[erlang-questions] Erlang and autoconf/make

Romain Lenglet rlenglet@REDACTED
Thu Nov 16 05:39:18 CET 2006

Richard A. O'Keefe wrote:
> Romain Lenglet wrote:
> 	> But I believed that pattern rules were a GNU Make'ism?
> Pupeno <pupeno@REDACTED> asked:
> 	Can any BSDer confirm this ?
> I don't run BSD on any of my machines.

I have installed NetBSD make (pmake) on Debian (package pmake): 
it supports pattern rules.

I have also found a FreeBSD 6.1 box here: its make does *NOT* 
support pattern rules.

And by the way, even when using implicit rules, the syntax:
SUFFIXES = .erl .beam
is *NOT* supported by FreeBSD make.

One must use:
.SUFFIXES: .erl .beam
This syntax is supported by GNU make, pmake and FreeBSD make.

Therefore, I strongly suggest to not use pattern rules, and to 
use implicit rules instead, such as:

.SUFFIXES: .erl .beam .rel .script .boot

	$(ERLC) $(ERLCFLAGS) -b beam $<
	$(ERLC) $(ERLCFLAGS) -b beam $<
	$(ERLC) $(ERLCFLAGS) -b beam $<

> However, I *can* tell you that
> (1) On Alpha OSF V5.1, the manual page for 'make' mentions %
> in only two contexts:  the shell prompt for sample commands
> and various NLS escapes in MANPATH.
> (2) I have an on-line copy of the Single Unix Specification,
> Version 3. The description of 'make' says "There are two types
> of rule: 1. Inference rules, which have one target name with
> at least one period ('.') and no slash ('/')
> 	2. Target rules, which can have more than one target name."
>     No pattern rules.  In fact the rationale at the end says
>        "Consideration was given to adding emtarules to the
> POSIX make.  This would make %.o: %.c the same as .c.o:.  This
> is quite useful and available from some vendors, but it would
> cause too many changes to this make to support,.  It would
> have introduced rule chaining and new substitution rules. 
> However, the rules for target names have been set to reserve
> the '%' and '"' characters. These are traditionally used to
> implement metarules and quoting of target names, respectively.
>  Implementors are strongly encouraged to use these characters
> only for these purposes."

Thanks for the information!

> If the Automake people didn't do their design with a copy of
> the SUS (or POSIX.2 or SVID or ...) in front of them, I will
> be very surprised.

Yes, Automake generates Makefiles that are portable and can be 
interpreted by any make.
It lets one write some GNU-specific extensions, like pattern 
rules, or the use of $< and $@ in explicit rules, but that is 
the coder's responsibility then if the Makefile is not portable.
The only GNU-specific extension supported by Automake is the += 
affectations of variables, cf. the Automake manual:
Note that most GNU make extensions are not recognized by 
Automake. Using such extensions in a Makefile.am will lead to 
errors or confusing behavior. 
A special exception is that the GNU make append operator, +=, is 
supported. This operator appends its right hand argument to the 
variable specified on the left. Automake will translate the 
operator into an ordinary = operator; += will thus work with any 
make program.



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