Re: [Boost-build] Failing dependency_test.py test.

Subject: Re: [Boost-build] Failing dependency_test.py test.
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2012-07-19 00:07:24

AMDG

On 07/18/2012 08:16 PM, Jurko Gospodnetić wrote:
> 
> -- 1 --
> 
>   Why would replacing the
> 
>     DEPENDS <scanner>x.cpp : x.cpp ;
> 
>   relationship with
> 
>     INCLUDES <scanner>x.cpp : x.cpp ;
> 
>   Cause problems?
> 
>   I tried it, it makes sense, fixes the problem at hand and no internal
> Boost Build tests fail with that code.
> 

It breaks header scanning for generated sources.

Here's why:

Consider this dependency graph (which
is what is generated by using INCLUDE)

  x.o -----> <scanner>x.cpp
   |
   |
   v
<scanner>x.cpp (internal node)
   |     \
   |      \
   v       \
  x.cpp     v
         x.cpp (internal node)

Now consider a possible execution order:
update <scanner>x.cpp
update x.cpp (internal node)
update x.cpp
  execute actions for x.cpp
  rescan x.cpp creating x.cpp (internal node 2)
update x.cpp (internal node 2)
update <scanner>x.cpp (internal node)
update x.o

Note how we never rescanned <scanner>x.cpp.
The dependency graph that we need for this
to work is

  x.o -----> <scanner>x.cpp (internal node)
   |                 |
   |                 |
   v                 |
<scanner>x.cpp       |
   |                 |
   |                 |
   v                 v
  x.cpp     x.cpp (internal node)

> 
> -- 2 --
>   I tried removing that DEPENDS relationship declaration all-together
> and replacing it with (code from virtual-target.actualize()):
> 
>   SEARCH on $(name) = [ path ] ;
> 
>   However - this does not not cause any <scanner>x.cpp --> x.cpp
> dependency to be added and so the action for building x.o gets run
> without x.cpp being generated first.
> 

This won't work correctly for NOTFILE targets.
I tried the attached (hackish) patch and it
seemed to work okay.

>   Am I missing something here or do we need to manually add a dependency
> between whomever is using <scanner>x.cpp and x.cpp? Effectively - this
> is the exact dependency added internally by having <scanner>x.cpp
> INCLUDE x.cpp.
> 

In Christ,
Steven Watanabe