[Scons-users] Extracting "-I" paths in a complex tree

[andreas.ames at de.transport.bombardier.com]

> I think what you're hoping for is to somehow do the scanning as part

> of the build process -- but of course it's too late then.  If foo.c

> depends on foo.h which is a generated header, by the time you compile

> foo.c and discover it needs foo.h it's too late to go back and

> generate it.  Scanning for deps has to be done before building.  If

> you're going to run the compiler (or at least preprocessor) you'll

> have to do it an extra time in the scanner.


You are right regarding of what I'm hoping for.  I should have explained 
the general idea before asking questions about it, sorry.  I'll try to 
make good for my omission, sticking with gcc as an example.

I would like to 'smuggle' an additional '-H' command line option into the 
command line associated with StaticObject (and SharedObject etc.) and 
filter the stderr for indications of include files being used by the 
preprocessor.  IIRC, gcc prints the absolute path of the include files, so 
these could be used without further ado.  Calling the 
compiler/preprocessor onece more time StaticObject seems wasteful to me 
(performance-wise).  Besides the performance gain the suggested approach 
would also ensure that the compiler configuration is implicitly the same 
for both target creation and computation of dependencies.

To be honest I can't see a principal problem with such an approach.  On 
the first scons run (let's say after VCS checkout or so) the target is not 
there yet, so a build is necessary anyway.  As part of this build the 
implicit dependencies are computed, which are used as inputs for the 
out-of-date analysis of the next run.  But it's well possible that I'm 
just missing something important here.


cheers,
 
aa
  
Please consider the environment before you print / Merci de penser à 
l'environnement avant d'imprimer / Bitte denken Sie an die Umwelt bevor 
Sie drucken 

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