From: ptkwt@... (Phil Tomson)
Date: 2004-06-22T15:53:12+09:00
Subject: Re: Rake and timestamps (ideoms or methods?)

In article <40D7A120.4010600@weirichhouse.org>,
Jim Weirich  <jim@weirichhouse.org> wrote:
>Phil Tomson wrote:
>
>> If I don't want to run certain tasks if the file the task is to work on 
>> already is up-to-date (like how make works) how do I tell Rake to not 
>> execute a particular task if the files being worked on are up-to-date?  
>
>Normal tasks don't look at timestamps.  If the goal of a task is to 
>create a file, then use a "file" task rather than a "task" task.  File 
>tasks will not trigger if the file named by the task is up to date with 
>its dependents (which should also be file tasks ... a file task is 
>always out of date if it depends on a regular task ... think about it).
>
>So a simple file task declaration could look like:
>
>    file "copy_of_a.txt" => ["a.txt"] do
>      cp "a.txt", "copy_of_a.txt"
>    end
>
>Translation: The copy depends on the original.  If the original changes, 
>then copy the original into the copy.
>
>> Also, notice the 'raise "blah" system("command")' that I'm doing above. 
>
>As long as your external programs exit with status 0 for normal and 
>non-zero for errors, then rake will automatically abort.  The explicit 
>tests and raises aren't needed
>
> > Here's my rakefile:
>
>And here's my translation.  I didn't understand everything you were 
>doing, so I made some of the following up.  But you should be able to 
>translated it into something appropriate.
>
>I assume that ncvhdl is some compiler-like script and the .vhd file is 
>the input.  I'm assuming that the output file will be a .vhdo file.
>
>I don't know what ncdlab does, so I just made it a normal task.  It will 
>run every time this way.
>

Jim,

Thanks, this helps explain a lot about Rake.

You guessed correctly that ncvhdl is a compiler.  ncelab is sort of like a 
linker.  Unfortuneatly each .vhd file doesn't compile to a 
corresponding .vhdo file (object file) - that would be nice.  All of the 
comilation units get put into a package file in a different directory - the 
same package file, so each .vhd file gets compiled and added to the 
project's .pkg file which makes it hard to figure out if you really need to 
recompile a particular .vhd file (not Rake's problem, though, this is  a 
problem with the compiler/linker tool and it would present a problem for 
make as well).


Phil


>Here's the file --------------------------------------------------------
>
>#!/usr/bin/env ruby
>
># This adds a :clean and :clobber target to your Rakefile.
># We also add all intermediate .vhdo files to the clobber target.
>require 'rake/clean'
>CLOBBER.include("*.vhdo")
>
># Lets make a list of all the .vhd source files in the directory.
>
>VHD_FILES = FileList['*.vhd']
>
># And now use that to make a list of all the .vhdo file we
># want to generate.
>
>VHDO_FILES = VHD_FILES.sub(/$/, 'o')
>
># No change to this task
>
>task :default => [ :sim_jtag_tb ] do
>   puts "done..."
>end
>
># I use "sh" instead of system.  "sh" understands
># when to echo commands in Rake.
>
>task :sim_jtag_tb => [ :build_jtag_tb ] do
>   puts "simulate it..."
>   sh %{ncsim -gui jtag_tb:jtag_tb_behavior}
>end
>
># I don't know what ncdlab does, but I'm assuming it needs
># all the .vhdo files to be present before it can run, so
># we make a dependency.  Fortunately, we already calculated
># the list of .vhdo files. (Note: If I know what kind of output
># file was produced in this step, I would make this a file task
># with the name of the output file.)
>
>task :build_jtag_tb => VHDO_FILES do
>   puts "build jtag_tb"
>   sh %{ncdlab jtag_tb:jtag_tb_behavior -access +r+w}
>end
>
># Here follows the three files that are processed by ncvhdl.
># The jtag_tb_c was bundled with :build_jtag_tb task before,
># but it looks to me like it could be broken out. (I could
># be wrong.)   Notice the "output file depends on input file"
># pattern.
>
>file "jtag_tb_c.vhdo" => ["jtag_tb_c.vhd"] do
>   puts "build jtag_tb_c"
>   sh %{ncvhdl -linedebug jtag_tb_c.vhd}
>end
>
>file "jtag_driver.vhdo" => ["jtag_driver.vhd"] do
>   puts "build jtag_driver"
>   sh %{ncvhdl -linedebug jtag_driver.vhd}
>end
>
>file "jtag.vhdo" => ["jtag.vhd"] do
>   puts "build jtag..."
>   sh %{ncvhdl -linedebug jtag.vhd}
>end
>
>End of Rakefile-------------------------------------------------
>
>There is a lot of duplication in those last three file tasks.  You could 
>  iterate over VHD_FILES and create the file tasks in a loop.  A simpler 
>way is to write a rule that describes how to turn .vhd files into .vhdo 
>files, e.g.
>
>   rule ".vhdo" => [".vhd"] do |t|
>     puts "build #{t.source}"
>     sh %{ncvhdl -linedebug #{t.source}}
>   end
>
>Use that single rule in place of the final three file tasks.  Here is 
>the output from the mockup I did...
>
>----------------------------------------------------
>$ rake
>(in /home/jim/pgm/misc/philtomson)
>build jtag.vhd
>ncvhdl -linedebug jtag.vhd
>Creating jtag.vhdo
>build jtag_driver.vhd
>ncvhdl -linedebug jtag_driver.vhd
>Creating jtag_driver.vhdo
>build jtag_tb_c.vhd
>ncvhdl -linedebug jtag_tb_c.vhd
>Creating jtag_tb_c.vhdo
>build jtag_tb
>ncdlab jtag_tb:jtag_tb_behavior -access +r+w
>simulate it...
>ncsim -gui jtag_tb:jtag_tb_behavior
>done...
>$
>$
>$ rake clobber
>(in /home/jim/pgm/misc/philtomson)
>rm -r jtag.vhdo
>rm -r jtag_driver.vhdo
>rm -r jtag_tb_c.vhdo
>----------------------------------------------------
>
>I hope this helps.
>
>-- 
>-- Jim Weirich    jim@weirichhouse.org     http://onestepback.org
>-----------------------------------------------------------------
>"Beware of bugs in the above code; I have only proved it correct,
>not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)
>
>
>