Bug#1054229: libcgns-dev: please also ship src/cgns_f.F90 to support Fortran compilers beyond gfortran

[Francesco Poli (wintermute)]

Package: libcgns-dev
Version: 3.4.0-3
Severity: wishlist

Hello and thanks for maintaining this useful library in Debian!

The CGNS library may be used from C/C++ programs/libraries and also
from Fortran programs/libraries.

In order to use the library from Fortran code, the

  use cgns

statement is required, which requires access to the 'cgns.mod' module
file, correctly shipped in package libcgns-dev as /usr/include/cgns.mod .

This works like a charm, as long you compile your own Fortran
program/library with the same Fortran compiler which was used to
generate the 'cgns.mod' module file.
But it may fail, when the two compilers are different, since,
unfortunately!, Fortran module files are [not portable] across
different compilers. 

[not portable]: <https://fortranwiki.org/fortran/show/Library+distribution>

Obviously, the 'cgns.mod' module file shipped in package libcgns-dev as
/usr/include/cgns.mod was compiled with gfortran.
As a consequence, if you also compile your own Fortran program/library
with gfortran, there's no issue at all in using libcgns-dev.

But, if you want to support compilation of your own Fortran program/library
with more than one compiler (for instance gfortran and the Intel 'ifort'
Fortran compiler), you cannot use the official Debian package libcgns-dev.

Well, I seem to have found a strategy to work around this issue.

I downloaded the 'src/cgns_f.F90' source file (from the libcgns Debian
source package, same exact version as the installed Debian binary package)
and compiled it with the incompatible Fortran compiler (e.g.: the Intel
'ifort' Fortran compiler), thus obtaining a 'cgns.mod' module file
compatible with the used Fortran compiler. Among the options passed to
the compiler, there were the following:

  -I/usr/include -c

Then I compiled my own Fortran program source files with the previously
obtained 'cgns.mod' module file in the same directory.
Again with:

  -I/usr/include -c

among the compiler options.
Finally, I linked my own Fortran program .o object files together, with the
following:

  -lcgns

among the passed options.

The strategy works and produces an executable, which is dynamically linked
(among other libraries) to the CGNS library:

  $ ldd my_own_fortran_program | grep cgns
        libcgns.so.3.4 => /lib/x86_64-linux-gnu/libcgns.so.3.4 (0x00007f3a4e9f3000)

The executable works correctly.



In conclusion, I would like to suggest to also ship the 'src/cgns_f.F90'
source file in package libcgns-dev, so that the CGNS library in Debian
becomes usable with Fortran compilers other than gfortran.

This would be highly useful, as it would increase the cross-compiler
compatibility of the CGNS library, as shipped in Debian!
And this would just require to ship one more file (less than 200 kbyte)
simply copied from the source Debian package to the libcgns-dev binary
Debian package.

Please consider accepting this proposal.
Thanks for your time and your dedication!

  
-- System Information:
Debian Release: trixie/sid
  APT prefers testing
  APT policy: (800, 'testing'), (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 6.5.0-1-amd64 (SMP w/4 CPU threads; PREEMPT)
Kernel taint flags: TAINT_FIRMWARE_WORKAROUND
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libcgns-dev depends on:
ii  libcgns3.4  3.4.0-3

libcgns-dev recommends no packages.

libcgns-dev suggests no packages.

-- no debconf information