**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

```