compiling dnsmasq v2.92test8 on FreeBSD 14.2-RELEASE (which uses clang 
18 as default compiler) yields a new warning:

> tftp.c:365:7: warning: variable 'filename' is used uninitialized 
> whenever '||' condition is true [-Wsometimes-uninitialized]
>  365 |   if (ntohs(*((unsigned short *)packet)) != OP_RRQ ||
>      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /usr/include/netinet/in.h:121:18: note: expanded from macro 'ntohs'
>  121 | #define ntohs(x)        __ntohs(x)
>      |                         ^
> /usr/include/sys/_endian.h:89:20: note: expanded from macro '__ntohs'
>   89 | #define __ntohs(x)      (__bswap16(x))
>      |                         ^
> tftp.c:370:12: note: uninitialized use occurs here
>  370 |       if (!filename)
>      |            ^~~~~~~~
> tftp.c:365:7: note: remove the '||' if its condition is always false
>  365 |   if (ntohs(*((unsigned short *)packet)) != OP_RRQ ||
>      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /usr/include/netinet/in.h:121:18: note: expanded from macro 'ntohs'
>  121 | #define ntohs(x)        __ntohs(x)
>      |                         ^
> /usr/include/sys/_endian.h:89:20: note: expanded from macro '__ntohs'
>   89 | #define __ntohs(x)      (__bswap16(x))
>      |                         ^
> tftp.c:48:17: note: initialize the variable 'filename' to silence this 
> warning
>   48 |   char *filename, *mode, *p, *end, *opt;
>      |                 ^
>      |                  = NULL
>
This is with our default compiler on FreeBSD, clang 18. (I tried GCC 15, 
which does not warn about this.)

> $ cc --version
> FreeBSD clang version 18.1.6 (https://github.com/llvm/llvm-project.git 
> llvmorg-18.1.6-0-g1118c2e05e67)
> Target: x86_64-unknown-freebsd14.2
> Thread model: posix
> InstalledDir: /usr/bin
>
And was apparently introduced this week with this commit:

> commit d1008215dc95334e88a4a8e9d0ba0975a94c1f63
> Author: Simon Kelley <simon at thekelleys.org.uk>
> Date:   Wed May 14 21:15:17 2025 +0100
>
>    Better error message when rejecting a TFTP transfer.
>
I don't oversee enough of the code to judge whether the 
first-16bits-of-packet-in-network-order != OP_RRQ is relevant here. If 
it's from the network, of course any garbage can be in there and kick 
the reporting in lines 370ff off balance.

What do you think?


Also, lower priority,

finding #2, the attached patch fixes a warning about an unused static 
function:

forward.c:673:23:warning: 'domain_find_sets' defined but not used 
[-Wunused-function]
  673 | static struct ipsets *domain_find_sets(struct ipsets *setlist, 
const char *domain) {
      | ^~~~~~~~~~~~~~~~


finding #3: GCC15 is a bit overzealous with its warnings and displays 
this on what seems reasonable code to me:

> edns0.c:In function 'add_umbrella_opt':
> edns0.c:512:30:warning: initializer-string for array of 'unsigned 
> char' truncates NUL terminator but destination lacks 'nonstring' 
> attribute (5 chars into 4 available) 
> [-Wunterminated-string-initialization]
>  512 |   struct umbrella_opt opt = {{"ODNS"}, UMBRELLA_VERSION, 0, {0}};
>      | ^

Cheers,
Matthias
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