Compiler warning issued when MDNS_MAX_SERVICES is 0 (IDFGH-13222)

[gudvinr]

Answers checklist.

• I have read the documentation for esp-protocols components and the issue is not addressed there.
• I have updated my esp-protocols branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

What component are you using? If you choose Other, provide details in More Information.

mDNS

component version

1.3.2

IDF version.

5.2.2

More Information.

There's a check in mdns.c:340 that uses MDNS_MAX_SERVICES value in runtime.

If it's set to 0 (when you only need domain resolution and not DNS-SD), you get a warning:
comparison is always true due to limited range of data type [-Wtype-limits]

Instead _mdns_can_add_more_services can return false straight away if MDNS_MAX_SERVICES defined as 0.

[david-cermak]

Thanks for reporting this issue!

Instead _mdns_can_add_more_services can return false straight away if MDNS_MAX_SERVICES defined as 0.

Good idea! Feel free to post a PR with this change.

Alternatively we can use const size_t instead of macros:

 static bool _mdns_can_add_more_services(void)
 {
+    const int max_services = CONFIG_MDNS_MAX_SERVICES;
     mdns_srv_item_t *s = _mdns_server->services;
     uint16_t service_num = 0;
     while (s) {
         service_num ++;
         s = s->next;
-        if (service_num >= MDNS_MAX_SERVICES) {
+        if (service_num >= max_services) {
             return false;
         }