Is "host" the build or the target system?

[Kelly O'Hair]

On May 28, 2012, at 6:59 AM, Magnus Ihse Bursie wrote:

> On 2012-05-25 20:00, Fredrik Öhrström wrote:
>> 
>> ----- kelly.ohair at oracle.com skrev:
>>> I myself am ok with just cringing everytime I use the --host options,
>>> but I still consider it an autoconf BUG,
>>> always will. 
>> It did make me cringe, but only for a while, I am used to it now. :-)
> 
> You might be, but you have worked extensively on the build system for a long time now. I think it is important that we build a system that is clear and accessible to all developers, with minimal need for documentation and education. 
> 
> Anyway, since obviously we're not all agreeing on how to solve this, let's try to break down the problem further instead of just pushing "my solution" against "Fredrik's solution". I think what the problem basically boils down to is two questions: how to control configure, and how to design our internal Makefiles.
> 
> 1. How to control configure
> 
> Autoconf has the tradition of specifying the target platform using "--host". In both Fredrik's and my solution will this still be a way to use configure. The question is instead if:
> 
> a) we should *only* allow this as the way to setup cross-compilation
> 
> b) we should extend the configure script to also allow "--target", in a non-autoconf-standard way, to specify the target platform, and document this as the default way to do cross-compilation configurations.
> 
> c) we should extend the configure script to also allow a new, third option, like --with-target-system, --jdk-target, --target-platform or something similar, and document this as the default way to do cross-compilation configurations. (Suggested privately to me by Kelly.)

I think I prefer c), make the option spelling explicitly for the jdk builds, and what we (the jdk team) need, and
defined the way we want. As autoconf upgrades, this is probably the least amount of work for us.

And it is probably a good policy and important to not change the behavior of the existing configure options, if at all possible.
Anyone mixing autoconf traditional host/target settings with --jdk-target gets what they get, we don't prevent it, and
we let the user figure out what it means.

Just my 2 cents worth.

> 
> 2. How to design our internal Makefiles
> 
> The other question, that has been somewhat dwarfed in the discussion, is how the decision above affect our internal Makefile architecture. We have basically two choices:
> 
> a) Our internal Makefile variables and functions specifying the target platform should be named HOST_...
> 
> b) Our internal Makefile variables and functions specifying the target platform should be named TARGET_...
> 
> The only reason for going with 2a) is to be consistent with the autoconf UI, so this solution only makes sense if you also go by solution 1a). However, and this is important to point out, it is a valid and meaningful combination to go with solution 1a) (i.e. to only allow --host) and still choose 2b (i.e. name our internal variables TARGET_...).
> 
> From my perspective, the most important question is 2). The way you start a cross-compilation only affects a few people, and even if this is counter-intuitive and would require a documentation/education effort, once you've learnt how to do it, it's not that hard to remember.
> 
> On the other hand, our internal Makefiles have TARGET_.../HOST_... variables all over the place. Every time you do something that is platform-specific, you will need to use them, regardless if you're cross-compiling or not. Educating *all* JDK developers who will develop platform specific code is a task on a completely different scale. 
> 
> As for question 1), I believe any of options b or c is good, and that option a is unneccessary restrictive and leads to an educational burden that should not really be needed. However, my opinion on this is not as strong as on question 2. (At least not as long as Fredrik answers all support questions on the build-dev list on how to chose the target when cross-compiling ;-))


I see no value in changing the jdk Makefiles, so I probably favor 2),  but maybe with a plan of changing the names
to JDK_HOST and JDK_TARGET eventually (or kind of match the --jdk-target spelling option), so we are less
likely to confuse autoconf 'host' and 'target' definitions.

---

The jdk build is not a cross compiler build, and the HOST and TARGET terminology, as it exists today in the
JDK makefiles, to me refers more to the JDK being used to build (BOOTDIR) or the JDK being built.
So I would like to see us avoid mixing these things up if at all possible, i.e. stray away from the autoconf
options and terminology that direct itself specifically at building cross compilers.
Create our own options that do what we want to do for jdk builds.

-kto

> 
> /Magnus
>