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

[Noel Yap]

I'm not sure if the following is feasible or advisable, but what could be done is to test some common, simple 
things like ":", "true", and "false" to see if $SHELL has it as a built-in.

Noel

David Boyce wrote:

> To clarify for anyone following along at home: this is different from 
> the normal GNU make "fast path" feature where it will run <command> 
> directly where possible rather than using the "traditional path" of 
> running '/bin/sh -c <command>'. The ":" is given a third way which we 
> might call the "blazing fast path"; it's not executed at all. The 
> discussion is of whether and how to promote true and false from the fast 
> path to the blazing fast path.
>
> Which raises the question: why wasn't the fast path in use in the truss 
> output I showed? The answer is apparently that the generated Perl 
> makefiles have an explicit SHELL=/bin/sh which disables the fast path. I 
> wonder if it would be possible to detect when assignment to SHELL is a 
> no-op and leave fast path on? Might be harder than it seems when 
> recursively expanded variables are involved. Unfortunately a lot of 
> generated makefiles have this tic. In fact ISTR reading somebody's "best 
> practices with make" paper which included an injunction to always assign 
> SHELL=/bin/sh explicitly. Not saying I agree with that but it's out 
> there and clearly a lot of people do.
>
> -David Boyce
>
>
>
> _______________________________________________
> Help-make mailing list
> address@hidden
> http://mail.gnu.org/mailman/listinfo/help-make