Append flags from environment variables.

[junaruga]

According to the mkmf.rb#init_mkmf, there are command line options below.

• --with-cflags to set the cflags
• --with-ldflags to set the ldflags

For example the following command compiles with the specified flags. Note that
MAKEFLAGS is to print the compiler command lines.

$ MAKEFLAGS="V=1" \
  bundle exec rake compile -- \
  --with-cflags="-Wundef -Werror" \
  --with-ldflags="-fstack-protector"

However, I couldn't find command line options to append the flags. And this
commit is to append the cflags and ldflags by the environment variables.

$ MAKEFLAGS="V=1" \
  RUBY_OPENSSL_EXTCFLAGS="-Wundef -Werror" \
  RUBY_OPENSSL_EXTLDFLAGS="-fstack-protector" \
  bundle exec rake compile

Details

The implementation was inspired by Nokogiri project.
https://github.com/sparklemotion/nokogiri/blob/30e965809c4c55b191c5c9f3a2cc5a289fce4681/ext/nokogiri/extconf.rb#L648-L651

# adopt environment config
append_cflags(ENV["CFLAGS"].split) unless ENV["CFLAGS"].nil?
append_cppflags(ENV["CPPFLAGS"].split) unless ENV["CPPFLAGS"].nil?
append_ldflags(ENV["LDFLAGS"].split) unless ENV["LDFLAGS"].nil?

However, I wanted to avoid the CFLAGS was loaded unintentionally. Because I see CFLAGS and LDFLAGS are already set in the build environment in Fedora project. Those are used to set the flags, not to append. So, I used the prefix RUBY_OPENSSL_. I also wanted to clarify that the value is used not to set but to append to the existing cflags coming from the rbconfig.rb. It seems the EXTLDFLAGS exists in the purpose of appendng the flags in the template/Makefile.in in ruby/ruby. So, I chose the RUBY_OPENSSL_EXTCFLAGS and RUBY_OPENSSL_EXTLDFLAGS.

You can also add your preferred debug flags like this.

$ MAKEFLAGS="V=1" \
  RUBY_OPENSSL_EXTCFLAGS="-O0 -g3 -ggdb3 -gdwarf-5" \
  bundle exec rake compile

[junaruga]

@MSP-Greg @ioquatix I saw your commit 4bb32c1 by the #279 appending the hard-coded cflags and ldflags in the case of mingw.

After this PR, can we remove the code below by setting it from the environment variables?

append_cflags '-D_FORTIFY_SOURCE=2'
append_ldflags '-fstack-protector'

[junaruga]

Here is my test log on Fedora 37. The appended cflags and ldflags are used in the gcc commands below.

$ gcc --version
gcc (GCC) 12.2.1 20221121 (Red Hat 12.2.1-4)
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ruby -v
ruby 3.3.0dev (2023-05-30T12:39:26Z master 30b960ba34) [x86_64-linux]

$ bundle -v
Bundler version 2.5.0.dev

$ MAKEFLAGS="V=1" \
  RUBY_OPENSSL_EXTCFLAGS="-Wundef -Werror" \
  RUBY_OPENSSL_EXTLDFLAGS="-fstack-protector -Wl,-z,now" \
  bundle exec rake compile
mkdir -p tmp/x86_64-linux/openssl/3.3.0
cd tmp/x86_64-linux/openssl/3.3.0
/home/jaruga/.local/ruby-30b960ba34-debug/bin/ruby -I. -r.rake-compiler-siteconf.rb ../../../../ext/openssl/extconf.rb
checking for whether -Wundef is accepted as CFLAGS... yes
checking for whether -Werror is accepted as CFLAGS... yes
checking for whether -fstack-protector is accepted as LDFLAGS... yes
checking for whether -Wl,-z,now is accepted as LDFLAGS... yes
...
gcc -I. -I/home/jaruga/.local/ruby-30b960ba34-debug/include/ruby-3.3.0+0/x86_64-linux -I/home/jaruga/.local/ruby-30b960ba34-debug/include/ruby-3.3.0+0/ruby/backward -I/home/jaruga/.local/ruby-30b960ba34-debug/include/ruby-3.3.0+0 -I../../../../ext/openssl  -DRUBY_EXTCONF_H=\"extconf.h\"    -fPIC -O0 -fno-fast-math -g3 -ggdb3 -gdwarf-4 -Wall -Wextra -Wdeprecated-declarations -Wdiv-by-zero -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wold-style-definition -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC -Wundef -Werror   -o openssl_missing.o -c ../../../../ext/openssl/openssl_missing.c
...
gcc -shared -o openssl.so openssl_missing.o ossl.o ossl_asn1.o ossl_bio.o ossl_bn.o ossl_cipher.o ossl_config.o ossl_digest.o ossl_engine.o ossl_hmac.o ossl_kdf.o ossl_ns_spki.o ossl_ocsp.o ossl_pkcs12.o ossl_pkcs7.o ossl_pkey.o ossl_pkey_dh.o ossl_pkey_dsa.o ossl_pkey_ec.o ossl_pkey_rsa.o ossl_rand.o ossl_ssl.o ossl_ssl_session.o ossl_ts.o ossl_x509.o ossl_x509attr.o ossl_x509cert.o ossl_x509crl.o ossl_x509ext.o ossl_x509name.o ossl_x509req.o ossl_x509revoked.o ossl_x509store.o -L. -L/home/jaruga/.local/ruby-30b960ba34-debug/lib -Wl,-rpath,/home/jaruga/.local/ruby-30b960ba34-debug/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed -fstack-protector -Wl,-z,now  -Wl,--compress-debug-sections=zlib    -Wl,-rpath,/home/jaruga/.local/ruby-30b960ba34-debug/lib -L/home/jaruga/.local/ruby-30b960ba34-debug/lib -lruby  -lssl -lcrypto -lm -lpthread  -lc
...

[ioquatix]

Nice work!