Replace uses of sprintf with snprintf

[timwoj]

The most recent version of the SDK on macOS recently started complaining about sprintf being deprecated, similar to this:

<>/c-ares/src/lib/ares_getnameinfo.c:371:11: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
          sprintf(&tmpbuf[1], "%u", (unsigned int)addr6->sin6_scope_id);
          ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/stdio.h:188:1: note: 'sprintf' has been explicitly marked deprecated here
__deprecated_msg("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead.")
^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/sys/cdefs.h:215:48: note: expanded from macro '__deprecated_msg'
        #define __deprecated_msg(_msg) __attribute__((__deprecated__(_msg)))

This PR replaces all uses of sprintf with snprintf, with appropriate size values for the buffers used. The only thing I'm concerned about here is this note in src/lib/config-dos.h:

  /* Because djgpp <= 2.03 doesn't have snprintf() etc. */
  #if (DJGPP_MINOR < 4)
    #define _MPRINTF_REPLACE
  #endif

I'm not sure if that's still an issue, and I don't have any way to test that it's good locally. I assume CI covers it.

[bradh352]

appears this PR causes failures on Windows. I haven't looked deeply at the changeset to see why it might only affect windows, but another PR came in and didn't have windows failures, and I just reissued a re-build of this pr and it still fails so I think that rules out any temporary AppVeyor issues.

[timwoj]

Interesting, the build itself passed just fine but the tests failed:

[  FAILED  ] DefaultChannelTest.LiveGetNameInfoV6Numeric
[  FAILED  ] DefaultChannelTest.LiveGetNameInfoV6Numeric_virtualized
[  FAILED  ] DefaultChannelTest.LiveGetNameInfoV6LinkLocal
[  FAILED  ] DefaultChannelTest.LiveGetNameInfoV6LinkLocal_virtualized
[  FAILED  ] DefaultChannelTest.LiveGetNameInfoV6NotFound
[  FAILED  ] DefaultChannelTest.LiveGetNameInfoV6NotFound_virtualized

I do have a Windows machine here. I'll see if I can reproduce it.

[timwoj]

Fixed it. There was an error in the math in inet_ntop6. Should be good to go now.