[Boost-build] Symbolic links and timestamps

Subject: [Boost-build] Symbolic links and timestamps
From: Phil Bass (Phil.Bass_at_[hidden])
Date: 2008-10-01 07:44:41

I'm converting an unwieldy set of make files to broadly equivalent jam 
files. Among other things the make files build an executable, load data 
into a database and make symbolic links to the executable and some data 
files. The jam files try to ensure that the data is loaded into the 
database before the symbolic links are created to ensure that the 
application runs correctly when invoked via the symlink. A timestamp 
file is used to record the time the data was loaded.

The symlink depends on the executable and the data-loaded timestamp 
file. Doing a build from scratch produces files in the order: 
data-loaded timestamp file, executable file, symbolic link to 
executable. Naturally, telling bjam to re-build the symbolic link at 
this point results in no actions. However, if the data-loaded timestamp 
file is removed using bjam --clean and the system built again, 
subsequent builds always trigger the creation of the symbolic link.

This seems to be because bjam is using the timestamp of the executable 
as the timestamp of the symlink. Here's a fragment of a build with -d+3 
as evidence:

     make    --       <pRunTime/ROWT/bin/gcc-x86/debug/link-static>Main
     make    --       <pRunTime/ROWT/bin/gcc-x86/debug/link-static>Main
     bind    --       <pRunTime/ROWT/bin/gcc-x86/debug/link-static>Main: 
RunTime/ROWT/Main
     time    --       <pRunTime/ROWT/bin/gcc-x86/debug/link-static>Main: 
Tue Sep 30 12:59:31 2008
     make    --        <pROWT_Gui/bin/gcc-x86/debug/link-static>Main
     make    --        <pROWT_Gui/bin/gcc-x86/debug/link-static>Main
     bind    --        <pROWT_Gui/bin/gcc-x86/debug/link-static>Main: 
ROWT_Gui/bin/gcc-x86/debug/link-static/Main
     time    --        <pROWT_Gui/bin/gcc-x86/debug/link-static>Main: 
Tue Sep 30 12:59:31 2008
     . . .
     made    stable    <pROWT_Gui/bin/gcc-x86/debug/link-static>Main
     made+   old      <pRunTime/ROWT/bin/gcc-x86/debug/link-static>Main

In this snippet RunTime/ROWT/Main is the symlink and ROWT_Gui/.../Main 
is the executable. The timestamp on the data-loaded timestamp file was 
2008-10-01 11:31, i.e. newer than the executable, but older than the 
symlink.

So, my question is, can bjam be persuaded to use the timestamp of a 
symlink file instead of the file it points to? Alternatively, is there a 
better way of achieving my objectives?

-- 
Phil Bass (pab_at_[hidden])
     The views expressed in this e-mail/posting are those of the author
     and do not necessarily reflect those of Isotek Electronics Ltd.