On Fri, Jun 3, 2016 at 8:41 AM, Edward Diener <eldiener@tropicsoft.com> wrote:
On 6/3/2016 9:18 AM, Rene Rivera wrote:
On Fri, Jun 3, 2016 at 7:17 AM, Edward Diener <eldiener@tropicsoft.com
 <mailto:eldiener@tropicsoft.com>> wrote:

    I am seeing in the predef.jam file a call to rule _message_ but I
    can find no information on it. Does this exist in some Boost Build
    jam file ?


That's not a rule.. It's a variable. Or rather, a group of variables.

How does the syntax:

_message_(/check/predef//predef_check_cc_$(key))

apply to a Boost Build variable ? I thought Boost Build variables ( which are list of strings ) had to use [n] to access a string in the list.

That's, literally, the name of the variable. Variables in bjam have almost no limitations on characters allowed. In this case, because it has a variable expansion in it, the name comes out to be something like:

  _message_(/check/predef//predef_check_cc_79054025255fb1a26e4bc422aef54eb4)

I.e. it's a variable that is specifically named for the target of a specific predef check sub/expression. If you where indexing an element in the variable's list value you would then end up with:

  _message_(/check/predef//predef_check_cc_79054025255fb1a26e4bc422aef54eb4)[0]

For example.

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