method

check_sizeof

v1_9_2_180 - Show latest stable - Class: Object

check_sizeof(type, headers = nil, opts = "", &b)

public

Returns the size of the given type. You may optionally specify additional headers to search in for the type.

If found, a macro is passed as a preprocessor constant to the compiler using the type name, in uppercase, prepended with ‘SIZEOF_’, followed by the type name, followed by ‘=X’ where ‘X’ is the actual size.

For example, if check_sizeof(‘mystruct’) returned 12, then the SIZEOF_MYSTRUCT=12 preprocessor macro would be passed to the compiler.

# File lib/mkmf.rb, line 1007
def check_sizeof(type, headers = nil, opts = "", &b)
  typename, member = type.split('.', 2)
  prelude = cpp_include(headers).split(/$/)
  prelude << "typedef #{typename} rbcv_typedef_;\n"
  prelude << "static rbcv_typedef_ *rbcv_ptr_;\n"
  prelude = [prelude]
  expr = "sizeof((*rbcv_ptr_)#{"." << member if member})"
  fmt = STRING_OR_FAILED_FORMAT
  checking_for checking_message("size of #{type}", headers), fmt do
    if UNIVERSAL_INTS.include?(type)
      type
    elsif size = UNIVERSAL_INTS.find {|t|
        try_static_assert("#{expr} == sizeof(#{t})", prelude, opts, &b)
      }
      $defs.push(format("-DSIZEOF_%s=SIZEOF_%s", type.tr_cpp, size.tr_cpp))
      size
    elsif size = try_constant(expr, prelude, opts, &b)
      $defs.push(format("-DSIZEOF_%s=%s", type.tr_cpp, size))
      size
    end
  end
end

check_sizeof

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