Re: [Boost-build] Conditional updating using NOUPDATE

Subject: Re: [Boost-build] Conditional updating using NOUPDATE
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2013-04-24 16:23:11

AMDG

On 04/24/2013 12:25 PM, Edward Mitchell wrote:
> Here is a brief overview of my problem. I have a target (scrape_flag.h)
> that I want to update in two cases:
> 
> 1) The file does not exist in the build directory.
> 2) A python script that runs at the beginning of the build exits with a
> 0 value.
> 
> <snip>
> 
> [code]
> rule scrape( dir )
> {
> out = [ SHELL "cd $(dir); export PYTHONPATH=`pwd`:${PYTHONPATH}; python
> $(.common)/symbolScraper.py *.cc *.h" : exit-status ] ;
>      local bname = $(dir:B)_scrape_flag.h ;
>      if $(out[2]) = 0 {
>          ECHO $(out[1]) ;
>      } else {
>         ECHO "No changes found" ;
>         NOUPDATE $(bname) ;
>      }
>      make $(bname) : : @cando.touch ;
> }
> 
> actions touch {
>     touch $(<)
> }
> [/code]
> 
> Is this the wrong way to use NOUPDATE, or is there a better way to
> approach the problem in general. Thank you for any help you can give me.
> 

NOUPDATE is a jam level rule.  The correct place to handle
this is:

rule touch ( targets + : sources * : properties * ) {
    if ... {
        NOUPDATE $(targets) ;
    }
}

In Christ,
Steven Watanabe