The PREPENDDEF( )
m4 directive allows you to insert new
information before that which was previously defined. To illustrate,
consider a custom C-language library you want searched first during
the loading phase of compiling, where the default list of libraries
(for SunOS.5.7) looks like this:
-lsocket -lnsl
If you need to insert another library at the head of this list,
without erasing what is already there, you can use this PREPENDDEF( )
directive:
PREPENDDEF(`confLIBS', `-llocal')
This causes the previous declaration to be prefixed with a new
(third) library:
-llocal -lsocket -lnsl
Note that you can safely use this PREPENDDEF( ) directive when in
doubt as to whether a macro has been given a value by default because
no harm can be caused by prepending to an empty definition. (See also
APPENDDEF( ).)
