End of Life Ruby 3.1 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →

instance method

MakeMakefile#have_var

have_var(var, headers = nil, opt = "", &b)

# File tmp/rubies/ruby-3.1.3/lib/mkmf.rb, line 1135
def have_var(var, headers = nil, opt = "", &b)
  checking_for checking_message(var, headers, opt) do
    if try_var(var, headers, opt, &b)
      $defs.push(format("-DHAVE_%s", var.tr_cpp))
      true
    else
      false
    end
  end
end

Returns whether or not the variable var can be found in the common header files, or within any headers that you provide. If found, a macro is passed as a preprocessor constant to the compiler using the variable name, in uppercase, prepended with HAVE_.

To check variables in an additional library, you need to check that library first using have_library().

For example, if have_var('foo') returned true, then the HAVE_FOO preprocessor macro would be passed to the compiler.

See also #have_type #link_command #have_struct_member #pkg_config also in 4.1 · 4.0 · 3.4 · 3.3 · 3.2 · 3.0

‹ prev#have_type next ›#link_command