Re: [Boost-bugs] [Boost C++ Libraries] #10248: Understanding generated files / targets.

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #10248: Understanding generated files / targets.
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-02-27 01:38:18

#10248: Understanding generated files / targets.
-------------------------------+----------------------------
  Reporter:  anonymous         |      Owner:  vladimir_prus
      Type:  Support Requests  |     Status:  new
 Milestone:  To Be Determined  |  Component:  build
   Version:  Boost 1.51.0      |   Severity:  Not Applicable
Resolution:                    |   Keywords:
-------------------------------+----------------------------

Comment (by steven_watanabe):

 * t1:
   Boost.Build assumes that if a target is updated, all
   dependent targets must be updated.  It does not recheck
   the timestamp after building a target to determine whether
   it really changed.  Instead of always-generate-main, you can
   use the print module, which will only update the target
   when its contents change.

 * t2:
   Boost.Build ignores t2.hpp because there's no rule for
   building an exe from a header.  You really do need
   <implicit-dependency> for this.  <implicit-dependency>
   does two things for you.  It forces the jam target for t2.hpp
   to be generated, so that t2.hpp can be found by the #include scanner,
   and it also adds an appropriate -I directive to the compile
   command line.  Remember that Boost.Build will put t2.hpp
   in some directory under bin/

 * t5:
   The reason that it doesn't relink is that there is no #include <t5.hpp>.
   <implicit-dependency> doesn't set up an actual dependency.  It only
   says that there's a possible dependency which should be found by
   scanning the source.  If you want an unconditional dependency, then
   use the <dependency> feature instead.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/10248#comment:1>
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