Don't predeclare enums with C++

[samuel40791765]

Issues:

Addresses CryptoAlg-2693

Description of changes:

We encountered this when trying to compile Xtrabackup on gcc versions lower than 10. Apparently scoped enums are a C++11 feature, which the compiler can't understand without additional linker flags.

/home/ubuntu/workplace/percona-xtrabackup/aws-lc/test_build_dir/include/openssl/ssl.h:174:30: warning: scoped enums only available with ‘-std=c++11’ or ‘-std=gnu++11’
  174 | #define BORINGSSL_ENUM_INT : int
      |                              ^~~
...
      |                              ^~~
/home/ubuntu/workplace/percona-xtrabackup/aws-lc/test_build_dir/include/openssl/ssl.h:4783:31: note: in expansion of macro ‘BORINGSSL_ENUM_INT’
 4783 | enum ssl_select_cert_result_t BORINGSSL_ENUM_INT {
      |                               ^~~~~~~~~~~~~~~~~~
make[2]: *** [libmysql/CMakeFiles/clientlib.dir/build.make:149: libmysql/CMakeFiles/clientlib.dir/__/sql-common/client_authentication.cc.o] Error 1
make[2]: Leaving directory '/home/ubuntu/workplace/percona-xtrabackup/build'

We also encountered this in 42a8dba, which prompted us to move it to ssl.h. Upon closer examination, I don't think the C++11 usage is a necessity especially with the pure C fallback that was included. Predeclaring enums reduces compilation dependencies and build times, but our build seems to work fine without it. Removing this would let us encounter less build issues with projects that aren't expecting C++ in our header files.

Call-outs:

N/A

Testing:

CI

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.03%. Comparing base (bd09b3a) to head (b0f8bd6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2193      +/-   ##
==========================================
- Coverage   79.03%   79.03%   -0.01%     
==========================================
  Files         612      612              
  Lines      106064   106066       +2     
  Branches    14984    14986       +2     
==========================================
- Hits        83829    83826       -3     
- Misses      21581    21587       +6     
+ Partials      654      653       -1     

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[justsmth]

Pre-push check is failing:

[Container] 2025/02/13 01:52:19.380053 Running command (cd util && go run ./doc.go)
Failed to generate output: while parsing include/openssl/ssl.h: comment for "SSL_CTX_get0_chain" doesn't seem to match line include/openssl/ssl.h:1274

exit status 1

[andrewhop]

Can you update c99_gcc_test.sh to also check for C++ header compatibility (and maybe rename the file). Also double check that it's running, I'm not sure anything defines AWSLC_C99_TEST right now....