method

check_sizeof

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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.

Show source

# File lib/mkmf.rb, line 1295
  def check_sizeof(type, headers = nil, opts = "", &b)
    typedef, member, prelude = typedef_expr(type, headers)
    prelude << "static #{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 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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