Issue #21111 has been updated by schneems (Richard Schneeman). I published this https://schneems.com/2025/03/17/installing-the-sassc-ruby-gem-on-a-mac-a-deb.... I've had a number of people tell me that it was helpful. I think this is a relatively common problem, though I don't know the specifics. I am guessing it has something to do with a mac OS update where one or more developer tools need to be reinstalled (purely a guess).
IMO forcing the Ruby build to fail when no C++ compiler is found isn’t ideal since Ruby itself doesn’t depend on C++ at all.
Agreed. Ideally, this would fail, but closer to where the actual need is i.e. in the native gem compilation. I'm not sure what levers we could pull. We could have rubygems be aware of the `false` and raise perhaps? But I don't think it actually knows what type of native extension is being built, so we would have to push that logic into N different gem compilation libraries that provide helpers (not super familiar here, check my statements). I think if it's not present on the system, then the most correct thing to have in the config file is to omit that line (as any value `nil` or `false` etc. is interpreted as a string literal). But I don't know the downstream impacts i.e. will that produce a failure in an understandable way? Someone could try to reproduce the situation by manually editing their config file to remove that line and then try installing `sassc` and report back with the results, that could help move things along. ---------------------------------------- Bug #21111: RbConfig::CONFIG['CXX'] quietly set to "false" when Ruby cannot build C++ programs https://bugs.ruby-lang.org/issues/21111#change-114190 * Author: stanhu (Stan Hu) * Status: Assigned * Assignee: katei (Yuta Saito) * ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +YJIT +PRISM [arm64-darwin24] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- As reported in https://gitlab.com/gitlab-org/gitlab-development-kit/-/issues/2222 and https://trac.macports.org/ticket/70750, we've had numerous macOS users experience problems with compiling Ruby C++ extensions after upgrading to XCode 16. Users have had to fix their XCode setups and reinstall Ruby when this happens. It turns out that when Ruby can't build a CXX program, it essentially sets CXX to the `false` string. From https://github.com/ruby/ruby/blob/7317f96727725ca37ddb06011918deb841de371c/c...: ``` AS_IF([test -n "${rb_there_is_in_fact_no_gplusplus_but_autoconf_is_cheating_us}"], [ AC_MSG_NOTICE([Test skipped due to lack of a C++ compiler.]) ], [test -n "${CXX}"], [ RUBY_WERROR_FLAG([ AC_MSG_CHECKING([whether CXXFLAGS is valid]) AC_LANG_PUSH(C++) AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[@%:@include <cstdio>]], [[]])], [AC_MSG_RESULT(yes)],[ AC_MSG_RESULT(no) # The message mentions CXXFLAGS, but CPPFLAGS might also affects. AC_MSG_WARN([something wrong with CXXFLAGS="$CXXFLAGS"]) CXX=false ``` This causes C++ extensions, such as `unf_ext`, to fail while attempting to compile native extensions. There are no error messages because `false` is executed, so users only see: ``` Installing unf_ext 0.0.8.2 with native extensions Gem::Ext::BuildError: ERROR: Failed to build gem native extension. current directory: /Users/myuser/.rvm/gems/ruby-3.3.7/gems/unf_ext-0.0.8.2/ext/unf_ext /Users/kerrizor/.rvm/rubies/ruby-3.3.7/bin/ruby extconf.rb checking for -lstdc++... yes creating Makefile current directory: /Users/myuser/.rvm/gems/ruby-3.3.7/gems/unf_ext-0.0.8.2/ext/unf_ext make DESTDIR\= sitearchdir\=./.gem.20250203-69237-u2oi17 sitelibdir\=./.gem.20250203-69237-u2oi17 clean current directory: /Users/myuser/.rvm/gems/ruby-3.3.7/gems/unf_ext-0.0.8.2/ext/unf_ext make DESTDIR\= sitearchdir\=./.gem.20250203-69237-u2oi17 sitelibdir\=./.gem.20250203-69237-u2oi17 compiling unf.cc make: *** [unf.o] Error 1 ``` `unf_ext` only checks whether `RbConfig::CONFIG['CXX']` is defined, not that it is `false`: https://github.com/knu/ruby-unf_ext/blob/c72a36d0a5ea9fe3950611b0f289fc68a25.... Questions: 1. Should CXX just be set to `nil`? Or should all C++ extensions be expected to check for `false`? The latter seems surprising to me. 2. Should there be a way to fail the Ruby build if a valid C++ compiler is not found? -- https://bugs.ruby-lang.org/