main()
--with-FOOlib
have_library()
have_func('foo')
have_var('foo')
have_header('foo.h')
have_framework('Ruby')
-I
have_struct_member('struct foo', 'bar')
have_type('foo')
[const, type]
have_const('foo')
=X
check_sizeof('mystruct')
SIZEOF_MYSTRUCT=12
check_signedness('size_t')
SIGNEDNESS_OF_SIZE_T=+1
SIGNEDNESS_OF_INT=-1
check_signedness('int')
convertible_int("foobar_t")
#ifndef
--with-foo-dir=prefix
--with-foo-include=dir
--with-foo-lib=dir
[cflags, ldflags, libs]
--with-{pkg}-config={command}
{command} {option}
{pkg}-config {option}
pkg-config {option} {pkg}
--cflags
option
RbConfig::CONFIG['sitearchdir']
make install