Re: [Boost-build] Using 'explicit' targets

Subject: Re: [Boost-build] Using 'explicit' targets
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2016-05-15 18:58:41

AMDG

On 05/15/2016 03:36 PM, Edward Diener wrote:
> On 5/15/2016 4:04 PM, Steven Watanabe wrote:
>> 
>> On 05/15/2016 11:43 AM, Edward Diener wrote:
>>> I think the way 'explicit' targets in a jamfile should work is that if
>>> you specify any 'explicit' targets b2 should check all targets in the
>>> jamfile along with the 'explicit' targets. Instead it only checks the
>>> 'explicit' targets if you specify them. I realize this is different from
>>> specifying non-explicit targets in a jamfile, but I think that
>>> 'explicit' defeats its purpose by not checking all non-explicit targets
>>> also when it is being used.
>>>
>>
>> I don't understand what you mean by checking a target.
> 
> I should have said 'build a target if it is out of date'.
> 
> Let's suppose I have a non-explicit targets 'nonexpl1' and 'nonexpl2'
> and explicit target 'expl' in a jamfile. Consider in each of the
> situations below that all are always out of date and need to be built. I
> invoke:
> 
> 1) 'b2 jamfile' = both 'nonexpl1' and 'nonexpl2' is built and 'expl' is
> not built.

Do you really mean to put 'jamfile' on the
command line?

> 2) 'b2 jamfile nonexpl1' = only 'nonexpl1' is built.
> 3) 'b2 jamfile nonexpl2' = only 'nonexpl2' is built.
> 4) 'b2 jamfile nonexpl1 expl' = both 'nonexpl1' and 'expl1' is built and
> 'nonexpl2' is no built.
> 5) 'b2 jamfile nonexpl2 expl' = both 'nonexpl2' and 'expl1' is built and
> 'nonexpl1' is not built.
> 6) 'b2 jamfile expl' = only 'expl' is built.
> 
> I disagree with 6). I think that if you specify an explicit target and
> no non-explicit targets then all non-explicit targets should be built.
> In other words if I specify only explcit targets to be built I shouldn't
> need to specify all the non-explicit targets individually to get them to
> be built. In the example above to get all targets to build I must
> specify each target in the jamfile. I think this hurts the functionality
> of 'explicit' in Boost Build. If I have a jamfile with a bunch of
> targets, one of which is explicit, I must tell the end-user that to
> build the explicit target it must be passed on the b2 command line but
> to build all targets in the jamfile, including the explicit target, he
> must pass all targets individually on the command line.
> 

  The current behavior is more consistent.
If some targets are specified, then exactly
those targets will be built, regardless
of whether they are explicit or not.  To
get the result that you want, you can use:

$ b2 . expl

i.e. build the non-explicit targets of the
project in the current directory and also
build expl.

As for why the behavior that you propose is
wrong, consider the following:

$ cd $BOOST_ROOT
$ b2 stage   # builds the libraries in stage/lib
$ b2         # equivalent to b2 stage
$ b2 install # Installs the headers and libraries
   in $PREFIX/include and $PREFIX/lib

When we run install, we do not want to run
stage as well.

In Christ,
Steven Watanabe