Re: shortcut of ":" but not /bin/true

[David Boyce]

At 09:46 AM 5/18/2004, Paul D. Smith wrote:
> %% David Boyce <address@hidden> writes:
>   db> Which raises the question: why wasn't the fast path in use in the
>   db> truss output I showed? The answer is apparently that the generated
>   db> Perl makefiles have an explicit SHELL=/bin/sh which disables the
>   db> fast path.
>
> Are you sure?  I'm surprised because there's some code in job.c which
> checks the value of the SHELL variable to see whether it looks like a
> valid shell; it basically does a strcmp() with "/bin/sh" and if it's
> different it uses the slow path.

No, I'm not at all sure. I merely noticed that the truss output appeared to 
show an unneeded shell invocation and when I noticed an assignment to SHELL 
in the Makefile(s) I assumed it was the culprit. I'll take a closer look 
and see if I can figure out what's going on without internalizing the 
entire Perl build model (which I could do without).

Argh. I just looked more closely into some of the ancillary Perl makefiles 
and found this:

NOOP = $(SHELL) -c true

followed by all kinds of underbrush like

all :: pure_all manifypods
        $(NOECHO) $(NOOP)

No accounting for taste, I guess.

-David Boyce