[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Undocumented stuff in `make'

From: Paul D. Smith
Subject: Re: Undocumented stuff in `make'
Date: Wed, 28 Mar 2001 17:25:01 -0500

%% Regarding Undocumented stuff in `make'; you wrote:

  ek> I discovered an undocumented feature in `make' (version 3.79.1
  ek> on MS-DOS). There seems to be a variable assignment operator,
  ek> `?:=', which is not worth a mention according to the `make'
  ek> documentation (file `info/make.info').

  ek> VAR ?:= $(FOO)


There is no undocumented feature, except that should probably be an
error or a warning.

All you've done is create a variable named $(VAR ?) here :).  Your echo
of $(VAR) gives the empty value because it _is_ empty: it was never

You can see this by giving -p to make and searching the output for VAR;
you'll find a variable "VAR ?" defined, but no variable named "VAR".

You could also enable --warn-undefined-variables and see that $(VAR) is
not defined.

 Paul D. Smith <address@hidden>          Find some GNU make tips at:
 http://www.gnu.org                      http://www.paulandlesley.org/gmake/
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist

reply via email to

[Prev in Thread] Current Thread [Next in Thread]