Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Wed, 8 Dec 2010 14:06:06 -0600

On Tuesday 07 December 2010 18:23:14 Jeff Hill wrote:
> > I have thought about something like that in the past, but I wasn't sure
> > where we'd put the files for cross-compiling where host os != target os.
>
> Perhaps when, os != target os, then target os files would go in a
> subdirectory of the host. Like this.
>
> configure/os/linux/             <= linux host build
> configure/os/linux/vxWorks      <= linux cross build for vxWorks

Don't like:
 * The tree gets too deep and sparse
 * Comparing and grepping for things becomes a pain
 * Hard to implement

It doesn't make sense that a self-hosting architecture uses just one level but 
a cross-build for the same OS uses a second level.  Case in point, linux-arm 
can self-build or be cross-built on linux-x86, but many of the values are 
going to be the same for both.

When GNUmake is executing, if it's set T_A contains both the OS and CPU, so it 
doesn't match your structure above.  The configure/CONFIG file currently finds 
the OS_CLASS by including $(CONFIG)/os/CONFIG.Common.$(T_A) which is required 
to set it.  With your structure we either wouldn't know the path to the file, 
or we'd have some files in one place and some in another.  I wouldn't suggest 
trying to use the target-arch as the dir-name, because of all the -debug and 
related targets that really belong with the base architecture.

> The issue is reasonably fast access. It gets a bit painful sometimes
> sifting through 162 files when you are looking for how its configured and
> you may not remember exactly what is in CONFIG.linux-x86.linux-x86 versus
> what is in CONFIG.Common.linux-x86. These two files are not close to each
> other in a file open dialog.

I agree that managing a directory with 244 files in it is a pain, but I think 
any major overhaul is going to take many trial implementations and I suspect 
would lose out on the orthogonality of the current system (settings can be 
overridden at many levels, and are in different files for different targets). 
Janet is not going to have the time to develop any major changes.

Michael suggested replacing our build system with CMake, but he did find some 
issues with doing so and I don't think that's up to the job, and it was not 
popular in my recent survey (aside from the effort needed to train and support 
all of the EPICS developers out there in any new system).

- Andrew
-- 
If a man is offered a fact which goes against his instincts, he will
scrutinize it closely, and unless the evidence is overwhelming, he will
refuse to believe it.  If, on the other hand, he is offered something
which affords a reason for acting in accordance to his instincts, he
will accept it even on the slightest evidence.  -- Bertrand Russell

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System