In some cases, it is desirable for a linker script to define a symbol
only if it is referenced and is not defined by any object included in
the link. For example, traditional linkers defined the symbol
`etext'. However, ANSI C requires that the user be able to use
`etext' as a function name without encountering an error. The
PROVIDE keyword may be used to define a symbol, such as
`etext', only if it is referenced but not defined. The syntax is
PROVIDE(symbol = expression).
Here is an example of using
PROVIDE to define `etext':
_etext = .;
PROVIDE(etext = .);
In this example, if the program defines `_etext' (with a leading
underscore), the linker will give a multiple definition error. If, on
the other hand, the program defines `etext' (with no leading
underscore), the linker will silently use the definition in the program.
If the program references `etext' but does not define it, the
linker will use the definition in the linker script.