different option arguments to enter additional undefined symbols. This
option is equivalent to the @code{EXTERN} linker script command.
+If this option is being used to force additional modules to be pulled
+into the link, and if it is an error for the symbol to remain
+undefined, then the option @option{--require-defined} should be used
+instead.
+
+@kindex --require-defined=@var{symbol}
+@cindex symbols, require defined
+@cindex defined symbol
+@item --require-defined=@var{symbol}
+Require that @var{symbol} is defined in the output file. This option
+is the same as option @option{--undefined} except that if @var{symbol}
+is not defined in the output file then the linker will issue an error
+and exit. The same effect can be achieved in a linker script by using
+@code{EXTERN}, @code{ASSERT} and @code{DEFINED} together. This option
+can be used multiple times to require additional symbols.
+
@kindex -Ur
@cindex constructors
@item -Ur
doesn't change the value of the location counter---it just does
arithmetic on it. The two operand @code{ALIGN} allows an arbitrary
expression to be aligned upwards (@code{ALIGN(@var{align})} is
-equivalent to @code{ALIGN(., @var{align})}).
+equivalent to @code{ALIGN(ABSOLUTE(.), @var{align})}).
Here is an example which aligns the output @code{.data} section to the
next @code{0x2000} byte boundary after the preceding section and sets a