[Plplot-devel] Command-line parsing improvements for both C and Fortran

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

Hi Arjen:

I have just finished (commit 71944db) implementing the C and Fortran
command-line parsing improvements that I first brought up with you
(off-list) just a few days ago. Please see the revised version of
README.release for the details concerning these changes. Since your
modern Fortran experience is more extensive than mine, and I felt
right on the edge of the limit of my own modern Fortran expertise when
implementing this, I would appreciate you reviewing the Fortran part
of this topic, for substance (should it work perfectly in all cases),
standards-compliance (i.e., should it work for nagfor), and overall
style.

On that style point, in the new function c_to_character_array
that appears in bindings/fortran/plplot_small_modules.f90 I implemented

do i_local = 1, length_column_local
     character_array(j_local)(i_local:i_local) = string_ptr(i_local)
enddo

to copy from a pointer vector of size length_column_local one-byte
characters to character_array(j_local), an element of a character
array whose length is the same as the string_ptr size. Is there a more
modern Fortran method of implementing the equivalent of this loop with
just one assignment statement or are we stuck with this do-loop style?

One caveat I discussed in README.release with the present
parsing-related additions to the Fortran
API is that API needs to be converted from the present assumed shape
character arrays to allocatable character arrays to simplify the
arguments and reduce the necessary size checking required with the
present static array approach.  But I am holding off from doing that change
because allocatable character arrays are not reliable on my present
Debian Jessie (gfortran-4.9.2) platform.  For example, this simple
test code,

irwin@raven> cat test_allocatable_character_arrays.f
c     test of allocatable character arrays
       character(len=100), dimension(10)  :: argv_array 
!      character(len=:), dimension(:), allocatable  :: argv_array 
!      allocate(character(len=100) :: argv_array(10))

       argv_array(5)(1:10) = "hello, world"
       write(*,'(a)') argv_array(5)(1:10)
       end

works fine as is on my platform, i.e. has perfect Valgrind results (0
errors, no leaks are possible). However, if you comment the second
line and uncomment the 3rd and 4th lines to change this from a static
character array test to an allocatable character array test, it
spectacularly fails (outputs gibberish) and valgrind also shows all
sorts of memory management issues.

Would you be willing to build and run both versions of the above test
code on Cygwin (with gfortran-6.4.0) to make sure no obvious problems
occur with that gfortran version? If your tests indicate no such
problems then I would encourage you to try updating the API to the
allocatable version as indicated in README.release, and test that
change as indicated there as well.  But if you don't have time for
that just now, I plan to make the change myself just as soon as I
upgrade to Debian Stretch.  I am assuming here (especially if you get
good results for the above test) that gfortran-6.3.0 that comes with
that platform will have no trouble with the above simple example and
also the allocatable version of the new code.

Merry Christmas to you, your family, and all others interested in
PLplot that are lurking here on this list!

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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