Re: build_system.htm#user_globals project-root clarification

From: Larry Evans (cppljevans_at_[hidden])
Date: 2004-05-10 13:32:26

On 05/10/2004 12:10 PM, David Abrahams wrote:
> Larry Evans <cppljevans_at_[hidden]> writes:
> 
> 
>>The #user_globals section contains:
>>
>> If there is a Jamfile in the project root directory, you should use
>> the project-root rule instead:
>>
>>However, I think the following would be clearer:
>>
>> If there is a project-root.jam file in the project root directory, you
>> should use the project-root rule instead:
> 
> 
> Doesn't that change the meaning?
> 
Probably. It's likely I don't understand the meaning and jumped to
the conclusion the above conclusion based on just browsing the directory
structure in 1.31.0 and noticing a project-root.jam file at the top.
Sorry.
> 
>>because it's unclear 'If there is a Jamfile' suggests ANY jam file, and
>>of course, there could be several higher level directories, each with
>>a .jam file.
> 
> 
> If clarification is needed, I suggest we insert two words: 
> 
> If there is a file named "Jamfile" in the project root directory, ...
> 

Ok, so I'm looking for a definition of "project root directory" ...
Searching in build/v1/build_system.htm, I see, just above the
bold-faced "Support Files", and example Jamfile with:

project-root ; # declare this to be the project root directory

from which I conclude that any Jamfile with this line in it is in
the "project root directory". But then 'If there is a file named 
"Jamfile" in the project root directory' seems redundant since,
according to my above reasoning, there MUST be a Jamfile in the
project root directory since the only way to "designate" a project
root directory is to have a Jamfile containing:

project-root ;

Or is there another way to designate the project root directory?
OOPS. Now maybe I see. A project root for some "current directory"
(CD) can be designated either by 1) a Jamfile in the CD containing:

subproject path-from-top ;

which might better be expressed as:

subproject path-from-project-root ;

or 2) by a file named "Jamfile" in some parent of the CD and containing 
the project-root rule.

But, of course, these could conflict, which is why, I suppose, the word
"should" was used in #user_globals.