[Boost-build] gcc precompiled headers

Subject: [Boost-build] gcc precompiled headers
From: Jeroen van der Wulp (J.v.d.Wulp_at_[hidden])
Date: 2008-11-16 12:25:35

Hello everyone,

I'm still looking at precompiled headers and I found another small 
issue. At some point it all seemed to work but today I found that the 
names of precompiled headers should be of the form x.hpp.gch for a 
header file x.hpp. With the Boost trunk version of Boost Build I am 
getting x.gch which I thought to be okay for some time.

The comment in gcc.jam suggests that it was once working this way:

# Calls the base version specifying source's name as the name of the created
# target. As result, the PCH will be named whatever.hpp.gch, and not
# whatever.gch.
rule generated-targets ( sources + : property-set : project name ? )

I prepared a small patch that solved the problem for me. Although it 
solves the problem it feels like a hack. Maybe someone more knowledgable 
can have a quick look.

Another problem I'm having is that I'm importing precompiled headers in 
library sources files as well as source files for executables. The 
differences between the two in my case are the setting of the -fPIC 
flag. The precompiled header cannot be used by both.

Can I also solve this problem by setting -fpic for all compilations in 
the project? For what platforms/gcc versions can this work and does this 
have any unwanted side-effects? On the other hand I was wondering 
whether an position independent code feature might help with this.

Thanks,

Jeroen

Index: tools/build/v2/tools/gcc.jam
===================================================================
--- tools/build/v2/tools/gcc.jam	(revision 49796)
+++ tools/build/v2/tools/gcc.jam	(working copy)
@@ -281,7 +281,7 @@
     {
         name = [ $(sources[1]).name ] ;
         return [ generator.generated-targets $(sources)
-          : $(property-set) : $(project) $(name) ] ;
+          : $(property-set) : $(project) $(name)$(name:S) ] ;
     }
 }