Re: [Boost-build] Problem with PCH

From: Vladimir Prus (ghost_at_[hidden])
Date: 2006-09-24 03:18:53

On Friday 22 September 2006 16:52, Bojan Resnik wrote:
>   A recent introduction of SORT in sequence.unique rule is causing PCH
> generation to fail sometimes by attempting to compile the header file
> instead of the source file. This happens in one of my projects, but I
> have been unable to create a reproducible test case.

I'm a bit unsure about sequence.unique changing the order of list elements, as 
there are cases where order matters. 

>   The problem actually exists and manifests itself when the source
> file object identifier is 'less' than the header's identifier:
>
>   lib a : [ pch apch : [ cast _ pcheader : a.h ] a.cpp ] ;
>
>   In my case, after the targets have been created,
> a.h=object(file-target)@2238, a.cpp=object(file-target)@400.  The
> sequence expected by pch-generator is a.h a.cpp. When sequence.unique
> rule is invoked from targets.jam:1187, it sorts the original sequence
> [ object(file-target)@2238 object(file-target)@400 ] into [
> object(file-target)@400 object(file-target)@2238 ], thus switching
> places of a.h and a.cpp. pch-generator then incorrectly creates
> <pch-source>a.h and <pch-header>a.cpp features, which causes the
> system to attempt to compile the header file.
>
>   Attached is patch to pch.jam that checks the types of arguments to
> make sure that the correct ones are used for source and header.

And what if not? 
+        if [ $(sources[2]).type ] = PCHEADER
+        {
+            cpp = $(sources[1]) ;
+            h   = $(sources[2]) ;
+        }

won't assign anything to 'cpp' and 'h' is the order is wrong, right? So PCH 
won't work?

- Volodya

-- 
Vladimir Prus
http://vladimir_prus.blogspot.com
Boost.Build V2: http://boost.org/boost-build2