I was trying to install puma extension in Ruby on Rails and getting this error.
C:/RailsInstaller/Ruby1.9.3/bin/ruby.exe extconf.rb creating Makefile make generating puma_http11-i386-mingw32.def compiling http11_parser.c ext/http11/http11_parser.rl: In function 'puma_parser_execute': ext/http11/http11_parser.rl:111:3: warning: comparison between signed and unsigned integer expressions compiling io_buffer.c io_buffer.c: In function 'buf_to_str': io_buffer.c:119:3: warning: pointer targets in passing argument 1 of 'rb_str_new' differ in signedness c:/RailsInstaller/Ruby1.9.3/include/ruby-1.9.1/ruby/intern.h:661:7: note: expected 'const char *' but argument is of type 'uint8_t *' compiling mini_ssl.c In file included from mini_ssl.c:3:0: c:/RailsInstaller/Ruby1.9.3/include/ruby-1.9.1/ruby/backward/rubyio.h:2:2: warning: #warning use "ruby/io.h" instead of "rubyio.h" mini_ssl.c:4:25: fatal error: openssl/bio.h: No such file or directory compilation terminated. make: *** [mini_ssl.o] Error 1 
