Re: Why is EpicsHostArch.pl not executable?

["Johnson, Andrew N. via Core-talk" <core-talk@aps.anl.gov>]

Hi Martin,

On 7/1/19 2:35 PM, Konrad, Martin wrote:

I just discovered that in contrast to all the other Perl scripts
EpicsHostArch.pl isn't marked executable. Steps to reproduce:

git clone https://git.launchpad.net/epics-base
cd epics-base/
make -s -j
ls -l lib/perl/EpicsHostArch.pl
-r--r--r-- 1 marko marko 2071 Jul  1 15:00 lib/perl/EpicsHostArch.pl

A look at the Makefile reveals that this file is being installed in a
different way [1]. The comment suggests that the different target is
intentional but I'm not so sure about the missing executable flag.

Could you please shine some light on this?

EpicsHostArch.pl must be installed into the architecture-independent lib/perl directory, because the build needs it to be able to work out what the host-arch should default to when the EPICS_HOST_ARCH environment variable hasn't been set. Because of its destination path the file gets installed using the build rule for installing perl modules, which aren't executable programs so that rule doesn't set the execute flags on the targets it installs (none of the files under lib/perl have their executable flag set).

The configure/CONFIG rule and the startup/* scripts all run EpicsHostArch.pl using
    perl path/to/EpicsHostArch.pl
so it will work without having its executable flag set. The Perl installation that the shell runs will of course control what host-arch gets returned by the script. If that doesn't work for some specific installation the correct fix is to set the EPICS_HOST_ARCH environment variable on that system (or adjust the PATH so the correct Perl appears first in the search order, but the other solution is probably less work).

Note that we can't use the $(PERL) macro in configure/CONFIG because that variable only gets set much later in an arch-specific configure/os file, and to find the right file we need to know the host-arch. Bootstrapping is a tricky process...

HTH,

- Andrew

-- 
Complexity comes for free, Simplicity you have to work for.