Re: patch for .SHELLFLAGS and .POSIX

On Fri, 2009-10-02 at 22:16 -0400, David Boyce wrote:
> The attached little patch appears to add the .SHELLFLAGS feature with
> .POSIX interaction as previously discussed:
> 
> % cat MF
> .PHONY: all
> .POSIX:
> all:
>         @echo SHELLFLAGS=$(.SHELLFLAGS)
>         @false; echo NOT POSIX BEHAVIOR
> 
> % ./make -f MF
> SHELLFLAGS=-ec
> make: *** [all] Error 255
> 
> Please let me know if and where it falls short.

Looks about right.  One open question is, what do we do about the
$(shell ...) function?  Do we use the value of $(SHELL) $(.SHELLFLAGS)
for this?  Or just always use /bin/sh -c?  I can see arguments both
ways.  If we go with the former than probably we need to move the
setting of .SHELLFLAGS so that the default value is set before we start
parsing makefiles (for $(shell ...) functions expanded during makefile
read-in), and reset it when posix_pedantic is set.

One concern is whether we should support expanding of .SHELLFLAGS; this
version just takes the value verbatim (doesn't it?)  What if someone
wanted to do something like:

	.SHELLFLAGS = -$(if $(DEBUG),x)c

or something like that?

The other thing is replacing "-" with "/" on OS/2.  I wonder if we
should not bother to do that, at least not for values that the user
sets.  That is, for the default value setting we can use /c if __EMX__
is defined, but after that we just use whatever is in .SHELLFLAGS
verbatim; if the user sets that value then they can figure out what it
should be.  Automatically modifying values like this makes me very
uncomfortable in general.

I don't think you need to set the "special" flag on .SHELLFLAGS.  This
is a marker to GNU make that there is something about this variable that
needs to be addressed as soon as the variable is set: for
example, .POSIX needs to set the posix_pedantic flag etc.

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