How common is :: in makefiles

[Sven L Eriksson]

The X11 makefiles (produced by Imakefile) uses a feature that isn't
documented in my system (Sys V.3.2) although it works.
They use a double : instead of a single in the dependency rules.
This allows several rules with the same name. The effect is that
all these rules are executed. If a makefile contains:

foo ::
	@echo making foo

bar ::
	@echo making bar

foo ::
	@echo making more foo

then "make foo" will produce

making foo
making more foo

If single : are used instead make will complain.

Is this a general undocumented feature of make?
X11 is portable to a lot of platforms so I guess they have
thought about this. But do make on all systems have it?
Dare I use it in makefiles that are going to be ported to many
different systems.

Thanks for any responses. / Sven
-- 
- Sven L Eriksson, 3S AB (Scandinavian System Support AB)    o O___ _________
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