Re: [Plplot-devel] Intermittent Ada example build failures are now gone again!

[Alan W. I. <ir...@be...>]

Hi Jerry:

On 2018-04-10 14:15-0700 lis...@ic... wrote:

> Thanks for your work on trying to figure this out. I really have no
idea what the problem could be. I’ve never had a problem with gnatmake
but you recall a problem from the past that pretty much escapes me by
now.

I was referring to your attempts to get the test_ada project to work
on Mac OS X.  I have forgotten the details, but as I recall you never
had complete success with that test.  But on the other hand, the issue
you discovered was consistent and that was also true for the issue
that Arjen discovered for Cygwin.  Therefore, it is likely the issues
you guys discovered on two different platforms don't have anything in
common with the issue I am dealing with.

[...]
> I don’t know if you will find this useful, but on
>
> https://docs.adacore.com/gnat_ugn-docs/html/gnat_ugn/gnat_ugn/building_executable_programs_with_gnat.html
>
> at the end of "4.1. Building with gnatmake" appears this:
>
> "Note that for advanced forms of project structure, we recommend
creating a project file as explained in the GNAT_Project_Manager
chapter in the GPRbuild User’s Guide, and using the gprbuild tool
which supports building with project files and works similarly to
gnatmake.”

[...]
Thanks for pointing out the gprbuild possibility.  From my further
reading in
<https://docs.adacore.com/gprbuild-docs/html/gprbuild_ug/building_with_gprbuild.html>
it appears gprbuild is designed to handle more project complexity than
gnatmake, but it is not of sufficient generality to implement complete
build systems like is possible with CMake.  Furthermore, it appears
that gprbuild does not use gnatmake but provides the same
functionality at the build level, i.e., it uses the same building
blocks (gcc to compile, gnatbind to bind, and gnatlink to link) that
gnatmake does.  Note it is the gnatlink step where the intermittent
errors occur for me.  So it is useful to know about the gprbuild
possibility, but since CMake has everything covered at the build
system level (i.e., does not need to use gprbuild) and gnatmake has
everything covered at the detailed (gcc, gnatbind, and gnatlink)
building block level I plan to stick with that combination.

Here is some recent news about these intermittent Ada build errors.

They disappeared for me for several comprehensive tests after a reboot
3 days ago, but yesterday they came back again!  That is, I built the
test_diff_psc target by hand from scratch and it failed due to Ada.
Then I repeated the exact test again, and it succeeded with perfect
(PostScript) results and no Ada build issues at all! So rebooting the
system may have nothing to do with these errors.

Of course, the possibility always exists that intermittent results are
due to hardware issues, and the gnat building process may be
particularly sensitive to such hardware issues.  So after the first
encounter with these intermittent Ada build failures, I did some
detailed comparisions of rsync results using the --checksum option
(which checked that 4 trillion bits on two rsynced disks were the
same), RAM tests, disk filesystem checks, and git filesystem checks to
see if any hardware issue shows up via such detailed checks, but none
did.  So those results pretty much restored my confidence that my
hardware was fine.

So once this Ada build issue appeared again for me yesterday after all
those previous successful hardware checks, I did a google search for
the terms (without the quotes) "gnatmake intermittent build error" and
found
<https://gcc.gnu.org/bugzilla/show_bug.cgi?format=multiple&id=65451>
which was a bug report in 2015 about intermittent Ada build issues
which was immediately fixed back then.  However, my gnat version (=
4.9.2) is from 2014 so I don't have that bugfix and I am pretty sure
at this stage that bug 65451 is the issue that is causing the
intermittent Ada build issues for me. Therefore, I plan to use the
-DENABLE_ada=OFF option for my further testing until I can get access
to a later version of the Ada build tools myself, and I suggest others
who currently don't have access to Ada build tools with bug 65451
fixed should do the same.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

Linux-powered Science
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