Re: Difference between $(call macro) and $(macro)

[Paul Smith]

On Tue, 2014-02-18 at 02:14 -0800, Rakesh Sharma wrote:
> What's going on here? Apparently,  the construct $(macro) picks up the
> $1/$2/... values from the macro in which it was placed. However, the
> construct $(call macro) picks up the $1/$2 ... values from its' own
> argument list. And, that is also why when we write $(macro,,) this
> seems to rid the problem of the unintentional grabbing of the parent
> macro's arguments.

This is definitely correct behavior.

When make sees $(call foo), that's an invocation of the user-defined
function "foo".  In preparation for calling that user-defined function,
make will bind the special argument variables $1, $2, etc. to the
arguments to the user-defined function.  Here there are no arguments
given in this invocation, so they are all bound to the empty value.

When make sees $(foo) that's a straightforward expansion of the macro
named "foo".  No special operations are involved, it just looks up the
macro named "foo", expands (or not, if "foo" is simple) the value, and
uses the result.  There's no special handling of $1, etc.

As for "$(foo,,)", that's expanding the variable named, literally,
"foo,,".  Since that variable likely doesn't exist this will always
expand to the empty string (unless you defined it of course).