Re: link: "Recursive Make Considered Harmful"
On Tue, 2005-01-11 at 22:22, Jeroen Ruigrok/asmodai wrote:
> -On [20050111 12:42], Christopher Vance (christopher@nu.org) wrote:
> >It's the use of shell commands to change make's behaviour - and not
> >just file content - that I consider a significant part of the problem.
>
> Nice to see you saying that, because I was wondering if a good build tool
> needs any external dependencies at all in the terms of shell scripts.
>
> The only things I can envision are things like compiler compilers and such
> tools that need to generate file X from template file Y.
>
> >I think building would be more maintainable if the shell stuff was up
> >front to set parameters, etc., before doing any file construction, and
> >then never got invoked again in all the myriad recursions.
>
> I agree to that. I am just hard thinking if this is a reasonable
> assumption. I cannot envision much right now that need external shell
> scripting or such given a sufficiently decent command set inside the build
> tool.
Some places where I have been forced to use shell variable assignment in
makefiles:
- os/arch/platform detection eg: 'uname' for multi-platform builds.
- converting pathnames (when dealing with Windoze systems)
- wild-carding, eg: just pull in *.c as sources without having to
specify them manually.
- interfacing to other build systems to extract variables
- interfacing to source code control systems
As previously stated, shell/external variable assignment is not bad/evil
if done up front before the construction phase. Its when its evaluated
partway through a build that prevents the dependency graph from being
pre-calculated up front.
The build tool would need to provide the flexibility to invoke
custom/external functions for assigning/mutating any number of variables
based on any number of input arguments. Such functions would have to be
idempotent (ie no side affects).
-Andrew Hacking
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