Re: Undocumented stuff in `make'

[Paul D. Smith]

%% 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)

Heh.

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
set.

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.

-- 
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