[Scons-users] Prefixing a command without messing up dependencies

[Chris BeHanna]

On Jul 17, 2012, at 12:57 , Greg Ward wrote:


> Hi all --

> 

> our build normally runs a lot of 

> 

>  javac ... <sources>

> 

> commands, and SCons correctly determines that the targets depend on

> javac as well as <sources>. However, javac emits lots of stupid

> warnings that are impossible to disable. I wrote a script to handle

> this, but it doesn't work like this:

> 

>  javac ... <sources> 2>&1 | filterJavac

> 

> because I want to keep stdout and stderr distinct. So instead it works

> like this:

> 

>  filterJavac [options] -- javac ... <sources>

> 

> where filterJavac runs javac as a subprocess and filters its stdout

> and stderr intelligently. Works great... except that now SCons thinks

> my compiler output depends on filterJavac, not on javac. I'd like to

> be able to toggle use of filterJavac with a command-line option, but

> that triggers lots of unnecessary rebuilds: "javac is no longer a

> dependency" and "filterJavac is a new dependency". Argh.

> 

> Suggestions? I think I could easily make those targets all depend on

> javac, but there's still the problem of an unwanted dependency on

> filterJavac. Is there a way to overrule the usual "depend on argv[0]"

> trick?


	Maybe make your command string something like

	$( $FILTERJAVAC $) javac ... <sources>

where you set env['FILTERJAVAC'] to 'filterJavac [options] --' when you toggle it on, and leave it empty otherwise?

	The $( and $) are supposed to prevent what lies between them from being used for hashing the command string.

-- 
Chris BeHanna
chris at behanna.org