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Before the 2.6.25 merge window closed...

Before the 2.6.25 merge window closed...

Posted Feb 18, 2008 11:02 UTC (Mon) by landley (subscriber, #6789)
In reply to: Before the 2.6.25 merge window closed... by nix
Parent article: Before the 2.6.25 merge window closed...

> There are some things worth worrying about, but I don't think this is
> one of them. The kernel can be cross-compiled, so its build
> requirements are really not that important. Nobody sane ever compiles
> Linux on an embedded system (by definition if it's embedded it's too
> small to do that sort of thing), and 99.999% of non-embedded Linux
> systems have Perl on them.

Apparently, I'm not sane then.

http://landley.net/code/firmware

I cross compile just enough of a native environment to be able to 
recompile itself, and then I boot it under qemu (where I have unlimited 
memory, hard drive, and can leverage cheap x86 CPU power) and native 
compile under an emulator.  Native compiling is MUCH easier than cross 
compiling, in general.

I accelerate this by using distcc to call out to the cross compiler 
(through the virtual network).  That's optional, but provides a nice 
speed boost without taking away from the fact that header #including and 
library linking and ./configure and all the _hard_ bits are run natively 
inside the emulator, where they "just work" without having to do the 
intricate and extensive "explaining things to the build, with a brick" 
that cross compiling requires.

> A Perl installation requires about 30Mb. There's no way you could
> sensibly compile a modern Linux kernel on a system with that little
> RAM, so what you're saying is we should optimize the kernel build
> process for systems that have less disk space than we need memory to
> complete the compilation?

No, I'm saying that gratuitous environmental dependencies more or less 
killed the gnucash project, and Linux has until now gone out of its way 
to avoid them.  There's _shipped logic to avoid the need for lex and yacc 
in kconfig, and you can run "oldconfig" without curses.  This perl 
dependency did not previously exist, and was introduced for very little 
reason.  Now there's talk of adding perl to kbuild.  So understanding the 
build process would now involve knowing three languages (Because nothing 
says "maintainability" like perl.  Or for that matter, having to know 
four different programming languages (C, BASH, gnu make, perl) to follow 
the build.)

Of course Python is just as widely deployed, so let's add that too.  (I 
love Python.  It doesn't belong in the kernel build unless perhaps you 
use it to REMOVE the dependencies on make and bash.)  And java's GPLv2 
now, why not throw that in as well?  Did you know PHP can be used 
standalone outside of web browsers?  And there are tons of fans of emacs 
lisp...

Where does it end?

> (And no, I don't much like Perl: I much prefer Python and C. But still, 
> this is a waste of human effort.)

Perl is not a language.  Perl is a program.  There are dozens of C 
compilers out there, several different javascript interpreters, even a 
python interpreter implemented in java.  But there is only a single 
implementation of perl, and attempts by the original development team to 
reimplement perl (in parrot) failed.  There is no standard, just a 
codebase that may or may not run your program.

The open source world was upset about Word files being considered a 
standard, and uncomfortable back when "it works on Netscape" was the sole 
definition of HTML, but Perl gets a pass on this.  I still don't 
understand why.  The IETF always insisted on two independent 
implementations before calling anything a standard.  To this day, Perl 
wouldn't pass muster there.

But that's a side issue.  So is perl's status as a write-only language.  
My objection is over adding complexity to the build process (in the form 
of environmental dependencies) without a compelling reason that outweighs 
the added complexity.


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Before the 2.6.25 merge window closed...

Posted Feb 19, 2008 7:40 UTC (Tue) by nix (subscriber, #2304) [Link]

> I cross compile just enough of a native environment to be able to 
> recompile itself, and then I boot it under qemu (where I have unlimited 
> memory, hard drive, and can leverage cheap x86 CPU power) and native 
> compile under an emulator.  Native compiling is MUCH easier than cross 
> compiling, in general.

Wow, that's weird. I'm not sure it's a common use case to be worth making 
changes for, but it's not as if this change is huge. :)

(I haven't found setting up cross compilers to be remotely as hard as you 
have, though, even without crosstool to help. For kernel builds (thus 
without libraries), it verges on trivial, certainly much easier than 
getting qemu working.)

> No, I'm saying that gratuitous environmental dependencies more or less 
> killed the gnucash project

g-wrap, and endless backend thrashing, more or less killed the gnucash 
project :) every distro on earth has guile and GNOME packaged. More recent 
gnucashes have dropped g-wrap and moved to SWIG, thank goodness.

> build process would now involve knowing three languages (Because nothing 
> says "maintainability" like perl.  Or for that matter, having to know 
> four different programming languages (C, BASH, gnu make, perl) to follow 
> the build.)

Call me an elitist but I'd be inclined to say that if you can't pick up 
languages as simple as C, the subset of make used in kernel makefiles, and 
so forth you probably shouldn't be hacking the kernel at all. (And I don't 
think I've ever met a kernel hacker who doesn't know shell: perl is 
similar enough to the shell that you can pick up enough to read it in a 
few hours, or less.)

You really are setting up some seriously weak straw men here. Your real 
motive is obviously minimalism for the sake of it, so why on earth not 
admit it?

> Of course Python is just as widely deployed, so let's add that too.  (I 
> love Python.  It doesn't belong in the kernel build unless perhaps you 
> use it to REMOVE the dependencies on make and bash.)  And java's GPLv2 
> now, why not throw that in as well?  Did you know PHP can be used 
> standalone outside of web browsers?  And there are tons of fans of emacs 
> lisp...

I'm not sure if this is straw men or taking the mickey. I'd expect random 
slashdotters to spot the logical fallacies here.

(Regarding Perl not being a language, you're probably right, at least in 
regard to Perl 5. Perl 6 *does* have a language spec, though.)

> My objection is over adding complexity to the build process (in the form 
> of environmental dependencies) without a compelling reason that
> outweighs the added complexity.

Yet you seem to have no objection to adding complexity by reimplementing 
the wheel in the actual code to avoid the environmental overheads. That 
would be strange if your reasons weren't actually minimalism for the sake 
of it :)


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