As of August 2020, the installation of cool.io used for puma and fluentd may fail.
current directory: /Users/example/src/nature-server/vendor/bundle/ruby/2.6.0/gems/cool.io-1.6.0/ext/cool.io
make "DESTDIR=" clean
current directory: /Users/example/src/nature-server/vendor/bundle/ruby/2.6.0/gems/cool.io-1.6.0/ext/cool.io
make "DESTDIR="
compiling cool.io_ext.c
In file included from cool.io_ext.c:11:
In file included from ./cool.io.h:11:
/Users/example/.rbenv/versions/2.6.6/include/ruby-2.6.0/ruby/backward/rubyio.h:2:2: warning: use "ruby/io.h" instead of "rubyio.h" [-W#warnings]
#warning use "ruby/io.h" instead of "rubyio.h"
....
The solution is to set --with-cflags ="-Wno-error = implicit-function-declaration ".
Reference Issue :) ctype.h missing from puma_http11.c
For bundle:
bundle config --local build.cool.io --with-cflags="-Wno-error=implicit-function-declaration"
bundle config --local build.puma --with-cflags="-Wno-error=implicit-function-declaration"
If you want to install gem directly:
gem install fluentd -- --with-cflags="-Wno-error=implicit-function-declaration"
gem install puma -- --with-cflags="-Wno-error=implicit-function-declaration"