svn commit: r289384 - head/lib

[Bryan Drewery]

On 10/15/2015 2:00 PM, Ian Lepore wrote:
> On Thu, 2015-10-15 at 13:54 -0700, Bryan Drewery wrote:
>> On 10/15/2015 1:27 PM, Bryan Drewery wrote:
>>> Author: bdrewery
>>> Date: Thu Oct 15 20:27:15 2015
>>> New Revision: 289384
>>> URL: https://svnweb.freebsd.org/changeset/base/289384
>>>
>>> Log:
>>>   Let the SUBDIR_DEPEND*c++ variables actually work rather than
>>> being parsed
>>>   as a +=.  These were safe due to a .WAIT very early on.
>>>   
>>
>> My analysis was wrong. The libc++ dependency on libcxxrt was actually
>> broken here and would not have built if you went directly into lib
>> and
>> built in parallel. It was hidden by the fact that a proper dependency
>> is
>> in Makefile.inc1 via an __L target. The power of redundancy!
>>
>> This too allows kerberos5/lib to work with SUBDIR_PARALLEL= since
>> it's
>> so greatly defined in Makefile.inc1.
>>
>>
> 
> But don't both sets of dependencies have to be correct?  As I vaguely
> recall, the ones in Makefile.inc1 are used during bootstrapping and
> tool building, and the ones in lib/Makefile are used when world
> -building.  It may be that when MACHINE_ARCH == TARGET_ARCH some of
> them are the same libraries and the Makefile.inc1 dependencies take
> care of everything.

It's complicated, my words may seem to contradict but it's just the
nature of the convoluted process that we bootstrap the build by.

Libraries, and anything else we list in the bootstrap phases, are
special. Their SUBDIR_depend are less needed in the context of
buildworld since they will already be built by the time the 'make
libraries' builds all of lib/ with a subdir build or the 'make all' is
ran on the tree, because of the __L dependencies. The special bootstrap
phase stuff and special libraries need to have all of the proper __L
targets to order them as they are built directly, not via bsd.subdir.mk
recursing.  One of the last steps of 'make libraries' does do a subdir
build in lib/ since _generic_libs contains 'lib'. So yes the
SUBDIR_depend are relevant for buildworld, but getting it wrong can be
fine in cases where the library was built early with proper __L deps listed.

The SUBDIR_depend are needed for manual direct subdir builds outside of
buildworld and the builds 'make libraries' and 'make all' phases which
use subdir builds to build things lacking a __L list.

I've noticed that when people add new libraries into the early phases
they usually follow-up with multiple commits trying to get it all right
and update all of the proper places.

Note that we actually have a 3rd dependency list in the tree now which
is in the scattered Makefile.depend files.  These are used for "meta
mode" which I do think is more on the right track as it lets a clean
build start from any directory.  It doesn't use the SUBDIR_depend or the
__L lists at all.  The problem with it is the auto-generated nature of
it can lead to problems with optional dependencies and adding new
directories.

-- 
Regards,
Bryan Drewery

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