Remove the need of -Wno-stringop-overflow warning suppression

[freak82]

The problem was that GCC complained for possibly incorrect usage of strncat due to the last argument being equal to the source string length. The last argument of strncat is supposed to be the remaining free space in the destination buffer.
Replaced the usage of strncat with the ATS function ink_strlcat.
More info about this can be found in this issue

[ezelkow1]

[approve ci]

[JosiahWI]

In function 'size_t str_concat(char*, size_t, const char*, size_t)',
    inlined from 'TSHttpStatus S3Request::authorizeV2(S3Config*)' at ../../../plugins/s3_auth/s3_auth.cc:920:25:
../../../plugins/s3_auth/s3_auth.cc:761:12: error: 'char* strncat(char*, const char*, size_t)' specified bound 1 equals source length [-Werror=stringop-overflow=]
  761 |     strncat(dst, src, to_copy);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~
In function 'size_t str_concat(char*, size_t, const char*, size_t)',
    inlined from 'TSHttpStatus S3Request::authorizeV2(S3Config*)' at ../../../plugins/s3_auth/s3_auth.cc:926:25:
../../../plugins/s3_auth/s3_auth.cc:761:12: error: 'char* strncat(char*, const char*, size_t)' specified bound 1 equals source length [-Werror=stringop-overflow=]
  761 |     strncat(dst, src, to_copy);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~

It looks like there is a possible similar incorrect usage of strncat in the s3_auth plugin that the CentOS build is now complaining about.

[freak82]

Hmm, I built all of the plugins and there was no other complains from GCC 13.2 on Debian.
I can see that the s3_auth plugin has been built. It has not been skipped.
Most likely this is due to different GCC versions.

It seems to me that in the plugins/s3_auth/s3_auth.cc the GCC analyzer is wrong about this warning:
It most likely get confused from this usage str_concat(&left[loff], (left_size - loff), "/", 1); and because in the str_concat there is std::min(dst_len, src_len) for the strncat size argument.

Maybe it'll be better if I change all of the remaining 5 usages of strncat in

plugins/s3_auth/s3_auth.cc (1)
plugins/experimental/url_sig/url_sig.cc (4)

with ink_strlcat?

Or the suppression can be left as it is at global level?

Or another option is the suppression to be set in the CMakeLists.txt of the s3_auth plugin?

[maskit]

I don't mind leaving the warning suppression. Sounds like the change is enough for you, and I'm not going to have you fix all the places. We can remove the warning suppression later when we are ready to do so. But if you are willing to make additional changes for the plugin code, please use TSstrlcat, which is exactly the same as ink_strlcat but it's exported for plugins.

[freak82]

I replaced the strncat usage in the s3_auth plugin with TSstrlcat.
Tested the build again with both GCC 11, which was giving the warning in the plugin, and with GCC 13.

[maskit]

Thank you!

[cmcfarlen]

Cherry-picked to v10.0.x