method

create_header

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What's this?

create_header(header = "extconf.h") public

Generates a header file consisting of the various macro definitions generated by other methods such as have_func and have_header. These are then wrapped in a custom #ifndef based on the header file name, which defaults to ‘extconf.h’.

For example:

# extconf.rb
require 'mkmf'
have_func('realpath')
have_header('sys/utime.h')
create_header
create_makefile('foo')

The above script would generate the following extconf.h file:

#ifndef EXTCONF_H
#define EXTCONF_H
#define HAVE_REALPATH 1
#define HAVE_SYS_UTIME_H 1
#endif

Given that the create_header method generates a file based on definitions set earlier in your extconf.rb file, you will probably want to make this one of the last methods you call in your script.

Show source

# File lib/mkmf.rb, line 1486
def create_header(header = "extconf.h")
  message "creating %s\n", header
  sym = header.tr_cpp
  hdr = ["#ifndef #{sym}\n#define #{sym}\n"]
  for line in $defs
    case line
    when /^-D([^=]+)(?:=(.*))?/
      hdr << "#define #$1 #{$2 ? Shellwords.shellwords($2)[0].gsub(/(?=\t+)/, "\\\n") : 1}\n"
    when /^-U(.*)/
      hdr << "#undef #$1\n"
    end
  end
  hdr << "#endif\n"
  hdr = hdr.join
  unless (IO.read(header) == hdr rescue false)
    open(header, "wb") do |hfile|
      hfile.write(hdr)
    end
  end
  $extconf_h = header
end

create_header

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