Checking compiler warnings as errors on CI

[junaruga]

Checking compiler warnings as errors on CI

[rhenium]

1. I want to prevent us (me) from unintentionally adding a code that triggers compiler warnings via a pull-request like this issue, [Warning: "OPENSSL_FIPS" is not defined, evaluates to 0 [-Wundef] #620](https://github.com/ruby/openssl/issues/620).

2. I want to avoid CI failures by a CI case upgrades a compiler to the newer version.

I'm sure the benefits of 1. will outweigh the risk of 2. Trivial C errors slipping through a review have happened many times!

👍

[junaruga]

I would close this ticket for now. When I am ready to send the pull-request for this feature, I reopen this ticket.

[junaruga]

Reopened this feature ticket, as I am almost ready to send the pull-request. I am working on the branch, https://github.com/junaruga/openssl/tree/wip/check-compiler-warnings.

[junaruga]

The issue #628 was found related to the -Werror flag.

[junaruga]

Note #603 (comment) .

[junaruga]

I am happy to see that you are positive about this feature. :)

I want to consider a logic to turn off of checking the compiler warnings on the GitHub Actions yaml file. It's useful when we see new compiler warnings from new compiler or new OpenSSL or etc, and if we cannot fix the warnings soon, and these warning checks block the CI pipelines.